hibernate/hibernate-orm · error · UnsupportedOperationException

Can't emulate '{}join' in a DB2 recursive query part

Error message

Can't emulate '{}join' in a DB2 recursive query part

What it means

Error "Can't emulate '{}join' in a DB2 recursive query part" thrown in hibernate/hibernate-orm.

Source

Thrown at hibernate-core/src/main/java/org/hibernate/dialect/sql/ast/DB2SqlAstTranslator.java:91

	}

	@Override
	protected void renderTableReferenceJoins(TableGroup tableGroup, LockMode lockMode, int swappedJoinIndex, boolean forceLeftJoin) {
		// When we are in a recursive CTE, we can't render joins on DB2...
		// See https://modern-sql.com/feature/with-recursive/db2/error-345-state-42836
		if ( isInRecursiveQueryPart() ) {
			final List<TableReferenceJoin> joins = tableGroup.getTableReferenceJoins();
			if ( joins == null || joins.isEmpty() ) {
				return;
			}

			for ( TableReferenceJoin tableJoin : joins ) {
				switch ( tableJoin.getJoinType() ) {
					case CROSS:
					case INNER:
						break;
					default:
						throw new UnsupportedOperationException( "Can't emulate '" + tableJoin.getJoinType().getText() + "join' in a DB2 recursive query part" );
				}
				appendSql( COMMA_SEPARATOR_CHAR );

				renderNamedTableReference( tableJoin.getJoinedTableReference(), lockMode );

				if ( tableJoin.getPredicate() != null && !tableJoin.getPredicate().isEmpty() ) {
					addAdditionalWherePredicate( tableJoin.getPredicate() );
				}
			}
		}
		else {
			super.renderTableReferenceJoins( tableGroup, lockMode, swappedJoinIndex, forceLeftJoin );
		}
	}

	@Override
	protected void renderTableGroupJoin(TableGroupJoin tableGroupJoin, List<TableGroupJoin> tableGroupJoinCollector) {
		if ( isInRecursiveQueryPart() ) {

View on GitHub (pinned to fad1729dce)

Solutions

1. Restructure the recursive query so the join does not appear inside the recursive part on DB2
2. Move the joined table out of the recursive CTE and join it in the outer query

When it happens

Trigger: Thrown at hibernate-core/src/main/java/org/hibernate/dialect/sql/ast/DB2SqlAstTranslator.java:91 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/17042f21608fe50c. Report an issue: GitHub.