active_sql_transaction REINDEX CONCURRENTLY cannot run inside a transaction block — 25001

Symptoms

REINDEX … CONCURRENTLY was issued inside a transaction block. Like other concurrent index operations, it commits in phases and cannot run inside an outer transaction, so PostgreSQL raises SQLSTATE 25001 (active_sql_transaction).

• REINDEX CONCURRENTLY issued after BEGIN.
• Common in migration tools that wrap statements.
• Must run standalone with autocommit.

What the server log shows

ERROR:  REINDEX CONCURRENTLY cannot run inside a transaction block

Why PostgreSQL raises this — what the manual says

the REINDEX reference (Notes):

“Another difference is that a regular REINDEX TABLE or REINDEX INDEX command can be performed within a transaction block, but REINDEX CONCURRENTLY cannot.”

The concurrent rebuild commits between phases so it never holds a long lock. Running inside an outer transaction would prevent those intermediate commits, so PostgreSQL rejects it with 25001.

Common causes

• Issuing REINDEX CONCURRENTLY after BEGIN.
• A migration framework wrapping statements in transactions.
• Autocommit disabled on the connection.

How to fix it

1. Run it standalone with autocommit on.
2. Mark the step as non-transactional in migration tools.
3. Use plain REINDEX if a brief lock is acceptable and you must stay in a transaction.

Related & next steps

• SQLSTATE 25001 — Active SQL Transaction (full reference)
• Message: CREATE INDEX CONCURRENTLY cannot run inside a transaction block
• Glossary: REINDEX

Reference: PostgreSQL 18 — REINDEX.