HHH-13785 : HQL/Criteria function support

- preliminary work on updated tree handling.  See SqmFunctionDescriptor, SqmFunctionRegistry and SqmFunction

hibernate-core/src/main/java/org/hibernate/boot/internal/SessionFactoryOptionsBuilder.java

@@ -60,7 +60,7 @@ import org.hibernate.query.ImmutableEntityUpdateQueryHandlingMode;
 import org.hibernate.query.criteria.LiteralHandlingMode;
 import org.hibernate.query.hql.HqlTranslator;
 import org.hibernate.query.sqm.mutation.spi.SqmMultiTableMutationStrategy;
-import org.hibernate.query.sqm.produce.function.SqmFunctionRegistry;
+import org.hibernate.query.sqm.function.SqmFunctionRegistry;
 import org.hibernate.query.sqm.sql.SqmTranslatorFactory;
 import org.hibernate.resource.jdbc.spi.PhysicalConnectionHandlingMode;
 import org.hibernate.resource.jdbc.spi.StatementInspector;

hibernate-core/src/main/java/org/hibernate/boot/spi/AbstractDelegatingSessionFactoryOptions.java

@@ -32,7 +32,7 @@ import org.hibernate.query.ImmutableEntityUpdateQueryHandlingMode;
 import org.hibernate.query.criteria.LiteralHandlingMode;
 import org.hibernate.query.hql.HqlTranslator;
 import org.hibernate.query.sqm.mutation.spi.SqmMultiTableMutationStrategy;
-import org.hibernate.query.sqm.produce.function.SqmFunctionRegistry;
+import org.hibernate.query.sqm.function.SqmFunctionRegistry;
 import org.hibernate.query.sqm.sql.SqmTranslatorFactory;
 import org.hibernate.resource.jdbc.spi.PhysicalConnectionHandlingMode;
 import org.hibernate.resource.jdbc.spi.StatementInspector;

hibernate-core/src/main/java/org/hibernate/boot/spi/SessionFactoryOptions.java

@@ -35,7 +35,7 @@ import org.hibernate.query.QueryLiteralRendering;
 import org.hibernate.query.criteria.LiteralHandlingMode;
 import org.hibernate.query.hql.HqlTranslator;
 import org.hibernate.query.sqm.mutation.spi.SqmMultiTableMutationStrategy;
-import org.hibernate.query.sqm.produce.function.SqmFunctionRegistry;
+import org.hibernate.query.sqm.function.SqmFunctionRegistry;
 import org.hibernate.query.sqm.sql.SqmTranslatorFactory;
 import org.hibernate.resource.jdbc.spi.PhysicalConnectionHandlingMode;
 import org.hibernate.resource.jdbc.spi.StatementInspector;

hibernate-core/src/main/java/org/hibernate/dialect/function/SQLFunction.java

@@ -11,6 +11,7 @@ import java.util.List;
 import org.hibernate.QueryException;
 import org.hibernate.engine.spi.Mapping;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
+import org.hibernate.query.sqm.tree.expression.SqmFunction;
 import org.hibernate.type.Type;
 
 /**
@@ -24,7 +25,7 @@ import org.hibernate.type.Type;
  * @author David Channon
  * @author Steve Ebersole
  *
- * @deprecated Replaced by {@link org.hibernate.query.sqm.function.SqmFunction}
+ * @deprecated Replaced by {@link SqmFunction}
  */
 @Deprecated
 public interface SQLFunction {

hibernate-core/src/main/java/org/hibernate/dialect/function/SQLFunctionRegistry.java

@@ -10,13 +10,14 @@ import java.util.Map;
 import java.util.TreeMap;
 
 import org.hibernate.dialect.Dialect;
+import org.hibernate.query.sqm.tree.expression.SqmFunction;
 
 /**
  * Defines a registry for SQLFunction instances
  *
  * @author Steve Ebersole
  *
- * @deprecated Replaced by {@link org.hibernate.query.sqm.function.SqmFunction}
+ * @deprecated Replaced by {@link SqmFunction}
  */
 @Deprecated
 public class SQLFunctionRegistry {

hibernate-core/src/main/java/org/hibernate/query/hql/internal/QuerySplitter.java

@@ -18,7 +18,6 @@ import org.hibernate.query.hql.spi.SqmCreationOptions;
 import org.hibernate.query.hql.spi.SqmCreationProcessingState;
 import org.hibernate.query.hql.spi.SqmCreationState;
 import org.hibernate.query.hql.spi.SqmPathRegistry;
-import org.hibernate.query.sqm.function.SqmFunction;
 import org.hibernate.query.sqm.spi.BaseSemanticQueryWalker;
 import org.hibernate.query.sqm.spi.SqmCreationContext;
 import org.hibernate.query.sqm.tree.delete.SqmDeleteStatement;
@@ -590,14 +589,6 @@ public class QuerySplitter {
 			);
 		}
 
-		@Override
-		public SqmFunction visitFunction(SqmFunction functionProducer) {
-			// todo (6.0) : likely this needs a copy too
-			//		how to model that?
-			//		for now, return the same reference
-			return functionProducer;
-		}
-
 		@Override
 		public SqmLiteral visitLiteral(SqmLiteral literal) {
 			return new SqmLiteral(

hibernate-core/src/main/java/org/hibernate/query/hql/internal/SemanticQueryBuilder.java

@@ -11,8 +11,8 @@ import java.math.BigInteger;
 import java.sql.Date;
 import java.sql.Time;
 import java.sql.Timestamp;
-import java.time.Instant;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
@@ -56,16 +56,11 @@ import org.hibernate.query.sqm.SqmQuerySource;
 import org.hibernate.query.sqm.SqmTreeCreationLogger;
 import org.hibernate.query.sqm.StrictJpaComplianceViolation;
 import org.hibernate.query.sqm.UnknownEntityException;
-import org.hibernate.query.sqm.function.SqmCastTarget;
+import org.hibernate.query.sqm.function.NamedSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SqmDistinct;
+import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SqmExtractUnit;
-import org.hibernate.query.sqm.function.SqmStar;
-import org.hibernate.query.sqm.function.SqmTrimSpecification;
 import org.hibernate.query.sqm.internal.ParameterCollector;
 import org.hibernate.query.sqm.internal.SqmDmlCreationProcessingState;
 import org.hibernate.query.sqm.internal.SqmQuerySpecCreationProcessingStateStandardImpl;
-import org.hibernate.query.sqm.produce.function.SqmFunctionTemplate;
-import org.hibernate.query.sqm.produce.function.spi.NamedSqmFunctionTemplate;
 import org.hibernate.query.sqm.spi.ParameterDeclarationContext;
 import org.hibernate.query.sqm.spi.SqmCreationContext;
 import org.hibernate.query.sqm.tree.SqmJoinType;
@@ -85,8 +80,13 @@ import org.hibernate.query.sqm.tree.expression.LiteralHelper;
 import org.hibernate.query.sqm.tree.expression.SqmBinaryArithmetic;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSearched;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSimple;
+import org.hibernate.query.sqm.tree.expression.SqmCastTarget;
+import org.hibernate.query.sqm.tree.expression.SqmCoalesce;
 import org.hibernate.query.sqm.tree.expression.SqmCollectionSize;
+import org.hibernate.query.sqm.tree.expression.SqmDistinct;
 import org.hibernate.query.sqm.tree.expression.SqmExpression;
+import org.hibernate.query.sqm.tree.expression.SqmExtractUnit;
+import org.hibernate.query.sqm.tree.expression.SqmFunction;
 import org.hibernate.query.sqm.tree.expression.SqmLiteral;
 import org.hibernate.query.sqm.tree.expression.SqmLiteralNull;
 import org.hibernate.query.sqm.tree.expression.SqmNamedParameter;
@@ -94,6 +94,8 @@ import org.hibernate.query.sqm.tree.expression.SqmParameter;
 import org.hibernate.query.sqm.tree.expression.SqmParameterizedEntityType;
 import org.hibernate.query.sqm.tree.expression.SqmPathEntityType;
 import org.hibernate.query.sqm.tree.expression.SqmPositionalParameter;
+import org.hibernate.query.sqm.tree.expression.SqmStar;
+import org.hibernate.query.sqm.tree.expression.SqmTrimSpecification;
 import org.hibernate.query.sqm.tree.expression.SqmUnaryOperation;
 import org.hibernate.query.sqm.tree.from.DowncastLocation;
 import org.hibernate.query.sqm.tree.from.SqmAttributeJoin;
@@ -131,6 +133,7 @@ import org.hibernate.query.sqm.tree.select.SqmSelection;
 import org.hibernate.query.sqm.tree.select.SqmSortSpecification;
 import org.hibernate.query.sqm.tree.select.SqmSubQuery;
 import org.hibernate.query.sqm.tree.update.SqmUpdateStatement;
+import org.hibernate.type.StandardBasicTypes;
 import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
 
 import org.jboss.logging.Logger;
@@ -1305,13 +1308,15 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		}
 
 		//noinspection unchecked
-		return getFunctionTemplate( "concat" ).makeSqmFunctionExpression(
+		return new SqmFunction(
-				(List) asList(
+				"concat",
+				getFunctionDescriptor( "concat" ),
+				StandardBasicTypes.STRING,
+				asList(
 						ctx.expression( 0 ).accept( this ),
 						ctx.expression( 1 ).accept( this )
 				),
-				resolveExpressableTypeBasic( String.class ),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 
@@ -1386,10 +1391,12 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		SqmExpression<?> divisor = (SqmExpression) ctx.expression( 1 ).accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("mod").makeSqmFunctionExpression(
+		return new SqmFunction(
-				asList( dividend, divisor ),
+				"mod",
+				getFunctionDescriptor( "mod" ),
 				(AllowableFunctionReturnType) dividend.getNodeType(),
-				creationContext.getQueryEngine()
+				asList( dividend, divisor ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -1455,37 +1462,45 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 
 	@Override
 	public SqmExpression visitCurrentDateFunction(HqlParser.CurrentDateFunctionContext ctx) {
-		return getFunctionTemplate("current_date")
+		//noinspection unchecked
-				.makeSqmFunctionExpression(
+		return new SqmFunction(
-						resolveExpressableTypeBasic( Date.class ),
+				"current_date",
-						creationContext.getQueryEngine()
+				getFunctionDescriptor( "current_date" ),
+				StandardBasicTypes.DATE,
+				creationContext.getNodeBuilder()
 		);
 	}
 
 	@Override
 	public SqmExpression visitCurrentTimeFunction(HqlParser.CurrentTimeFunctionContext ctx) {
-		return getFunctionTemplate("current_time")
+		//noinspection unchecked
-				.makeSqmFunctionExpression(
+		return new SqmFunction(
-						resolveExpressableTypeBasic( Time.class ),
+				"current_time",
-						creationContext.getQueryEngine()
+				getFunctionDescriptor( "current_time" ),
+				StandardBasicTypes.TIME,
+				creationContext.getNodeBuilder()
 		);
 	}
 
 	@Override
 	public SqmExpression visitCurrentTimestampFunction(HqlParser.CurrentTimestampFunctionContext ctx) {
-		return getFunctionTemplate("current_timestamp")
+		//noinspection unchecked
-				.makeSqmFunctionExpression(
+		return new SqmFunction(
-						resolveExpressableTypeBasic( Timestamp.class ),
+				"current_timestamp",
-						creationContext.getQueryEngine()
+				getFunctionDescriptor( "current_timestamp" ),
+				StandardBasicTypes.TIMESTAMP,
+				creationContext.getNodeBuilder()
 		);
 	}
 
 	@Override
 	public SqmExpression visitCurrentInstantFunction(HqlParser.CurrentInstantFunctionContext ctx) {
-		return getFunctionTemplate("current_timestamp")
+		//noinspection unchecked
-				.makeSqmFunctionExpression(
+		return new SqmFunction(
-						resolveExpressableTypeBasic( Instant.class ),
+				"current_instant",
-						creationContext.getQueryEngine()
+				getFunctionDescriptor( "current_instant" ),
+				StandardBasicTypes.INSTANT,
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -1502,11 +1517,13 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 			type = arg.getNodeType();
 		}
 
-		return getFunctionTemplate("least")
+		//noinspection unchecked
-				.makeSqmFunctionExpression(
+		return new SqmFunction(
-						arguments,
+				"least",
+				getFunctionDescriptor( "least" ),
 				(AllowableFunctionReturnType<?>) type,
-						creationContext.getQueryEngine()
+				arguments,
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -1523,11 +1540,13 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 			type = arg.getNodeType();
 		}
 
-		return getFunctionTemplate("greatest")
+		//noinspection unchecked
-				.makeSqmFunctionExpression(
+		return new SqmFunction(
+				"greatest",
+				getFunctionDescriptor( "greatest" ),
+				type,
 				arguments,
-						(AllowableFunctionReturnType<?>) type,
+				creationContext.getNodeBuilder()
-						creationContext.getQueryEngine()
 		);
 	}
 
@@ -1544,11 +1563,13 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 			type = arg.getNodeType();
 		}
 
-		return getFunctionTemplate("coalesce")
+		//noinspection unchecked
-				.makeSqmFunctionExpression(
+		return new SqmFunction(
+				"coalesce",
+				getFunctionDescriptor( "coalesce" ),
+				type,
 				arguments,
-						(AllowableFunctionReturnType<?>) type,
+				creationContext.getNodeBuilder()
-						creationContext.getQueryEngine()
 		);
 	}
 
@@ -1558,10 +1579,12 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression arg2 = (SqmExpression) ctx.nullIf().expression( 1 ).accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("nullif").makeSqmFunctionExpression(
+		return new SqmFunction(
+				"nullif",
+				getFunctionDescriptor( "nullif" ),
+				arg1.getNodeType(),
 				asList( arg1, arg2 ),
-				(AllowableFunctionReturnType) arg1.getNodeType(),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 
@@ -1819,14 +1842,18 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final String functionName = ctx.jpaNonStandardFunctionName().STRING_LITERAL().getText().toLowerCase();
 		final List<SqmTypedNode<?>> functionArguments = visitNonStandardFunctionArguments( ctx.nonStandardFunctionArguments() );
 
-		SqmFunctionTemplate functionTemplate = getFunctionTemplate( functionName );
+		SqmFunctionDescriptor functionDescriptor = getFunctionDescriptor( functionName );
-		if (functionTemplate == null) {
+		if (functionDescriptor == null) {
-			functionTemplate = new NamedSqmFunctionTemplate( functionName, true, null, null );
+			functionDescriptor = new NamedSqmFunctionDescriptor( functionName, functionName, true, null );
 		}
-		return functionTemplate.makeSqmFunctionExpression(
+
-				functionArguments,
+		//noinspection unchecked
+		return new SqmFunction(
+				functionName,
+				functionDescriptor,
 				null,
-				creationContext.getQueryEngine()
+				functionArguments,
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -1843,14 +1870,18 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final String functionName = ctx.nonStandardFunctionName().getText().toLowerCase();
 		final List<SqmTypedNode<?>> functionArguments = visitNonStandardFunctionArguments( ctx.nonStandardFunctionArguments() );
 
-		SqmFunctionTemplate functionTemplate = getFunctionTemplate( functionName);
+		SqmFunctionDescriptor functionDescriptor = getFunctionDescriptor( functionName);
-		if (functionTemplate == null) {
+		if ( functionDescriptor == null ) {
-			functionTemplate = new NamedSqmFunctionTemplate( functionName, true, null, null );
+			functionDescriptor = new NamedSqmFunctionDescriptor( functionName, functionName, true, null );
 		}
-		return functionTemplate.makeSqmFunctionExpression(
+
-				functionArguments,
+		//noinspection unchecked
+		return new SqmFunction(
+				functionName,
+				functionDescriptor,
 				null,
-				creationContext.getQueryEngine()
+				functionArguments,
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -1888,10 +1919,12 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression arg = (SqmExpression) ctx.expression().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("ceiling").makeSqmFunctionExpression(
+		return new SqmFunction(
-				arg,
+				"ceiling",
-				(AllowableFunctionReturnType) resolveExpressableTypeBasic( Long.class ),
+				getFunctionDescriptor( "ceiling" ),
-				creationContext.getQueryEngine()
+				StandardBasicTypes.LONG,
+				Collections.singletonList( arg ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -1900,15 +1933,17 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression arg = (SqmExpression) ctx.expression().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("floor").makeSqmFunctionExpression(
+		return new SqmFunction(
-				arg,
+				"floor",
-				(AllowableFunctionReturnType) resolveExpressableTypeBasic( Long.class ),
+				getFunctionDescriptor( "floor" ),
-				creationContext.getQueryEngine()
+				StandardBasicTypes.LONG,
+				Collections.singletonList( arg ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
-	private SqmFunctionTemplate getFunctionTemplate(String name) {
+	private SqmFunctionDescriptor getFunctionDescriptor(String name) {
-		return creationContext.getQueryEngine().getSqmFunctionRegistry().findFunctionTemplate( name );
+		return creationContext.getQueryEngine().getSqmFunctionRegistry().findFunctionDescriptor( name );
 	}
 
 	@Override
@@ -1916,10 +1951,12 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression arg = (SqmExpression) ctx.expression().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("abs").makeSqmFunctionExpression(
+		return new SqmFunction(
-				arg,
+				"abs",
-				(AllowableFunctionReturnType) arg.getNodeType(),
+				getFunctionDescriptor( "abs" ),
-				creationContext.getQueryEngine()
+				arg.getNodeType(),
+				Collections.singletonList( arg ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -1928,10 +1965,12 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression arg = (SqmExpression) ctx.expression().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("sign").makeSqmFunctionExpression(
+		return new SqmFunction(
-				arg,
+				"sign",
-				(AllowableFunctionReturnType) resolveExpressableTypeBasic( Integer.class ),
+				getFunctionDescriptor( "sign" ),
-				creationContext.getQueryEngine()
+				StandardBasicTypes.INTEGER,
+				Collections.singletonList( arg ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -1941,10 +1980,12 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression divisor = (SqmExpression) ctx.modDivisorArgument().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("mod").makeSqmFunctionExpression(
+		return new SqmFunction(
+				"mod",
+				getFunctionDescriptor( "mod" ),
+				dividend.getNodeType(),
 				asList( dividend, divisor ),
-				(AllowableFunctionReturnType) dividend.getNodeType(),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 
@@ -1954,21 +1995,28 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression power = (SqmExpression) ctx.powerPowerArgument().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("power").makeSqmFunctionExpression(
+		return new SqmFunction(
+				"power",
+				getFunctionDescriptor( "power" ),
+				base.getNodeType(),
 				asList( base, power ),
-				(AllowableFunctionReturnType) base.getNodeType(),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
+
 	}
 
 	@Override
 	public SqmExpression visitTrigFunction(HqlParser.TrigFunctionContext ctx) {
+		final String functionName = ctx.trigFunctionName().getText();
 		final SqmExpression arg = (SqmExpression) ctx.expression().accept( this );
 
