38004ERRORTier 2 — Caution✅ HIGH confidencereading SQL data not permitted
Category: External Routine ExceptionVersions: All Postgres versions
What this means
SQLSTATE 38004 is raised when an external routine declared as NO SQL attempts to read data with a SELECT statement.
Why it happens
- 1An external function declared NO SQL executes a SELECT or other read statement
How to reproduce
NO SQL external function executing a SELECT.
trigger — this will ERROR
ERROR: reading SQL-data not permitted
Fix 1: Change the function attribute to READS SQL DATA
When the function needs to read data.
fix
CREATE FUNCTION my_fn() RETURNS INT
AS 'my_ext', 'my_fn'
LANGUAGE C
READS SQL DATA;Why this works
READS SQL DATA permits SELECT statements in the function.
Sources
📚 Official docs: https://www.postgresql.org/docs/current/errcodes-appendix.html
🔧 Source ref: Class 38 — External Routine Exception
Confidence assessment
✅ HIGH confidence
Standard SQLSTATE. Stable across versions.
See also
🔗 Related errors
📄 Reference pages
External Language FunctionsCREATE FUNCTION
⚙️ This error reference was generated with AI assistance and reviewed for accuracy. Examples are provided to illustrate common scenarios and may not cover every case. Always test fixes in a development environment before applying to production. Spotted an error? Suggest a correction →