PG_LWLOCKS

PG_LWLOCKS provides information on lightweight locks currently held or being waited for by the current instance. This view is supported only by 9.1.0.200 and later cluster versions.

**Table 1** PG_LWLOCKS columns
Column	Type	Description
pid	Bigint	ID of the backend thread.
query_id	Bigint	ID of a query.
lwtid	Integer	Lightweight thread ID of the backend thread.
reqlockid	Integer	ID of the lightweight lock that is being requested by the current thread.
reqlock	Text	Name of the lightweight lock corresponding to reqlockid.
heldlocknums	Integer	Number of lightweight locks obtained by the current thread.
heldlockid	Integer	Lightweight lock ID obtained by the current thread.
heldlock	Text	Name of the lightweight lock corresponding to heldlockid.
heldlockmode	Text	Lightweight lock mode corresponding to heldlockid.

Example

Use the PG_LWLOCKS view to query information about lightweight locks that are being held or waiting for the current instance.

      
           SELECT * FROM pg_lwlocks;
       pid       |     query_id      | lwtid | reqlockid | reqlock | heldlocknums | heldlockid |      heldlock      | heldlockmode
-----------------+-------------------+-------+-----------+---------+--------------+------------+--------------------+--------------
 139810224192480 |                 0 | 54842 |           |         |            1 |          7 | WALWriteLock       | Exclusive
 139810224199520 | 78250043526306022 | 54963 |           |         |            1 |     193860 | BUFFER_POOL_LWLOCK | Exclusive
(2 rows)