1ALTER TABLE(7) PostgreSQL 16.1 Documentation ALTER TABLE(7)
2
6 ALTER_TABLE - change the definition of a table
7
9 ALTER TABLE [ IF EXISTS ] [ ONLY ] name [ * ]
10 action [, ... ]
11 ALTER TABLE [ IF EXISTS ] [ ONLY ] name [ * ]
12 RENAME [ COLUMN ] column_name TO new_column_name
13 ALTER TABLE [ IF EXISTS ] [ ONLY ] name [ * ]
14 RENAME CONSTRAINT constraint_name TO new_constraint_name
15 ALTER TABLE [ IF EXISTS ] name
16 RENAME TO new_name
17 ALTER TABLE [ IF EXISTS ] name
18 SET SCHEMA new_schema
19 ALTER TABLE ALL IN TABLESPACE name [ OWNED BY role_name [, ... ] ]
20 SET TABLESPACE new_tablespace [ NOWAIT ]
21 ALTER TABLE [ IF EXISTS ] name
22 ATTACH PARTITION partition_name { FOR VALUES partition_bound_spec | DEFAULT }
23 ALTER TABLE [ IF EXISTS ] name
24 DETACH PARTITION partition_name [ CONCURRENTLY | FINALIZE ]
25 where action is one of:
27 ADD [ COLUMN ] [ IF NOT EXISTS ] column_name data_type [ COLLATE collation ] [ column_constraint [ ... ] ]
29 DROP [ COLUMN ] [ IF EXISTS ] column_name [ RESTRICT | CASCADE ]
30 ALTER [ COLUMN ] column_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ USING expression ]
31 ALTER [ COLUMN ] column_name SET DEFAULT expression
32 ALTER [ COLUMN ] column_name DROP DEFAULT
33 ALTER [ COLUMN ] column_name { SET | DROP } NOT NULL
34 ALTER [ COLUMN ] column_name DROP EXPRESSION [ IF EXISTS ]
35 ALTER [ COLUMN ] column_name ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( sequence_options ) ]
36 ALTER [ COLUMN ] column_name { SET GENERATED { ALWAYS | BY DEFAULT } | SET sequence_option | RESTART [ [ WITH ] restart ] } [...]
37 ALTER [ COLUMN ] column_name DROP IDENTITY [ IF EXISTS ]
38 ALTER [ COLUMN ] column_name SET STATISTICS integer
39 ALTER [ COLUMN ] column_name SET ( attribute_option = value [, ... ] )
40 ALTER [ COLUMN ] column_name RESET ( attribute_option [, ... ] )
41 ALTER [ COLUMN ] column_name SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN | DEFAULT }
42 ALTER [ COLUMN ] column_name SET COMPRESSION compression_method
43 ADD table_constraint [ NOT VALID ]
44 ADD table_constraint_using_index
45 ALTER CONSTRAINT constraint_name [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
46 VALIDATE CONSTRAINT constraint_name
47 DROP CONSTRAINT [ IF EXISTS ] constraint_name [ RESTRICT | CASCADE ]
48 DISABLE TRIGGER [ trigger_name | ALL | USER ]
49 ENABLE TRIGGER [ trigger_name | ALL | USER ]
50 ENABLE REPLICA TRIGGER trigger_name
51 ENABLE ALWAYS TRIGGER trigger_name
52 DISABLE RULE rewrite_rule_name
53 ENABLE RULE rewrite_rule_name
54 ENABLE REPLICA RULE rewrite_rule_name
55 ENABLE ALWAYS RULE rewrite_rule_name
56 DISABLE ROW LEVEL SECURITY
57 ENABLE ROW LEVEL SECURITY
58 FORCE ROW LEVEL SECURITY
59 NO FORCE ROW LEVEL SECURITY
60 CLUSTER ON index_name
61 SET WITHOUT CLUSTER
62 SET WITHOUT OIDS
63 SET ACCESS METHOD new_access_method
64 SET TABLESPACE new_tablespace
65 SET { LOGGED | UNLOGGED }
66 SET ( storage_parameter [= value] [, ... ] )
67 RESET ( storage_parameter [, ... ] )
68 INHERIT parent_table
69 NO INHERIT parent_table
70 OF type_name
71 NOT OF
72 OWNER TO { new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
73 REPLICA IDENTITY { DEFAULT | USING INDEX index_name | FULL | NOTHING }
74 and partition_bound_spec is:
76 IN ( partition_bound_expr [, ...] ) |
78 FROM ( { partition_bound_expr | MINVALUE | MAXVALUE } [, ...] )
79 TO ( { partition_bound_expr | MINVALUE | MAXVALUE } [, ...] ) |
80 WITH ( MODULUS numeric_literal, REMAINDER numeric_literal )
81 and column_constraint is:
83 [ CONSTRAINT constraint_name ]
85 { NOT NULL |
86 NULL |
87 CHECK ( expression ) [ NO INHERIT ] |
88 DEFAULT default_expr |
89 GENERATED ALWAYS AS ( generation_expr ) STORED |
90 GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( sequence_options ) ] |
91 UNIQUE [ NULLS [ NOT ] DISTINCT ] index_parameters |
92 PRIMARY KEY index_parameters |
93 REFERENCES reftable [ ( refcolumn ) ] [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ]
94 [ ON DELETE referential_action ] [ ON UPDATE referential_action ] }
95 [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
96 and table_constraint is:
98 [ CONSTRAINT constraint_name ]
100 { CHECK ( expression ) [ NO INHERIT ] |
101 UNIQUE [ NULLS [ NOT ] DISTINCT ] ( column_name [, ... ] ) index_parameters |
102 PRIMARY KEY ( column_name [, ... ] ) index_parameters |
103 EXCLUDE [ USING index_method ] ( exclude_element WITH operator [, ... ] ) index_parameters [ WHERE ( predicate ) ] |
104 FOREIGN KEY ( column_name [, ... ] ) REFERENCES reftable [ ( refcolumn [, ... ] ) ]
105 [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE referential_action ] [ ON UPDATE referential_action ] }
106 [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
107 and table_constraint_using_index is:
109 [ CONSTRAINT constraint_name ]
111 { UNIQUE | PRIMARY KEY } USING INDEX index_name
112 [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
113 index_parameters in UNIQUE, PRIMARY KEY, and EXCLUDE constraints are:
115 [ INCLUDE ( column_name [, ... ] ) ]
117 [ WITH ( storage_parameter [= value] [, ... ] ) ]
118 [ USING INDEX TABLESPACE tablespace_name ]
119 exclude_element in an EXCLUDE constraint is:
121 { column_name | ( expression ) } [ opclass ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ]
123 referential_action in a FOREIGN KEY/REFERENCES constraint is:
125 { NO ACTION | RESTRICT | CASCADE | SET NULL [ ( column_name [, ... ] ) ] | SET DEFAULT [ ( column_name [, ... ] ) ] }
127
129 ALTER TABLE changes the definition of an existing table. There are
130 several subforms described below. Note that the lock level required may
131 differ for each subform. An ACCESS EXCLUSIVE lock is acquired unless
132 explicitly noted. When multiple subcommands are given, the lock
133 acquired will be the strictest one required by any subcommand.
