Informix Error -788: Unknown operator/type.

Reasons / Common Causes

-788 is flagged by the official text as an internal error involving an operator or type the server's internal expression handling doesn't recognize, with no documented application-level trigger.

1. A genuine internal engine condition, per the official guidance's framing, with no documented application-level cause.
2. An extended/opaque data type or a user-defined operator involved in an expression, plausible given the "operator/type" framing, though not explicitly named by the sparse official text — DataBlade or UDT-related expressions are a more complex code path than built-in types.

Solutions / Resolution

1. If you cannot find a direct cause, note all circumstances and contact IBM Informix Technical Support, per the official guidance — there is no documented general application-level fix.
2. Check whether the failing statement involves an extended/opaque type or a user-defined operator, given the error's specific "operator/type" framing, and capture that detail for escalation.
3. Try simplifying the expression, as a practical first step, isolating which specific operator or type reference triggers the failure.

Examples

Capturing circumstances for escalation

-- Record the exact expression, and whether it involves an extended/opaque
-- type or user-defined operator, for escalation.

Diagnostic Checks

1. Check for extended/opaque types or user-defined operators in the failing expression.
2. Try simplifying the expression to isolate the specific operator/type involved.

Related Errors / Related Topics

• -789 — "Internal error, expression not properly defined." A related internal expression-handling error, in the same general area of expression evaluation.

An internal expression-handling error — check for extended/opaque types or user-defined operators before escalating.