-		return getFunctionTemplate( ctx.trigFunctionName().getText() ).makeSqmFunctionExpression(
+		//noinspection unchecked
-				arg,
+		return new SqmFunction(
-				resolveExpressableTypeBasic( Double.class ),
+				functionName,
-				creationContext.getQueryEngine()
+				getFunctionDescriptor( functionName ),
+				StandardBasicTypes.DOUBLE,
+				Collections.singletonList( arg ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -1977,10 +2025,12 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression arg = (SqmExpression) ctx.expression().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("sqrt").makeSqmFunctionExpression(
+		return new SqmFunction(
-				arg,
+				"sqrt",
-				(AllowableFunctionReturnType) arg.getNodeType(),
+				getFunctionDescriptor( "sqrt" ),
-				creationContext.getQueryEngine()
+				arg.getNodeType(),
+				Collections.singletonList( arg ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -1990,10 +2040,12 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression precision = (SqmExpression) ctx.roundFunctionPrecision().expression().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("round").makeSqmFunctionExpression(
+		return new SqmFunction(
+				"round",
+				getFunctionDescriptor( "round" ),
+				arg.getNodeType(),
 				asList( arg, precision ),
-				(AllowableFunctionReturnType) arg.getNodeType(),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 
@@ -2003,10 +2055,12 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression cos = (SqmExpression) ctx.expression().get( 1).accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("atan2").makeSqmFunctionExpression(
+		return new SqmFunction(
+				"atan2",
+				getFunctionDescriptor( "atan2" ),
+				sin.getNodeType(),
 				asList(sin, cos),
-				(AllowableFunctionReturnType) sin.getNodeType(),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 
@@ -2015,12 +2069,13 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression arg = (SqmExpression) ctx.expression().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("ln").makeSqmFunctionExpression(
+		return new SqmFunction(
-				arg,
+				"ln",
-				(AllowableFunctionReturnType) arg.getNodeType(),
+				getFunctionDescriptor( "ln" ),
-				creationContext.getQueryEngine()
+				arg.getNodeType(),
+				Collections.singletonList( arg ),
+				creationContext.getNodeBuilder()
 		);
-
 	}
 
 	@Override
@@ -2028,10 +2083,12 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression arg = (SqmExpression) ctx.expression().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("exp").makeSqmFunctionExpression(
+		return new SqmFunction(
-				arg,
+				"exp",
-				(AllowableFunctionReturnType) arg.getNodeType(),
+				getFunctionDescriptor( "exp" ),
-				creationContext.getQueryEngine()
+				arg.getNodeType(),
+				Collections.singletonList( arg ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -2156,29 +2213,27 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		}
 
 		//noinspection unchecked
-		return getFunctionTemplate("extract").makeSqmFunctionExpression(
+		return new SqmFunction(
+				"extract",
+				getFunctionDescriptor( "extract" ),
+				extractFieldExpression.getNodeType(),
 				asList( extractFieldExpression, expressionToExtract ),
-				extractFieldExpression.getType(),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 
 	@Override
 	public SqmExpression visitCastFunction(HqlParser.CastFunctionContext ctx) {
-
 		final SqmExpression<?> expressionToCast = (SqmExpression) ctx.expression().accept( this );
 		final SqmCastTarget<?> castTargetExpression = interpretCastTarget( ctx.castTarget() );
 
-		//getSessionFactory().getTypeConfiguration().resolveCastTargetType( ctx.dataType().IDENTIFIER().getText() )
+		//noinspection unchecked
-
+		return new SqmFunction(
-//		if ( !AllowableFunctionReturnType.class.isInstance( castTargetExpression ) ) {
+				"cast",
-//			throw new SqmProductionException( "Found cast target expression [%s] which is not allowed as a function return" );
+				getFunctionDescriptor( "cast" ),
-//		}
+				castTargetExpression.getNodeType(),
-
-		return getFunctionTemplate("cast").makeSqmFunctionExpression(
 				asList( expressionToCast, castTargetExpression ),
-				castTargetExpression.getType(),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 
@@ -2252,23 +2307,25 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 	public SqmExpression visitUpperFunction(HqlParser.UpperFunctionContext ctx) {
 		final SqmExpression expression = (SqmExpression) ctx.expression().accept( this );
 		//noinspection unchecked
-		return getFunctionTemplate("upper").makeSqmFunctionExpression(
+		return new SqmFunction(
-				expression,
+				"upper",
-				(AllowableFunctionReturnType) expression.getNodeType(),
+				getFunctionDescriptor( "upper" ),
-				creationContext.getQueryEngine()
+				expression.getNodeType(),
+				Collections.singletonList( expression ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
 	@Override
 	public SqmExpression visitLowerFunction(HqlParser.LowerFunctionContext ctx) {
-		// todo (6.0) : why pass both the expression and its expression-type?
-		//			can't we just pass the expression?
 		final SqmExpression expression = (SqmExpression) ctx.expression().accept( this );
 		//noinspection unchecked
-		return getFunctionTemplate("lower").makeSqmFunctionExpression(
+		return new SqmFunction(
-				expression,
+				"lower",
-				(AllowableFunctionReturnType) expression.getNodeType(),
+				getFunctionDescriptor( "lower" ),
-				creationContext.getQueryEngine()
+				expression.getNodeType(),
+				Collections.singletonList( expression ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -2279,10 +2336,13 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 			arguments.add( (SqmTypedNode<?>) argument.accept( this ) );
 		}
 
-		return getFunctionTemplate("concat").makeSqmFunctionExpression(
+		//noinspection unchecked
+		return new SqmFunction(
+				"concat",
+				getFunctionDescriptor( "concat" ),
+				StandardBasicTypes.STRING,
 				arguments,
-				resolveExpressableTypeBasic( String.class ),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 
@@ -2290,10 +2350,13 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 	public Object visitLengthFunction(HqlParser.LengthFunctionContext ctx) {
 		final SqmExpression arg = (SqmExpression) ctx.expression().accept( this );
 
-		return getFunctionTemplate("character_length").makeSqmFunctionExpression(
+		//noinspection unchecked
-				arg,
+		return new SqmFunction(
-				resolveExpressableTypeBasic( Integer.class ),
+				"character_length",
-				creationContext.getQueryEngine()
+				getFunctionDescriptor( "character_length" ),
+				StandardBasicTypes.INTEGER,
+				Collections.singletonList( arg ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -2302,10 +2365,13 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression<?> string = (SqmExpression) ctx.positionFunctionStringArgument().accept( this );
 		final SqmExpression<?> pattern = (SqmExpression) ctx.positionFunctionPatternArgument().accept( this );
 
-		return getFunctionTemplate("locate").makeSqmFunctionExpression(
+		//noinspection unchecked
+		return new SqmFunction(
+				"locate",
+				getFunctionDescriptor( "locate" ),
+				StandardBasicTypes.INTEGER,
 				asList( pattern, string ),
-				resolveExpressableTypeBasic( Integer.class ),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 
@@ -2317,12 +2383,15 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 				? null
 				: (SqmExpression) ctx.locateFunctionStartArgument().accept( this );
 
-		return getFunctionTemplate("locate").makeSqmFunctionExpression(
+		//noinspection unchecked
+		return new SqmFunction(
+				"locate",
+				getFunctionDescriptor( "locate" ),
+				StandardBasicTypes.INTEGER,
 				start == null
 						? asList( pattern, string )
 						: asList( pattern, string, start ),
-				resolveExpressableTypeBasic( Integer.class ),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 
@@ -2333,84 +2402,110 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression<?> pattern = (SqmExpression) ctx.replaceFunctionPatternArgument().accept( this );
 		final SqmExpression<?> replacement = (SqmExpression) ctx.replaceFunctionReplacementArgument().accept( this );
 
-		return getFunctionTemplate("replace").makeSqmFunctionExpression(
+		//noinspection unchecked
+		return new SqmFunction(
+				"replace",
+				getFunctionDescriptor( "replace" ),
+				StandardBasicTypes.INTEGER,
 				asList( string, pattern, replacement ),
-				resolveExpressableTypeBasic( String.class ),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 
 	@Override
 	public Object visitStrFunction(HqlParser.StrFunctionContext ctx) {
 		final SqmExpression<?> arg = (SqmExpression) ctx.expression().accept( this );
-		AllowableFunctionReturnType<String> type = resolveExpressableTypeBasic( String.class );
+		final AllowableFunctionReturnType<String> type = resolveExpressableTypeBasic( String.class );
-		return getFunctionTemplate("cast").makeSqmFunctionExpression(
+		final SqmCastTarget<String> castTarget = new SqmCastTarget<>( type, creationContext.getNodeBuilder() );
-				asList( arg, new SqmCastTarget<>( type, creationContext.getNodeBuilder() ) ),
+
+		//noinspection unchecked
+		return new SqmFunction(
+				"cast",
+				getFunctionDescriptor( "cast" ),
 				type,
-				creationContext.getQueryEngine()
+				asList( arg, castTarget ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
 	@Override
 	public SqmExpression visitMaxFunction(HqlParser.MaxFunctionContext ctx) {
 		final SqmExpression<?> arg = (SqmExpression) ctx.expression().accept( this );
-		//ignore DISTINCT
+
-		return getFunctionTemplate("max").makeSqmFunctionExpression(
+		//noinspection unchecked
-				arg,
+		return new SqmFunction(
-				(AllowableFunctionReturnType<?>) arg.getNodeType(),
+				"max",
-				creationContext.getQueryEngine()
+				getFunctionDescriptor( "max" ),
+				arg.getNodeType(),
+				Collections.singletonList( arg ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
 	@Override
 	public SqmExpression visitMinFunction(HqlParser.MinFunctionContext ctx) {
 		final SqmExpression<?> arg = (SqmExpression) ctx.expression().accept( this );
-		//ignore DISTINCT
+
-		return getFunctionTemplate("min").makeSqmFunctionExpression(
+		//noinspection unchecked
-				arg,
+		return new SqmFunction(
-				(AllowableFunctionReturnType<?>) arg.getNodeType(),
+				"min",
-				creationContext.getQueryEngine()
+				getFunctionDescriptor( "min" ),
+				arg.getNodeType(),
+				Collections.singletonList( arg ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
 	@Override
 	public SqmExpression visitSumFunction(HqlParser.SumFunctionContext ctx) {
-
 		final SqmExpression<?> arg = (SqmExpression) ctx.expression().accept( this );
-		SqmTypedNode<?> argument = ctx.DISTINCT() != null ? new SqmDistinct<>( arg, getCreationContext().getNodeBuilder()) : arg;
+		final SqmTypedNode<?> argument = ctx.DISTINCT() != null
+				? new SqmDistinct<>( arg, getCreationContext().getNodeBuilder() )
+				: arg;
 
-		return getFunctionTemplate("sum").makeSqmFunctionExpression(
+		//noinspection unchecked
-				argument,
+		return new SqmFunction(
-				(AllowableFunctionReturnType<?>) arg.getNodeType(),
+				"sum",
-				creationContext.getQueryEngine()
+				getFunctionDescriptor( "sum" ),
+				arg.getNodeType(),
+				Collections.singletonList( argument ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
 	@Override
 	public SqmExpression visitAvgFunction(HqlParser.AvgFunctionContext ctx) {
-
 		final SqmExpression<?> arg = (SqmExpression) ctx.expression().accept( this );
-		SqmTypedNode<?> argument = ctx.DISTINCT() != null ? new SqmDistinct<>( arg, getCreationContext().getNodeBuilder()) : arg;
+		final SqmTypedNode<?> argument = ctx.DISTINCT() != null
+				? new SqmDistinct<>( arg, getCreationContext().getNodeBuilder() )
+				: arg;
 
-		return getFunctionTemplate("avg").makeSqmFunctionExpression(
+		//noinspection unchecked
-				argument,
+		return new SqmFunction(
-				resolveExpressableTypeBasic( Double.class ),
+				"avg",
-				creationContext.getQueryEngine()
+				getFunctionDescriptor( "avg" ),
+				arg.getNodeType(),
+				Collections.singletonList( argument ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
 	@Override
 	public SqmExpression visitCountFunction(HqlParser.CountFunctionContext ctx) {
-
 		final SqmExpression<?> arg = ctx.ASTERISK() != null
 				? new SqmStar( getCreationContext().getNodeBuilder() )
 				: (SqmExpression) ctx.expression().accept( this );
-		SqmTypedNode<?> argument = ctx.DISTINCT() != null ? new SqmDistinct<>( arg, getCreationContext().getNodeBuilder() ) : arg;
+		final SqmTypedNode<?> argument = ctx.DISTINCT() != null
+				? new SqmDistinct<>( arg, getCreationContext().getNodeBuilder() )
+				: arg;
 
-		return getFunctionTemplate("count").makeSqmFunctionExpression(
+		//noinspection unchecked
-				argument,
+		return new SqmFunction(
-				resolveExpressableTypeBasic( Long.class ),
+				"count",
-				creationContext.getQueryEngine()
+				getFunctionDescriptor( "count" ),
+				StandardBasicTypes.LONG,
+				Collections.singletonList( argument ),
+				creationContext.getNodeBuilder()
 		);
 	}
 
@@ -2423,12 +2518,13 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 				: (SqmExpression) ctx.substringFunctionLengthArgument().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("substring").makeSqmFunctionExpression(
+		return new SqmFunction(
+				"substring",
+				getFunctionDescriptor( "substring" ),
+				StandardBasicTypes.STRING,
 				length == null ? asList( source, start ) : asList( source, start, length ),
-				resolveExpressableTypeBasic( String.class ),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
-
 	}
 
 	@Override
@@ -2436,14 +2532,16 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final SqmExpression source = (SqmExpression) ctx.expression().accept( this );
 
 		//noinspection unchecked
-		return getFunctionTemplate("trim").makeSqmFunctionExpression(
+		return new SqmFunction(
+				"trim",
+				getFunctionDescriptor( "trim" ),
+				StandardBasicTypes.STRING,
 				asList(
 						interpretTrimSpecification( ctx.trimSpecification() ),
 						visitTrimCharacter( ctx.trimCharacter() ),
 						source
 				),
-				resolveExpressableTypeBasic( String.class ),
+				creationContext.getNodeBuilder()
-				creationContext.getQueryEngine()
 		);
 	}
 

hibernate-core/src/main/java/org/hibernate/query/spi/QueryEngine.java

@@ -29,7 +29,7 @@ import org.hibernate.query.named.NamedQueryRepository;
 import org.hibernate.query.sqm.NodeBuilder;
 import org.hibernate.query.sqm.internal.SqmCreationOptionsStandard;
 import org.hibernate.query.sqm.internal.SqmCriteriaNodeBuilder;
-import org.hibernate.query.sqm.produce.function.SqmFunctionRegistry;
+import org.hibernate.query.sqm.function.SqmFunctionRegistry;
 import org.hibernate.query.sqm.spi.SqmCreationContext;
 import org.hibernate.query.sqm.sql.SqmTranslatorFactory;
 import org.hibernate.query.sqm.sql.StandardSqmTranslatorFactory;

hibernate-core/src/main/java/org/hibernate/query/sqm/NodeBuilder.java

@@ -50,7 +50,6 @@ import org.hibernate.query.sqm.tree.domain.SqmPath;
 import org.hibernate.query.sqm.tree.domain.SqmSetJoin;
 import org.hibernate.query.sqm.tree.domain.SqmSingularJoin;
 import org.hibernate.query.sqm.tree.expression.SqmExpression;
-import org.hibernate.query.sqm.tree.expression.SqmParameter;
 import org.hibernate.query.sqm.tree.expression.SqmRestrictedSubQueryExpression;
 import org.hibernate.query.sqm.tree.expression.SqmTuple;
 import org.hibernate.query.sqm.tree.from.SqmRoot;
@@ -62,7 +61,7 @@ import org.hibernate.query.sqm.tree.select.SqmSortSpecification;
 import org.hibernate.query.sqm.tree.select.SqmSubQuery;
 import org.hibernate.query.sqm.tree.update.SqmUpdateStatement;
 import org.hibernate.service.ServiceRegistry;
-import org.hibernate.query.sqm.function.SqmFunction;
+import org.hibernate.query.sqm.tree.expression.SqmFunction;
 import org.hibernate.type.spi.TypeConfiguration;
 
 /**

hibernate-core/src/main/java/org/hibernate/query/sqm/SemanticQueryWalker.java

@@ -25,8 +25,11 @@ import org.hibernate.query.sqm.tree.domain.SqmTreatedPath;
 import org.hibernate.query.sqm.tree.expression.SqmBinaryArithmetic;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSearched;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSimple;
+import org.hibernate.query.sqm.tree.expression.SqmCastTarget;
+import org.hibernate.query.sqm.tree.expression.SqmCoalesce;
 import org.hibernate.query.sqm.tree.expression.SqmCollectionSize;
 import org.hibernate.query.sqm.tree.expression.JpaCriteriaParameter;
+import org.hibernate.query.sqm.tree.expression.SqmFunction;
 import org.hibernate.query.sqm.tree.expression.SqmParameterizedEntityType;
 import org.hibernate.query.sqm.tree.expression.SqmEnumLiteral;
 import org.hibernate.query.sqm.tree.expression.SqmExpression;
@@ -39,12 +42,10 @@ import org.hibernate.query.sqm.tree.expression.SqmPositionalParameter;
 import org.hibernate.query.sqm.tree.expression.SqmRestrictedSubQueryExpression;
 import org.hibernate.query.sqm.tree.expression.SqmTuple;
 import org.hibernate.query.sqm.tree.expression.SqmUnaryOperation;
-import org.hibernate.query.sqm.function.SqmCastTarget;
+import org.hibernate.query.sqm.tree.expression.SqmDistinct;
-import org.hibernate.query.sqm.function.SqmDistinct;
+import org.hibernate.query.sqm.tree.expression.SqmExtractUnit;
-import org.hibernate.query.sqm.function.SqmExtractUnit;
+import org.hibernate.query.sqm.tree.expression.SqmStar;
-import org.hibernate.query.sqm.function.SqmFunction;
+import org.hibernate.query.sqm.tree.expression.SqmTrimSpecification;
-import org.hibernate.query.sqm.function.SqmStar;
-import org.hibernate.query.sqm.function.SqmTrimSpecification;
 import org.hibernate.query.sqm.tree.from.SqmAttributeJoin;
 import org.hibernate.query.sqm.tree.from.SqmCrossJoin;
 import org.hibernate.query.sqm.tree.from.SqmEntityJoin;
@@ -196,15 +197,21 @@ public interface SemanticQueryWalker<T> {
 
 	T visitUnaryOperationExpression(SqmUnaryOperation<?> expression);
 
+	T visitFunction(SqmFunction tSqmFunction);
 
-	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+	T visitExtractUnit(SqmExtractUnit extractUnit);
-	// expressions - non-standard functions
 
