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's json_value emulation (json_extract_string plus optional cast) always returns null when the document/path is invalid, so the dialect only supports the default 'null on error' behavior. If the HQL json_value() explicitly asks for 'error on error' or 'default <expr> on error', SingleStoreJsonValueFunction.render throws this QueryException because raising a SQL error (or producing a default value) cannot be emulated.

Source

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

/**
 * SingleStore json_value function.
 */
public class SingleStoreJsonValueFunction extends JsonValueFunction {

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

	@Override
	protected void render(
			SqlAppender sqlAppender,
			JsonValueArguments arguments,
			ReturnableType<?> returnType,
			SqlAstTranslator<?> walker) {

		if ( arguments.errorBehavior() != null && arguments.errorBehavior() != JsonValueErrorBehavior.NULL ) {
			throw new QueryException( "Can't emulate on error clause on SingleStore" );
		}
		if ( arguments.emptyBehavior() != null && arguments.emptyBehavior() != JsonValueEmptyBehavior.NULL ) {
			throw new QueryException( "Can't emulate on empty clause on SingleStore" );
		}
		if ( arguments.returningType() != null ) {
			if ( arguments.returningType().getJdbcMapping().getJdbcType().isBoolean() ) {
				sqlAppender.append( "case " );
			}
			else {
				sqlAppender.append( "cast(" );
			}
		}
		final String jsonPath;
		try {
			jsonPath = walker.getLiteralValue( arguments.jsonPath() );
		}
		catch (Exception ex) {
			throw new QueryException( "SingleStore json_value only support literal json paths, but got " + arguments.jsonPath() );

View on GitHub (pinned to fad1729dce)

Solutions

1. Drop the 'on error' clause - the implicit null-on-error behavior is what SingleStore provides.
2. If you must detect bad documents, validate with json_exists or a separate well-formedness check and branch in Java.
3. Use 'null on error' explicitly when the query is shared with other dialects.
4. Fall back to native SQL if raising on error is mandatory.

Example fix

// before - throws on SingleStore
select json_value(e.doc, '$.count' error on error) from Event e

// after - default null on error
select json_value(e.doc, '$.count') from Event e

// Omit 'on error' - implicit null-on-error is the only supported behavior on SingleStore
String hql = "select json_value(e.doc, '$.count') from Event e";

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

When it happens

Trigger: HQL like: select json_value(e.doc, '$.x' error on error) from Event e, or json_value(e.doc, '$.x' default 'n/a' on error). The check is arguments.errorBehavior() != null && arguments.errorBehavior() != JsonValueErrorBehavior.NULL (note JsonValueErrorBehavior has ERROR, NULL, and defaultOnError(expr) variants).

Common situations: Queries written for the SQL standard default (ERROR ON ERROR) or using DEFAULT ... ON ERROR; strict validation queries that want an exception on malformed JSON; migrating to SingleStore.

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 CockroachDB

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/be6248822226b591. Report an issue: GitHub.