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	PG_DATABASE.oid	OID of the database in which the locked object exists. - The OID is 0 if the object is a shared object. - The OID is NULL if the object is a transaction ID.
relation	oid	PG_CLASS.oid	OID of the relationship targeted by the lock. The value is NULL if the object is not a relationship or part of a relationship.
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	-	Bucket number corresponding to the child table. The value is NULL if the target is not a table.
virtualxid	text	-	Virtual ID of the transaction targeted by the lock. The value is NULL if the object is not a virtual transaction ID.
transactionid	xid	-	ID of the transaction targeted by the lock. The value is NULL if the object is not a transaction ID.
classid	oid	PG_CLASS.oid	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. The value is 0 if the object is some other object type. The value is NULL if the object 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 holding or awaiting this 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	-	Lock information that the session waits for. It can be parsed using the locktag_decode() function.
global_sessionid	text		Global session ID