Updated on 2023-10-23 GMT+08:00

PG_LOCKS

PG_LOCKS displays information about locks held by open transactions.

Table 1 PG_LOCKS columns

Name

Type

Reference

Description

locktype

text

-

Type of the locked object: relation, extend, page, tuple, transactionid, virtualxid, object, userlock, or advisory

database

oid

OID in PG_DATABASE

OID of the database in which the locked target exists

  • The OID is 0 if the target is a shared object.
  • The OID is NULL if the locked target is a transaction.

relation

oid

OID in PG_CLASS

OID of the relationship targeted by the lock (NULL if the object is not a relation or part of a relation)

page

integer

-

Page number targeted by the lock within the relation (NULL if the object is not a relation page or row page)

tuple

smallint

-

Row number targeted by the lock within the page (NULL if the object is not a row)

bucket

integer

-

Hash bucket ID

virtualxid

text

-

Virtual ID of the transaction targeted by the lock (NULL if the object is not a virtual transaction)

transactionid

xid

-

ID of the transaction targeted by the lock (NULL if the object is not a transaction)

classid

oid

OID in PG_CLASS

OID of the system catalog that contains the object (NULL if the object is not a general database object)

objid

oid

-

OID of the lock target within its system table (NULL if the target is not a general database object)

objsubid

smallint

-

Column number for a column in the table (0 if the target is of other object type and NULL if the target is not a general database object)

virtualtransaction

text

-

Virtual ID of the transaction holding or awaiting this lock

pid

bigint

-

Logical ID of the server thread holding or awaiting this lock (NULL if the lock is held by a prepared transaction)

sessionid

bigint

-

ID of the session that holds or waits for the lock

mode

text

-

Lock mode held or desired by this thread

granted

boolean

-

  • The value is TRUE if the lock is a held lock.
  • The value is FALSE if the lock is an awaited lock.

fastpath

boolean

-

The value is TRUE if the lock is obtained through fast-path, and is FALSE if the lock is obtained through the main lock table.

locktag

text

-

Information about the lock that the session waits for. It can be parsed using the locktag_decode() function.

global_sessionid

text

-

Global session ID