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ALTER TABLE

   ALTER TABLE — change the definition of a table

Synopsis

ALTER TABLE [ IF EXISTS ] [ ONLY ] name [ * ]
    action [, ... ]
ALTER TABLE [ IF EXISTS ] [ ONLY ] name [ * ]
    RENAME [ COLUMN ] column_name TO new_column_name
ALTER TABLE [ IF EXISTS ] [ ONLY ] name [ * ]
    RENAME CONSTRAINT constraint_name TO new_constraint_name
ALTER TABLE [ IF EXISTS ] name
    RENAME TO new_name
ALTER TABLE [ IF EXISTS ] name
    SET SCHEMA new_schema
ALTER TABLE ALL IN TABLESPACE name [ OWNED BY role_name [, ... ] ]
    SET TABLESPACE new_tablespace [ NOWAIT ]
ALTER TABLE [ IF EXISTS ] name
    ATTACH PARTITION partition_name { FOR VALUES partition_bound_spec | DEFAULT
}
ALTER TABLE [ IF EXISTS ] name
    DETACH PARTITION partition_name [ CONCURRENTLY | FINALIZE ]

where action is one of:

    ADD [ COLUMN ] [ IF NOT EXISTS ] column_name data_type [ COLLATE collation ]
 [ column_constraint [ ... ] ]
    DROP [ COLUMN ] [ IF EXISTS ] column_name [ RESTRICT | CASCADE ]
    ALTER [ COLUMN ] column_name [ SET DATA ] TYPE data_type [ COLLATE collation
 ] [ USING expression ]
    ALTER [ COLUMN ] column_name SET DEFAULT expression
    ALTER [ COLUMN ] column_name DROP DEFAULT
    ALTER [ COLUMN ] column_name { SET | DROP } NOT NULL
    ALTER [ COLUMN ] column_name SET EXPRESSION AS ( expression )
    ALTER [ COLUMN ] column_name DROP EXPRESSION [ IF EXISTS ]
    ALTER [ COLUMN ] column_name ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTI
TY [ ( sequence_options ) ]
    ALTER [ COLUMN ] column_name { SET GENERATED { ALWAYS | BY DEFAULT } | SET s
equence_option | RESTART [ [ WITH ] restart ] } [...]
    ALTER [ COLUMN ] column_name DROP IDENTITY [ IF EXISTS ]
    ALTER [ COLUMN ] column_name SET STATISTICS { integer | DEFAULT }
    ALTER [ COLUMN ] column_name SET ( attribute_option = value [, ... ] )
    ALTER [ COLUMN ] column_name RESET ( attribute_option [, ... ] )
    ALTER [ COLUMN ] column_name SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAI
N | DEFAULT }
    ALTER [ COLUMN ] column_name SET COMPRESSION compression_method
    ADD table_constraint [ NOT VALID ]
    ADD table_constraint_using_index
    ALTER CONSTRAINT constraint_name [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY
 DEFERRED | INITIALLY IMMEDIATE ] [ ENFORCED | NOT ENFORCED ]
    ALTER CONSTRAINT constraint_name [ INHERIT | NO INHERIT ]
    VALIDATE CONSTRAINT constraint_name
    DROP CONSTRAINT [ IF EXISTS ]  constraint_name [ RESTRICT | CASCADE ]
    DISABLE TRIGGER [ trigger_name | ALL | USER ]
    ENABLE TRIGGER [ trigger_name | ALL | USER ]
    ENABLE REPLICA TRIGGER trigger_name
    ENABLE ALWAYS TRIGGER trigger_name
    DISABLE RULE rewrite_rule_name
    ENABLE RULE rewrite_rule_name
    ENABLE REPLICA RULE rewrite_rule_name
    ENABLE ALWAYS RULE rewrite_rule_name
    DISABLE ROW LEVEL SECURITY
    ENABLE ROW LEVEL SECURITY
    FORCE ROW LEVEL SECURITY
    NO FORCE ROW LEVEL SECURITY
    CLUSTER ON index_name
    SET WITHOUT CLUSTER
    SET WITHOUT OIDS
    SET ACCESS METHOD { new_access_method | DEFAULT }
    SET TABLESPACE new_tablespace
    SET { LOGGED | UNLOGGED }
    SET ( storage_parameter [= value] [, ... ] )
    RESET ( storage_parameter [, ... ] )
    INHERIT parent_table
    NO INHERIT parent_table
    OF type_name
    NOT OF
    OWNER TO { new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
    REPLICA IDENTITY { DEFAULT | USING INDEX index_name | FULL | NOTHING }

and partition_bound_spec is:

