Extension

Mechanism

PG_WAIT_EXTENSION at src/backend/utils/activity/wait_event.c:165 is the grep-verified reporting path. The public identity/resource is mapped at src/backend/utils/activity/wait_event_names.txt:296. The instrumented operation is: Waiting in an extension. Extension code registers or uses the Extension wait class and reports the wait around its own blocking operation. The exact resource and owner belong to the installed extension, not PostgreSQL core.

Expected behavior

Normality depends on the exact extension, version, and operation documented by its author.

When to investigate

Investigate when the custom name persists with service impact, or when the extension cannot explain which peer or resource makes progress.

Diagnostic actions

• Record the extension name and exact extversion.
• Query the local PG17+ pg_wait_events view for registered names.
• Inspect the extension source and runbook for its paired wait start/end calls.

Diagnostic queries

Sessions waiting on Extension/Extension

SELECT pid, backend_type, usename, datname, application_name,
       state, now() - query_start AS query_age,
       now() - xact_start AS xact_age,
       wait_event_type, wait_event,
       pg_blocking_pids(pid) AS blocking_pids,
       left(query, 160) AS query
FROM pg_stat_activity
WHERE wait_event_type = 'Extension'
  AND wait_event = 'Extension'
ORDER BY query_age DESC NULLS LAST;

Current Extension cohort

SELECT wait_event, count(*) AS waiting_sessions,
       count(*) FILTER (WHERE state = 'active') AS active_waiters,
       max(now() - query_start) AS oldest_query
FROM pg_stat_activity
WHERE wait_event_type = 'Extension'
GROUP BY wait_event
ORDER BY waiting_sessions DESC, wait_event;

Lock and relation context for these sessions

SELECT a.pid, l.locktype, l.mode, l.granted, l.fastpath,
       d.datname, n.nspname, c.relname,
       l.page, l.tuple, l.virtualxid, l.transactionid,
       l.classid, l.objid, l.objsubid
FROM pg_stat_activity AS a
LEFT JOIN pg_locks AS l ON l.pid = a.pid
LEFT JOIN pg_database AS d ON d.oid = l.database
LEFT JOIN pg_class AS c
  ON c.oid = l.relation
 AND l.database = (
       SELECT oid FROM pg_database WHERE datname = current_database()
     )
LEFT JOIN pg_namespace AS n ON n.oid = c.relnamespace
WHERE a.wait_event_type = 'Extension'
  AND a.wait_event = 'Extension'
ORDER BY a.pid, l.granted, l.locktype, l.mode;