-	T visitFunction(SqmFunction<?> sqmFunction);
+	T visitCastTarget(SqmCastTarget sqmCastTarget);
+
+	T visitTrimSpecification(SqmTrimSpecification trimSpecification);
+
+	T visitDistinct(SqmDistinct distinct);
+
+	T visitStar(SqmStar sqmStar);
+
+	T visitCoalesce(SqmCoalesce sqmCoalesce);
 
 
-	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-	// expressions - standard functions
 
 	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 	// predicates
@@ -262,14 +269,4 @@ public interface SemanticQueryWalker<T> {
 	T visitMapEntryFunction(SqmMapEntryReference function);
 
 	T visitFullyQualifiedClass(Class<?> namedClass);
-
-	T visitExtractUnit(SqmExtractUnit extractUnit);
-
-	T visitCastTarget(SqmCastTarget sqmCastTarget);
-
-	T visitTrimSpecification(SqmTrimSpecification trimSpecification);
-
-	T visitDistinct(SqmDistinct distinct);
-
-	T visitStar(SqmStar sqmStar);
 }

hibernate-core/src/main/java/org/hibernate/query/sqm/function/AbstractSelfRenderingFunctionTemplate.java

@@ -0,0 +1,111 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.query.sqm.function;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.function.Supplier;
+
+import org.hibernate.engine.spi.SessionFactoryImplementor;
+import org.hibernate.metamodel.mapping.MappingModelExpressable;
+import org.hibernate.query.sqm.produce.function.ArgumentsValidator;
+import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
+import org.hibernate.query.sqm.sql.SqmToSqlAstConverter;
+import org.hibernate.query.sqm.tree.SqmVisitableNode;
+import org.hibernate.sql.ast.SqlAstWalker;
+import org.hibernate.sql.ast.spi.SqlAppender;
+import org.hibernate.sql.ast.spi.SqlAstCreationState;
+import org.hibernate.sql.ast.tree.SqlAstNode;
+import org.hibernate.sql.ast.tree.expression.Expression;
+import org.hibernate.sql.ast.tree.expression.SelfRenderingExpression;
+
+/**
+ * @author Steve Ebersole
+ */
+public abstract class AbstractSelfRenderingFunctionTemplate extends AbstractSqmFunctionDescriptor {
+	private final ArgumentsValidator argumentsValidator;
+
+	public AbstractSelfRenderingFunctionTemplate(ArgumentsValidator argumentsValidator) {
+		super();
+
+		this.argumentsValidator = argumentsValidator == null
+				? StandardArgumentsValidators.NONE
+				: argumentsValidator;
+	}
+
+	@Override
+	public Expression generateSqlExpression(
+			String functionName,
+			List<? extends SqmVisitableNode> sqmArguments,
+			Supplier<MappingModelExpressable> inferableTypeAccess,
+			SqmToSqlAstConverter converter,
+			SqlAstCreationState creationState) {
+		argumentsValidator.validate( sqmArguments );
+
+		// todo (6.0) : work out the specifics of the type resolution
+
+		final List<SqlAstNode> sqlAstArgs;
+		if ( sqmArguments == null || sqmArguments.isEmpty() ) {
+			sqlAstArgs = Collections.emptyList();
+		}
+		else if ( sqmArguments.size() == 1 ) {
+			sqlAstArgs = Collections.singletonList(
+					(SqlAstNode) sqmArguments.get( 0 ).accept( converter )
+			);
+		}
+		else {
+			sqlAstArgs = new ArrayList<>( sqmArguments.size() );
+			for ( int i = 0; i < sqmArguments.size(); i++ ) {
+				final SqmVisitableNode sqmVisitableNode = sqmArguments.get( i );
+				sqlAstArgs.add( (SqlAstNode) sqmVisitableNode.accept( converter ) );
+			}
+		}
+
+		return new SelfRenderingSqlFunctionExpression(
+				functionName,
+				inferableTypeAccess.get(),
+				sqlAstArgs,
+				getRenderingSupport()
+		);
+	}
+
+	protected abstract FunctionRenderingSupport getRenderingSupport();
+
+
+	private static class SelfRenderingSqlFunctionExpression implements SelfRenderingExpression {
+		private final String name;
+		private final MappingModelExpressable type;
+		private final List<SqlAstNode> arguments;
+
+		private final FunctionRenderingSupport renderingSupport;
+
+		public SelfRenderingSqlFunctionExpression(
+				String name,
+				MappingModelExpressable type,
+				List<SqlAstNode> arguments,
+				FunctionRenderingSupport renderingSupport) {
+			this.name = name;
+			this.type = type;
+			this.arguments = arguments;
+			this.renderingSupport = renderingSupport;
+		}
+
+		@Override
+		public void renderToSql(
+				SqlAppender sqlAppender,
+				SqlAstWalker walker,
+				SessionFactoryImplementor sessionFactory) {
+			renderingSupport.render( sqlAppender, name, arguments, walker, sessionFactory );
+		}
+
+		@Override
+		public MappingModelExpressable getExpressionType() {
+			return type;
+		}
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/sqm/function/AbstractSqmFunctionDescriptor.java

@@ -0,0 +1,115 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.query.sqm.function;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.function.Supplier;
+
+import org.hibernate.engine.spi.SessionFactoryImplementor;
+import org.hibernate.metamodel.mapping.MappingModelExpressable;
+import org.hibernate.query.sqm.produce.function.ArgumentsValidator;
+import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
+import org.hibernate.query.sqm.sql.SqmToSqlAstConverter;
+import org.hibernate.query.sqm.tree.SqmVisitableNode;
+import org.hibernate.sql.ast.SqlAstWalker;
+import org.hibernate.sql.ast.spi.SqlAppender;
+import org.hibernate.sql.ast.spi.SqlAstCreationState;
+import org.hibernate.sql.ast.tree.SqlAstNode;
+import org.hibernate.sql.ast.tree.expression.Expression;
+import org.hibernate.sql.ast.tree.expression.SelfRenderingExpression;
+
+/**
+ * Support for SQM function descriptors which ultimately render themselves
+ *
+ * @author Steve Ebersole
+ */
+public abstract class AbstractSqmFunctionDescriptor implements SqmFunctionDescriptor {
+	private final ArgumentsValidator argumentsValidator;
+
+	public AbstractSqmFunctionDescriptor() {
+		this( null );
+	}
+
+	public AbstractSqmFunctionDescriptor(ArgumentsValidator argumentsValidator) {
+		this.argumentsValidator = argumentsValidator == null
+				? StandardArgumentsValidators.NONE
+				: argumentsValidator;
+	}
+
+	@Override
+	public Expression generateSqlExpression(
+			String functionName,
+			List<? extends SqmVisitableNode> sqmArguments,
+			Supplier<MappingModelExpressable> inferableTypeAccess,
+			SqmToSqlAstConverter converter,
+			SqlAstCreationState creationState) {
+		argumentsValidator.validate( sqmArguments );
+
+		// todo (6.0) : work out the specifics of the type resolution
+
+		final List<SqlAstNode> sqlAstArgs;
+		if ( sqmArguments == null || sqmArguments.isEmpty() ) {
+			sqlAstArgs = Collections.emptyList();
+		}
+		else if ( sqmArguments.size() == 1 ) {
+			sqlAstArgs = Collections.singletonList(
+					(SqlAstNode) sqmArguments.get( 0 ).accept( converter )
+			);
+		}
+		else {
+			sqlAstArgs = new ArrayList<>( sqmArguments.size() );
+			for ( int i = 0; i < sqmArguments.size(); i++ ) {
+				final SqmVisitableNode sqmVisitableNode = sqmArguments.get( i );
+				sqlAstArgs.add( (SqlAstNode) sqmVisitableNode.accept( converter ) );
+			}
+		}
+
+		return new SelfRenderingSqlFunctionExpression(
+				functionName,
+				inferableTypeAccess.get(),
+				sqlAstArgs,
+				getRenderingSupport()
+		);
+	}
+
+	protected abstract FunctionRenderingSupport getRenderingSupport();
+
+
+	private static class SelfRenderingSqlFunctionExpression implements SelfRenderingExpression {
+		private final String name;
+		private final MappingModelExpressable type;
+		private final List<SqlAstNode> arguments;
+
+		private final FunctionRenderingSupport renderingSupport;
+
+		public SelfRenderingSqlFunctionExpression(
+				String name,
+				MappingModelExpressable type,
+				List<SqlAstNode> arguments,
+				FunctionRenderingSupport renderingSupport) {
+			this.name = name;
+			this.type = type;
+			this.arguments = arguments;
+			this.renderingSupport = renderingSupport;
+		}
+
+		@Override
+		public void renderToSql(
+				SqlAppender sqlAppender,
+				SqlAstWalker walker,
+				SessionFactoryImplementor sessionFactory) {
+			renderingSupport.render( sqlAppender, name, arguments, walker, sessionFactory );
+		}
+
+		@Override
+		public MappingModelExpressable getExpressionType() {
+			return type;
+		}
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/sqm/function/FunctionAsExpressionTemplate.java

@@ -4,18 +4,14 @@
  * License: GNU Lesser General Public License (LGPL), version 2.1 or later
  * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
  */
-package org.hibernate.query.sqm.produce.function.spi;
+package org.hibernate.query.sqm.function;
 
 import java.util.List;
 
 import org.hibernate.engine.spi.SessionFactoryImplementor;
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.produce.function.ArgumentsValidator;
-import org.hibernate.query.sqm.produce.function.FunctionReturnTypeResolver;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-import org.hibernate.sql.ast.spi.SqlAppender;
 import org.hibernate.sql.ast.SqlAstWalker;
+import org.hibernate.sql.ast.spi.SqlAppender;
 import org.hibernate.sql.ast.tree.SqlAstNode;
 
 import org.jboss.logging.Logger;
@@ -24,8 +20,8 @@ import org.jboss.logging.Logger;
  * @author Steve Ebersole
  */
 public class FunctionAsExpressionTemplate
-		extends AbstractSelfRenderingFunctionTemplate
+		extends AbstractSqmFunctionDescriptor
-		implements SelfRenderingFunctionSupport {
+		implements FunctionRenderingSupport {
 
 	private static final Logger log = Logger.getLogger( FunctionAsExpressionTemplate.class );
 
@@ -37,28 +33,22 @@ public class FunctionAsExpressionTemplate
 			String expressionStart,
 			String argumentSeparator,
 			String expressionEnd,
-			FunctionReturnTypeResolver returnTypeResolver,
+			ArgumentsValidator argumentsValidator) {
-			ArgumentsValidator argumentsValidator,
+		super( argumentsValidator );
-			String name) {
-		super( name, returnTypeResolver, argumentsValidator );
 		this.expressionStart = expressionStart;
 		this.argumentSeparator = argumentSeparator;
 		this.expressionEnd = expressionEnd;
 	}
 
 	@Override
-	protected SelfRenderingFunctionSupport getRenderingFunctionSupport(
+	protected FunctionRenderingSupport getRenderingSupport() {
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<?> resolvedReturnType,
-			QueryEngine queryEngine) {
 		return this;
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public void render(
 			SqlAppender sqlAppender,
-			List<SqlAstNode> sqlAstArguments,
+			String functionName, List<SqlAstNode> sqlAstArguments,
 			SqlAstWalker walker,
 			SessionFactoryImplementor sessionFactory) {
 		sqlAppender.appendSql( expressionStart );
@@ -68,31 +58,15 @@ public class FunctionAsExpressionTemplate
 		}
 		else {
 			// render the first argument..
-			renderArgument( sqlAppender, sqlAstArguments.get( 0 ), walker, sessionFactory );
+			sqlAstArguments.get( 0 ).accept( walker );
 
 			// render the rest of the arguments, preceded by the separator
 			for ( int i = 1; i < sqlAstArguments.size(); i++ ) {
 				sqlAppender.appendSql( argumentSeparator );
-				renderArgument( sqlAppender, sqlAstArguments.get( i ), walker, sessionFactory );
+				sqlAstArguments.get( i ).accept( walker );
 			}
 		}
 
 		sqlAppender.appendSql( expressionEnd );
 	}
-
-	/**
-	 * Called from {@link #render} to render an argument.
-	 *
-	 * @param sqlAppender The sql appender to append the rendered argument.
-	 * @param sqlAstArgument The argument being processed.
-	 * @param walker The walker to use for rendering {@link SqlAstNode} expressions
-	 * @param sessionFactory The session factory
-	 */
-	protected void renderArgument(
-			SqlAppender sqlAppender,
-			SqlAstNode sqlAstArgument,
-			SqlAstWalker walker,
-			SessionFactoryImplementor sessionFactory) {
-		sqlAstArgument.accept( walker );
-	}
 }

hibernate-core/src/main/java/org/hibernate/query/sqm/function/FunctionRenderingSupport.java

@@ -4,7 +4,7 @@
  * License: GNU Lesser General Public License (LGPL), version 2.1 or later
  * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
  */
-package org.hibernate.query.sqm.produce.function.spi;
+package org.hibernate.query.sqm.function;
 
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.sql.ast.spi.SqlAppender;
@@ -14,14 +14,14 @@ import org.hibernate.sql.ast.tree.SqlAstNode;
 import java.util.List;
 
 /**
- * Support for SqmFunctionTemplates that ultimately want to
+ * Support for SqmFunctionDescriptors that ultimately want to perform SQL rendering themselves
- * perform SQL rendering themselves
  *
  * @author Steve Ebersole
  */
-public interface SelfRenderingFunctionSupport {
+public interface FunctionRenderingSupport {
 	void render(
 			SqlAppender sqlAppender,
+			String functionName,
 			List<SqlAstNode> sqlAstArguments,
 			SqlAstWalker walker,
 			SessionFactoryImplementor sessionFactory);

hibernate-core/src/main/java/org/hibernate/query/sqm/function/JdbcEscapeFunctionDescriptor.java

@@ -0,0 +1,76 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.query.sqm.function;
+
+import java.util.List;
+import java.util.function.Supplier;
+
+import org.hibernate.engine.spi.SessionFactoryImplementor;
+import org.hibernate.metamodel.mapping.MappingModelExpressable;
+import org.hibernate.query.sqm.sql.SqmToSqlAstConverter;
+import org.hibernate.query.sqm.tree.SqmVisitableNode;
+import org.hibernate.sql.ast.SqlAstWalker;
+import org.hibernate.sql.ast.spi.SqlAppender;
+import org.hibernate.sql.ast.spi.SqlAstCreationState;
+import org.hibernate.sql.ast.tree.expression.Expression;
+import org.hibernate.sql.ast.tree.expression.SelfRenderingExpression;
+
+/**
+ * Acts as a wrapper to another SqmFunctionTemplate - upon rendering uses the
+ * standard JDBC escape sequence (i.e. `{fn blah}`) when rendering the SQL.
+ *
+ * @author Steve Ebersole
+ */
+public class JdbcEscapeFunctionDescriptor implements SqmFunctionDescriptor {
+	private final SqmFunctionDescriptor wrapped;
+
+	@SuppressWarnings("WeakerAccess")
+	public JdbcEscapeFunctionDescriptor(SqmFunctionDescriptor wrapped) {
+		this.wrapped = wrapped;
+	}
+
+	@Override
+	public Expression generateSqlExpression(
+			String functionName,
+			List<? extends SqmVisitableNode> sqmArguments,
+			Supplier<MappingModelExpressable> inferableTypeAccess,
+			SqmToSqlAstConverter converter,
+			SqlAstCreationState creationState) {
+		final Expression wrappedExpression = wrapped.generateSqlExpression(
+				functionName,
+				sqmArguments,
+				inferableTypeAccess,
+				converter,
+				creationState
+		);
+
+		return new EscapeExpression( wrappedExpression );
+	}
+
+	private static class EscapeExpression implements SelfRenderingExpression {
+		private final Expression wrappedExpression;
+
+		EscapeExpression(Expression wrappedExpression) {
+			this.wrappedExpression = wrappedExpression;
+		}
+
+		@Override
+		public void renderToSql(
+				SqlAppender sqlAppender,
+				SqlAstWalker walker,
+				SessionFactoryImplementor sessionFactory) {
+			sqlAppender.appendSql( "{fn " );
+			wrappedExpression.accept( walker );
+			sqlAppender.appendSql( "}" );
+		}
+
+		@Override
+		public MappingModelExpressable getExpressionType() {
+			return wrappedExpression.getExpressionType();
+		}
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/sqm/function/NamedSqmFunctionDescriptor.java

@@ -0,0 +1,82 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.query.sqm.function;
+
+import java.util.Locale;
+
+import org.hibernate.query.sqm.produce.function.ArgumentsValidator;
+import org.hibernate.sql.ast.tree.SqlAstNode;
+
+/**
+ * Provides a standard implementation that supports the majority of the HQL
+ * functions that are translated to SQL. The Dialect and its sub-classes use
+ * this class to provide details required for processing of the associated
+ * function.
+ *
+ * @author David Channon
+ * @author Steve Ebersole
+ */
+public class NamedSqmFunctionDescriptor extends AbstractSqmFunctionDescriptor {
+	private final String functionKey;
+	private final String functionName;
+	private final boolean useParenthesesWhenNoArgs;
+
+	public NamedSqmFunctionDescriptor(
+			String functionKey,
+			String functionName,
+			boolean useParenthesesWhenNoArgs,
+			ArgumentsValidator argumentsValidator) {
+		super( argumentsValidator );
+		this.functionKey = functionKey;
+
+		this.functionName = functionName;
+		this.useParenthesesWhenNoArgs = useParenthesesWhenNoArgs;
+	}
+
+	public String getFunctionKey() {
+		return functionKey;
+	}
+
+	public String getFunctionName() {
+		return functionName;
+	}
+
+	@Override
+	protected FunctionRenderingSupport getRenderingSupport() {
+		return (sqlAppender, functionName1, sqlAstArguments, walker, sessionFactory) -> {
+			final boolean useParens = useParenthesesWhenNoArgs || !sqlAstArguments.isEmpty();
+
+			sqlAppender.appendSql( functionName );
+			if ( useParens ) {
+				sqlAppender.appendSql( "(" );
+			}
+
+			boolean firstPass = true;
+			for ( SqlAstNode sqlAstArgument : sqlAstArguments ) {
+				if ( !firstPass ) {
+					sqlAppender.appendSql( ", " );
+				}
+				sqlAstArgument.accept( walker );
+				firstPass = false;
+			}
+
+			if ( useParens ) {
+				sqlAppender.appendSql( ")" );
+			}
+		};
+	}
+
+	@Override
+	public String toString() {
+		return String.format(
+				Locale.ROOT,
+				"NamedSqmFunctionTemplate(%s)",
+				functionName
+		);
+	}
+
+}

hibernate-core/src/main/java/org/hibernate/query/sqm/function/PatternBasedSqmFunctionTemplate.java

