HHH-8864 count distinct tuples for postgres and h2

hibernate-core/src/main/java/org/hibernate/dialect/Dialect.java

@@ -2576,6 +2576,15 @@ public abstract class Dialect implements ConversionContext {
 		return true;
 	}
 	
+	/**
+	 * If {@link #supportsTupleDistinctCounts()} is true, does the Dialect require the tuple to be wrapped with parens?
+	 * 
+	 * @return boolean
+	 */
+	public boolean requiresParensForTupleDistinctCounts() {
+		return false;
+	}
+
 	/**
 	 * Return the limit that the underlying database places on the number elements in an {@code IN} predicate.
 	 * If the database defines no such limits, simply return zero or less-than-zero.

hibernate-core/src/main/java/org/hibernate/dialect/H2Dialect.java

@@ -413,8 +413,8 @@ public class H2Dialect extends Dialect {
 	}
 
 	@Override
-	public boolean supportsTupleDistinctCounts() {
+	public boolean requiresParensForTupleDistinctCounts() {
-		return false;
+		return true;
 	}
 
 	@Override

hibernate-core/src/main/java/org/hibernate/dialect/PostgreSQL81Dialect.java

@@ -361,8 +361,8 @@ public class PostgreSQL81Dialect extends Dialect {
 	}
 
 	@Override
-	public boolean supportsTupleDistinctCounts() {
+	public boolean requiresParensForTupleDistinctCounts() {
-		return false;
+		return true;
 	}
 
 	@Override

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

@@ -30,6 +30,7 @@ import java.util.Map;
 
 import org.hibernate.MappingException;
 import org.hibernate.QueryException;
+import org.hibernate.dialect.Dialect;
 import org.hibernate.engine.spi.Mapping;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.type.StandardBasicTypes;
@@ -58,15 +59,16 @@ public class StandardAnsiSqlAggregationFunctions {
 		public String render(Type firstArgumentType, List arguments, SessionFactoryImplementor factory) {
 			if ( arguments.size() > 1 ) {
 				if ( "distinct".equalsIgnoreCase( arguments.get( 0 ).toString() ) ) {
-					return renderCountDistinct( arguments );
+					return renderCountDistinct( arguments, factory.getDialect() );
 				}
 			}
 			return super.render( firstArgumentType, arguments, factory );
 		}
 
-		private String renderCountDistinct(List arguments) {
+		private String renderCountDistinct(List arguments, Dialect dialect) {
 			final StringBuilder buffer = new StringBuilder();
 			buffer.append( "count(distinct " );
+			if (dialect.requiresParensForTupleDistinctCounts()) buffer.append("(");
 			String sep = "";
 			final Iterator itr = arguments.iterator();
 			// intentionally skip first
@@ -75,6 +77,7 @@ public class StandardAnsiSqlAggregationFunctions {
 				buffer.append( sep ).append( itr.next() );
 				sep = ", ";
 			}
+			if (dialect.requiresParensForTupleDistinctCounts()) buffer.append(")");
 			return buffer.append( ")" ).toString();
 		}
 	}

hibernate-core/src/main/java/org/hibernate/hql/internal/ast/tree/DotNode.java

@@ -260,7 +260,10 @@ public class DotNode extends FromReferenceNode implements DisplayableNode, Selec
 	private void initText() {
 		String[] cols = getColumns();
 		String text = StringHelper.join( ", ", cols );
-		if ( cols.length > 1 && getWalker().isComparativeExpressionClause() ) {
+		boolean countDistinct = getWalker().isInCountDistinct()
+				&& getWalker().getSessionFactoryHelper().getFactory().getDialect().requiresParensForTupleDistinctCounts();
+		if ( cols.length > 1 &&
+				( getWalker().isComparativeExpressionClause() || countDistinct ) ) {
 			text = "(" + text + ")";
 		}
 		setText( text );

hibernate-core/src/main/java/org/hibernate/hql/internal/ast/tree/IdentNode.java

@@ -27,6 +27,7 @@ package org.hibernate.hql.internal.ast.tree;
 import java.util.List;
 
 import org.hibernate.QueryException;
+import org.hibernate.dialect.Dialect;
 import org.hibernate.dialect.function.SQLFunction;
 import org.hibernate.hql.internal.antlr.HqlSqlTokenTypes;
 import org.hibernate.hql.internal.antlr.SqlTokenTypes;
@@ -173,10 +174,14 @@ public class IdentNode extends FromReferenceNode implements SelectExpression {
 			}
 		}
 
