HHH-18497 Add xmlagg function

Author: beikov

documentation/src/main/asciidoc/userguide/chapters/query/hql/QueryLanguage.adoc

@@ -2178,6 +2178,7 @@ it is necessary to enable the `hibernate.query.hql.xml_functions_enabled` config
 | `xmlpi()` | Constructs an XML processing instruction
 | `xmlquery()` | Extracts content from XML document using XQuery or XPath
 | `xmlexists()` | Checks if an XQuery or XPath expression exists in an XML document
+| `xmlagg()` | Aggregates XML elements by concatenation
 |===
 
 
@@ -2350,6 +2351,30 @@ include::{xml-example-dir-hql}/XmlExistsTest.java[tags=hql-xmlexists-example]
 
 WARNING: SAP HANA, MySQL, MariaDB and HSQLDB do not support this function.
 
+[[hql-xmlagg-function]]
+===== `xmlagg()`
+
+Aggregates XML elements by concatenation.
+
+[[hql-xmlexists-bnf]]
+[source, antlrv4, indent=0]
+----
+include::{extrasdir}/xmlagg_bnf.txt[]
+----
+
+This aggregate function is similar to an <<hql-aggregate-functions-orderedset,_ordered set aggregate function_>>
+since it allows to specify the order in which elements are aggregated, but uses a special syntax.
+
+[[hql-xmlagg-example]]
+====
+[source, java, indent=0]
+----
+include::{xml-example-dir-hql}/XmlAggTest.java[tags=hql-xmlagg-example]
+----
+====
+
+WARNING: SAP HANA, MySQL, MariaDB and HSQLDB do not support this function.
+
 [[hql-user-defined-functions]]
 ==== Native and user-defined functions
 

documentation/src/main/asciidoc/userguide/chapters/query/hql/extras/xmlagg_bnf.txt

@@ -0,0 +1 @@
+"xmlagg(" expression orderByClause? ")" filterClause? overClause?

hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/DB2LegacyDialect.java

@@ -448,6 +448,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlpi();
 		functionFactory.xmlquery_db2();
 		functionFactory.xmlexists();
+		functionFactory.xmlagg();
 	}
 
 	@Override

hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/OracleLegacyDialect.java

@@ -333,6 +333,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlpi();
 		functionFactory.xmlquery_oracle();
 		functionFactory.xmlexists();
+		functionFactory.xmlagg();
 	}
 
 	@Override

hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/PostgreSQLLegacyDialect.java

@@ -676,6 +676,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlpi();
 		functionFactory.xmlquery_postgresql();
 		functionFactory.xmlexists();
+		functionFactory.xmlagg();
 
 		if ( getVersion().isSameOrAfter( 9, 4 ) ) {
 			functionFactory.makeDateTimeTimestamp();

hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/SQLServerLegacyDialect.java

@@ -420,6 +420,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlpi_sqlserver();
 		functionFactory.xmlquery_sqlserver();
 		functionFactory.xmlexists_sqlserver();
+		functionFactory.xmlagg_sqlserver();
 		if ( getVersion().isSameOrAfter( 14 ) ) {
 			functionFactory.listagg_stringAggWithinGroup( "varchar(max)" );
 			functionFactory.jsonArrayAgg_sqlserver( getVersion().isSameOrAfter( 16 ) );

hibernate-core/src/main/antlr/org/hibernate/grammars/hql/HqlLexer.g4

@@ -330,6 +330,7 @@ WITH				: [wW] [iI] [tT] [hH];
 WITHIN				: [wW] [iI] [tT] [hH] [iI] [nN];
 WITHOUT				: [wW] [iI] [tT] [hH] [oO] [uU] [tT];
 WRAPPER				: [wW] [rR] [aA] [pP] [pP] [eE] [rR];
+XMLAGG				: [xX] [mM] [lL] [aA] [gG] [gG];
 XMLATTRIBUTES		: [xX] [mM] [lL] [aA] [tT] [tT] [rR] [iI] [bB] [uU] [tT] [eE] [sS];
 XMLELEMENT			: [xX] [mM] [lL] [eE] [lL] [eE] [mM] [eE] [nN] [tT];
 XMLEXISTS			: [xX] [mM] [lL] [eE] [xX] [iI] [sS] [tT] [sS];

hibernate-core/src/main/antlr/org/hibernate/grammars/hql/HqlParser.g4

@@ -1723,6 +1723,7 @@ xmlFunction
 	| xmlpiFunction
 	| xmlqueryFunction
 	| xmlexistsFunction
+	| xmlaggFunction
 	;
 
 /**
@@ -1767,6 +1768,13 @@ xmlexistsFunction
 	: XMLEXISTS LEFT_PAREN expression PASSING expression RIGHT_PAREN
 	;
 
+/**
+ * The 'xmlexists()' function
+ */
+xmlaggFunction
+	: XMLAGG LEFT_PAREN expression orderByClause? RIGHT_PAREN filterClause? overClause?
+	;
+
 /**
  * Support for "soft" keywords which may be used as identifiers
  *
@@ -1973,6 +1981,7 @@ xmlexistsFunction
 	| WITHIN
 	| WITHOUT
 	| WRAPPER
+	| XMLAGG
 	| XMLATTRIBUTES
 	| XMLELEMENT
 	| XMLEXISTS

hibernate-core/src/main/java/org/hibernate/dialect/DB2Dialect.java

@@ -433,6 +433,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlpi();
 		functionFactory.xmlquery_db2();
 		functionFactory.xmlexists();
+		functionFactory.xmlagg();
 	}
 
 	@Override

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

@@ -423,6 +423,7 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
 		functionFactory.xmlpi();
 		functionFactory.xmlquery_oracle();
 		functionFactory.xmlexists();
+		functionFactory.xmlagg();
 	}
 
 	@Override