SQLSTATE P0003Severity lowLab verified

Incident brief

Too many rows

A PL/pgSQL SELECT ... INTO STRICT matched more than one row. PostgreSQL raised an error instead of silently picking one of them.

Reproduced on PostgreSQL 16.14Verified 2026-07-16 (Docker lab, PostgreSQL 16.14)Reviewed by Verified against PostgreSQL 16.14 in an isolated lab environment

In 10 seconds

What: Too many rows
What triggers it: Run SELECT ... INTO STRICT against a query that matches two or more rows.
The fix: Add ORDER BY plus LIMIT 1 to the STRICT select if exactly one specific row is genuinely the right answer.
Proof: Reproduced on PostgreSQL 16.14 → A SELECT ... INTO STRICT that matched two rows was rejected with SQLSTATE P0003. The session was unaffected afterward.

The fix

What to do right now

The immediate, application-level response to this error.

Add ORDER BY plus LIMIT 1 to the STRICT select if exactly one specific row is genuinely the right answer.
Or restructure the query to aggregate or otherwise guarantee a single row, if that's the actual intent.

Fix — SQL

DO $$
DECLARE
  x int;
BEGIN
  SELECT n INTO STRICT x FROM (VALUES (1),(2)) t(n) ORDER BY n LIMIT 1;
  RAISE NOTICE 'x = %', x;
END $$;

Diagnose

See it live on the server

Run these against the affected instance to confirm the diagnosis before you act.

Standard triage — not specific to this error

These are canonical PostgreSQL system-catalog queries, shown as SQL to run. No sample output is attached because this is general triage, not a captured lab transcript.

This SQLSTATE does not have an error-specific live snapshot yet. These are the canonical system-catalog queries you run against the affected server to see the problem in real time — standard triage, not a reproduced transcript.

What is running right now

Active backends, how long each has been running, and what it is waiting on.

SELECT pid,
       state,
       wait_event_type,
       wait_event,
       now() - query_start AS running_for,
       left(query, 80)     AS query
FROM   pg_stat_activity
WHERE  state <> 'idle'
  AND  pid <> pg_backend_pid()
ORDER  BY running_for DESC NULLS LAST;

Who is blocking whom

Turn raw blocking PIDs into the actual queries on both sides of the wait.

SELECT blocked.pid    AS blocked_pid,
       blocked.query  AS blocked_query,
       blocking.pid   AS blocking_pid,
       blocking.query AS blocking_query
FROM   pg_stat_activity AS blocked
JOIN   LATERAL unnest(pg_blocking_pids(blocked.pid)) AS b(pid) ON true
JOIN   pg_stat_activity AS blocking ON blocking.pid = b.pid
WHERE  cardinality(pg_blocking_pids(blocked.pid)) > 0;

Locks that are still waiting

Every lock a backend has requested but not yet been granted.

SELECT l.pid,
       l.locktype,
       l.mode,
       l.granted,
       COALESCE(c.relname, l.transactionid::text) AS object
FROM   pg_locks l
LEFT   JOIN pg_class c ON c.oid = l.relation
WHERE  NOT l.granted
ORDER  BY l.pid;

Reproduce & verify

A real, single-session PostgreSQL reproduction

A literal transcript of SQL run against a live PostgreSQL instance in an isolated lab — the commands below are exactly what was executed.

1Run SELECT ... INTO STRICT against a query that matches two or more rows.
2SQLSTATE P0003 is reported; the block aborts.

One client: a DO block runs SELECT ... INTO STRICT against an inline VALUES list matching two rows.

Schema setup

-- No table needed: the failure is self-contained via an inline VALUES list.
SELECT 'no schema required' AS setup_note;

The STRICT select with two matching rows

DO $$
DECLARE
  x int;
BEGIN
  SELECT n INTO STRICT x FROM (VALUES (1),(2)) t(n);
END $$;

Confirming the session still works

SELECT 1 AS session_still_alive;

What PostgreSQL actually returned

Schema setup output

     setup_note     
--------------------
 no schema required
(1 row)

The STRICT select with two matching rows output

ERROR:  query returned more than one row
HINT:  Make sure the query returns a single row, or use LIMIT 1.
CONTEXT:  PL/pgSQL function inline_code_block line 5 at SQL statement

Confirming the session still works output

 session_still_alive 
---------------------
                   1
(1 row)

Related & next steps

Follow the thread

Everything this error touches — jump straight to the sibling error, term, runbook, or parameter.

Verification

PG 16.14

Last verified: 2026-07-16 (Docker lab, PostgreSQL 16.14)
Reviewed by: Verified against PostgreSQL 16.14 in an isolated lab environment
Audit status: reviewed