134 ADD COLUMN [ IF NOT EXISTS ]
136 This form adds a new column to the table, using the same syntax as
137 CREATE TABLE. If IF NOT EXISTS is specified and a column already
138 exists with this name, no error is thrown.
139 DROP COLUMN [ IF EXISTS ]
141 This form drops a column from a table. Indexes and table
142 constraints involving the column will be automatically dropped as
143 well. Multivariate statistics referencing the dropped column will
144 also be removed if the removal of the column would cause the
145 statistics to contain data for only a single column. You will need
146 to say CASCADE if anything outside the table depends on the column,
147 for example, foreign key references or views. If IF EXISTS is
148 specified and the column does not exist, no error is thrown. In
149 this case a notice is issued instead.
150 SET DATA TYPE
152 This form changes the type of a column of a table. Indexes and
153 simple table constraints involving the column will be automatically
154 converted to use the new column type by reparsing the originally
155 supplied expression. The optional COLLATE clause specifies a
156 collation for the new column; if omitted, the collation is the
157 default for the new column type. The optional USING clause
158 specifies how to compute the new column value from the old; if
159 omitted, the default conversion is the same as an assignment cast
160 from old data type to new. A USING clause must be provided if there
161 is no implicit or assignment cast from old to new type.
162 When this form is used, the column's statistics are removed, so
164 running ANALYZE on the table afterwards is recommended.
165 SET/DROP DEFAULT
167 These forms set or remove the default value for a column (where
168 removal is equivalent to setting the default value to NULL). The
169 new default value will only apply in subsequent INSERT or UPDATE
170 commands; it does not cause rows already in the table to change.
171 SET/DROP NOT NULL
173 These forms change whether a column is marked to allow null values
174 or to reject null values.
175 SET NOT NULL may only be applied to a column provided none of the
177 records in the table contain a NULL value for the column.
178 Ordinarily this is checked during the ALTER TABLE by scanning the
179 entire table; however, if a valid CHECK constraint is found which
180 proves no NULL can exist, then the table scan is skipped.
181 If this table is a partition, one cannot perform DROP NOT NULL on a
183 column if it is marked NOT NULL in the parent table. To drop the
184 NOT NULL constraint from all the partitions, perform DROP NOT NULL
185 on the parent table. Even if there is no NOT NULL constraint on the
186 parent, such a constraint can still be added to individual
187 partitions, if desired; that is, the children can disallow nulls
188 even if the parent allows them, but not the other way around.
189 DROP EXPRESSION [ IF EXISTS ]
191 This form turns a stored generated column into a normal base
192 column. Existing data in the columns is retained, but future
193 changes will no longer apply the generation expression.
194 If DROP EXPRESSION IF EXISTS is specified and the column is not a
196 stored generated column, no error is thrown. In this case a notice
197 is issued instead.
198 ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY
200 SET GENERATED { ALWAYS | BY DEFAULT }
201 DROP IDENTITY [ IF EXISTS ]
202 These forms change whether a column is an identity column or change
203 the generation attribute of an existing identity column. See CREATE
204 TABLE for details. Like SET DEFAULT, these forms only affect the
205 behavior of subsequent INSERT and UPDATE commands; they do not
206 cause rows already in the table to change.
207 If DROP IDENTITY IF EXISTS is specified and the column is not an
209 identity column, no error is thrown. In this case a notice is
210 issued instead.
211 SET sequence_option
213 RESTART
214 These forms alter the sequence that underlies an existing identity
215 column. sequence_option is an option supported by ALTER SEQUENCE
216 such as INCREMENT BY.
217 SET STATISTICS
219 This form sets the per-column statistics-gathering target for
220 subsequent ANALYZE operations. The target can be set in the range 0
221 to 10000; alternatively, set it to -1 to revert to using the system
222 default statistics target (default_statistics_target). For more
223 information on the use of statistics by the PostgreSQL query
224 planner, refer to Section 14.2.