@@ -4,22 +4,19 @@
  * License: GNU Lesser General Public License (LGPL), version 2.1 or later
  * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
  */
-package org.hibernate.query.sqm.produce.function.spi;
+package org.hibernate.query.sqm.function;
+
+import java.util.List;
 
 import org.hibernate.engine.spi.SessionFactoryImplementor;
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.produce.function.ArgumentsValidator;
 import org.hibernate.query.sqm.produce.function.FunctionReturnTypeResolver;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.internal.PatternRenderer;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-import org.hibernate.sql.ast.spi.SqlAppender;
 import org.hibernate.sql.ast.SqlAstWalker;
+import org.hibernate.sql.ast.spi.SqlAppender;
 import org.hibernate.sql.ast.tree.SqlAstNode;
 
-import java.util.List;
-
 /**
  * Represents HQL functions that can have different representations in different SQL dialects where that
  * difference can be handled via a template/pattern.
@@ -33,8 +30,8 @@ import java.util.List;
  * @author <a href="mailto:alex@jboss.org">Alexey Loubyansky</a>
  */
 public class PatternBasedSqmFunctionTemplate
-		extends AbstractSelfRenderingFunctionTemplate
+		extends AbstractSqmFunctionDescriptor
-		implements SelfRenderingFunctionSupport {
+		implements FunctionRenderingSupport {
 	private final PatternRenderer renderer;
 
 	/**
@@ -43,11 +40,8 @@ public class PatternBasedSqmFunctionTemplate
 	public PatternBasedSqmFunctionTemplate(
 			PatternRenderer renderer,
 			ArgumentsValidator argumentsValidator,
-			FunctionReturnTypeResolver returnTypeResolver,
+			FunctionReturnTypeResolver returnTypeResolver) {
-			String name) {
 		super(
-				name,
-				returnTypeResolver,
 				argumentsValidator != null
 						? argumentsValidator
 						// If no validator is given, it's still better to validate against the parameter count as given
@@ -58,16 +52,14 @@ public class PatternBasedSqmFunctionTemplate
 	}
 
 	@Override
-	protected SelfRenderingFunctionSupport getRenderingFunctionSupport(
+	protected FunctionRenderingSupport getRenderingSupport() {
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<?> impliedResultType,
-			QueryEngine queryEngine) {
 		return this;
 	}
 
 	@Override
 	public void render(
 			SqlAppender sqlAppender,
+			String functionName,
 			List<SqlAstNode> sqlAstArguments,
 			SqlAstWalker walker,
 			SessionFactoryImplementor sessionFactory) {

hibernate-core/src/main/java/org/hibernate/query/sqm/function/SqmFunction.java

@@ -1,40 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
- */
-package org.hibernate.query.sqm.function;
-
-import org.hibernate.query.criteria.JpaFunction;
-import org.hibernate.query.sqm.SemanticQueryWalker;
-import org.hibernate.query.sqm.tree.expression.SqmExpression;
-import org.hibernate.query.sqm.sql.internal.DomainResultProducer;
-
-/**
- * Contract for functions impls that would like to control the
- * translation of the SQM expression into the SQL AST function
- * <p/>
- * {@link #convertToSqlAst} is the main contract here.  It will
- * be called as we walk the SQM tree to generate SQL AST and
- * asked to produce the equivalent SQL AST expression
- *
- * @author Steve Ebersole
- */
-public interface SqmFunction<T> extends SqmExpression<T>, JpaFunction<T>, DomainResultProducer<T> {
-//	/**
-//	 * Generate the SQL AST form of the function as an expression.
-//	 *
-//	 * To be able to use this in the select-clause, the returned
-//	 * expression must also implement the
-//	 * {@link DomainResultProducer}
-//	 * contract
-//	 */
-//	Expression convertToSqlAst(SqmToSqlAstConverter walker);
-//
-	@Override
-	default <X> X accept(SemanticQueryWalker<X> walker) {
-		return walker.visitFunction( this );
-	}
-
-}

hibernate-core/src/main/java/org/hibernate/query/sqm/function/SqmFunctionDescriptor.java

@@ -0,0 +1,39 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.query.sqm.function;
+
+import java.util.List;
+import java.util.function.Supplier;
+
+import org.hibernate.Incubating;
+import org.hibernate.metamodel.mapping.MappingModelExpressable;
+import org.hibernate.query.sqm.sql.SqmToSqlAstConverter;
+import org.hibernate.query.sqm.tree.SqmVisitableNode;
+import org.hibernate.sql.ast.spi.SqlAstCreationState;
+import org.hibernate.sql.ast.tree.expression.Expression;
+
+/**
+ * Extension for supplying support for non-standard (ANSI SQL) functions in HQL and Criteria queries.
+ *
+ * Ultimately acts as a factory for SQM function expressions.
+ *
+ * @author David Channon
+ * @author Steve Ebersole
+ */
+@Incubating
+public interface SqmFunctionDescriptor {
+	/**
+	 * Generate a representation of the described function as a SQL AST node
+	 */
+	Expression generateSqlExpression(
+			String functionName,
+			List<? extends SqmVisitableNode> arguments,
+			Supplier<MappingModelExpressable> inferableTypeAccess,
+			SqmToSqlAstConverter converter,
+			SqlAstCreationState creationState);
+
+}

hibernate-core/src/main/java/org/hibernate/query/sqm/function/SqmFunctionRegistry.java

@@ -0,0 +1,218 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.query.sqm.function;
+
+import java.util.Map;
+import java.util.TreeMap;
+
+import org.hibernate.Incubating;
+import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
+import org.hibernate.query.sqm.produce.function.NamedFunctionDescriptorBuilder;
+import org.hibernate.query.sqm.produce.function.PatternFunctionDescriptorBuilder;
+import org.hibernate.query.sqm.produce.function.VarArgsFunctionDescriptorBuilder;
+
+import org.jboss.logging.Logger;
+
+import static java.lang.String.CASE_INSENSITIVE_ORDER;
+
+/**
+ * Defines a registry for SQLFunction instances
+ *
+ * @author Steve Ebersole
+ */
+@Incubating
+public class SqmFunctionRegistry {
+	private static final Logger log = Logger.getLogger( SqmFunctionRegistry.class );
+
+	private final Map<String, SqmFunctionDescriptor> functionMap = new TreeMap<>( CASE_INSENSITIVE_ORDER );
+	private final Map<String,String> alternateKeyMap = new TreeMap<>( CASE_INSENSITIVE_ORDER );
+
+	public SqmFunctionRegistry() {
+		log.tracef( "SqmFunctionRegistry created" );
+	}
+
+	/**
+	 * Find a SqmFunctionTemplate by name.  Returns {@code null} if
+	 * no such function is found.
+	 */
+	public SqmFunctionDescriptor findFunctionDescriptor(String functionName) {
+		SqmFunctionDescriptor found = null;
+
+		final String alternateKeyResolution = alternateKeyMap.get( functionName );
+		if ( alternateKeyResolution != null ) {
+			found = functionMap.get( alternateKeyResolution );
+		}
+
+		if ( found == null ) {
+			found = functionMap.get( functionName );
+		}
+
+		return found;
+	}
+
+	/**
+	 * Register a function descriptor by name
+	 */
+	public SqmFunctionDescriptor register(String registrationKey, SqmFunctionDescriptor function) {
+		final SqmFunctionDescriptor priorRegistration = functionMap.put( registrationKey, function );
+		log.debugf(
+				"Registered SqmFunctionTemplate [%s] under %s; prior registration was %s",
+				function,
+				registrationKey,
+				priorRegistration
+		);
+
+		return function;
+	}
+
+	/**
+	 * Register a pattern-based descriptor by name.  Shortcut for building the descriptor via
+	 * {@link #patternDescriptorBuilder} accepting its defaults.
+	 */
+	public SqmFunctionDescriptor registerPattern(String name, String pattern) {
+		return patternDescriptorBuilder( name, pattern ).register();
+	}
+
+	/**
+	 * Register a pattern-based descriptor by name and invariant return type.  Shortcut for building the descriptor
+	 * via {@link #patternDescriptorBuilder} accepting its defaults.
+	 */
+	public SqmFunctionDescriptor registerPattern(String name, String pattern, AllowableFunctionReturnType returnType) {
+		return patternDescriptorBuilder( name, pattern )
+				.setInvariantType( returnType )
+				.register();
+	}
+
+	/**
+	 * Get a builder for creating and registering a pattern-based function descriptor.
+	 *
+	 * @param registrationKey The name under which the descriptor will get registered
+	 * @param pattern The pattern defining the the underlying function call
+	 *
+	 * @return The builder
+	 */
+	public PatternFunctionDescriptorBuilder patternDescriptorBuilder(String registrationKey, String pattern) {
+		return new PatternFunctionDescriptorBuilder( this, registrationKey, pattern );
+	}
+
+	/**
+	 * Register a descriptor by name.  Shortcut for building a descriptor via {@link #namedDescriptorBuilder} using the
+	 * passed name as both the registration key and underlying SQL function name and accepting the builder's defaults.
+	 *
+	 * @param name The function name (and registration key)
+	 */
+	public SqmFunctionDescriptor registerNamed(String name) {
+		return namedDescriptorBuilder( name ).register();
+	}
+
+	/**
+	 * Register a named descriptor by name and invariant return type.  Shortcut for building
+	 * a descriptor via {@link #namedDescriptorBuilder} using the passed name as both the
+	 * registration key and underlying SQL function name and accepting the builder's defaults.
+	 *
+	 * @param name The function name (and registration key)
+	 */
+	public SqmFunctionDescriptor registerNamed(String name, AllowableFunctionReturnType returnType) {
+		return namedDescriptorBuilder( name ).setInvariantType( returnType ).register();
+	}
+
+	/**
+	 * Get a builder for creating and registering a name-based function descriptor using the passed name as
+	 * both the registration key and underlying SQL function name
+	 *
+	 * @param name The function name (and registration key)
+	 *
+	 * @return The builder
+	 */
+	public NamedFunctionDescriptorBuilder namedDescriptorBuilder(String name) {
+		return namedDescriptorBuilder( name, name );
+	}
+
+	/**
+	 * Get a builder for creating and registering a name-based function descriptor.
+	 *
+	 * @param registrationKey The name under which the descriptor will get registered
+	 * @param name The underlying SQL function name to use
+	 *
+	 * @return The builder
+	 */
+	public NamedFunctionDescriptorBuilder namedDescriptorBuilder(String registrationKey, String name) {
+		return new NamedFunctionDescriptorBuilder( this, registrationKey, name );
+	}
+
+	public NamedFunctionDescriptorBuilder noArgsBuilder(String name) {
+		return noArgsBuilder( name, name );
+	}
+
+	public NamedFunctionDescriptorBuilder noArgsBuilder(String registrationKey, String name) {
+		return namedDescriptorBuilder( registrationKey, name )
+				.setExactArgumentCount( 0 );
+	}
+
+	public VarArgsFunctionDescriptorBuilder varArgsBuilder(String registrationKey, String begin, String sep, String end) {
+		return new VarArgsFunctionDescriptorBuilder( this, registrationKey, begin, sep, end );
+	}
+
+	/**
+	 * Specialized registration method for registering a named template for functions
+	 * expecting zero arguments.  Short-cut for building a named template via
+	 * {@link #namedDescriptorBuilder} specifying zero arguments and accepting the
+	 * rest of the builder's defaults.
+	 *
+	 * @param name The function name (and registration key)
+	 */
+	public SqmFunctionDescriptor registerNoArgs(String name) {
+		return registerNoArgs( name, name );
+	}
+
+	public SqmFunctionDescriptor registerNoArgs(String registrationKey, String name) {
+		return noArgsBuilder( registrationKey, name ).register();
+	}
+
+	public SqmFunctionDescriptor registerNoArgs(String name, AllowableFunctionReturnType returnType) {
+		return registerNoArgs( name, name, returnType );
+	}
+
+	public SqmFunctionDescriptor registerNoArgs(String registrationKey, String name, AllowableFunctionReturnType returnType) {
+		return noArgsBuilder( registrationKey, name )
+				.setInvariantType( returnType )
+				.register();
+	}
+
+	public SqmFunctionDescriptor registerVarArgs(String registrationKey, AllowableFunctionReturnType returnType, String begin, String sep, String end) {
+		return varArgsBuilder( registrationKey, begin, sep, end )
+				.setInvariantType( returnType )
+				.register();
+	}
+
+	public SqmFunctionDescriptor wrapInJdbcEscape(String registrationKey, SqmFunctionDescriptor wrapped) {
+		final JdbcEscapeFunctionDescriptor wrapperTemplate = new JdbcEscapeFunctionDescriptor( wrapped );
+		register( registrationKey, wrapperTemplate );
+		return wrapperTemplate;
+	}
+
+	public void registerAlternateKey(String alternateKey, String mappedKey) {
+		log.debugf( "Registering alternate key : %s -> %s", alternateKey, mappedKey );
+		alternateKeyMap.put( alternateKey, mappedKey );
+	}
+
+	/**
+	 * Overlay the functions registered here on top of the
+	 * incoming registry, potentially overriding its registrations
+	 */
+	public void overlay(SqmFunctionRegistry registryToOverly) {
+		// NOTE : done in this "direction" as it is easier to access the
+		//		functionMap directly in performing this operation
+		functionMap.forEach( registryToOverly::register );
+		alternateKeyMap.forEach( registryToOverly::registerAlternateKey );
+	}
+
+	public void close() {
+		functionMap.clear();
+		alternateKeyMap.clear();
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/sqm/function/SqmJdbcFunctionEscapeWrapper.java

@@ -1,52 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
- */
-package org.hibernate.query.sqm.function;
-
-import org.hibernate.query.sqm.NodeBuilder;
-import org.hibernate.query.sqm.produce.function.internal.SelfRenderingSqmFunction;
-
-/**
- * Adds a JDBC function escape (i.e. `{fn <wrapped-function-call>})  around the wrapped function
- *
- * @author Steve Ebersole
- * @author Gavin King
- */
-public class SqmJdbcFunctionEscapeWrapper<T>
-		extends SelfRenderingSqmFunction<T> {
-	private final SelfRenderingSqmFunction<?> wrappedSqmFunction;
-
-	public SqmJdbcFunctionEscapeWrapper(
-			SelfRenderingSqmFunction<T> wrappedSqmFunction,
-			NodeBuilder nodeBuilder) {
-		super(
-				(sqlAppender,
-				sqlAstArguments,
-				walker,
-				sessionFactory) -> {
-					sqlAppender.appendSql( "{fn " );
-					wrappedSqmFunction.getRenderingSupport().render(
-							sqlAppender,
-							sqlAstArguments,
-							walker,
-							sessionFactory
-					);
-					sqlAppender.appendSql( "}" );
-				},
-				wrappedSqmFunction.getArguments(),
-				wrappedSqmFunction.getNodeType(),
-				nodeBuilder,
-				wrappedSqmFunction.getFunctionName()
-		);
-		this.wrappedSqmFunction = wrappedSqmFunction;
-	}
-
-	@Override
-	public String asLoggableText() {
-		return "wrapped-function[ " + wrappedSqmFunction.asLoggableText() + " ]";
-	}
-
-}

hibernate-core/src/main/java/org/hibernate/query/sqm/function/package-info.java

@@ -47,6 +47,6 @@
  * 				* str 			- generally defined as `cast(?1 as CHAR )`
  * 		* non-standard functions
  * 			* using JPA's function('function_name', [args]*) syntax.
- * 			* directly leveraging Hibernate's {@link org.hibernate.query.sqm.produce.function.SqmFunctionRegistry}
+ * 			* directly leveraging Hibernate's {@link org.hibernate.query.sqm.function.SqmFunctionRegistry}
  */
 package org.hibernate.query.sqm.function;

hibernate-core/src/main/java/org/hibernate/query/sqm/internal/SqmCriteriaNodeBuilder.java

@@ -37,12 +37,13 @@ import org.hibernate.QueryException;
 import org.hibernate.SortOrder;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.internal.util.collections.ArrayHelper;
+import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.metamodel.model.domain.BasicDomainType;
 import org.hibernate.metamodel.model.domain.DomainType;
 import org.hibernate.metamodel.model.domain.JpaMetamodel;
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.BinaryArithmeticOperator;
 import org.hibernate.query.ComparisonOperator;
+import org.hibernate.query.SemanticException;
 import org.hibernate.query.TrimSpec;
 import org.hibernate.query.UnaryArithmeticOperator;
 import org.hibernate.query.criteria.JpaCoalesce;
@@ -52,12 +53,10 @@ import org.hibernate.query.criteria.JpaSelection;
 import org.hibernate.query.internal.QueryHelper;
 import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.NodeBuilder;
-import org.hibernate.query.SemanticException;
 import org.hibernate.query.sqm.SqmQuerySource;
-import org.hibernate.query.sqm.produce.function.SqmFunctionTemplate;
+import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SqmCastTarget;
+import org.hibernate.query.sqm.spi.SqmCreationContext;
-import org.hibernate.query.sqm.function.SqmDistinct;
+import org.hibernate.query.sqm.tree.SqmNode;
-import org.hibernate.query.sqm.function.SqmTrimSpecification;
 import org.hibernate.query.sqm.tree.SqmTypedNode;
 import org.hibernate.query.sqm.tree.delete.SqmDeleteStatement;
 import org.hibernate.query.sqm.tree.domain.SqmBagJoin;
@@ -66,18 +65,22 @@ import org.hibernate.query.sqm.tree.domain.SqmMapJoin;
 import org.hibernate.query.sqm.tree.domain.SqmPath;
 import org.hibernate.query.sqm.tree.domain.SqmSetJoin;
 import org.hibernate.query.sqm.tree.domain.SqmSingularJoin;
+import org.hibernate.query.sqm.tree.expression.JpaCriteriaParameter;
 import org.hibernate.query.sqm.tree.expression.SqmBinaryArithmetic;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSearched;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSimple;
+import org.hibernate.query.sqm.tree.expression.SqmCastTarget;
+import org.hibernate.query.sqm.tree.expression.SqmCoalesce;
 import org.hibernate.query.sqm.tree.expression.SqmCollectionSize;
-import org.hibernate.query.sqm.tree.expression.JpaCriteriaParameter;
+import org.hibernate.query.sqm.tree.expression.SqmDistinct;
 import org.hibernate.query.sqm.tree.expression.SqmExpression;
+import org.hibernate.query.sqm.tree.expression.SqmFunction;
 import org.hibernate.query.sqm.tree.expression.SqmLiteral;
 import org.hibernate.query.sqm.tree.expression.SqmLiteralNull;
 import org.hibernate.query.sqm.tree.expression.SqmRestrictedSubQueryExpression;
+import org.hibernate.query.sqm.tree.expression.SqmTrimSpecification;
 import org.hibernate.query.sqm.tree.expression.SqmTuple;
 import org.hibernate.query.sqm.tree.expression.SqmUnaryOperation;
-import org.hibernate.query.sqm.function.SqmCoalesce;
 import org.hibernate.query.sqm.tree.from.SqmRoot;
 import org.hibernate.query.sqm.tree.insert.SqmInsertSelectStatement;
 import org.hibernate.query.sqm.tree.predicate.SqmAndPredicate;
@@ -100,7 +103,6 @@ import org.hibernate.query.sqm.tree.select.SqmSortSpecification;
 import org.hibernate.query.sqm.tree.select.SqmSubQuery;
 import org.hibernate.query.sqm.tree.update.SqmUpdateStatement;
 import org.hibernate.service.ServiceRegistry;
-import org.hibernate.query.sqm.function.SqmFunction;
 import org.hibernate.type.StandardBasicTypes;
 
 import static java.util.Arrays.asList;
@@ -112,7 +114,7 @@ import static org.hibernate.query.internal.QueryHelper.highestPrecedenceType;
  * 
  * @author Steve Ebersole
  */
-public class SqmCriteriaNodeBuilder implements NodeBuilder {
+public class SqmCriteriaNodeBuilder implements NodeBuilder, SqmCreationContext {
 	/**
 	 * Simplified creation from a SessionFactory
 	 */
@@ -152,6 +154,11 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 		return queryEngine;
 	}
 