IN ( partition_bound_expr [, ...] ) |
FROM ( { partition_bound_expr | MINVALUE | MAXVALUE } [, ...] )
  TO ( { partition_bound_expr | MINVALUE | MAXVALUE } [, ...] ) |
WITH ( MODULUS numeric_literal, REMAINDER numeric_literal )

and column_constraint is:

[ CONSTRAINT constraint_name ]
{ NOT NULL [ NO INHERIT ] |
  NULL |
  CHECK ( expression ) [ NO INHERIT ] |
  DEFAULT default_expr |
  GENERATED ALWAYS AS ( generation_expr ) [ STORED | VIRTUAL ] |
  GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( sequence_options ) ] |
  UNIQUE [ NULLS [ NOT ] DISTINCT ] index_parameters |
  PRIMARY KEY index_parameters |
  REFERENCES reftable [ ( refcolumn ) ] [ MATCH FULL | MATCH PARTIAL | MATCH SIM
PLE ]
    [ ON DELETE referential_action ] [ ON UPDATE referential_action ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ] [ E
NFORCED | NOT ENFORCED ]

and table_constraint is:

[ CONSTRAINT constraint_name ]
{ CHECK ( expression ) [ NO INHERIT ] |
  NOT NULL column_name [ NO INHERIT ] |
  UNIQUE [ NULLS [ NOT ] DISTINCT ] ( column_name [, ... ] [, column_name WITHOU
T OVERLAPS ] ) index_parameters |
  PRIMARY KEY ( column_name [, ... ] [, column_name WITHOUT OVERLAPS ] ) index_p
arameters |
  EXCLUDE [ USING index_method ] ( exclude_element WITH operator [, ... ] ) inde
x_parameters [ WHERE ( predicate ) ] |
  FOREIGN KEY ( column_name [, ... ] [, PERIOD column_name ] ) REFERENCES reftab
le [ ( refcolumn [, ... ]  [, PERIOD refcolumn ] ) ]
    [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE referential_action
 ] [ ON UPDATE referential_action ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ] [ E
NFORCED | NOT ENFORCED ]

and table_constraint_using_index is:

    [ CONSTRAINT constraint_name ]
    { UNIQUE | PRIMARY KEY } USING INDEX index_name
    [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]

index_parameters in UNIQUE, PRIMARY KEY, and EXCLUDE constraints are:

[ INCLUDE ( column_name [, ... ] ) ]
[ WITH ( storage_parameter [= value] [, ... ] ) ]
[ USING INDEX TABLESPACE tablespace_name ]

exclude_element in an EXCLUDE constraint is:

{ column_name | ( expression ) } [ COLLATE collation ] [ opclass [ ( opclass_par
ameter = value [, ... ] ) ] ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ]

referential_action in a FOREIGN KEY/REFERENCES constraint is:

{ NO ACTION | RESTRICT | CASCADE | SET NULL [ ( column_name [, ... ] ) ] | SET D
EFAULT [ ( column_name [, ... ] ) ] }

Description

   ALTER TABLE changes the definition of an existing table. There are
   several subforms described below. Note that the lock level required may
   differ for each subform. An ACCESS EXCLUSIVE lock is acquired unless
   explicitly noted. When multiple subcommands are given, the lock
   acquired will be the strictest one required by any subcommand.

   ADD COLUMN [ IF NOT EXISTS ] #
          This form adds a new column to the table, using the same syntax
          as CREATE TABLE. If IF NOT EXISTS is specified and a column
          already exists with this name, no error is thrown.