225 SET STATISTICS acquires a SHARE UPDATE EXCLUSIVE lock.
227 SET ( attribute_option = value [, ... ] )
229 RESET ( attribute_option [, ... ] )
230 This form sets or resets per-attribute options. Currently, the only
231 defined per-attribute options are n_distinct and
232 n_distinct_inherited, which override the number-of-distinct-values
233 estimates made by subsequent ANALYZE operations. n_distinct
234 affects the statistics for the table itself, while
235 n_distinct_inherited affects the statistics gathered for the table
236 plus its inheritance children. When set to a positive value,
237 ANALYZE will assume that the column contains exactly the specified
238 number of distinct nonnull values. When set to a negative value,
239 which must be greater than or equal to -1, ANALYZE will assume that
240 the number of distinct nonnull values in the column is linear in
241 the size of the table; the exact count is to be computed by
242 multiplying the estimated table size by the absolute value of the
243 given number. For example, a value of -1 implies that all values in
244 the column are distinct, while a value of -0.5 implies that each
245 value appears twice on the average. This can be useful when the
246 size of the table changes over time, since the multiplication by
247 the number of rows in the table is not performed until query
248 planning time. Specify a value of 0 to revert to estimating the
249 number of distinct values normally. For more information on the use
250 of statistics by the PostgreSQL query planner, refer to
251 Section 14.2.
252 Changing per-attribute options acquires a SHARE UPDATE EXCLUSIVE
254 lock.
255 SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN | DEFAULT }
257 This form sets the storage mode for a column. This controls whether
258 this column is held inline or in a secondary TOAST table, and
259 whether the data should be compressed or not. PLAIN must be used
260 for fixed-length values such as integer and is inline,
261 uncompressed. MAIN is for inline, compressible data. EXTERNAL is
262 for external, uncompressed data, and EXTENDED is for external,
263 compressed data. Writing DEFAULT sets the storage mode to the
264 default mode for the column's data type. EXTENDED is the default
265 for most data types that support non-PLAIN storage. Use of EXTERNAL
266 will make substring operations on very large text and bytea values
267 run faster, at the penalty of increased storage space. Note that
268 ALTER TABLE ... SET STORAGE doesn't itself change anything in the
269 table; it just sets the strategy to be pursued during future table
270 updates. See Section 73.2 for more information.
271 SET COMPRESSION compression_method
273 This form sets the compression method for a column, determining how
274 values inserted in future will be compressed (if the storage mode
275 permits compression at all). This does not cause the table to be
276 rewritten, so existing data may still be compressed with other
277 compression methods. If the table is restored with pg_restore, then
278 all values are rewritten with the configured compression method.
279 However, when data is inserted from another relation (for example,
280 by INSERT ... SELECT), values from the source table are not
281 necessarily detoasted, so any previously compressed data may retain
282 its existing compression method, rather than being recompressed
283 with the compression method of the target column. The supported
284 compression methods are pglz and lz4. (lz4 is available only if
285 --with-lz4 was used when building PostgreSQL.) In addition,
286 compression_method can be default, which selects the default
287 behavior of consulting the default_toast_compression setting at the
288 time of data insertion to determine the method to use.
289 ADD table_constraint [ NOT VALID ]
291 This form adds a new constraint to a table using the same
292 constraint syntax as CREATE TABLE, plus the option NOT VALID, which
293 is currently only allowed for foreign key and CHECK constraints.
294 Normally, this form will cause a scan of the table to verify that
296 all existing rows in the table satisfy the new constraint. But if
297 the NOT VALID option is used, this potentially-lengthy scan is
298 skipped. The constraint will still be enforced against subsequent
299 inserts or updates (that is, they'll fail unless there is a
300 matching row in the referenced table, in the case of foreign keys,
301 or they'll fail unless the new row matches the specified check
302 condition). But the database will not assume that the constraint
303 holds for all rows in the table, until it is validated by using the
304 VALIDATE CONSTRAINT option. See Notes below for more information
305 about using the NOT VALID option.
306 Although most forms of ADD table_constraint require an ACCESS
308 EXCLUSIVE lock, ADD FOREIGN KEY requires only a SHARE ROW EXCLUSIVE
309 lock. Note that ADD FOREIGN KEY also acquires a SHARE ROW EXCLUSIVE
310 lock on the referenced table, in addition to the lock on the table
311 on which the constraint is declared.
312 Additional restrictions apply when unique or primary key
314 constraints are added to partitioned tables; see CREATE TABLE.
315 Also, foreign key constraints on partitioned tables may not be
316 declared NOT VALID at present.
317 ADD table_constraint_using_index
319 This form adds a new PRIMARY KEY or UNIQUE constraint to a table
320 based on an existing unique index. All the columns of the index
321 will be included in the constraint.
322 The index cannot have expression columns nor be a partial index.
324 Also, it must be a b-tree index with default sort ordering. These
325 restrictions ensure that the index is equivalent to one that would
326 be built by a regular ADD PRIMARY KEY or ADD UNIQUE command.
327 If PRIMARY KEY is specified, and the index's columns are not
329 already marked NOT NULL, then this command will attempt to do ALTER
330 COLUMN SET NOT NULL against each such column. That requires a full
331 table scan to verify the column(s) contain no nulls. In all other
332 cases, this is a fast operation.
333 If a constraint name is provided then the index will be renamed to
335 match the constraint name. Otherwise the constraint will be named
336 the same as the index.
337 After this command is executed, the index is “owned” by the
339 constraint, in the same way as if the index had been built by a
340 regular ADD PRIMARY KEY or ADD UNIQUE command. In particular,
341 dropping the constraint will make the index disappear too.
342 This form is not currently supported on partitioned tables.
344 Note
346 Adding a constraint using an existing index can be helpful in
347 situations where a new constraint needs to be added without
348 blocking table updates for a long time. To do that, create the
349 index using CREATE INDEX CONCURRENTLY, and then install it as
350 an official constraint using this syntax. See the example
351 below.
352 ALTER CONSTRAINT
354 This form alters the attributes of a constraint that was previously
355 created. Currently only foreign key constraints may be altered.
356 VALIDATE CONSTRAINT
358 This form validates a foreign key or check constraint that was
359 previously created as NOT VALID, by scanning the table to ensure
360 there are no rows for which the constraint is not satisfied.
