PGXC_LWLOCKS

PGXC_LWLOCK offers details on lightweight locks that are currently held or being waited for by all instances in the cluster. This view is supported only by 9.1.0.200 and later cluster versions.

**Table 1** PGXC_LWLOCKS columns
Name	Type	Description
nodename	name	Name of the node where the locked object resides
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 PGXC_LWLOCKS view to get details on lightweight locks that are currently held or being waited for by all instances in the cluster.

     
          SELECT * FROM pgxc_lwlocks;
 nodename  |       pid       |     query_id      | lwtid | reqlockid | reqlock | heldlocknums | heldlockid |      heldlock      | heldlockmode
-----------+-----------------+-------------------+-------+-----------+---------+--------------+------------+--------------------+--------------
 datanode1 | 139810224193360 | 78250043525924188 | 54844 |           |         |            1 |      76390 | BUFFER_POOL_LWLOCK | Shared
 datanode1 | 139810224198200 | 78250043525924886 | 54922 |           |         |            1 |     957438 | PGPROC_LWLOCK      | Exclusive
 datanode2 | 140262654050288 |                 0 | 54832 |           |         |            1 |          7 | WALWriteLock       | Exclusive
 datanode2 | 140262654052488 | 78250043525923195 | 54847 |           |         |            1 |      15862 | BUFFER_POOL_LWLOCK | Shared
(4 rows)