+	@Override
+	public JpaMetamodel getJpaMetamodel() {
+		return domainModel;
+	}
+
 	public void close() {
 		// for potential future use
 	}
@@ -188,13 +195,14 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 
 	@Override
 	public 	<X, T> SqmExpression<X> cast(JpaExpression<T> expression, Class<X> castTargetJavaType) {
+		final BasicDomainType type = getTypeConfiguration().standardBasicTypeForJavaType( castTargetJavaType );
 		//noinspection unchecked
-		BasicDomainType<X> type = getTypeConfiguration().standardBasicTypeForJavaType( castTargetJavaType );
+		return new SqmFunction(
-		//noinspection unchecked
+				"cast",
-		return getFunctionTemplate("cast").makeSqmFunctionExpression(
+				getFunctionDescriptor( "cast" ),
-				asList( (SqmTypedNode) expression, new SqmCastTarget<>( type, this ) ),
 				type,
-				queryEngine
+				asList( (SqmTypedNode) expression, new SqmCastTarget<>( type, this ) ),
+				this
 		);
 	}
 
@@ -439,19 +447,24 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 	@Override
 	public <N extends Number> SqmExpression<Double> avg(Expression<N> argument) {
 		//noinspection unchecked
-		return getFunctionTemplate("avg").makeSqmFunctionExpression(
+		return new SqmFunction(
-				(SqmTypedNode) argument,
+				"avg",
+				getFunctionDescriptor( "avg" ),
 				StandardBasicTypes.DOUBLE,
-				queryEngine
+				Collections.singletonList( (SqmTypedNode) argument ),
+				this
 		);
 	}
 
 	@Override
 	public <N extends Number> SqmExpression<N> sum(Expression<N> argument) {
-		return getFunctionTemplate("sum").makeSqmFunctionExpression(
+		//noinspection unchecked
-				(SqmTypedNode) argument,
+		return new SqmFunction(
-				(AllowableFunctionReturnType<N>) ((SqmExpression<N>) argument).getNodeType(),
+				"sum",
-				queryEngine
+				getFunctionDescriptor( "sum" ),
+				( (SqmExpression<N>) argument ).getNodeType(),
+				Collections.singletonList( (SqmTypedNode) argument ),
+				this
 		);
 	}
 
@@ -467,19 +480,25 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 
 	@Override
 	public <N extends Number> SqmExpression<N> max(Expression<N> argument) {
-		return getFunctionTemplate("max").makeSqmFunctionExpression(
+		//noinspection unchecked
-				(SqmTypedNode) argument,
+		return new SqmFunction(
-				(AllowableFunctionReturnType<N>) ((SqmExpression<N>) argument).getNodeType(),
+				"max",
-				queryEngine
+				getFunctionDescriptor( "max" ),
+				( (SqmExpression<N>) argument ).getNodeType(),
+				Collections.singletonList( (SqmTypedNode) argument ),
+				this
 		);
 	}
 
 	@Override
 	public <N extends Number> SqmExpression<N> min(Expression<N> argument) {
-		return getFunctionTemplate("min").makeSqmFunctionExpression(
+		//noinspection unchecked
-				(SqmTypedNode) argument,
+		return new SqmFunction(
-				(AllowableFunctionReturnType<N>) ((SqmExpression<N>) argument).getNodeType(),
+				"min",
-				queryEngine
+				getFunctionDescriptor( "min" ),
+				( (SqmExpression<N>) argument ).getNodeType(),
+				Collections.singletonList( (SqmTypedNode) argument ),
+				this
 		);
 	}
 
@@ -496,20 +515,24 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 	@Override
 	public SqmExpression<Long> count(Expression<?> argument) {
 		//noinspection unchecked
-		return getFunctionTemplate("count").makeSqmFunctionExpression(
+		return new SqmFunction(
-				(SqmTypedNode) argument,
+				"count",
+				getFunctionDescriptor( "count" ),
 				StandardBasicTypes.LONG,
-				queryEngine
+				Collections.singletonList( (SqmExpression) argument ),
+				this
 		);
 	}
 
 	@Override
 	public SqmExpression<Long> countDistinct(Expression<?> argument) {
 		//noinspection unchecked
-		return getFunctionTemplate("count").makeSqmFunctionExpression(
+		return new SqmFunction(
-				new SqmDistinct<>( (SqmExpression<?>) argument, getQueryEngine().getCriteriaBuilder() ),
+				"count",
+				getFunctionDescriptor( "count" ),
 				StandardBasicTypes.LONG,
-				queryEngine
+				Collections.singletonList( new SqmDistinct( (SqmExpression) argument, this )  ),
+				this
 		);
 	}
 
@@ -524,10 +547,13 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 
 	@Override
 	public <N extends Number> SqmExpression<N> abs(Expression<N> x) {
-		return getFunctionTemplate("abs").makeSqmFunctionExpression(
+		//noinspection unchecked
-				(SqmTypedNode) x,
+		return new SqmFunction(
-				(AllowableFunctionReturnType<N>) ((SqmExpression<N>) x).getNodeType(),
+				"abs",
-				queryEngine
+				getFunctionDescriptor( "abs" ),
+				( (SqmExpression<N>) x ).getNodeType(),
+				Collections.singletonList( (SqmExpression) x ),
+				this
 		);
 	}
 
@@ -663,13 +689,15 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 	@Override
 	public SqmExpression<Double> sqrt(Expression<? extends Number> x) {
 		//noinspection unchecked
-		return getFunctionTemplate("sqrt").makeSqmFunctionExpression(
+		return new SqmFunction(
-				(SqmTypedNode) x,
+				"sqrt",
-				(AllowableFunctionReturnType) QueryHelper.highestPrecedenceType2(
+				getFunctionDescriptor( "sqrt" ),
+				QueryHelper.highestPrecedenceType2(
 						( (SqmExpression) x ).getNodeType(),
 						StandardBasicTypes.DOUBLE
 				),
-				queryEngine
+				Collections.singletonList( (SqmExpression) x ),
+				this
 		);
 	}
 
@@ -787,14 +815,16 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 		final SqmExpression xSqmExpression = (SqmExpression) x;
 		final SqmExpression ySqmExpression = (SqmExpression) y;
 		//noinspection unchecked
-		return getFunctionTemplate( "concat" ).makeSqmFunctionExpression(
+		return new SqmFunction(
-				asList( xSqmExpression, ySqmExpression ),
+				"concat",
-				(AllowableFunctionReturnType) highestPrecedenceType(
+				getFunctionDescriptor( "concat" ),
+				highestPrecedenceType(
 						xSqmExpression.getNodeType(),
 						ySqmExpression.getNodeType(),
 						StandardBasicTypes.STRING
 				),
-				getQueryEngine()
+				asList( xSqmExpression, ySqmExpression ),
+				this
 		);
 	}
 
@@ -803,14 +833,16 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 		final SqmExpression xSqmExpression = (SqmExpression) x;
 		final SqmExpression ySqmExpression = literal( y );
 		//noinspection unchecked
-		return getFunctionTemplate( "concat" ).makeSqmFunctionExpression(
+		return new SqmFunction(
-				asList( xSqmExpression, ySqmExpression ),
+				"concat",
-				(AllowableFunctionReturnType) highestPrecedenceType(
+				getFunctionDescriptor( "concat" ),
+				highestPrecedenceType(
 						xSqmExpression.getNodeType(),
 						ySqmExpression.getNodeType(),
 						StandardBasicTypes.STRING
 				),
-				getQueryEngine()
+				asList( xSqmExpression, ySqmExpression ),
+				this
 		);
 	}
 
@@ -819,14 +851,16 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 		final SqmExpression xSqmExpression = literal( x );
 		final SqmExpression ySqmExpression = (SqmExpression) y;
 		//noinspection unchecked
-		return getFunctionTemplate( "concat" ).makeSqmFunctionExpression(
+		return new SqmFunction(
-				asList( xSqmExpression, ySqmExpression ),
+				"concat",
-				(AllowableFunctionReturnType) highestPrecedenceType(
+				getFunctionDescriptor( "concat" ),
+				highestPrecedenceType(
 						xSqmExpression.getNodeType(),
 						ySqmExpression.getNodeType(),
 						StandardBasicTypes.STRING
 				),
-				getQueryEngine()
+				asList( xSqmExpression, ySqmExpression ),
+				this
 		);
 	}
 
@@ -835,14 +869,16 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 		final SqmExpression xSqmExpression = literal( x );
 		final SqmExpression ySqmExpression = literal( y );
 		//noinspection unchecked
-		return getFunctionTemplate( "concat" ).makeSqmFunctionExpression(
+		return new SqmFunction(
-				asList( xSqmExpression, ySqmExpression ),
+				"concat",
-				(AllowableFunctionReturnType) highestPrecedenceType(
+				getFunctionDescriptor( "concat" ),
+				highestPrecedenceType(
 						xSqmExpression.getNodeType(),
 						ySqmExpression.getNodeType(),
 						StandardBasicTypes.STRING
 				),
-				getQueryEngine()
+				asList( xSqmExpression, ySqmExpression ),
+				this
 		);
 	}
 
@@ -862,10 +898,12 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 		);
 
 		//noinspection unchecked
-		return getFunctionTemplate( "substring" ).makeSqmFunctionExpression(
+		return new SqmFunction(
-				len==null ? asList( source, from ) : asList( source, from, len ),
+				"substring",
+				getFunctionDescriptor( "substring" ),
 				resultType,
-				getQueryEngine()
+				len==null ? asList( source, from ) : asList( source, from, len ),
+				this
 		);
 	}
 
@@ -903,7 +941,8 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 
 	private SqmFunction<String> createTrimNode(TrimSpec trimSpecification, SqmExpression trimCharacter, SqmExpression source) {
 
-		final ArrayList<SqmTypedNode<?>> arguments = new ArrayList<>();
+		final ArrayList<SqmNode> arguments = new ArrayList<>();
+
 		if ( trimSpecification != null ) {
 			arguments.add(
 					new SqmTrimSpecification( trimSpecification, this )
@@ -917,10 +956,12 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 		arguments.add( source );
 
 		//noinspection unchecked
-			return getFunctionTemplate( "trim" ).makeSqmFunctionExpression(
+		return new SqmFunction(
+				"trim",
+				getFunctionDescriptor( "trim" ),
+				QueryHelper.highestPrecedenceType2( source.getNodeType(), StandardBasicTypes.STRING ),
 				arguments,
-					(AllowableFunctionReturnType) QueryHelper.highestPrecedenceType2( source.getNodeType(), StandardBasicTypes.STRING ),
+				this
-					getQueryEngine()
 		);
 	}
 
@@ -978,10 +1019,12 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 		);
 
 		//noinspection unchecked
-		return getFunctionTemplate( "lower" ).makeSqmFunctionExpression(
+		return new SqmFunction(
-				(SqmExpression) x,
+				"lower",
+				getFunctionDescriptor( "lower" ),
 				type,
-				getQueryEngine()
+				Collections.singletonList( (SqmExpression) x ),
+				this
 		);
 	}
 
@@ -993,24 +1036,27 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 		);
 
 		//noinspection unchecked
-		return getFunctionTemplate( "upper" ).makeSqmFunctionExpression(
+		return new SqmFunction(
-				(SqmExpression) x,
+				"upper",
+				getFunctionDescriptor( "upper" ),
 				type,
-				getQueryEngine()
+				Collections.singletonList( (SqmExpression) x ),
+				this
 		);
 	}
 
 	@Override
 	public SqmFunction<Integer> length(Expression<String> argument) {
-
 		//noinspection unchecked
-		return getFunctionTemplate( "length" ).makeSqmFunctionExpression(
+		return new SqmFunction(
-				(SqmExpression) argument,
+				"length",
+				getFunctionDescriptor( "length" ),
 				(AllowableFunctionReturnType) highestPrecedenceType(
 						((SqmExpression) argument).getNodeType(),
 						StandardBasicTypes.INTEGER
 				),
-				getQueryEngine()
+				Collections.singletonList( (SqmExpression) argument ),
+				this
 		);
 	}
 
@@ -1047,12 +1093,13 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 		}
 
 		//noinspection unchecked
-		return getFunctionTemplate("locate").makeSqmFunctionExpression(
+		return new SqmFunction(
-				arguments,
+				"locate",
+				getFunctionDescriptor( "locate" ),
 				type,
-				getQueryEngine()
+				arguments,
+				this
 		);
-
 	}
 
 	@Override
@@ -1085,55 +1132,65 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 	@Override
 	public SqmFunction<Date> currentDate() {
 		//noinspection unchecked
-//		return getFunctionTemplate("current_date").makeSqmFunctionExpression(
+		return new SqmFunction(
-//				StandardBasicTypes.DATE,
+				"current_date",
-//				queryEngine
+				getFunctionDescriptor( "current_date" ),
-//		);
+				StandardBasicTypes.DATE,
-
+				Collections.emptyList(),
-		throw new NotYetImplementedFor6Exception( getClass() );
+				this
+		);
 	}
 
 	@Override
 	public SqmFunction<Timestamp> currentTimestamp() {
 		//noinspection unchecked
-//		return getFunctionTemplate("current_timestamp").makeSqmFunctionExpression(
+		return new SqmFunction(
-//				StandardBasicTypes.TIMESTAMP,
+				"current_timestamp",
-//				queryEngine
+				getFunctionDescriptor( "current_timestamp" ),
-//		);
+				StandardBasicTypes.TIMESTAMP,
-		throw new NotYetImplementedFor6Exception( getClass() );
+				Collections.emptyList(),
+				this
+		);
 	}
 
 	@Override
 	public SqmFunction<Time> currentTime() {
 		//noinspection unchecked
-//		return getFunctionTemplate("current_time").makeSqmFunctionExpression(
+		return new SqmFunction(
-//				StandardBasicTypes.TIME,
+				"current_time",
-//				queryEngine
+				getFunctionDescriptor( "current_time" ),
-//		);
+				StandardBasicTypes.TIME,
-		throw new NotYetImplementedFor6Exception( getClass() );
+				Collections.emptyList(),
+				this
+		);
 	}
 
 	@Override
 	public SqmFunction<Instant> currentInstant() {
 		//noinspection unchecked
-		return getFunctionTemplate("current_timestamp").makeSqmFunctionExpression(
+		return new SqmFunction(
+				"current_instant",
+				getFunctionDescriptor( "current_instant" ),
 				StandardBasicTypes.INSTANT,
-				queryEngine
+				Collections.emptyList(),
+				this
 		);
 	}
 
 	@Override
 	public <T> SqmFunction<T> function(String name, Class<T> type, Expression<?>[] args) {
-		final SqmFunctionTemplate functionTemplate = getFunctionTemplate(name);
+		final SqmFunctionDescriptor functionTemplate = getFunctionDescriptor( name);
 		if ( functionTemplate == null ) {
 			throw new SemanticException( "Could not resolve function named `" + name + "`" );
 		}
 
 		//noinspection unchecked
-		return functionTemplate.makeSqmFunctionExpression(
+		return new SqmFunction<>(
-				(List) expressionList( args ),
+				name,
+				getFunctionDescriptor( name ),
 				getTypeConfiguration().standardBasicTypeForJavaType( type ),
-				getQueryEngine()
+				(List) expressionList( args ),
+				this
 		);
 	}
 
@@ -1254,16 +1311,17 @@ public class SqmCriteriaNodeBuilder implements NodeBuilder {
 				second.getNodeType()
 		);
 
-		return getFunctionTemplate("nullif").makeSqmFunctionExpression(
+		return new SqmFunction<>(
-				asList( first, second ),
+				"nullif",
+				getFunctionDescriptor( "nullif" ),
 				type,
-				getQueryEngine()
+				asList( first, second ),
+				this
 		);
-
 	}
 
-	private SqmFunctionTemplate getFunctionTemplate(String name) {
+	private SqmFunctionDescriptor getFunctionDescriptor(String name) {
-		return queryEngine.getSqmFunctionRegistry().findFunctionTemplate(name);
+		return queryEngine.getSqmFunctionRegistry().findFunctionDescriptor( name);
 	}
 
 	@Override

hibernate-core/src/main/java/org/hibernate/query/sqm/internal/SqmTreePrinter.java

@@ -27,29 +27,30 @@ import org.hibernate.query.sqm.tree.domain.SqmMinElementPath;
 import org.hibernate.query.sqm.tree.domain.SqmMinIndexPath;
 import org.hibernate.query.sqm.tree.domain.SqmPluralValuedSimplePath;
 import org.hibernate.query.sqm.tree.domain.SqmTreatedPath;
+import org.hibernate.query.sqm.tree.expression.JpaCriteriaParameter;
 import org.hibernate.query.sqm.tree.expression.SqmBinaryArithmetic;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSearched;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSimple;
+import org.hibernate.query.sqm.tree.expression.SqmCastTarget;
+import org.hibernate.query.sqm.tree.expression.SqmCoalesce;
 import org.hibernate.query.sqm.tree.expression.SqmCollectionSize;
-import org.hibernate.query.sqm.tree.expression.JpaCriteriaParameter;
+import org.hibernate.query.sqm.tree.expression.SqmDistinct;
-import org.hibernate.query.sqm.tree.expression.SqmParameterizedEntityType;
 import org.hibernate.query.sqm.tree.expression.SqmEnumLiteral;
 import org.hibernate.query.sqm.tree.expression.SqmExpression;
+import org.hibernate.query.sqm.tree.expression.SqmExtractUnit;
 import org.hibernate.query.sqm.tree.expression.SqmFieldLiteral;
+import org.hibernate.query.sqm.tree.expression.SqmFunction;
 import org.hibernate.query.sqm.tree.expression.SqmLiteral;
 import org.hibernate.query.sqm.tree.expression.SqmLiteralEntityType;
 import org.hibernate.query.sqm.tree.expression.SqmNamedParameter;
+import org.hibernate.query.sqm.tree.expression.SqmParameterizedEntityType;
 import org.hibernate.query.sqm.tree.expression.SqmPathEntityType;
 import org.hibernate.query.sqm.tree.expression.SqmPositionalParameter;
 import org.hibernate.query.sqm.tree.expression.SqmRestrictedSubQueryExpression;
+import org.hibernate.query.sqm.tree.expression.SqmStar;
+import org.hibernate.query.sqm.tree.expression.SqmTrimSpecification;
 import org.hibernate.query.sqm.tree.expression.SqmTuple;
 import org.hibernate.query.sqm.tree.expression.SqmUnaryOperation;
-import org.hibernate.query.sqm.function.SqmCastTarget;
-import org.hibernate.query.sqm.function.SqmDistinct;
-import org.hibernate.query.sqm.function.SqmExtractUnit;
-import org.hibernate.query.sqm.function.SqmFunction;
-import org.hibernate.query.sqm.function.SqmStar;
-import org.hibernate.query.sqm.function.SqmTrimSpecification;
 import org.hibernate.query.sqm.tree.from.SqmAttributeJoin;
 import org.hibernate.query.sqm.tree.from.SqmCrossJoin;
 import org.hibernate.query.sqm.tree.from.SqmEntityJoin;
@@ -605,7 +606,12 @@ public class SqmTreePrinter implements SemanticQueryWalker<Object> {
 	}
 