-		final boolean isInNonDistinctCount = getWalker().isInCount() && ! getWalker().isInCountDistinct();
+		final Dialect dialect = getWalker().getSessionFactoryHelper().getFactory().getDialect();
+		final boolean isInCount = getWalker().isInCount();
+		final boolean isInDistinctCount = isInCount && getWalker().isInCountDistinct();
+		final boolean isInNonDistinctCount = isInCount && ! getWalker().isInCountDistinct();
 		final boolean isCompositeValue = columnExpressions.length > 1;
 		if ( isCompositeValue ) {
-			if ( isInNonDistinctCount && ! getWalker().getSessionFactoryHelper().getFactory().getDialect().supportsTupleCounts() ) {
+			if ( isInNonDistinctCount && ! dialect.supportsTupleCounts() ) {
+				// TODO: #supportsTupleCounts currently false for all Dialects -- could this be cleaned up?
 				setText( columnExpressions[0] );
 			}
 			else {
@@ -184,7 +189,8 @@ public class IdentNode extends FromReferenceNode implements SelectExpression {
 				// avoid wrapping in parenthesis (explicit tuple treatment) if possible due to varied support for
 				// tuple syntax across databases..
 				final boolean shouldSkipWrappingInParenthesis =
-						getWalker().isInCount()
+						(isInDistinctCount && ! dialect.requiresParensForTupleDistinctCounts())
+						|| isInNonDistinctCount
 						|| getWalker().getCurrentTopLevelClauseType() == HqlSqlTokenTypes.ORDER
 						|| getWalker().getCurrentTopLevelClauseType() == HqlSqlTokenTypes.GROUP;
 				if ( ! shouldSkipWrappingInParenthesis ) {

hibernate-core/src/test/java/org/hibernate/test/cid/CompositeIdTest.java

@@ -23,24 +23,25 @@
  */
 package org.hibernate.test.cid;
 
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
 import java.math.BigDecimal;
 import java.util.Calendar;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 
-import org.junit.Test;
-
 import org.hibernate.Hibernate;
 import org.hibernate.Session;
 import org.hibernate.Transaction;
 import org.hibernate.engine.query.spi.HQLQueryPlan;
+import org.hibernate.exception.SQLGrammarException;
 import org.hibernate.hql.spi.QueryTranslator;
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
-
+import org.junit.Test;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
 
 /**
  * @author Gavin King
@@ -93,6 +94,45 @@ public class CompositeIdTest extends BaseCoreFunctionalTestCase {
 		final String countExpressionFragment = generatedSql.substring( countExpressionListStart+6, countExpressionListEnd+1 );
 		assertTrue( countExpressionFragment.startsWith( "distinct" ) );
 		assertTrue( countExpressionFragment.contains( "," ) );
+		
+		Session s = openSession();
+		s.beginTransaction();
+		Customer c = new Customer();
+		c.setCustomerId( "1" );
+		c.setAddress("123 somewhere");
+		c.setName("Brett");
+		Order o1 = new Order( c );
+		o1.setOrderDate( Calendar.getInstance() );
+		Order o2 = new Order( c );
+		o2.setOrderDate( Calendar.getInstance() );
+		s.persist( c );
+		s.persist( o1 );
+		s.persist( o2 );
+		s.getTransaction().commit();
+		s.clear();
+
+		s.beginTransaction();
+		try {
+			long count = ( Long ) s.createQuery( "select count(distinct o) FROM Order o" ).uniqueResult();
+			if ( ! getDialect().supportsTupleDistinctCounts() ) {
+				fail( "expected SQLGrammarException" );
+			}
+			assertEquals( 2l, count );
+		}
+		catch ( SQLGrammarException e ) {
+			if ( getDialect().supportsTupleDistinctCounts() ) {
+				throw e;
+			}
+		}
+		s.getTransaction().commit();
+		s.close();
+		
+		s = openSession();
+		s.beginTransaction();
+		s.createQuery("delete from Order").executeUpdate();
+		s.createQuery("delete from Customer").executeUpdate();
+		s.getTransaction().commit();
+		s.close();
 	}
 
 	@Test