SYSTEM VIEW · System view

pg_locks

The view pg_locks provides access to information about the locks held by active processes within the database server. See Chapter 13 for more discussion of locking. pg_locks contains one row per active lockable object, requested lock mode, and relevant process. Thus, the same lockable object might appear many times, if multiple processes are holding or waiting for locks on it. However, an object that currently has no locks on it will not appear at all. There are several distinct types of lockable objects: whole relations (e.g., tables), individual pages of relations, individual tuples of relations, transaction IDs (both virtual and permanent IDs), and general database objects (identified by class OID and object OID, in the same way as in pg_description or pg_depend). Also, the right to extend a relation is represented as a separate lockable object, as is the right to update pg_database.datfrozenxid. Also, “advisory” locks can be taken on numbers that have user-defined meanings.

First seen PG 9.0Last seen PG 19Columns 16

9.0 9.1 9.2 9.3 9.4 9.5 9.6 10 11 12 13 14 15 16 17 18 19^β3

Checked column by column against a PostgreSQL 18.6 instance · Raw measurement record ↗

Columns PostgreSQL 18

pg_locks

COLUMN	TYPE	DESCRIPTION
`locktype`	`text`	Type of the lockable object: relation, extend, frozenid, page, tuple, transactionid, virtualxid, spectoken, object, userlock, advisory, or applytransaction. (See also Table 27.11.)
`database`	`oid`	OID of the database in which the lock target exists, or zero if the target is a shared object, or null if the target is a transaction IDReferences:`pg_database.oid`
`relation`	`oid`	OID of the relation targeted by the lock, or null if the target is not a relation or part of a relationReferences:`pg_class.oid`
`page`	`integer`Documented as:`int4`	Page number targeted by the lock within the relation, or null if the target is not a relation page or tuple
`tuple`	`smallint`Documented as:`int2`	Tuple number targeted by the lock within the page, or null if the target is not a tuple
`virtualxid`	`text`	Virtual ID of the transaction targeted by the lock, or null if the target is not a virtual transaction ID; see Chapter 67
`transactionid`	`xid`	ID of the transaction targeted by the lock, or null if the target is not a transaction ID; Chapter 67
`classid`	`oid`	OID of the system catalog containing the lock target, or null if the target is not a general database objectReferences:`pg_class.oid`
`objid`	`oid`	OID of the lock target within its system catalog, or null if the target is not a general database objectReferences:`any OID column`
`objsubid`	`smallint`Documented as:`int2`	Column number targeted by the lock (the classid and objid refer to the table itself), or zero if the target is some other general database object, or null if the target is not a general database object
`virtualtransaction`	`text`	Virtual ID of the transaction that is holding or awaiting this lock
`pid`	`integer`Documented as:`int4`	Process ID of the server process holding or awaiting this lock, or null if the lock is held by a prepared transaction
`mode`	`text`	Name of the lock mode held or desired by this process (see Section 13.3.1 and Section 13.2.3)
`granted`	`boolean`Documented as:`bool`	True if lock is held, false if lock is awaited
`fastpath`	`boolean`Documented as:`bool`	True if lock was taken via fast path, false if taken via main lock table
`waitstart`	`timestamp with time zone`Documented as:`timestamptz`	Time when the server process started waiting for this lock, or null if the lock is held. Note that this can be null for a very short period of time after the wait started even though granted is false.

Columns marked "implicit" are not included in SELECT *; some early statistics views are completed from same-version source, and the extra provenance is shown in the column description.

Column evolution matrix

Hover a cell for the column type

PresentAdded / type or attribute changeRemoved

COLUMN	9.0	9.1	9.2	9.3	9.4	9.5	9.6	10	11	12	13
`locktype`
`database`
`relation`
`page`
`tuple`
`virtualxid`
`transactionid`
`classid`
`objid`
`objsubid`
`virtualtransaction`
`pid`
`mode`
`granted`
`fastpath`	–	–
`waitstart`	–	–	–	–	–	–	–	–	–	–	–

9.0 is the coverage baseline; a column already present in the baseline is not marked as added. The matrix aligns columns by name, so a rename appears as the old column removed and a new column added.

Evolution timeline

Changes between adjacent majors

PostgreSQL 18 ← 17

2 column description updates

PostgreSQL 17 ← 16

3 column description updates

PostgreSQL 16 ← 15

3 column description updates

PostgreSQL 14 ← 13

+ waitstart1 column description updates

PostgreSQL 13 ← 12

1 column description updates

PostgreSQL 10 ← 9.6

Catalog description updated

PostgreSQL 9.6 ← 9.5

Catalog description updated

PostgreSQL 9.5 ← 9.4

1 column description updatesCatalog description updated

PostgreSQL 9.2 ← 9.1

+ fastpath8 column description updates

PostgreSQL 9.1 ← 9.0

3 column description updatesCatalog description updated

Compare any two versions

FROMTOInclude description updates

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