 	@Override
-	public Object visitFunction(SqmFunction sqmFunction) {
+	public Object visitFunction(SqmFunction tSqmFunction) {
+		return null;
+	}
+
+	@Override
+	public Object visitCoalesce(SqmCoalesce sqmCoalesce) {
 		return null;
 	}
 

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/ArgumentsValidator.java

@@ -8,16 +8,16 @@ package org.hibernate.query.sqm.produce.function;
 
 import java.util.List;
 
-import org.hibernate.query.sqm.tree.SqmTypedNode;
+import org.hibernate.query.sqm.tree.SqmVisitableNode;
-import org.hibernate.query.sqm.tree.expression.SqmExpression;
 
 /**
  * @author Steve Ebersole
  */
+@FunctionalInterface
 public interface ArgumentsValidator {
 	/**
-	 * The main (functional) operation defining validation
+	 * Validate the arguments
 	 */
-	void validate(List<SqmTypedNode<?>> arguments);
+	void validate(List<? extends SqmVisitableNode> arguments);
 
 }

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/JdbcFunctionEscapeWrapperTemplate.java

@@ -1,46 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
- */
-package org.hibernate.query.sqm.produce.function;
-
-import java.util.List;
-
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.produce.function.internal.SelfRenderingSqmFunction;
-import org.hibernate.query.sqm.produce.function.spi.AbstractSqmFunctionTemplate;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-import org.hibernate.query.sqm.function.SqmJdbcFunctionEscapeWrapper;
-
-/**
- * Acts as a wrapper to another SqmFunctionTemplate - upon rendering uses the
- * standard JDBC escape sequence (i.e. `{fn blah}`) when rendering the SQL.
- *
- * @author Steve Ebersole
- */
-public class JdbcFunctionEscapeWrapperTemplate
-		extends AbstractSqmFunctionTemplate {
-	private final SqmFunctionTemplate wrapped;
-
-	public JdbcFunctionEscapeWrapperTemplate(SqmFunctionTemplate wrapped) {
-		this.wrapped = wrapped;
-	}
-
-	@Override
-	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine) {
-		return new SqmJdbcFunctionEscapeWrapper<>(
-				wrapped.makeSqmFunctionExpression(
-						arguments,
-						impliedResultType,
-						queryEngine
-				),
-				queryEngine.getCriteriaBuilder()
-		);
-	}
-}

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/NamedFunctionDescriptorBuilder.java

@@ -7,15 +7,17 @@
 package org.hibernate.query.sqm.produce.function;
 
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.sqm.produce.function.spi.NamedSqmFunctionTemplate;
+import org.hibernate.query.sqm.function.SqmFunctionRegistry;
+import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
+import org.hibernate.query.sqm.function.NamedSqmFunctionDescriptor;
 
 import org.jboss.logging.Logger;
 
 /**
  * @author Steve Ebersole
  */
-public class NamedFunctionTemplateBuilder {
+public class NamedFunctionDescriptorBuilder {
-	private static final Logger log = Logger.getLogger( NamedFunctionTemplateBuilder.class );
+	private static final Logger log = Logger.getLogger( NamedFunctionDescriptorBuilder.class );
 
 	private final SqmFunctionRegistry registry;
 	private final String registrationKey;
@@ -27,54 +29,53 @@ public class NamedFunctionTemplateBuilder {
 
 	private boolean useParenthesesWhenNoArgs;
 
-	public NamedFunctionTemplateBuilder(SqmFunctionRegistry registry, String registrationKey, String functionName) {
+	public NamedFunctionDescriptorBuilder(SqmFunctionRegistry registry, String registrationKey, String functionName) {
 		this.registry = registry;
 		this.registrationKey = registrationKey;
 		this.functionName = functionName;
 	}
 
-	public NamedFunctionTemplateBuilder setArgumentsValidator(ArgumentsValidator argumentsValidator) {
+	public NamedFunctionDescriptorBuilder setArgumentsValidator(ArgumentsValidator argumentsValidator) {
 		this.argumentsValidator = argumentsValidator;
 		return this;
 	}
 
-	public NamedFunctionTemplateBuilder setArgumentCountBetween(int min, int max) {
+	public NamedFunctionDescriptorBuilder setArgumentCountBetween(int min, int max) {
 		return setArgumentsValidator( StandardArgumentsValidators.between( min, max ) );
 	}
 
-	public NamedFunctionTemplateBuilder setExactArgumentCount(int exactArgumentCount) {
+	public NamedFunctionDescriptorBuilder setExactArgumentCount(int exactArgumentCount) {
 		return setArgumentsValidator( StandardArgumentsValidators.exactly( exactArgumentCount ) );
 	}
 
-	public NamedFunctionTemplateBuilder setReturnTypeResolver(FunctionReturnTypeResolver returnTypeResolver) {
+	public NamedFunctionDescriptorBuilder setReturnTypeResolver(FunctionReturnTypeResolver returnTypeResolver) {
 		this.returnTypeResolver = returnTypeResolver;
 		return this;
 	}
 
-	public NamedFunctionTemplateBuilder setInvariantType(AllowableFunctionReturnType invariantType) {
+	public NamedFunctionDescriptorBuilder setInvariantType(AllowableFunctionReturnType invariantType) {
 		setReturnTypeResolver( StandardFunctionReturnTypeResolvers.invariant( invariantType ) );
 		return this;
 	}
 
-	public NamedFunctionTemplateBuilder setUseParenthesesWhenNoArgs(boolean useParenthesesWhenNoArgs) {
+	public NamedFunctionDescriptorBuilder setUseParenthesesWhenNoArgs(boolean useParenthesesWhenNoArgs) {
 		this.useParenthesesWhenNoArgs = useParenthesesWhenNoArgs;
 		return this;
 	}
 
-	public SqmFunctionTemplate register() {
+	public SqmFunctionDescriptor register() {
 		return registry.register(
 				registrationKey,
-				template()
+				build()
 		);
 	}
 
-	public SqmFunctionTemplate template() {
+	public SqmFunctionDescriptor build() {
-		return new NamedSqmFunctionTemplate(
+		return new NamedSqmFunctionDescriptor(
+				registrationKey,
 				functionName,
 				useParenthesesWhenNoArgs,
-				argumentsValidator,
+				argumentsValidator
-				returnTypeResolver,
-				registrationKey
 		);
 	}
 }

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/PatternFunctionDescriptorBuilder.java

@@ -7,13 +7,15 @@
 package org.hibernate.query.sqm.produce.function;
 
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
+import org.hibernate.query.sqm.function.SqmFunctionRegistry;
+import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
 import org.hibernate.query.sqm.produce.function.internal.PatternRenderer;
-import org.hibernate.query.sqm.produce.function.spi.PatternBasedSqmFunctionTemplate;
+import org.hibernate.query.sqm.function.PatternBasedSqmFunctionTemplate;
 
 /**
  * @author Steve Ebersole
  */
-public class PatternFunctionTemplateBuilder {
+public class PatternFunctionDescriptorBuilder {
 	private final SqmFunctionRegistry registry;
 	private final String registrationKey;
 	private final String pattern;
@@ -23,50 +25,49 @@ public class PatternFunctionTemplateBuilder {
 
 	private boolean useParenthesesWhenNoArgs;
 
-	public PatternFunctionTemplateBuilder(SqmFunctionRegistry registry, String registrationKey, String pattern) {
+	public PatternFunctionDescriptorBuilder(SqmFunctionRegistry registry, String registrationKey, String pattern) {
 		this.registry = registry;
 		this.registrationKey = registrationKey;
 		this.pattern = pattern;
 	}
 
-	public PatternFunctionTemplateBuilder setArgumentsValidator(ArgumentsValidator argumentsValidator) {
+	public PatternFunctionDescriptorBuilder setArgumentsValidator(ArgumentsValidator argumentsValidator) {
 		this.argumentsValidator = argumentsValidator;
 		return this;
 	}
 
-	public PatternFunctionTemplateBuilder setExactArgumentCount(int exactArgumentCount) {
+	public PatternFunctionDescriptorBuilder setExactArgumentCount(int exactArgumentCount) {
 		return setArgumentsValidator( StandardArgumentsValidators.exactly( exactArgumentCount ) );
 	}
 
-	public PatternFunctionTemplateBuilder setArgumentCountBetween(int min, int max) {
+	public PatternFunctionDescriptorBuilder setArgumentCountBetween(int min, int max) {
 		return setArgumentsValidator( StandardArgumentsValidators.between( min, max ) );
 	}
 
-	public PatternFunctionTemplateBuilder setReturnTypeResolver(FunctionReturnTypeResolver returnTypeResolver) {
+	public PatternFunctionDescriptorBuilder setReturnTypeResolver(FunctionReturnTypeResolver returnTypeResolver) {
 		this.returnTypeResolver = returnTypeResolver;
 		return this;
 	}
 
-	public PatternFunctionTemplateBuilder setInvariantType(AllowableFunctionReturnType invariantType) {
+	public PatternFunctionDescriptorBuilder setInvariantType(AllowableFunctionReturnType invariantType) {
 		setReturnTypeResolver( StandardFunctionReturnTypeResolvers.invariant( invariantType ) );
 		return this;
 	}
 
-	public PatternFunctionTemplateBuilder setUseParenthesesWhenNoArgs(boolean useParenthesesWhenNoArgs) {
+	public PatternFunctionDescriptorBuilder setUseParenthesesWhenNoArgs(boolean useParenthesesWhenNoArgs) {
 		this.useParenthesesWhenNoArgs = useParenthesesWhenNoArgs;
 		return this;
 	}
 
-	public SqmFunctionTemplate register() {
+	public SqmFunctionDescriptor register() {
 		return registry.register( registrationKey, template() );
 	}
 
-	public SqmFunctionTemplate template() {
+	public SqmFunctionDescriptor template() {
 		return new PatternBasedSqmFunctionTemplate(
 				new PatternRenderer( pattern, useParenthesesWhenNoArgs ),
 				argumentsValidator,
-				returnTypeResolver,
+				returnTypeResolver
-				registrationKey
 		);
 	}
 }

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/SqmFunctionRegistry.java

@@ -1,215 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
- */
-package org.hibernate.query.sqm.produce.function;
-
-import java.util.Map;
-import java.util.TreeMap;
-
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-
-import org.jboss.logging.Logger;
-
-import static java.lang.String.CASE_INSENSITIVE_ORDER;
-
-/**
- * Defines a registry for SQLFunction instances
- *
- * @author Steve Ebersole
- */
-public class SqmFunctionRegistry {
-	private static final Logger log = Logger.getLogger( SqmFunctionRegistry.class );
-
-	private final Map<String,SqmFunctionTemplate> functionMap = new TreeMap<>( CASE_INSENSITIVE_ORDER );
-	private final Map<String,String> alternateKeyMap = new TreeMap<>( CASE_INSENSITIVE_ORDER );
-
-	public SqmFunctionRegistry() {
-		log.tracef( "SqmFunctionRegistry created" );
-	}
-
-	/**
-	 * Find a SqmFunctionTemplate by name.  Returns {@code null} if
-	 * no such function is found.
-	 */
-	public SqmFunctionTemplate findFunctionTemplate(String functionName) {
-		SqmFunctionTemplate found = null;
-
-		final String alternateKeyResolution = alternateKeyMap.get( functionName );
-		if ( alternateKeyResolution != null ) {
-			found = functionMap.get( alternateKeyResolution );
-		}
-
-		if ( found == null ) {
-			found = functionMap.get( functionName );
-		}
-
-		return found;
-	}
-
-	/**
-	 * Register a function template by name
-	 */
-	public SqmFunctionTemplate register(String registrationKey, SqmFunctionTemplate function) {
-		final SqmFunctionTemplate priorRegistration = functionMap.put( registrationKey, function );
-		log.debugf(
-				"Registered SqmFunctionTemplate [%s] under %s; prior registration was %s",
-				function,
-				registrationKey,
-				priorRegistration
-		);
-
-		return function;
-	}
-
-	/**
-	 * Register a pattern-based template by name.  Shortcut for building the template
-	 * via {@link #patternTemplateBuilder} accepting its defaults.
-	 */
-	public SqmFunctionTemplate registerPattern(String name, String pattern) {
-		return patternTemplateBuilder( name, pattern ).register();
-	}
-
-	/**
-	 * Register a pattern-based template by name and invariant return type.  Shortcut for building the template
-	 * via {@link #patternTemplateBuilder} accepting its defaults.
-	 */
-	public SqmFunctionTemplate registerPattern(String name, String pattern, AllowableFunctionReturnType returnType) {
-		return patternTemplateBuilder( name, pattern )
-				.setInvariantType( returnType )
-				.register();
-	}
-
-	/**
-	 * Get a builder for creating and registering a pattern-based function template.
-	 *
-	 * @param registrationKey The name under which the template will get registered
-	 * @param pattern The pattern defining the the underlying function call
-	 *
-	 * @return The builder
-	 */
-	public PatternFunctionTemplateBuilder patternTemplateBuilder(String registrationKey, String pattern) {
-		return new PatternFunctionTemplateBuilder( this, registrationKey, pattern );
-	}
-
-	/**
-	 * Register a named template by name.  Shortcut for building a template via
-	 * {@link #namedTemplateBuilder} using the passed name as both the registration
-	 * key and underlying SQL function name and accepting the builder's defaults.
-	 *
-	 * @param name The function name (and registration key)
-	 */
-	public SqmFunctionTemplate registerNamed(String name) {
-		return namedTemplateBuilder( name ).register();
-	}
-
-	/**
-	 * Register a named template by name and invariant return type.  Shortcut for building
-	 * a template via {@link #namedTemplateBuilder} using the passed name as both the
-	 * registration key and underlying SQL function name and accepting the builder's defaults.
-	 *
-	 * @param name The function name (and registration key)
-	 */
-	public SqmFunctionTemplate registerNamed(String name, AllowableFunctionReturnType returnType) {
-		return namedTemplateBuilder( name ).setInvariantType( returnType ).register();
-	}
-
-	/**
-	 * Get a builder for creating and registering a name-based function template
-	 * using the passed name as both the registration key and underlying SQL
-	 * function name
-	 *
-	 * @param name The function name (and registration key)
-	 *
-	 * @return The builder
-	 */
-	public NamedFunctionTemplateBuilder namedTemplateBuilder(String name) {
-		return namedTemplateBuilder( name, name );
-	}
-
-	/**
-	 * Get a builder for creating and registering a name-based function template.
-	 *
-	 * @param registrationKey The name under which the template will get registered
-	 * @param name The underlying SQL function name to use
-	 *
-	 * @return The builder
-	 */
-	public NamedFunctionTemplateBuilder namedTemplateBuilder(String registrationKey, String name) {
-		return new NamedFunctionTemplateBuilder( this, registrationKey, name );
-	}
-
-	public NamedFunctionTemplateBuilder noArgsBuilder(String name) {
-		return noArgsBuilder( name, name );
-	}
-
-	public NamedFunctionTemplateBuilder noArgsBuilder(String registrationKey, String name) {
-		return namedTemplateBuilder( registrationKey, name )
-				.setExactArgumentCount( 0 );
-	}
-
-	public VarArgsFunctionTemplateBuilder varArgsBuilder(String registrationKey, String begin, String sep, String end) {
-		return new VarArgsFunctionTemplateBuilder( this, registrationKey, begin, sep, end );
-	}
-
-	/**
-	 * Specialized registration method for registering a named template for functions
-	 * expecting zero arguments.  Short-cut for building a named template via
-	 * {@link #namedTemplateBuilder} specifying zero arguments and accepting the
-	 * rest of the builder's defaults.
-	 *
-	 * @param name The function name (and registration key)
-	 */
-	public SqmFunctionTemplate registerNoArgs(String name) {
-		return registerNoArgs( name, name );
-	}
-
-	public SqmFunctionTemplate registerNoArgs(String registrationKey, String name) {
-		return noArgsBuilder( registrationKey, name ).register();
-	}
-
-	public SqmFunctionTemplate registerNoArgs(String name, AllowableFunctionReturnType returnType) {
-		return registerNoArgs( name, name, returnType );
-	}
-
-	public SqmFunctionTemplate registerNoArgs(String registrationKey, String name, AllowableFunctionReturnType returnType) {
-		return noArgsBuilder( registrationKey, name )
-				.setInvariantType( returnType )
-				.register();
-	}
-
-	public SqmFunctionTemplate registerVarArgs(String registrationKey, AllowableFunctionReturnType returnType, String begin, String sep, String end) {
-		return varArgsBuilder( registrationKey, begin, sep, end )
-				.setInvariantType( returnType )
-				.register();
-	}
-
-	public SqmFunctionTemplate wrapInJdbcEscape(String registrationKey, SqmFunctionTemplate wrapped) {
-		final JdbcFunctionEscapeWrapperTemplate wrapperTemplate = new JdbcFunctionEscapeWrapperTemplate( wrapped );
-		register( registrationKey, wrapperTemplate );
-		return wrapperTemplate;
-	}
-
-	public void registerAlternateKey(String alternateKey, String mappedKey) {
-		log.debugf( "Registering alternate key : %s -> %s", alternateKey, mappedKey );
-		alternateKeyMap.put( alternateKey, mappedKey );
-	}
-
-	/**
-	 * Overlay the functions registered here on top of the
-	 * incoming registry, potentially overriding its registrations
-	 */
-	public void overlay(SqmFunctionRegistry registryToOverly) {
-		// NOTE : done in this "direction" as it is easier to access the
-		//		functionMap directly in performing this operation
-		functionMap.forEach( registryToOverly::register );
-		alternateKeyMap.forEach( registryToOverly::registerAlternateKey );
-	}
-
-	public void close() {
-		functionMap.clear();
-		alternateKeyMap.clear();
-	}
-}

