allow collation names to be quoted

documentation/src/main/asciidoc/introduction/Mapping.adoc

@@ -797,6 +797,7 @@ Here we summarize the ones we've just seen in the second half of this chapter, a
 | `@Struct` | Map an embeddable to a SQL UDT with the given name
 | `@TimeZoneStorage` | Specify how the time zone information should be persisted
 | `@JdbcType` or `@JdbcTypeCode` | Use an implementation of `JdbcType` to map an arbitrary SQL type
+| `@Collate` | Specify a collation for a column
 |===
 
 In addition, there are some configuration properties which have a _global_ affect on how basic types map to SQL column types:

documentation/src/main/asciidoc/querylanguage/Expressions.adoc

@@ -876,13 +876,17 @@ Its BNF is given by:
 [discrete]
 ===== Collations
 
-Selects a collation to be used for its string-valued argument.
+The `collate()` function selects a collation to be used for its string-valued argument.
 Collations are useful for <<relational-comparisons,binary comparisons>> with `<` or `>`, and in the <<order-by,order by clause>>.
 
 For example, `collate(p.name as ucs_basic)` specifies the SQL standard collation `ucs_basic`.
 
 IMPORTANT: Collations aren't very portable between databases.
 
+TIP: Some PostgreSQL collation names must be quoted with backticks, for example, ``collate(name as \`zh_TW.UTF-8`)``.
+
+TIP: The `@Collate` annotation may be used to specify the collation of a column, which is usually more convenient than using the `collate()` function.
+
 [[functions-numeric]]
 ==== Numeric functions
 

hibernate-core/src/main/java/org/hibernate/internal/util/StringHelper.java

@@ -742,7 +742,7 @@ public final class StringHelper {
 		final char first = name.charAt( 0 );
 		final char last = name.charAt( name.length() - 1 );
 
-		return ( ( first == last ) && ( first == '`' || first == '"' ) );
+		return first == last && ( first == '`' || first == '"' );
 	}
 
 	/**

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

@@ -39,7 +39,6 @@ import org.hibernate.grammars.hql.HqlLexer;
 import org.hibernate.grammars.hql.HqlParser;
 import org.hibernate.grammars.hql.HqlParserBaseVisitor;
 import org.hibernate.internal.util.CharSequenceHelper;
-import org.hibernate.internal.util.QuotingHelper;
 import org.hibernate.internal.util.collections.Stack;
 import org.hibernate.internal.util.collections.StandardStack;
 import org.hibernate.metamodel.CollectionClassification;
@@ -247,7 +246,10 @@ import static org.hibernate.grammars.hql.HqlParser.INTERSECT;
 import static org.hibernate.grammars.hql.HqlParser.ListaggFunctionContext;
 import static org.hibernate.grammars.hql.HqlParser.OnOverflowClauseContext;
 import static org.hibernate.grammars.hql.HqlParser.PLUS;
+import static org.hibernate.grammars.hql.HqlParser.QUOTED_IDENTIFIER;
 import static org.hibernate.grammars.hql.HqlParser.UNION;
+import static org.hibernate.internal.util.QuotingHelper.unquoteIdentifier;
+import static org.hibernate.internal.util.QuotingHelper.unquoteJavaStringLiteral;
 import static org.hibernate.internal.util.QuotingHelper.unquoteStringLiteral;
 import static org.hibernate.query.hql.internal.SqmTreeCreationHelper.extractJpaCompliantAlias;
 import static org.hibernate.query.sqm.TemporalUnit.DATE;
@@ -1953,8 +1955,8 @@ public class SemanticQueryBuilder<R> extends HqlParserBaseVisitor<Object> implem
 	public String visitNakedIdentifier(HqlParser.NakedIdentifierContext ctx) {
 		final TerminalNode node = (TerminalNode) ctx.getChild( 0 );
 		final String text = node.getText();
-		return node.getSymbol().getType() == HqlParser.QUOTED_IDENTIFIER
-				? QuotingHelper.unquoteIdentifier( text )
+		return node.getSymbol().getType() == QUOTED_IDENTIFIER
+				? unquoteIdentifier( text )
 				: text;
 	}
 
@@ -3166,9 +3168,21 @@ public class SemanticQueryBuilder<R> extends HqlParserBaseVisitor<Object> implem
 
 	@Override
 	public Object visitCollation(HqlParser.CollationContext ctx) {
-		return new SqmCollation(
-				ctx.simplePath().getText(),
-				null,
+		final StringBuilder collation = new StringBuilder();
+		final HqlParser.SimplePathContext simplePathContext = ctx.simplePath();
+		final boolean quoted = simplePathContext.getStart().getType() == QUOTED_IDENTIFIER;
+		if ( quoted ) {
+			collation.append("\"");
+		}
+		collation.append( visitIdentifier( simplePathContext.identifier() ) );
+		for ( HqlParser.SimplePathElementContext pathElementContext
+				: simplePathContext.simplePathElement() ) {
+			collation.append( visitIdentifier( pathElementContext.identifier() ) );
+		}
+		if ( quoted ) {
+			collation.append("\"");
+		}
+		return new SqmCollation( collation.toString(), null,
 				creationContext.getNodeBuilder() );
 	}
 
@@ -3721,7 +3735,7 @@ public class SemanticQueryBuilder<R> extends HqlParserBaseVisitor<Object> implem
 	}
 
 	private SqmLiteral<String> javaStringLiteral(String text) {
-		String unquoted = QuotingHelper.unquoteJavaStringLiteral( text );
+		String unquoted = unquoteJavaStringLiteral( text );
 		return new SqmLiteral<>(
 				unquoted,
 				resolveExpressibleTypeBasic( String.class ),

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

@@ -51,6 +51,12 @@ public class CollateTests {
 
 	@Test @RequiresDialect(PostgreSQLDialect.class)
 	public void testCollatePostgreSQL(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					session.createQuery("from EntityOfBasics e where e.theString is not null order by collate(e.theString as `ucs_basic`)").getResultList();
+					assertThat( session.createQuery("select collate('bar' as `ucs_basic`) < 'foo'").getSingleResult(), is(true) );
+				}
+		);
 		scope.inTransaction(
 				session -> {
 					session.createQuery("from EntityOfBasics e where e.theString is not null order by collate(e.theString as ucs_basic)").getResultList();