361 Nothing happens if the constraint is already marked valid. (See
362 Notes below for an explanation of the usefulness of this command.)
363 This command acquires a SHARE UPDATE EXCLUSIVE lock.
365 DROP CONSTRAINT [ IF EXISTS ]
367 This form drops the specified constraint on a table, along with any
368 index underlying the constraint. If IF EXISTS is specified and the
369 constraint does not exist, no error is thrown. In this case a
370 notice is issued instead.
371 DISABLE/ENABLE [ REPLICA | ALWAYS ] TRIGGER
373 These forms configure the firing of trigger(s) belonging to the
374 table. A disabled trigger is still known to the system, but is not
375 executed when its triggering event occurs. (For a deferred trigger,
376 the enable status is checked when the event occurs, not when the
377 trigger function is actually executed.) One can disable or enable a
378 single trigger specified by name, or all triggers on the table, or
379 only user triggers (this option excludes internally generated
380 constraint triggers, such as those that are used to implement
381 foreign key constraints or deferrable uniqueness and exclusion
382 constraints). Disabling or enabling internally generated constraint
383 triggers requires superuser privileges; it should be done with
384 caution since of course the integrity of the constraint cannot be
385 guaranteed if the triggers are not executed.
386 The trigger firing mechanism is also affected by the configuration
388 variable session_replication_role. Simply enabled triggers (the
389 default) will fire when the replication role is “origin” (the
390 default) or “local”. Triggers configured as ENABLE REPLICA will
391 only fire if the session is in “replica” mode, and triggers
392 configured as ENABLE ALWAYS will fire regardless of the current
393 replication role.
394 The effect of this mechanism is that in the default configuration,
396 triggers do not fire on replicas. This is useful because if a
397 trigger is used on the origin to propagate data between tables,
398 then the replication system will also replicate the propagated
399 data; so the trigger should not fire a second time on the replica,
400 because that would lead to duplication. However, if a trigger is
401 used for another purpose such as creating external alerts, then it
402 might be appropriate to set it to ENABLE ALWAYS so that it is also
403 fired on replicas.
404 When this command is applied to a partitioned table, the states of
406 corresponding clone triggers in the partitions are updated too,
407 unless ONLY is specified.
408 This command acquires a SHARE ROW EXCLUSIVE lock.
410 DISABLE/ENABLE [ REPLICA | ALWAYS ] RULE
412 These forms configure the firing of rewrite rules belonging to the
413 table. A disabled rule is still known to the system, but is not
414 applied during query rewriting. The semantics are as for
415 disabled/enabled triggers. This configuration is ignored for ON
416 SELECT rules, which are always applied in order to keep views
417 working even if the current session is in a non-default replication
418 role.
419 The rule firing mechanism is also affected by the configuration
421 variable session_replication_role, analogous to triggers as
422 described above.
423 DISABLE/ENABLE ROW LEVEL SECURITY
425 These forms control the application of row security policies
426 belonging to the table. If enabled and no policies exist for the
427 table, then a default-deny policy is applied. Note that policies
428 can exist for a table even if row-level security is disabled. In
429 this case, the policies will not be applied and the policies will
430 be ignored. See also CREATE POLICY.
431 NO FORCE/FORCE ROW LEVEL SECURITY
433 These forms control the application of row security policies
434 belonging to the table when the user is the table owner. If
435 enabled, row-level security policies will be applied when the user
436 is the table owner. If disabled (the default) then row-level
437 security will not be applied when the user is the table owner. See
438 also CREATE POLICY.
439 CLUSTER ON
441 This form selects the default index for future CLUSTER operations.
442 It does not actually re-cluster the table.
443 Changing cluster options acquires a SHARE UPDATE EXCLUSIVE lock.
445 SET WITHOUT CLUSTER
447 This form removes the most recently used CLUSTER index
448 specification from the table. This affects future cluster
449 operations that don't specify an index.
450 Changing cluster options acquires a SHARE UPDATE EXCLUSIVE lock.
452 SET WITHOUT OIDS
454 Backward-compatible syntax for removing the oid system column. As
455 oid system columns cannot be added anymore, this never has an
456 effect.
457 SET ACCESS METHOD
459 This form changes the access method of the table by rewriting it.
460 See Chapter 63 for more information.
461 SET TABLESPACE
463 This form changes the table's tablespace to the specified
464 tablespace and moves the data file(s) associated with the table to
465 the new tablespace. Indexes on the table, if any, are not moved;
466 but they can be moved separately with additional SET TABLESPACE
467 commands. When applied to a partitioned table, nothing is moved,
468 but any partitions created afterwards with CREATE TABLE PARTITION
469 OF will use that tablespace, unless overridden by a TABLESPACE
470 clause.
471 All tables in the current database in a tablespace can be moved by
473 using the ALL IN TABLESPACE form, which will lock all tables to be
474 moved first and then move each one. This form also supports OWNED
475 BY, which will only move tables owned by the roles specified. If
476 the NOWAIT option is specified then the command will fail if it is
477 unable to acquire all of the locks required immediately. Note that
478 system catalogs are not moved by this command; use ALTER DATABASE
479 or explicit ALTER TABLE invocations instead if desired. The
480 information_schema relations are not considered part of the system
481 catalogs and will be moved. See also CREATE TABLESPACE.
482 SET { LOGGED | UNLOGGED }
484 This form changes the table from unlogged to logged or vice-versa
485 (see UNLOGGED). It cannot be applied to a temporary table.
486 This also changes the persistence of any sequences linked to the
488 table (for identity or serial columns). However, it is also
489 possible to change the persistence of such sequences separately.
490 SET ( storage_parameter [= value] [, ... ] )
492 This form changes one or more storage parameters for the table. See
493 Storage Parameters in the CREATE TABLE documentation for details on
494 the available parameters. Note that the table contents will not be
495 modified immediately by this command; depending on the parameter
496 you might need to rewrite the table to get the desired effects.
