googleapis--mcp-toolbox/docs/en/integrations/postgres/tools/postgres-list-locks.md

title, type, weight, description

title	type	weight	description
postgres-list-locks	docs	1	The "postgres-list-locks" tool lists active locks in the database, including the associated process, lock type, relation, mode, and the query holding or waiting on the lock.

About

The postgres-list-locks tool displays information about active locks by joining pg_stat_activity with pg_locks. This is useful to find transactions holding or waiting for locks and to troubleshoot contention.

This tool identifies all locks held by active processes showing the process ID, user, query text, and an aggregated list of all transactions and specific locks (relation, mode, grant status) associated with each process.

Compatible Sources

{{< compatible-sources others="integrations/alloydb, integrations/cloud-sql-pg">}}

Example

kind: tool
name: list_locks
type: postgres-list-locks
source: postgres-source
description: "Lists active locks with associated process and query information."

Query

The tool aggregates locks per backend (process) and returns the concatenated transaction ids and lock entries. The SQL used by the tool looks like:

SELECT
    locked.pid,
    locked.usename,
    locked.query,
    string_agg(locked.transactionid::text,':') as trxid,
    string_agg(locked.lockinfo,'||') as locks
FROM
    (SELECT
      a.pid,
      a.usename,
      a.query,
      l.transactionid,
      (l.granted::text||','||coalesce(l.relation::regclass,0)::text||','||l.mode::text)::text as lockinfo
    FROM
      pg_stat_activity a
      JOIN pg_locks l ON l.pid = a.pid  AND a.pid != pg_backend_pid()) as locked
GROUP BY 
    locked.pid, locked.usename, locked.query;

Output Format

Example response element (aggregated per process):

{
  "pid": 23456,
  "usename": "dbuser",
  "query": "INSERT INTO orders (...) VALUES (...);",
  "trxid": "12345:0",
  "locks": "true,public.orders,RowExclusiveLock||false,0,ShareUpdateExclusiveLock"
}

Reference

field	type	required	description
pid	integer	true	Process id (backend pid).
usename	string	true	Database user.
query	string	true	SQL text associated with the session.
trxid	string	true	Aggregated transaction ids for the process, joined by ':' (string). Each element is the transactionid as text.
locks	string	true	Aggregated lock info entries for the process, joined by '