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/SqmFunctionTemplate.java

@@ -1,85 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
- */
-package org.hibernate.query.sqm.produce.function;
-
-import java.util.List;
-
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.produce.function.internal.SelfRenderingSqmFunction;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-
-import static java.util.Collections.emptyList;
-import static java.util.Collections.singletonList;
-
-/**
- * Extension for supplying support for non-standard (ANSI SQL) functions
- * in HQL and Criteria queries.
- * <p/>
- * Ultimately acts as a factory for SQM function expressions.
- *
- * @author David Channon
- * @author Steve Ebersole
- */
-public interface SqmFunctionTemplate {
-	/**
-	 * Generate an SqmExpression instance from this template.
-	 * <p/>
-	 * Note that this returns SqmExpression rather than the more
-	 * restrictive SqmFunctionExpression to allow implementors
-	 * to transform the source function expression into any
-	 * "expressable form".
-	 */
-	<T> SelfRenderingSqmFunction<T> makeSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine);
-
-	default <T> SelfRenderingSqmFunction<T> makeSqmFunctionExpression(
-			SqmTypedNode<?> argument,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine) {
-		return makeSqmFunctionExpression(
-				singletonList(argument),
-				impliedResultType,
-				queryEngine
-		);
-	}
-
-	default <T> SelfRenderingSqmFunction<T> makeSqmFunctionExpression(
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine) {
-		return makeSqmFunctionExpression(
-				emptyList(),
-				impliedResultType,
-				queryEngine
-		);
-	}
-
-	/**
-	 * Will a call to the described function always include
-	 * parentheses?
-	 * <p>
-	 * SqmFunctionTemplate is generally used for rendering of a function.
-	 * However there are cases where Hibernate needs to consume a fragment
-	 * and decide if a token represents a function name.  In cases where
-	 * the token is followed by an open-paren we can safely assume the
-	 * token is a function name.  However, if the next token is not an
-	 * open-paren, the token can still represent a function provided that
-	 * the function has a "no paren" form in the case of no arguments.  E.g.
-	 * Many databases do not require parentheses on functions like
-	 * `current_timestamp`, etc.  This method helps account for those
-	 * cases.
-	 * <p>
-	 * Note that the most common case, by far, is that a function will always
-	 * include the parentheses - therefore this return is defined as true by
-	 * default.
-	 */
-	default boolean alwaysIncludesParentheses() {
-		return true;
-	}
-}

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/StandardArgumentsValidators.java

@@ -11,6 +11,7 @@ import java.util.List;
 import java.util.Locale;
 
 import org.hibernate.QueryException;
+import org.hibernate.query.sqm.tree.SqmTypedNode;
 
 /**
  * @author Steve Ebersole
@@ -100,7 +101,8 @@ public final class StandardArgumentsValidators {
 	public static ArgumentsValidator of(Class<?> javaType) {
 		return arguments -> arguments.forEach(
 				arg -> {
-					Class<?> argType = arg.getNodeType().getExpressableJavaTypeDescriptor().getJavaType();
+					if ( arg instanceof SqmTypedNode ) {
+						Class<?> argType = ( (SqmTypedNode) arg ).getNodeType().getExpressableJavaTypeDescriptor().getJavaType();
 						if ( !javaType.isAssignableFrom(argType) ) {
 							throw new QueryException(
 									String.format(
@@ -112,6 +114,10 @@ public final class StandardArgumentsValidators {
 							);
 						}
 					}
+					else {
+						throw new QueryException( "Found un-typed arguments with typed argument validator" );
+					}
+				}
 		);
 	}
 

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/VarArgsFunctionDescriptorBuilder.java

@@ -7,15 +7,17 @@
 package org.hibernate.query.sqm.produce.function;
 
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.sqm.produce.function.spi.FunctionAsExpressionTemplate;
+import org.hibernate.query.sqm.function.FunctionAsExpressionTemplate;
+import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
+import org.hibernate.query.sqm.function.SqmFunctionRegistry;
 
 import org.jboss.logging.Logger;
 
 /**
  * @author Christian Beikov
  */
-public class VarArgsFunctionTemplateBuilder {
+public class VarArgsFunctionDescriptorBuilder {
-	private static final Logger log = Logger.getLogger( VarArgsFunctionTemplateBuilder.class );
+	private static final Logger log = Logger.getLogger( VarArgsFunctionDescriptorBuilder.class );
 
 	private final SqmFunctionRegistry registry;
 	private final String registrationKey;
@@ -25,9 +27,8 @@ public class VarArgsFunctionTemplateBuilder {
 	private final String end;
 
 	private ArgumentsValidator argumentsValidator;
-	private FunctionReturnTypeResolver returnTypeResolver;
 
-	public VarArgsFunctionTemplateBuilder(SqmFunctionRegistry registry, String registrationKey, String begin, String sep, String end) {
+	public VarArgsFunctionDescriptorBuilder(SqmFunctionRegistry registry, String registrationKey, String begin, String sep, String end) {
 		this.registry = registry;
 		this.registrationKey = registrationKey;
 		this.begin = begin;
@@ -35,43 +36,41 @@ public class VarArgsFunctionTemplateBuilder {
 		this.end = end;
 	}
 
-	public VarArgsFunctionTemplateBuilder setArgumentsValidator(ArgumentsValidator argumentsValidator) {
+	public VarArgsFunctionDescriptorBuilder setArgumentsValidator(ArgumentsValidator argumentsValidator) {
 		this.argumentsValidator = argumentsValidator;
 		return this;
 	}
 
-	public VarArgsFunctionTemplateBuilder setArgumentCountBetween(int min, int max) {
+	public VarArgsFunctionDescriptorBuilder setArgumentCountBetween(int min, int max) {
 		return setArgumentsValidator( StandardArgumentsValidators.between( min, max ) );
 	}
 
-	public VarArgsFunctionTemplateBuilder setMinArgumentCount(int min) {
+	public VarArgsFunctionDescriptorBuilder setMinArgumentCount(int min) {
 		return setArgumentsValidator( StandardArgumentsValidators.min( min ) );
 	}
 
-	public VarArgsFunctionTemplateBuilder setExactArgumentCount(int exactArgumentCount) {
+	public VarArgsFunctionDescriptorBuilder setExactArgumentCount(int exactArgumentCount) {
 		return setArgumentsValidator( StandardArgumentsValidators.exactly( exactArgumentCount ) );
 	}
 
-	public VarArgsFunctionTemplateBuilder setReturnTypeResolver(FunctionReturnTypeResolver returnTypeResolver) {
+	public VarArgsFunctionDescriptorBuilder setReturnTypeResolver(FunctionReturnTypeResolver returnTypeResolver) {
-		this.returnTypeResolver = returnTypeResolver;
+//		this.returnTypeResolver = returnTypeResolver;
 		return this;
 	}
 
-	public VarArgsFunctionTemplateBuilder setInvariantType(AllowableFunctionReturnType invariantType) {
+	public VarArgsFunctionDescriptorBuilder setInvariantType(AllowableFunctionReturnType invariantType) {
 		setReturnTypeResolver( StandardFunctionReturnTypeResolvers.invariant( invariantType ) );
 		return this;
 	}
 
-	public SqmFunctionTemplate register() {
+	public SqmFunctionDescriptor register() {
 		return registry.register(
 				registrationKey,
 				new FunctionAsExpressionTemplate(
 						begin,
 						sep,
 						end,
-						returnTypeResolver,
+						argumentsValidator
-						argumentsValidator,
-						registrationKey
 				)
 		);
 	}

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/internal/SelfRenderingSqmFunction.java

@@ -1,58 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
- */
-package org.hibernate.query.sqm.produce.function.internal;
-
-import java.util.List;
-
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.sqm.NodeBuilder;
-import org.hibernate.query.sqm.function.SqmFunction;
-import org.hibernate.query.sqm.produce.function.spi.SelfRenderingFunctionSupport;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-import org.hibernate.query.sqm.tree.expression.AbstractSqmExpression;
-
-/**
- * @author Steve Ebersole
- */
-public class SelfRenderingSqmFunction<T>
-		extends AbstractSqmExpression<T>
-		implements SqmFunction<T> {
-	private final String name;
-	private final SelfRenderingFunctionSupport renderingSupport;
-	private final List<SqmTypedNode<?>> arguments;
-
-	public SelfRenderingSqmFunction(
-			SelfRenderingFunctionSupport renderingSupport,
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			NodeBuilder nodeBuilder,
-			String name) {
-		super( impliedResultType, nodeBuilder );
-		this.renderingSupport = renderingSupport;
-		this.arguments = arguments;
-		this.name = name;
-	}
-
-	public List<SqmTypedNode<?>> getArguments() {
-		return arguments;
-	}
-
-	@Override
-	public AllowableFunctionReturnType<T> getNodeType() {
-		return (AllowableFunctionReturnType<T>) super.getNodeType();
-	}
-
-	public SelfRenderingFunctionSupport getRenderingSupport() {
-		return renderingSupport;
-	}
-
-	@Override
-	public String getFunctionName() {
-		return name;
-	}
-
-}

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/package-info.java

@@ -6,7 +6,7 @@
  */
 
 /**
- * Package defining support for {@link org.hibernate.query.sqm.produce.function.SqmFunctionTemplate} handling.
+ * Package defining support for {@link org.hibernate.query.sqm.function.SqmFunctionDescriptor} handling.
  * <p/>
  * Between {@link org.hibernate.query.sqm.produce.function.ArgumentsValidator} and
  * {@link org.hibernate.query.sqm.produce.function.FunctionReturnTypeResolver} creating

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/spi/AbstractSelfRenderingFunctionTemplate.java

@@ -1,51 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
- */
-package org.hibernate.query.sqm.produce.function.spi;
-
-import java.util.List;
-
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.produce.function.ArgumentsValidator;
-import org.hibernate.query.sqm.produce.function.FunctionReturnTypeResolver;
-import org.hibernate.query.sqm.produce.function.internal.SelfRenderingSqmFunction;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-
-/**
- * @author Steve Ebersole
- */
-public abstract class AbstractSelfRenderingFunctionTemplate extends AbstractSqmFunctionTemplate {
-	private final String name;
-
-	public AbstractSelfRenderingFunctionTemplate(
-			String name,
-			FunctionReturnTypeResolver returnTypeResolver,
-			ArgumentsValidator argumentsValidator) {
-		super( argumentsValidator, returnTypeResolver );
-		this.name = name;
-	}
-
-	@Override
-	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> resolvedReturnType,
-			QueryEngine queryEngine) {
-		//noinspection unchecked
-		return new SelfRenderingSqmFunction(
-				getRenderingFunctionSupport( arguments, resolvedReturnType, queryEngine ),
-				arguments,
-				resolvedReturnType,
-				queryEngine.getCriteriaBuilder(),
-				name
-		);
-	}
-
-	protected abstract SelfRenderingFunctionSupport getRenderingFunctionSupport(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<?> resolvedReturnType,
-			QueryEngine queryEngine);
-}

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/spi/AbstractSqmFunctionTemplate.java

@@ -1,67 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
- */
-package org.hibernate.query.sqm.produce.function.spi;
-
-import java.util.List;
-
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.produce.function.ArgumentsValidator;
-import org.hibernate.query.sqm.produce.function.FunctionReturnTypeResolver;
-import org.hibernate.query.sqm.produce.function.SqmFunctionTemplate;
-import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
-import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
-import org.hibernate.query.sqm.produce.function.internal.SelfRenderingSqmFunction;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-
-/**
- * @author Steve Ebersole
- */
-public abstract class AbstractSqmFunctionTemplate implements SqmFunctionTemplate {
-	private final ArgumentsValidator argumentsValidator;
-	private final FunctionReturnTypeResolver returnTypeResolver;
-
-	public AbstractSqmFunctionTemplate() {
-		this( null, null );
-	}
-
-	public AbstractSqmFunctionTemplate(ArgumentsValidator argumentsValidator) {
-		this( argumentsValidator, null );
-	}
-
-	public AbstractSqmFunctionTemplate(
-			ArgumentsValidator argumentsValidator,
-			FunctionReturnTypeResolver returnTypeResolver) {
-		this.argumentsValidator = argumentsValidator == null
-				? StandardArgumentsValidators.NONE
-				: argumentsValidator;
-		this.returnTypeResolver = returnTypeResolver == null
-				? StandardFunctionReturnTypeResolvers.useFirstNonNull()
-				: returnTypeResolver;
-	}
-
-	@Override
-	@SuppressWarnings("unchecked")
-	public final <T> SelfRenderingSqmFunction<T> makeSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine) {
-		argumentsValidator.validate( arguments );
-
-		return generateSqmFunctionExpression(
-				arguments,
-				(AllowableFunctionReturnType<T>) //this cast is not truly correct
-						returnTypeResolver.resolveFunctionReturnType( impliedResultType, arguments ),
-				queryEngine
-		);
-	}
-
-	protected abstract <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine);
-}

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/spi/NamedSqmFunctionTemplate.java

@@ -1,126 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
- */
-package org.hibernate.query.sqm.produce.function.spi;
-
-import org.hibernate.engine.spi.SessionFactoryImplementor;
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.produce.function.ArgumentsValidator;
-import org.hibernate.query.sqm.produce.function.FunctionReturnTypeResolver;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-import org.hibernate.sql.ast.spi.SqlAppender;
-import org.hibernate.sql.ast.SqlAstWalker;
-import org.hibernate.sql.ast.tree.SqlAstNode;
-
-import java.util.List;
-import java.util.Locale;
-
-/**
- * Provides a standard implementation that supports the majority of the HQL
- * functions that are translated to SQL. The Dialect and its sub-classes use
- * this class to provide details required for processing of the associated
- * function.
- *
- * @author David Channon
- * @author Steve Ebersole
- */
-public class NamedSqmFunctionTemplate
-		extends AbstractSelfRenderingFunctionTemplate
-		implements SelfRenderingFunctionSupport {
-	private final String functionName;
-	private final boolean useParenthesesWhenNoArgs;
-
-	public NamedSqmFunctionTemplate(
-			String functionName,
-			boolean useParenthesesWhenNoArgs,
-			ArgumentsValidator argumentsValidator,
-			FunctionReturnTypeResolver returnTypeResolver) {
-		this( functionName, useParenthesesWhenNoArgs, argumentsValidator, returnTypeResolver, functionName );
-	}
-
-	public NamedSqmFunctionTemplate(
-			String functionName,
-			boolean useParenthesesWhenNoArgs,
-			ArgumentsValidator argumentsValidator,
-			FunctionReturnTypeResolver returnTypeResolver,
-			String name) {
-		super( name, returnTypeResolver, argumentsValidator );
-
-		this.functionName = functionName;
-		this.useParenthesesWhenNoArgs = useParenthesesWhenNoArgs;
-	}
-
-	/**
-	 * Function name accessor
-	 *
-	 * @return The function name.
-	 */
-	public String getName() {
-		return functionName;
-	}
-
-	@Override
-	protected SelfRenderingFunctionSupport getRenderingFunctionSupport(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<?> impliedResultType,
-			QueryEngine queryEngine) {
-		return this;
-	}
-
-	@Override
-	public void render(
-			SqlAppender sqlAppender,
-			List<SqlAstNode> sqlAstArguments,
-			SqlAstWalker walker,
-			SessionFactoryImplementor sessionFactory) {
-		final boolean useParens = useParenthesesWhenNoArgs || !sqlAstArguments.isEmpty();
-
-		sqlAppender.appendSql( functionName );
-		if ( useParens ) {
-			sqlAppender.appendSql( "(" );
-		}
-
-		boolean firstPass = true;
-		for ( SqlAstNode sqlAstArgument : sqlAstArguments ) {
-			if ( !firstPass ) {
-				sqlAppender.appendSql( ", " );
-			}
-			renderArgument( sqlAppender, sqlAstArgument, walker, sessionFactory );
-			firstPass = false;
-		}
-
-		if ( useParens ) {
-			sqlAppender.appendSql( ")" );
-		}
-	}
-
-	/**
-	 * Called from {@link #render} to render an argument.
-	 *
-	 * @param sqlAppender The sql appender to append the rendered argument.
-	 * @param sqlAstArgument The argument being processed.
-	 * @param walker The walker to use for rendering {@link SqlAstNode} expressions
-	 * @param sessionFactory The session factory
-	 */
-	protected void renderArgument(
-			SqlAppender sqlAppender,
-			SqlAstNode sqlAstArgument,
-			SqlAstWalker walker,
-			SessionFactoryImplementor sessionFactory) {
-		sqlAstArgument.accept( walker );
-	}
-
-	@Override
-	public String toString() {
-		return String.format(
-				Locale.ROOT,
-				"NamedSqmFunctionTemplate(%s)",
-				functionName
-		);
-	}
-
-}

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/spi/PairedFunctionTemplate.java

@@ -1,66 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
- * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
- */
-package org.hibernate.query.sqm.produce.function.spi;
-
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.produce.function.SqmFunctionTemplate;
-import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
-import org.hibernate.query.sqm.produce.function.internal.SelfRenderingSqmFunction;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-
-import java.util.List;
-
-/**
- * @author Gavin King
- */
-public class PairedFunctionTemplate extends AbstractSqmFunctionTemplate {
-
-	private SqmFunctionTemplate binaryFunction;
-	private SqmFunctionTemplate ternaryFunction;
-
-	public PairedFunctionTemplate(
-			SqmFunctionTemplate binaryFunction,
-			SqmFunctionTemplate ternaryFunction) {
-		super( StandardArgumentsValidators.between( 2, 3 ) );
-		this.binaryFunction = binaryFunction;
-		this.ternaryFunction = ternaryFunction;
-	}
-
-	public static void register(
-			QueryEngine queryEngine,
-			String name,
-			AllowableFunctionReturnType type,
-			String pattern2,
-			String pattern3) {
-		queryEngine.getSqmFunctionRegistry().register(
-				name,
-				new PairedFunctionTemplate(
-						queryEngine.getSqmFunctionRegistry()
-								.patternTemplateBuilder( name, pattern2 )
-								.setExactArgumentCount( 2 )
-								.setInvariantType( type)
-								.template(),
-						queryEngine.getSqmFunctionRegistry()
-								.patternTemplateBuilder( name, pattern3 )
-								.setExactArgumentCount( 3 )
-								.setInvariantType( type )
-								.template()
-				)
-		);
-	}
-
-
-	@Override
-	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine) {
-		return ( arguments.size()<3 ? binaryFunction : ternaryFunction )
-				.makeSqmFunctionExpression( arguments, impliedResultType, queryEngine );
-	}
-}

hibernate-core/src/main/java/org/hibernate/query/sqm/spi/BaseSemanticQueryWalker.java