497 That can be done with VACUUM FULL, CLUSTER or one of the forms of
498 ALTER TABLE that forces a table rewrite. For planner related
499 parameters, changes will take effect from the next time the table
500 is locked so currently executing queries will not be affected.
501 SHARE UPDATE EXCLUSIVE lock will be taken for fillfactor, toast and
503 autovacuum storage parameters, as well as the planner parameter
504 parallel_workers.
505 RESET ( storage_parameter [, ... ] )
507 This form resets one or more storage parameters to their defaults.
508 As with SET, a table rewrite might be needed to update the table
509 entirely.
510 INHERIT parent_table
512 This form adds the target table as a new child of the specified
513 parent table. Subsequently, queries against the parent will include
514 records of the target table. To be added as a child, the target
515 table must already contain all the same columns as the parent (it
516 could have additional columns, too). The columns must have matching
517 data types, and if they have NOT NULL constraints in the parent
518 then they must also have NOT NULL constraints in the child.
519 There must also be matching child-table constraints for all CHECK
521 constraints of the parent, except those marked non-inheritable
522 (that is, created with ALTER TABLE ... ADD CONSTRAINT ... NO
523 INHERIT) in the parent, which are ignored; all child-table
524 constraints matched must not be marked non-inheritable. Currently
525 UNIQUE, PRIMARY KEY, and FOREIGN KEY constraints are not
526 considered, but this might change in the future.
527 NO INHERIT parent_table
529 This form removes the target table from the list of children of the
530 specified parent table. Queries against the parent table will no
531 longer include records drawn from the target table.
532 OF type_name
534 This form links the table to a composite type as though CREATE
535 TABLE OF had formed it. The table's list of column names and types
536 must precisely match that of the composite type. The table must not
537 inherit from any other table. These restrictions ensure that CREATE
538 TABLE OF would permit an equivalent table definition.
539 NOT OF
541 This form dissociates a typed table from its type.
542 OWNER TO
544 This form changes the owner of the table, sequence, view,
545 materialized view, or foreign table to the specified user.
546 REPLICA IDENTITY
548 This form changes the information which is written to the
549 write-ahead log to identify rows which are updated or deleted. In
550 most cases, the old value of each column is only logged if it
551 differs from the new value; however, if the old value is stored
552 externally, it is always logged regardless of whether it changed.
553 This option has no effect except when logical replication is in
554 use.
555 DEFAULT
557 Records the old values of the columns of the primary key, if
558 any. This is the default for non-system tables.
559 USING INDEX index_name
561 Records the old values of the columns covered by the named
562 index, that must be unique, not partial, not deferrable, and
563 include only columns marked NOT NULL. If this index is dropped,
564 the behavior is the same as NOTHING.
565 FULL
567 Records the old values of all columns in the row.
568 NOTHING
570 Records no information about the old row. This is the default
571 for system tables.
572 RENAME
574 The RENAME forms change the name of a table (or an index, sequence,
575 view, materialized view, or foreign table), the name of an
576 individual column in a table, or the name of a constraint of the
577 table. When renaming a constraint that has an underlying index, the
578 index is renamed as well. There is no effect on the stored data.
579 SET SCHEMA
581 This form moves the table into another schema. Associated indexes,
582 constraints, and sequences owned by table columns are moved as
583 well.
584 ATTACH PARTITION partition_name { FOR VALUES partition_bound_spec |
586 DEFAULT }
587 This form attaches an existing table (which might itself be
588 partitioned) as a partition of the target table. The table can be
589 attached as a partition for specific values using FOR VALUES or as
590 a default partition by using DEFAULT. For each index in the target
591 table, a corresponding one will be created in the attached table;
592 or, if an equivalent index already exists, it will be attached to
593 the target table's index, as if ALTER INDEX ATTACH PARTITION had
594 been executed. Note that if the existing table is a foreign table,
595 it is currently not allowed to attach the table as a partition of
596 the target table if there are UNIQUE indexes on the target table.
597 (See also CREATE FOREIGN TABLE (CREATE_FOREIGN_TABLE(7)).) For each
598 user-defined row-level trigger that exists in the target table, a
599 corresponding one is created in the attached table.
600 A partition using FOR VALUES uses same syntax for
602 partition_bound_spec as CREATE TABLE. The partition bound
603 specification must correspond to the partitioning strategy and
604 partition key of the target table. The table to be attached must
605 have all the same columns as the target table and no more;
606 moreover, the column types must also match. Also, it must have all
607 the NOT NULL and CHECK constraints of the target table. Currently
608 FOREIGN KEY constraints are not considered. UNIQUE and PRIMARY KEY
609 constraints from the parent table will be created in the partition,
610 if they don't already exist. If any of the CHECK constraints of the
611 table being attached are marked NO INHERIT, the command will fail;
612 such constraints must be recreated without the NO INHERIT clause.
613 If the new partition is a regular table, a full table scan is
615 performed to check that existing rows in the table do not violate
616 the partition constraint. It is possible to avoid this scan by
617 adding a valid CHECK constraint to the table that allows only rows
618 satisfying the desired partition constraint before running this
619 command. The CHECK constraint will be used to determine that the
620 table need not be scanned to validate the partition constraint.
621 This does not work, however, if any of the partition keys is an
622 expression and the partition does not accept NULL values. If
623 attaching a list partition that will not accept NULL values, also
624 add a NOT NULL constraint to the partition key column, unless it's
625 an expression.
626 If the new partition is a foreign table, nothing is done to verify
628 that all the rows in the foreign table obey the partition
629 constraint. (See the discussion in CREATE FOREIGN TABLE
630 (CREATE_FOREIGN_TABLE(7)) about constraints on the foreign table.)
631 When a table has a default partition, defining a new partition
633 changes the partition constraint for the default partition. The
634 default partition can't contain any rows that would need to be
635 moved to the new partition, and will be scanned to verify that none
636 are present. This scan, like the scan of the new partition, can be
637 avoided if an appropriate CHECK constraint is present. Also like
638 the scan of the new partition, it is always skipped when the
639 default partition is a foreign table.
