hibernate/hibernate-orm · error · QueryException

Can't emulate on error clause on SingleStore

Error message

Can't emulate on error clause on SingleStore

What it means

SingleStore has no ON ERROR clause for json_query, so the community dialect can only render the default behavior (ERROR). When an HQL json_query() specifies any other error behavior - 'null on error', 'empty array on error', or 'empty object on error' - SingleStoreJsonQueryFunction.render throws this QueryException during SQL translation because there is no way to emulate swallowing or rewriting errors in json_extract_string.

Source

Thrown at hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/function/json/SingleStoreJsonQueryFunction.java:36

import org.hibernate.type.spi.TypeConfiguration;

/**
 * SingleStore json_query function.
 */
public class SingleStoreJsonQueryFunction extends JsonQueryFunction {

	public SingleStoreJsonQueryFunction(TypeConfiguration typeConfiguration) {
		super( typeConfiguration, true, false );
	}

	@Override
	protected void render(
			SqlAppender sqlAppender,
			JsonQueryArguments arguments,
			ReturnableType<?> returnType,
			SqlAstTranslator<?> walker) {
		if ( arguments.errorBehavior() != null && arguments.errorBehavior() != JsonQueryErrorBehavior.ERROR ) {
			throw new QueryException( "Can't emulate on error clause on SingleStore" );
		}
		if ( arguments.emptyBehavior() != null && arguments.emptyBehavior() != JsonQueryEmptyBehavior.NULL ) {
			throw new QueryException( "Can't emulate on empty clause on SingleStore" );
		}
		else {
			final String jsonPath;
			try {
				jsonPath = walker.getLiteralValue( arguments.jsonPath() );
			}
			catch (Exception ex) {
				throw new QueryException( "SingleStore json_query only support literal json paths, but got " + arguments.jsonPath() );
			}
			final List<JsonPathHelper.JsonPathElement> jsonPathElements = JsonPathHelper.parseJsonPathElements( jsonPath );
			final JsonQueryWrapMode wrapMode = arguments.wrapMode();
			final DecorationMode decorationMode = determineDecorationMode( wrapMode );
			if ( decorationMode == DecorationMode.WRAP ) {
				sqlAppender.appendSql( "concat('['," );
			}

View on GitHub (pinned to fad1729dce)

Solutions

1. Drop the 'on error' clause from the HQL json_query call - the default (error) is exactly what SingleStore does.
2. Keep the clause but only as 'error on error' (equivalent to the default) for cross-dialect portability.
3. Pre-validate the document with json_exists() (or a try/catch around query execution) and branch in Java instead of asking the database to swallow errors.
4. Fall back to a native query wrapping json_extract_string in logic that returns null on error.

Example fix

// before - throws on SingleStore
select json_query(e.doc, '$.tags' null on error) from Event e

// after - default error behavior, handle null result in Java if path misses
select json_query(e.doc, '$.tags') from Event e

// Keep json_query clauses dialect-portable: omit 'on error' entirely (default ERROR is supported everywhere)
String hql = "select json_query(e.doc, '$.tags') from Event e";

try {
    return session.createQuery(hql, String.class).getSingleResult();
} catch (QueryException e) {
    if (e.getMessage().contains("on error clause")) {
        return null; // emulate 'null on error' in application code
    }
    throw e;
}

When it happens

Trigger: HQL like: select json_query(e.doc, '$.tags' null on error) from Event e (also triggers with 'empty array on error' / 'empty object on error'). The check is arguments.errorBehavior() != null && arguments.errorBehavior() != JsonQueryErrorBehavior.ERROR, i.e. any explicit non-default error behavior.

Common situations: Defensive JSON queries written for PostgreSQL/Oracle that ask for NULL instead of an exception on malformed documents; migrating an application to SingleStore (via the hibernate-community-dialects SingleStoreDialect) and re-running existing HQL; shared query libraries used across multiple databases.

Related errors

• Can't emulate on empty clause on SingleStore
• Can't emulate json_objectagg filter clause when using 'null
• Can't emulate on error clause on SingleStore
• Can't emulate on empty clause on SingleStore
• Can't emulate on error clause on H2

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/42c18944d22534d0. Report an issue: GitHub.