   DROP COLUMN [ IF EXISTS ] #
          This form drops a column from a table. Indexes and table
          constraints involving the column will be automatically dropped
          as well. Multivariate statistics referencing the dropped column
          will also be removed if the removal of the column would cause
          the statistics to contain data for only a single column. You
          will need to say CASCADE if anything outside the table depends
          on the column, for example, foreign key references or views. If
          IF EXISTS is specified and the column does not exist, no error
          is thrown. In this case a notice is issued instead.

   SET DATA TYPE #
          This form changes the type of a column of a table. Indexes and
          simple table constraints involving the column will be
          automatically converted to use the new column type by reparsing
          the originally supplied expression. The optional COLLATE clause
          specifies a collation for the new column; if omitted, the
          collation is the default for the new column type. The optional
          USING clause specifies how to compute the new column value from
          the old; if omitted, the default conversion is the same as an
          assignment cast from old data type to new. A USING clause must
          be provided if there is no implicit or assignment cast from old
          to new type.

          When this form is used, the column's statistics are removed, so
          running ANALYZE on the table afterwards is recommended. For a
          virtual generated column, ANALYZE is not necessary because such
          columns never have statistics.

   SET/DROP DEFAULT #
          These forms set or remove the default value for a column (where
          removal is equivalent to setting the default value to NULL). The
          new default value will only apply in subsequent INSERT or UPDATE
          commands; it does not cause rows already in the table to change.

   SET/DROP NOT NULL #
          These forms change whether a column is marked to allow null
          values or to reject null values.

          SET NOT NULL may only be applied to a column provided none of
          the records in the table contain a NULL value for the column.
          Ordinarily this is checked during the ALTER TABLE by scanning
          the entire table, unless NOT VALID is specified; however, if a
          valid CHECK constraint exists (and is not dropped in the same
          command) which proves no NULL can exist, then the table scan is
          skipped. If a column has an invalid not-null constraint, SET NOT
          NULL validates it.

          If this table is a partition, one cannot perform DROP NOT NULL
          on a column if it is marked NOT NULL in the parent table. To
          drop the NOT NULL constraint from all the partitions, perform
          DROP NOT NULL on the parent table. Even if there is no NOT NULL
          constraint on the parent, such a constraint can still be added
          to individual partitions, if desired; that is, the children can
          disallow nulls even if the parent allows them, but not the other
          way around. It is also possible to drop the NOT NULL constraint
          from ONLY the parent table, which does not remove it from the
          children.

   SET EXPRESSION AS #
          This form replaces the expression of a generated column.
          Existing data in a stored generated column is rewritten and all
          the future changes will apply the new generation expression.

          When this form is used on a stored generated column, its
          statistics are removed, so running ANALYZE on the table
          afterwards is recommended. For a virtual generated column,
          ANALYZE is not necessary because such columns never have
          statistics.

   DROP EXPRESSION [ IF EXISTS ] #
          This form turns a stored generated column into a normal base
          column. Existing data in the columns is retained, but future
          changes will no longer apply the generation expression.

          This form is currently only supported for stored generated
          columns (not virtual ones).

          If DROP EXPRESSION IF EXISTS is specified and the column is not
          a generated column, no error is thrown. In this case a notice is
          issued instead.

   ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY
          SET GENERATED { ALWAYS | BY DEFAULT }
          DROP IDENTITY [ IF EXISTS ] #
          These forms change whether a column is an identity column or
          change the generation attribute of an existing identity column.
          See CREATE TABLE for details. Like SET DEFAULT, these forms only
          affect the behavior of subsequent INSERT and UPDATE commands;
          they do not cause rows already in the table to change.

          If DROP IDENTITY IF EXISTS is specified and the column is not an
          identity column, no error is thrown. In this case a notice is
          issued instead.

   SET sequence_option
          RESTART #
          These forms alter the sequence that underlies an existing
          identity column. sequence_option is an option supported by ALTER
          SEQUENCE such as INCREMENT BY.

