MyCATApache/Mycat-Server · error · SQLNonTransientException

unsupported mysql function expression

Error message

unsupported mysql function expression: {expr}

What it means

MysqlMethodInvocationHandler rewrites supported MySQL function expressions (NOW, ADDDATE, etc.) during SQL parsing. If a method-invoke expression is not one of the supported functions (doInvoke returns null), invoke() throws this error with the original expression text.

Solutions

  1. Replace the unsupported function with a supported one (e.g. use NOW() instead of an unmapped time function) or compute the value in the application and pass it as a literal
  2. Add a case for the function in MysqlMethodInvocationHandler.doInvoke that returns the rewritten expression
  3. Downgrade or rewrite the SQL/rule expression to use only functions listed in the switch

Example fix

// before (rule expression)
DATE_FORMAT(create_time, '%Y%m')
// after
-- compute in app or use a supported function
YEAR(create_time)*100 + MONTH(create_time)
Defensive patterns

Strategy: try-catch

Validate before calling

private static final Set<String> SUPPORTED = Set.of("NOW","ADDDATE","SUBDATE", /* ... */);
if (!SUPPORTED.contains(fn.toUpperCase())) {
    throw new IllegalArgumentException("function not supported by Mycat parser: " + fn);
}

Try / catch

try { String v = handler.invoke(methodInvokeExpr); } catch (SQLNonTransientException e) { if (e.getMessage().startsWith("unsupported mysql function expression")) { evaluateInAppAndInlineLiteral(); } }

Prevention

When it happens

Trigger: Routing SQL containing a MySQL function not in the handler's switch (methodName.toUpperCase() has no case), e.g. UNIX_TIMESTAMP with args, DATE_FORMAT, or user-defined functions, wherever the handler is applied (e.g. in partition/routing expression evaluation).

Common situations: Newer MySQL functions used in rule/partition expressions; UDFs; less-common date functions in default-value or routing expressions; upgrading MySQL and adopting functions Mycat doesn't map.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of MyCATApache/Mycat-Server@65f8d8beb7 (2026-09-11). Data as JSON: /api/errors/e69e2caa4eb02336. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/io/mycat/route/parser/druid/impl/MysqlMethodInvocationHandler.java:41

 *
 * @author zhuyiqiang
 * @version 2018/9/3
 */
public class MysqlMethodInvocationHandler implements SqlMethodInvocationHandler {
    protected static final Logger LOGGER = LoggerFactory.getLogger(MysqlMethodInvocationHandler.class);
    private final String[] SUPPORT_PATTERNS = {
            "yyyy-MM-dd HH:mm:ss",
            "yyyy-MM-dd",
            "yyyy-MM-dd HH:mm"
    };

    @Override
    public String invoke(SQLMethodInvokeExpr expr) throws SQLNonTransientException {
        SQLExpr ret = doInvoke(expr);
        if (ret != null) {
            return ret.toString();
        }
        throw new SQLNonTransientException("unsupported mysql function expression: " + expr.toString());
    }

    private SQLExpr doInvoke(SQLMethodInvokeExpr expr) throws SQLNonTransientException {
        String methodName = expr.getMethodName().toUpperCase();
        switch (methodName) {
            case "NOW":
            case "SYSDATE":
            case "CURRENT_TIMESTAMP":
                return invokeNow();
            case "ADDDATE":
            case "DATE_ADD":
                return invokeAddDate(expr, false);
            case "SUBDATE":
            case "DATE_SUB":
                return invokeAddDate(expr, true);
        }
        return null;
    }

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