hibernate/hibernate-orm · error · QueryException

Can't emulate json_objectagg 'with unique keys' clause.

Error message

Can't emulate json_objectagg 'with unique keys' clause.

What it means

Error "Can't emulate json_objectagg 'with unique keys' clause." thrown in hibernate/hibernate-orm.

Source

Thrown at hibernate-core/src/main/java/org/hibernate/dialect/function/json/PostgreSQLJsonObjectAggFunction.java:42

	public PostgreSQLJsonObjectAggFunction(boolean supportsStandard, TypeConfiguration typeConfiguration) {
		super( ":", true, typeConfiguration );
		this.supportsStandard = supportsStandard;
	}

	@Override
	protected void render(
			SqlAppender sqlAppender,
			JsonObjectAggArguments arguments,
			Predicate filter,
			ReturnableType<?> returnType,
			SqlAstTranslator<?> translator) {
		if ( supportsStandard ) {
			super.render( sqlAppender, arguments, filter, returnType, translator );
		}
		else {
			if ( arguments.uniqueKeysBehavior() == JsonObjectAggUniqueKeysBehavior.WITH ) {
				throw new QueryException( "Can't emulate json_objectagg 'with unique keys' clause." );
			}
			final String jsonTypeName = translator.getSessionFactory().getTypeConfiguration().getDdlTypeRegistry()
					.getTypeName( SqlTypes.JSON, translator.getSessionFactory().getJdbcServices().getDialect() );
			sqlAppender.appendSql( jsonTypeName );
			sqlAppender.appendSql( "_object_agg" );
			sqlAppender.appendSql( '(' );
			arguments.key().accept( translator );
			sqlAppender.appendSql( ',' );
			arguments.value().accept( translator );
			sqlAppender.appendSql( ')' );

			if ( filter != null ) {
				translator.getCurrentClauseStack().push( Clause.WHERE );
				sqlAppender.appendSql( " filter (where " );
				filter.accept( translator );
				if ( arguments.nullBehavior() != JsonNullBehavior.NULL ) {
					sqlAppender.appendSql( " and " );
					arguments.value().accept( translator );

View on GitHub (pinned to fad1729dce)

Solutions

1. Remove the WITH UNIQUE KEYS clause.

When it happens

Trigger: Triggered when the application calls a Hibernate dialect feature that the configured database dialect cannot provide: Can't emulate json_objectagg 'with unique keys' clause (PostgreSQL).

Common situations: Common when running against a database whose dialect lacks this capability, when a mapping or HQL/Criteria query requests unsupported functionality, or when the wrong dialect is configured for the database in use. Error: Can't emulate json_objectagg 'with unique keys' clause (PostgreSQL).

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/9a43de8e12422007. Report an issue: GitHub.