640 Attaching a partition acquires a SHARE UPDATE EXCLUSIVE lock on the
642 parent table, in addition to the ACCESS EXCLUSIVE locks on the
643 table being attached and on the default partition (if any).
644 Further locks must also be held on all sub-partitions if the table
646 being attached is itself a partitioned table. Likewise if the
647 default partition is itself a partitioned table. The locking of the
648 sub-partitions can be avoided by adding a CHECK constraint as
649 described in Section 5.11.2.2.
650 DETACH PARTITION partition_name [ CONCURRENTLY | FINALIZE ]
652 This form detaches the specified partition of the target table. The
653 detached partition continues to exist as a standalone table, but no
654 longer has any ties to the table from which it was detached. Any
655 indexes that were attached to the target table's indexes are
656 detached. Any triggers that were created as clones of those in the
657 target table are removed. SHARE lock is obtained on any tables
658 that reference this partitioned table in foreign key constraints.
659 If CONCURRENTLY is specified, it runs using a reduced lock level to
661 avoid blocking other sessions that might be accessing the
662 partitioned table. In this mode, two transactions are used
663 internally. During the first transaction, a SHARE UPDATE EXCLUSIVE
664 lock is taken on both parent table and partition, and the partition
665 is marked as undergoing detach; at that point, the transaction is
666 committed and all other transactions using the partitioned table
667 are waited for. Once all those transactions have completed, the
668 second transaction acquires SHARE UPDATE EXCLUSIVE on the
669 partitioned table and ACCESS EXCLUSIVE on the partition, and the
670 detach process completes. A CHECK constraint that duplicates the
671 partition constraint is added to the partition. CONCURRENTLY
672 cannot be run in a transaction block and is not allowed if the
673 partitioned table contains a default partition.
674 If FINALIZE is specified, a previous DETACH CONCURRENTLY invocation
676 that was canceled or interrupted is completed. At most one
677 partition in a partitioned table can be pending detach at a time.
678 All the forms of ALTER TABLE that act on a single table, except RENAME,
680 SET SCHEMA, ATTACH PARTITION, and DETACH PARTITION can be combined into
681 a list of multiple alterations to be applied together. For example, it
682 is possible to add several columns and/or alter the type of several
683 columns in a single command. This is particularly useful with large
684 tables, since only one pass over the table need be made.
685 You must own the table to use ALTER TABLE. To change the schema or
687 tablespace of a table, you must also have CREATE privilege on the new
688 schema or tablespace. To add the table as a new child of a parent
689 table, you must own the parent table as well. Also, to attach a table
690 as a new partition of the table, you must own the table being attached.
691 To alter the owner, you must be able to SET ROLE to the new owning
692 role, and that role must have CREATE privilege on the table's schema.
693 (These restrictions enforce that altering the owner doesn't do anything
694 you couldn't do by dropping and recreating the table. However, a
695 superuser can alter ownership of any table anyway.) To add a column or
696 alter a column type or use the OF clause, you must also have USAGE
697 privilege on the data type.
698
700 IF EXISTS
701 Do not throw an error if the table does not exist. A notice is
702 issued in this case.
703 name
705 The name (optionally schema-qualified) of an existing table to
706 alter. If ONLY is specified before the table name, only that table
707 is altered. If ONLY is not specified, the table and all its
708 descendant tables (if any) are altered. Optionally, * can be
709 specified after the table name to explicitly indicate that
710 descendant tables are included.
711 column_name
713 Name of a new or existing column.
714 new_column_name
716 New name for an existing column.
717 new_name
719 New name for the table.
720 data_type
722 Data type of the new column, or new data type for an existing
723 column.
724 table_constraint
726 New table constraint for the table.
727 constraint_name
729 Name of a new or existing constraint.
730 CASCADE
732 Automatically drop objects that depend on the dropped column or
733 constraint (for example, views referencing the column), and in turn
734 all objects that depend on those objects (see Section 5.14).
735 RESTRICT
737 Refuse to drop the column or constraint if there are any dependent
738 objects. This is the default behavior.
739 trigger_name
741 Name of a single trigger to disable or enable.
742 ALL
744 Disable or enable all triggers belonging to the table. (This
745 requires superuser privilege if any of the triggers are internally
746 generated constraint triggers, such as those that are used to
747 implement foreign key constraints or deferrable uniqueness and
748 exclusion constraints.)
749 USER
751 Disable or enable all triggers belonging to the table except for
752 internally generated constraint triggers, such as those that are
753 used to implement foreign key constraints or deferrable uniqueness
754 and exclusion constraints.
755 index_name
757 The name of an existing index.
758 storage_parameter
760 The name of a table storage parameter.
761 value
763 The new value for a table storage parameter. This might be a number
764 or a word depending on the parameter.
765 parent_table
767 A parent table to associate or de-associate with this table.
768 new_owner
770 The user name of the new owner of the table.
771 new_access_method
773 The name of the access method to which the table will be converted.
774 new_tablespace
776 The name of the tablespace to which the table will be moved.
777 new_schema
779 The name of the schema to which the table will be moved.
780 partition_name
782 The name of the table to attach as a new partition or to detach
783 from this table.
784 partition_bound_spec
786 The partition bound specification for a new partition. Refer to
787 CREATE TABLE (CREATE_TABLE(7)) for more details on the syntax of
788 the same.
789
791 The key word COLUMN is noise and can be omitted.
792 When a column is added with ADD COLUMN and a non-volatile DEFAULT is
794 specified, the default is evaluated at the time of the statement and
795 the result stored in the table's metadata. That value will be used for
796 the column for all existing rows. If no DEFAULT is specified, NULL is
797 used. In neither case is a rewrite of the table required.
