25004ERRORTier 2 — Caution✅ HIGH confidence

inappropriate isolation level for branch transaction

Category: Invalid Transaction StateVersions: All Postgres versions

What this means

SQLSTATE 25004 is raised when the isolation level set for a transaction is not compatible with the isolation level of the branch transaction or the current session requirements.

Why it happens

1Attempting to set an isolation level incompatible with an active branch transaction

How to reproduce

Isolation level mismatch in a branch transaction context.

trigger — this will ERROR

ERROR: inappropriate isolation level for branch transaction

Fix 1: Match the isolation level to what the branch transaction requires

When isolation level conflicts arise.

fix

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;

Why this works

Set the isolation level at the start of the transaction before any statements are executed.

Sources

📚 Official docs: https://www.postgresql.org/docs/current/errcodes-appendix.html

🔧 Source ref: Class 25 — Invalid Transaction State

Confidence assessment

✅ HIGH confidence

Standard SQLSTATE. Stable across versions.