Incident brief
nth_value argument must be positive
nth_value(expr, n) returns the value from the n-th row of the window frame and requires n to be a positive integer; zero or a negative position raises this data exception.
In 10 seconds
- What
- nth_value argument must be positive
- What triggers it
- Use nth_value(expr, n) OVER (...) with n set to zero or a negative value.
- The fix
- Pass a positive row position to nth_value().
- Proof
- Reproduced on PostgreSQL 18.4 → A single windowed SELECT reproduces SQLSTATE 22016; nth_value rejects the non-positive position.
The fix
What to do right now
The immediate, application-level response to this error.
- Pass a positive row position to nth_value().
- Validate any dynamic position before the call so it is always 1 or greater.
-- nth_value positions are 1-based and must be positive.
SELECT nth_value(g, 1) OVER (ORDER BY g) FROM generate_series(1,3) g;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;Why it happens
What PostgreSQL is telling you
The mechanism behind the error, grounded in the official manual — not paraphrased.
PostgreSQL 18 Documentation — Appendix A. PostgreSQL Error Codes (Table A.1, Class 22 — Data Exception)
22016 → invalid_argument_for_nth_value_functionRead the full section on postgresql.org →
Calling nth_value with a non-positive position
nth_value positions are 1-based, so nth_value(expr, 0) raises 'argument of nth_value must be greater than zero'.The session continues normally
The failing statement ran outside a transaction block, so nothing was left in a bad state — the next statement in the same connection runs normally.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.
- 1Use nth_value(expr, n) OVER (...) with n set to zero or a negative value.
- 2PostgreSQL validates the row-position argument as the frame is evaluated.
- 3A non-positive n aborts the statement with SQLSTATE 22016.
A query pulled 'the n-th event in each session' where n came from a parameter, and a zero position aborted the window query.
-- The error is self-contained in one statement; no schema is required.
SELECT 'no schema needed' AS setup_note;SELECT nth_value(g, 0) OVER (ORDER BY g) FROM generate_series(1,3) g;SELECT 'ok' AS session_after_error;What PostgreSQL actually returned
setup_note
------------------
no schema needed
(1 row)ERROR: argument of nth_value must be greater than zero session_after_error
---------------------
ok
(1 row)The same query works once nth_value is given a positive position.
We rerun nth_value with position 1 to show the value it returns per frame.
Without this
Before: a zero position aborts
With this, tested
After: nth_value(g, 1) returns the first value
What Pro unlocks here
- The exact prevention SQL — copy-paste ready
- Raw psql output captured from the Docker lab
- A senior-DBA action list to take it further
- Live monitoring queries to catch it in production
- The deeper audit: fix-that-fails counterexample, GUC before/after, server-log evidence
Related & next steps
Follow the thread
Everything this error touches — jump straight to the sibling error, term, runbook, or parameter.
Verification
- Last verified
- 2026-07-24 (isolated lab, PostgreSQL 18.4)
- Reviewed by
- Verified against PostgreSQL 18.4 in an isolated lab environment
- Audit status
- reviewed