798 Adding a column with a volatile DEFAULT or changing the type of an
800 existing column will require the entire table and its indexes to be
801 rewritten. As an exception, when changing the type of an existing
802 column, if the USING clause does not change the column contents and the
803 old type is either binary coercible to the new type or an unconstrained
804 domain over the new type, a table rewrite is not needed. However,
805 indexes must always be rebuilt unless the system can verify that the
806 new index would be logically equivalent to the existing one. For
807 example, if the collation for a column has been changed, an index
808 rebuild is always required because the new sort order might be
809 different. However, in the absence of a collation change, a column can
810 be changed from text to varchar (or vice versa) without rebuilding the
811 indexes because these data types sort identically. Table and/or index
812 rebuilds may take a significant amount of time for a large table; and
813 will temporarily require as much as double the disk space.
814 Adding a CHECK or NOT NULL constraint requires scanning the table to
816 verify that existing rows meet the constraint, but does not require a
817 table rewrite.
818 Similarly, when attaching a new partition it may be scanned to verify
820 that existing rows meet the partition constraint.
821 The main reason for providing the option to specify multiple changes in
823 a single ALTER TABLE is that multiple table scans or rewrites can
824 thereby be combined into a single pass over the table.
825 Scanning a large table to verify a new foreign key or check constraint
827 can take a long time, and other updates to the table are locked out
828 until the ALTER TABLE ADD CONSTRAINT command is committed. The main
829 purpose of the NOT VALID constraint option is to reduce the impact of
830 adding a constraint on concurrent updates. With NOT VALID, the ADD
831 CONSTRAINT command does not scan the table and can be committed
832 immediately. After that, a VALIDATE CONSTRAINT command can be issued to
833 verify that existing rows satisfy the constraint. The validation step
834 does not need to lock out concurrent updates, since it knows that other
835 transactions will be enforcing the constraint for rows that they insert
836 or update; only pre-existing rows need to be checked. Hence, validation
837 acquires only a SHARE UPDATE EXCLUSIVE lock on the table being altered.
838 (If the constraint is a foreign key then a ROW SHARE lock is also
839 required on the table referenced by the constraint.) In addition to
840 improving concurrency, it can be useful to use NOT VALID and VALIDATE
841 CONSTRAINT in cases where the table is known to contain pre-existing
842 violations. Once the constraint is in place, no new violations can be
843 inserted, and the existing problems can be corrected at leisure until
844 VALIDATE CONSTRAINT finally succeeds.
845 The DROP COLUMN form does not physically remove the column, but simply
847 makes it invisible to SQL operations. Subsequent insert and update
848 operations in the table will store a null value for the column. Thus,
849 dropping a column is quick but it will not immediately reduce the
850 on-disk size of your table, as the space occupied by the dropped column
851 is not reclaimed. The space will be reclaimed over time as existing
852 rows are updated.
853 To force immediate reclamation of space occupied by a dropped column,
855 you can execute one of the forms of ALTER TABLE that performs a rewrite
856 of the whole table. This results in reconstructing each row with the
857 dropped column replaced by a null value.
858 The rewriting forms of ALTER TABLE are not MVCC-safe. After a table
860 rewrite, the table will appear empty to concurrent transactions, if
861 they are using a snapshot taken before the rewrite occurred. See
862 Section 13.6 for more details.
863 The USING option of SET DATA TYPE can actually specify any expression
865 involving the old values of the row; that is, it can refer to other
866 columns as well as the one being converted. This allows very general
867 conversions to be done with the SET DATA TYPE syntax. Because of this
868 flexibility, the USING expression is not applied to the column's
869 default value (if any); the result might not be a constant expression
870 as required for a default. This means that when there is no implicit or
871 assignment cast from old to new type, SET DATA TYPE might fail to
872 convert the default even though a USING clause is supplied. In such
873 cases, drop the default with DROP DEFAULT, perform the ALTER TYPE, and
874 then use SET DEFAULT to add a suitable new default. Similar
875 considerations apply to indexes and constraints involving the column.
876 If a table has any descendant tables, it is not permitted to add,
878 rename, or change the type of a column in the parent table without
879 doing the same to the descendants. This ensures that the descendants
880 always have columns matching the parent. Similarly, a CHECK constraint
881 cannot be renamed in the parent without also renaming it in all
882 descendants, so that CHECK constraints also match between the parent
883 and its descendants. (That restriction does not apply to index-based
884 constraints, however.) Also, because selecting from the parent also
885 selects from its descendants, a constraint on the parent cannot be
886 marked valid unless it is also marked valid for those descendants. In
887 all of these cases, ALTER TABLE ONLY will be rejected.
888 A recursive DROP COLUMN operation will remove a descendant table's
890 column only if the descendant does not inherit that column from any
891 other parents and never had an independent definition of the column. A
892 nonrecursive DROP COLUMN (i.e., ALTER TABLE ONLY ... DROP COLUMN) never
893 removes any descendant columns, but instead marks them as independently
894 defined rather than inherited. A nonrecursive DROP COLUMN command will
895 fail for a partitioned table, because all partitions of a table must
896 have the same columns as the partitioning root.
897 The actions for identity columns (ADD GENERATED, SET etc., DROP
899 IDENTITY), as well as the actions CLUSTER, OWNER, and TABLESPACE never
900 recurse to descendant tables; that is, they always act as though ONLY
901 were specified. Actions affecting trigger states recurse to partitions
902 of partitioned tables (unless ONLY is specified), but never to
903 traditional-inheritance descendants. Adding a constraint recurses only
904 for CHECK constraints that are not marked NO INHERIT.
905 Changing any part of a system catalog table is not permitted.
907 Refer to CREATE TABLE (CREATE_TABLE(7)) for a further description of
909 valid parameters. Chapter 5 has further information on inheritance.
910
912 To add a column of type varchar to a table:
913 ALTER TABLE distributors ADD COLUMN address varchar(30);
915 That will cause all existing rows in the table to be filled with null
917 values for the new column.
