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, and 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 object is a transaction.
relation	oid	oid in PG_CLASS	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 relationship (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	-	ID of the virtual transaction The value is NULL if the object is not a virtual transaction.
transactionid	xid	-	ID of the transaction targeted by the lock. The value is NULL if the object is not a transaction ID.
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 locked object within its system catalog. The value is NULL if the object is not a general database object.
objsubid	smallint	-	Column number for a column in the table (0 if the object is of other object type and NULL if the object is not a general database object).
virtualtransaction	text	-	ID of the virtual transaction holding or awaiting this lock.
pid	bigint	-	ID of the server logic thread that holds or waits for the 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	-	Lock information that the session waits for. It can be parsed using the locktag_decode() function.
global_sessionid	text	-	Global session ID.