@@ -8,12 +8,6 @@ package org.hibernate.query.sqm.spi;
 
 import org.hibernate.NotYetImplementedFor6Exception;
 import org.hibernate.query.sqm.SemanticQueryWalker;
-import org.hibernate.query.sqm.function.SqmCastTarget;
-import org.hibernate.query.sqm.function.SqmDistinct;
-import org.hibernate.query.sqm.function.SqmExtractUnit;
-import org.hibernate.query.sqm.function.SqmFunction;
-import org.hibernate.query.sqm.function.SqmStar;
-import org.hibernate.query.sqm.function.SqmTrimSpecification;
 import org.hibernate.query.sqm.tree.cte.SqmCteConsumer;
 import org.hibernate.query.sqm.tree.cte.SqmCteStatement;
 import org.hibernate.query.sqm.tree.delete.SqmDeleteStatement;
@@ -34,19 +28,26 @@ import org.hibernate.query.sqm.tree.expression.JpaCriteriaParameter;
 import org.hibernate.query.sqm.tree.expression.SqmBinaryArithmetic;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSearched;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSimple;
+import org.hibernate.query.sqm.tree.expression.SqmCastTarget;
+import org.hibernate.query.sqm.tree.expression.SqmCoalesce;
 import org.hibernate.query.sqm.tree.expression.SqmCollectionSize;
-import org.hibernate.query.sqm.tree.expression.SqmParameterizedEntityType;
 import org.hibernate.query.sqm.tree.expression.SqmEnumLiteral;
 import org.hibernate.query.sqm.tree.expression.SqmExpression;
 import org.hibernate.query.sqm.tree.expression.SqmFieldLiteral;
+import org.hibernate.query.sqm.tree.expression.SqmFunction;
 import org.hibernate.query.sqm.tree.expression.SqmLiteral;
 import org.hibernate.query.sqm.tree.expression.SqmLiteralEntityType;
 import org.hibernate.query.sqm.tree.expression.SqmNamedParameter;
+import org.hibernate.query.sqm.tree.expression.SqmParameterizedEntityType;
 import org.hibernate.query.sqm.tree.expression.SqmPathEntityType;
 import org.hibernate.query.sqm.tree.expression.SqmPositionalParameter;
 import org.hibernate.query.sqm.tree.expression.SqmRestrictedSubQueryExpression;
 import org.hibernate.query.sqm.tree.expression.SqmTuple;
 import org.hibernate.query.sqm.tree.expression.SqmUnaryOperation;
+import org.hibernate.query.sqm.tree.expression.SqmDistinct;
+import org.hibernate.query.sqm.tree.expression.SqmExtractUnit;
+import org.hibernate.query.sqm.tree.expression.SqmStar;
+import org.hibernate.query.sqm.tree.expression.SqmTrimSpecification;
 import org.hibernate.query.sqm.tree.from.SqmAttributeJoin;
 import org.hibernate.query.sqm.tree.from.SqmCrossJoin;
 import org.hibernate.query.sqm.tree.from.SqmEntityJoin;
@@ -81,7 +82,6 @@ import org.hibernate.query.sqm.tree.update.SqmAssignment;
 import org.hibernate.query.sqm.tree.update.SqmSetClause;
 import org.hibernate.query.sqm.tree.update.SqmUpdateStatement;
 import org.hibernate.service.ServiceRegistry;
-import org.hibernate.sql.ast.tree.expression.Expression;
 
 /**
  * Base support for an SQM walker
@@ -494,6 +494,11 @@ public class BaseSemanticQueryWalker implements SemanticQueryWalker<Object> {
 		return castTarget;
 	}
 
+	@Override
+	public Object visitCoalesce(SqmCoalesce sqmCoalesce) {
+		return sqmCoalesce;
+	}
+
 	@Override
 	public Object visitTrimSpecification(SqmTrimSpecification trimSpecification) {
 		return trimSpecification;

hibernate-core/src/main/java/org/hibernate/query/sqm/sql/BaseSqmToSqlAstConverter.java

@@ -37,7 +37,7 @@ import org.hibernate.query.spi.QueryParameterImplementor;
 import org.hibernate.query.sqm.InterpretationException;
 import org.hibernate.query.sqm.SqmExpressable;
 import org.hibernate.query.sqm.SqmPathSource;
-import org.hibernate.query.sqm.function.SqmFunction;
+import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
 import org.hibernate.query.sqm.internal.DomainParameterXref;
 import org.hibernate.query.sqm.internal.SqmMappingModelHelper;
 import org.hibernate.query.sqm.spi.BaseSemanticQueryWalker;
@@ -66,6 +66,7 @@ import org.hibernate.query.sqm.tree.expression.SqmCaseSimple;
 import org.hibernate.query.sqm.tree.expression.SqmEnumLiteral;
 import org.hibernate.query.sqm.tree.expression.SqmExpression;
 import org.hibernate.query.sqm.tree.expression.SqmFieldLiteral;
+import org.hibernate.query.sqm.tree.expression.SqmFunction;
 import org.hibernate.query.sqm.tree.expression.SqmJpaCriteriaParameterWrapper;
 import org.hibernate.query.sqm.tree.expression.SqmLiteral;
 import org.hibernate.query.sqm.tree.expression.SqmNamedParameter;
@@ -924,42 +925,27 @@ public abstract class BaseSqmToSqlAstConverter
 	}
 
 
-	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-	// non-standard functions
-
-
 	@Override
-	public Object visitFunction(SqmFunction sqmFunction) {
+	public Expression visitFunction(SqmFunction sqmFunction) {
-		throw new NotYetImplementedFor6Exception( getClass() );
+		final SqmFunctionDescriptor functionDescriptor = creationContext.getSessionFactory()
-//		shallownessStack.push( Shallowness.FUNCTION );
+				.getQueryEngine()
-//		try {
+				.getSqmFunctionRegistry()
-//			return new NonStandardFunction(
+				.findFunctionDescriptor( sqmFunction.getFunctionName() );
-//					sqmFunction.getFunctionName(),
+
-//					determineValueMapping( sqmFunction ),
+		shallownessStack.push( Shallowness.FUNCTION );
-//					visitArguments( sqmFunction.getArguments() )
+		try {
-//			);
+			return functionDescriptor.generateSqlExpression(
-//		}
+					sqmFunction.getFunctionName(),
-//		finally {
+					sqmFunction.getArguments(),
-//			shallownessStack.pop();
+					inferableTypeAccessStack.getCurrent(),
-//		}
+					this,
+					this
+			);
+		}
+		finally {
+			shallownessStack.pop();
+		}
 	}
-
-//	private List<Expression> visitArguments(List<SqmExpression> sqmArguments) {
-//		if ( sqmArguments == null || sqmArguments.isEmpty() ) {
-//			return Collections.emptyList();
-//		}
-//
-//		final ArrayList<Expression> sqlAstArguments = new ArrayList<>();
-//		for ( SqmExpression sqmArgument : sqmArguments ) {
-//			sqlAstArguments.add( (Expression) sqmArgument.accept( this ) );
-//		}
-//
-//		return sqlAstArguments;
-//	}
-
-
-	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-	// standard functions
 
 
 //	@Override

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/expression/SqmCastTarget.java

@@ -4,12 +4,12 @@
  * License: GNU Lesser General Public License (LGPL), version 2.1 or later
  * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
  */
-package org.hibernate.query.sqm.function;
+package org.hibernate.query.sqm.tree.expression;
 
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.sqm.NodeBuilder;
-import org.hibernate.query.sqm.SqmExpressable;
 import org.hibernate.query.sqm.SemanticQueryWalker;
+import org.hibernate.query.sqm.SqmExpressable;
 import org.hibernate.query.sqm.tree.AbstractSqmNode;
 import org.hibernate.query.sqm.tree.SqmTypedNode;
 import org.hibernate.query.sqm.tree.SqmVisitableNode;
@@ -25,17 +25,13 @@ public class SqmCastTarget<T> extends AbstractSqmNode implements SqmTypedNode<T>
 		this.type = type;
 	}
 
-	public AllowableFunctionReturnType<T> getType() {
-		return type;
-	}
-
-	@Override
-	public <T> T accept(SemanticQueryWalker<T> walker) {
-		return walker.visitCastTarget(this);
-	}
-
 	@Override
 	public SqmExpressable<T> getNodeType() {
 		return type;
 	}
+
+	@Override
+	public <X> X accept(SemanticQueryWalker<X> walker) {
+		return walker.visitCastTarget( this );
+	}
 }

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/expression/SqmCoalesce.java

@@ -4,11 +4,10 @@
  * License: GNU Lesser General Public License (LGPL), version 2.1 or later
  * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
  */
-package org.hibernate.query.sqm.function;
+package org.hibernate.query.sqm.tree.expression;
 
 import java.util.ArrayList;
 import java.util.List;
-
 import javax.persistence.criteria.Expression;
 
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
@@ -16,38 +15,39 @@ import org.hibernate.query.criteria.JpaCoalesce;
 import org.hibernate.query.criteria.JpaExpression;
 import org.hibernate.query.sqm.NodeBuilder;
 import org.hibernate.query.sqm.SemanticQueryWalker;
-import org.hibernate.query.sqm.produce.function.SqmFunctionTemplate;
+import org.hibernate.query.sqm.SqmExpressable;
-import org.hibernate.query.sqm.tree.expression.AbstractSqmExpression;
+import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
-import org.hibernate.query.sqm.tree.expression.SqmExpression;
-import org.hibernate.query.sqm.sql.internal.DomainResultProducer;
 
 /**
- * Specialized CASE statement for resolving the first non-null value in a list of values
- *
  * @author Steve Ebersole
  * @author Gavin King
  */
-public class SqmCoalesce<T> extends AbstractSqmExpression<T> implements JpaCoalesce<T>, DomainResultProducer<T> {
+public class SqmCoalesce<T> extends AbstractSqmExpression<T> implements JpaCoalesce<T> {
-
+	private final SqmFunctionDescriptor functionDescriptor;
-	private List<SqmExpression<? extends T>> arguments = new ArrayList<>();
+	private final List<SqmExpression<? extends T>> arguments;
-	private SqmFunctionTemplate coalesceFunction;
 
 	public SqmCoalesce(NodeBuilder nodeBuilder) {
 		this( null, nodeBuilder );
 	}
 
-	public SqmCoalesce(AllowableFunctionReturnType<T> type, NodeBuilder nodeBuilder) {
+	public SqmCoalesce(SqmExpressable<T> type, NodeBuilder nodeBuilder) {
 		super( type, nodeBuilder );
-		coalesceFunction = nodeBuilder.getQueryEngine().getSqmFunctionRegistry().findFunctionTemplate("coalesce");
+		functionDescriptor = nodeBuilder.getQueryEngine().getSqmFunctionRegistry().findFunctionDescriptor( "coalesce" );
+		this.arguments = new ArrayList<>();
+	}
+
+	public SqmCoalesce(SqmExpressable<T> type, int numberOfArguments, NodeBuilder nodeBuilder) {
+		super( type, nodeBuilder );
+		functionDescriptor = nodeBuilder.getQueryEngine().getSqmFunctionRegistry().findFunctionDescriptor( "coalesce" );
+		this.arguments = new ArrayList<>( numberOfArguments );
+	}
+
+	public SqmFunctionDescriptor getFunctionDescriptor() {
+		return functionDescriptor;
 	}
 
 	public void value(SqmExpression<? extends T> expression) {
 		arguments.add( expression );
-
-		//TODO: improve this
-//		if ( getNodeType() == null ) {
-			setExpressableType( expression.getNodeType() );
-//		}
 	}
 
 	public List<SqmExpression<? extends T>> getArguments() {
@@ -56,13 +56,7 @@ public class SqmCoalesce<T> extends AbstractSqmExpression<T> implements JpaCoale
 
 	@Override
 	public <X> X accept(SemanticQueryWalker<X> walker) {
-		return walker.visitFunction(
+		return walker.visitCoalesce( this );
-				coalesceFunction.makeSqmFunctionExpression(
-						new ArrayList<>(arguments),
-						(AllowableFunctionReturnType<?>) getNodeType(),
-						nodeBuilder().getQueryEngine()
-				)
-		);
 	}
 
 	@Override

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/expression/SqmDistinct.java

@@ -4,7 +4,7 @@
  * License: GNU Lesser General Public License (LGPL), version 2.1 or later
  * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
  */
-package org.hibernate.query.sqm.function;
+package org.hibernate.query.sqm.tree.expression;
 
 import org.hibernate.query.sqm.NodeBuilder;
 import org.hibernate.query.sqm.SqmExpressable;

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/expression/SqmExpression.java

@@ -13,7 +13,6 @@ import java.util.function.Consumer;
 import javax.persistence.criteria.Expression;
 
 import org.hibernate.annotations.Remove;
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.metamodel.model.domain.DomainType;
 import org.hibernate.query.criteria.JpaExpression;
 import org.hibernate.query.sqm.SqmExpressable;
@@ -100,11 +99,14 @@ public interface SqmExpression<T> extends SqmSelectableNode<T>, JpaExpression<T>
 	SqmPredicate in(Expression<Collection<?>> values);
 
 	default <X> SqmExpression<X> castAs(DomainType<X> type) {
-		return nodeBuilder().getQueryEngine()
+		return new SqmFunction<>(
+				"cast",
+				nodeBuilder().getQueryEngine()
 						.getSqmFunctionRegistry()
-				.findFunctionTemplate( "cast" )
+						.findFunctionDescriptor( "cast" ),
-				.makeSqmFunctionExpression( this, ( AllowableFunctionReturnType<X>) type, nodeBuilder().getQueryEngine() );
+				type,
+				nodeBuilder()
+		);
 	}
 
-
 }

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/expression/SqmExtractUnit.java

@@ -4,7 +4,7 @@
  * License: GNU Lesser General Public License (LGPL), version 2.1 or later
  * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
  */
-package org.hibernate.query.sqm.function;
+package org.hibernate.query.sqm.tree.expression;
 
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.sqm.NodeBuilder;

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/expression/SqmFunction.java

@@ -0,0 +1,77 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.query.sqm.tree.expression;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.hibernate.query.criteria.JpaFunction;
+import org.hibernate.query.sqm.NodeBuilder;
+import org.hibernate.query.sqm.SemanticQueryWalker;
+import org.hibernate.query.sqm.SqmExpressable;
+import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
+import org.hibernate.query.sqm.sql.internal.DomainResultProducer;
+import org.hibernate.query.sqm.tree.SqmNode;
+import org.hibernate.query.sqm.tree.SqmVisitableNode;
+
+/**
+ * An SQM function
+ *
+ * @author Steve Ebersole
+ */
+public class SqmFunction<T> extends AbstractSqmExpression<T> implements JpaFunction<T>, DomainResultProducer<T> {
+	// this function-name is the one used to resolve the descriptor from the function registry (which may or may not be a db function name)
+	private final String functionName;
+	private final SqmFunctionDescriptor functionDescriptor;
+
+	private List<SqmVisitableNode> arguments;
+
+	public SqmFunction(
+			String functionName,
+			SqmFunctionDescriptor functionDescriptor,
+			SqmExpressable<T> type,
+			NodeBuilder criteriaBuilder) {
+		super( type, criteriaBuilder );
+		this.functionName = functionName;
+		this.functionDescriptor = functionDescriptor;
+	}
+
+	public SqmFunction(
+			String functionName,
+			SqmFunctionDescriptor functionDescriptor,
+			SqmExpressable<T> type,
+			List<SqmVisitableNode> arguments,
+			NodeBuilder criteriaBuilder) {
+		super( type, criteriaBuilder );
+		this.functionName = functionName;
+		this.functionDescriptor = functionDescriptor;
+		this.arguments = arguments;
+	}
+
+	@Override
+	public String getFunctionName() {
+		return functionName;
+	}
+
+	public List<SqmVisitableNode> getArguments() {
+		return arguments;
+	}
+
+	public void addArgument(SqmVisitableNode argument) {
+		assert argument != null;
+
+		if ( arguments == null ) {
+			arguments = new ArrayList<>();
+		}
+		arguments.add( argument );
+	}
+
+	@Override
+	public <X> X accept(SemanticQueryWalker<X> walker) {
+		return walker.visitFunction( this );
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/expression/SqmStar.java

@@ -4,11 +4,10 @@
  * License: GNU Lesser General Public License (LGPL), version 2.1 or later
  * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
  */
-package org.hibernate.query.sqm.function;
+package org.hibernate.query.sqm.tree.expression;
 
 import org.hibernate.query.sqm.NodeBuilder;
 import org.hibernate.query.sqm.SemanticQueryWalker;
-import org.hibernate.query.sqm.tree.expression.AbstractSqmExpression;
 
 /**
  * @author Gavin King

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/expression/SqmTrimSpecification.java

@@ -4,7 +4,7 @@
  * License: GNU Lesser General Public License (LGPL), version 2.1 or later
  * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
  */
-package org.hibernate.query.sqm.function;
+package org.hibernate.query.sqm.tree.expression;
 
 import org.hibernate.query.TrimSpec;
 import org.hibernate.query.sqm.NodeBuilder;

hibernate-core/src/test/java/org/hibernate/orm/test/query/hql/CaseExpressionsTest.java

@@ -8,16 +8,15 @@ package org.hibernate.orm.test.query.hql;
 
 import org.hibernate.orm.test.query.sqm.BaseSqmUnitTest;
 import org.hibernate.orm.test.query.sqm.domain.Person;
-import org.hibernate.query.sqm.function.SqmCoalesce;
 import org.hibernate.query.sqm.tree.domain.SqmPath;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSearched;
 import org.hibernate.query.sqm.tree.expression.SqmCaseSimple;
+import org.hibernate.query.sqm.tree.expression.SqmFunction;
 import org.hibernate.query.sqm.tree.expression.SqmLiteral;
 import org.hibernate.query.sqm.tree.predicate.SqmComparisonPredicate;
 import org.hibernate.query.sqm.tree.select.SqmSelectStatement;
 import org.hibernate.query.sqm.tree.select.SqmSelectableNode;
 
-import org.hibernate.testing.orm.junit.FailureExpected;
 import org.hibernate.testing.orm.junit.TestingUtil;
 import org.junit.jupiter.api.Test;
 
@@ -87,7 +86,6 @@ public class CaseExpressionsTest extends BaseSqmUnitTest {
 	}
 
 	@Test
-	@FailureExpected( reason = "Support for functions not yet defined" )
 	public void testBasicCoalesceExpression() {
 		SqmSelectStatement select = interpretSelect(
 				"select coalesce(p.nickName, p.mate.nickName) from Person p"
@@ -95,9 +93,9 @@ public class CaseExpressionsTest extends BaseSqmUnitTest {
 
 		assertThat( select.getQuerySpec().getSelectClause().getSelections(), hasSize( 1 ) );
 
-		final SqmCoalesce<?> coalesce = TestingUtil.cast(
+		final SqmFunction<?> coalesce = TestingUtil.cast(
 				select.getQuerySpec().getSelectClause().getSelections().get( 0 ).getSelectableNode(),
-				SqmCoalesce.class
+				SqmFunction.class
 		);
 
 		assertThat( coalesce.getArguments(), hasSize( 2 ) );
@@ -105,7 +103,6 @@ public class CaseExpressionsTest extends BaseSqmUnitTest {
 	}
 
 	@Test
-	@FailureExpected( reason = "Support for functions not yet defined" )
 	public void testBasicNullifExpression() {
 		SqmSelectStatement select = interpretSelect(
 				"select nullif(p.nickName, p.mate.nickName) from Person p"