918 To add a column with a non-null default:
920 ALTER TABLE measurements
922 ADD COLUMN mtime timestamp with time zone DEFAULT now();
923 Existing rows will be filled with the current time as the value of the
925 new column, and then new rows will receive the time of their insertion.
926 To add a column and fill it with a value different from the default to
928 be used later:
929 ALTER TABLE transactions
931 ADD COLUMN status varchar(30) DEFAULT 'old',
932 ALTER COLUMN status SET default 'current';
933 Existing rows will be filled with old, but then the default for
935 subsequent commands will be current. The effects are the same as if the
936 two sub-commands had been issued in separate ALTER TABLE commands.
937 To drop a column from a table:
939 ALTER TABLE distributors DROP COLUMN address RESTRICT;
941 To change the types of two existing columns in one operation:
943 ALTER TABLE distributors
945 ALTER COLUMN address TYPE varchar(80),
946 ALTER COLUMN name TYPE varchar(100);
947 To change an integer column containing Unix timestamps to timestamp
949 with time zone via a USING clause:
950 ALTER TABLE foo
952 ALTER COLUMN foo_timestamp SET DATA TYPE timestamp with time zone
953 USING
954 timestamp with time zone 'epoch' + foo_timestamp * interval '1 second';
955 The same, when the column has a default expression that won't
957 automatically cast to the new data type:
958 ALTER TABLE foo
960 ALTER COLUMN foo_timestamp DROP DEFAULT,
961 ALTER COLUMN foo_timestamp TYPE timestamp with time zone
962 USING
963 timestamp with time zone 'epoch' + foo_timestamp * interval '1 second',
964 ALTER COLUMN foo_timestamp SET DEFAULT now();
965 To rename an existing column:
967 ALTER TABLE distributors RENAME COLUMN address TO city;
969 To rename an existing table:
971 ALTER TABLE distributors RENAME TO suppliers;
973 To rename an existing constraint:
975 ALTER TABLE distributors RENAME CONSTRAINT zipchk TO zip_check;
977 To add a not-null constraint to a column:
979 ALTER TABLE distributors ALTER COLUMN street SET NOT NULL;
981 To remove a not-null constraint from a column:
983 ALTER TABLE distributors ALTER COLUMN street DROP NOT NULL;
985 To add a check constraint to a table and all its children:
987 ALTER TABLE distributors ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5);
989 To add a check constraint only to a table and not to its children:
991 ALTER TABLE distributors ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5) NO INHERIT;
993 (The check constraint will not be inherited by future children,
995 either.)
996 To remove a check constraint from a table and all its children:
998 ALTER TABLE distributors DROP CONSTRAINT zipchk;
1000 To remove a check constraint from one table only:
1002 ALTER TABLE ONLY distributors DROP CONSTRAINT zipchk;
1004 (The check constraint remains in place for any child tables.)
1006 To add a foreign key constraint to a table:
1008 ALTER TABLE distributors ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES addresses (address);
1010 To add a foreign key constraint to a table with the least impact on
1012 other work:
1013 ALTER TABLE distributors ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES addresses (address) NOT VALID;
1015 ALTER TABLE distributors VALIDATE CONSTRAINT distfk;
1016 To add a (multicolumn) unique constraint to a table:
1018 ALTER TABLE distributors ADD CONSTRAINT dist_id_zipcode_key UNIQUE (dist_id, zipcode);
1020 To add an automatically named primary key constraint to a table, noting
1022 that a table can only ever have one primary key:
1023 ALTER TABLE distributors ADD PRIMARY KEY (dist_id);
1025 To move a table to a different tablespace:
1027 ALTER TABLE distributors SET TABLESPACE fasttablespace;
1029 To move a table to a different schema:
1031 ALTER TABLE myschema.distributors SET SCHEMA yourschema;
1033 To recreate a primary key constraint, without blocking updates while
1035 the index is rebuilt:
1036 CREATE UNIQUE INDEX CONCURRENTLY dist_id_temp_idx ON distributors (dist_id);
1038 ALTER TABLE distributors DROP CONSTRAINT distributors_pkey,
1039 ADD CONSTRAINT distributors_pkey PRIMARY KEY USING INDEX dist_id_temp_idx;
1040 To attach a partition to a range-partitioned table:
1042 ALTER TABLE measurement
1044 ATTACH PARTITION measurement_y2016m07 FOR VALUES FROM ('2016-07-01') TO ('2016-08-01');
1045 To attach a partition to a list-partitioned table:
1047 ALTER TABLE cities
1049 ATTACH PARTITION cities_ab FOR VALUES IN ('a', 'b');
1050 To attach a partition to a hash-partitioned table:
1052 ALTER TABLE orders
1054 ATTACH PARTITION orders_p4 FOR VALUES WITH (MODULUS 4, REMAINDER 3);
1055 To attach a default partition to a partitioned table:
1057 ALTER TABLE cities
1059 ATTACH PARTITION cities_partdef DEFAULT;
1060 To detach a partition from a partitioned table:
1062 ALTER TABLE measurement
1064 DETACH PARTITION measurement_y2015m12;
1065
1067 The forms ADD (without USING INDEX), DROP [COLUMN], DROP IDENTITY,
1068 RESTART, SET DEFAULT, SET DATA TYPE (without USING), SET GENERATED, and
1069 SET sequence_option conform with the SQL standard. The other forms are
1070 PostgreSQL extensions of the SQL standard. Also, the ability to specify
1071 more than one manipulation in a single ALTER TABLE command is an
1072 extension.
1073 ALTER TABLE DROP COLUMN can be used to drop the only column of a table,
1075 leaving a zero-column table. This is an extension of SQL, which
1076 disallows zero-column tables.
1077
1079 CREATE TABLE (CREATE_TABLE(7))
1080PostgreSQL 16.1 2023 ALTER TABLE(7)