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.
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)