   SET STATISTICS #
          This form sets the per-column statistics-gathering target for
          subsequent ANALYZE operations. The target can be set in the
          range 0 to 10000. Set it to DEFAULT to revert to using the
          system default statistics target (default_statistics_target).
          (Setting to a value of -1 is an obsolete way spelling to get the
          same outcome.) For more information on the use of statistics by
          the PostgreSQL query planner, refer to Section 14.2.

          SET STATISTICS acquires a SHARE UPDATE EXCLUSIVE lock.

   SET ( attribute_option = value [, ... ] )
          RESET ( attribute_option [, ... ] ) #
          This form sets or resets per-attribute options. Currently, the
          only defined per-attribute options are n_distinct and
          n_distinct_inherited, which override the
          number-of-distinct-values estimates made by subsequent ANALYZE
          operations. n_distinct affects the statistics for the table
          itself, while n_distinct_inherited affects the statistics
          gathered for the table plus its inheritance children. When set
          to a positive value, ANALYZE will assume that the column
          contains exactly the specified number of distinct nonnull
          values. When set to a negative value, which must be greater than
          or equal to -1, ANALYZE will assume that the number of distinct
          nonnull values in the column is linear in the size of the table;
          the exact count is to be computed by multiplying the estimated
          table size by the absolute value of the given number. For
          example, a value of -1 implies that all values in the column are
          distinct, while a value of -0.5 implies that each value appears
          twice on the average. This can be useful when the size of the
          table changes over time, since the multiplication by the number
          of rows in the table is not performed until query planning time.
          Specify a value of 0 to revert to estimating the number of
          distinct values normally. For more information on the use of
          statistics by the PostgreSQL query planner, refer to
          Section 14.2.

          Changing per-attribute options acquires a SHARE UPDATE EXCLUSIVE
          lock.

   SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN | DEFAULT } #
          This form sets the storage mode for a column. This controls
          whether this column is held inline or in a secondary TOAST
          table, and whether the data should be compressed or not. PLAIN
          must be used for fixed-length values such as integer and is
          inline, uncompressed. MAIN is for inline, compressible data.
          EXTERNAL is for external, uncompressed data, and EXTENDED is for
          external, compressed data. Writing DEFAULT sets the storage mode
          to the default mode for the column's data type. EXTENDED is the
          default for most data types that support non-PLAIN storage. Use
          of EXTERNAL will make substring operations on very large text
          and bytea values run faster, at the penalty of increased storage
          space. Note that ALTER TABLE ... SET STORAGE doesn't itself
          change anything in the table; it just sets the strategy to be
          pursued during future table updates. See Section 66.2 for more
          information.

   SET COMPRESSION compression_method #
          This form sets the compression method for a column, determining
          how values inserted in future will be compressed (if the storage
          mode permits compression at all). This does not cause the table
          to be rewritten, so existing data may still be compressed with
          other compression methods. If the table is restored with
          pg_restore, then all values are rewritten with the configured
          compression method. However, when data is inserted from another
          relation (for example, by INSERT ... SELECT), values from the
          source table are not necessarily detoasted, so any previously
          compressed data may retain its existing compression method,
          rather than being recompressed with the compression method of
          the target column. The supported compression methods are pglz
          and lz4. (lz4 is available only if --with-lz4 was used when
          building PostgreSQL.) In addition, compression_method can be
          default, which selects the default behavior of consulting the
          default_toast_compression setting at the time of data insertion
          to determine the method to use.

   ADD table_constraint [ NOT VALID ] #
          This form adds a new constraint to a table using the same
          constraint syntax as CREATE TABLE, plus the option NOT VALID,
          which is currently only allowed for foreign-key, CHECK, and
          not-null constraints.

          Normally, this form will cause a scan of the table to verify
          that all existing rows in the table satisfy the new constraint.
          But if the NOT VALID option is used, this potentially-lengthy
          scan is skipped. The constraint will still be applied against
          subsequent inserts or updates (that is, they'll fail unless
          there is a matching row in the referenced table, in the case of
          foreign keys, or they'll fail unless the new row matches the
          specified check condition). But the database will not assume
          that the constraint holds for all rows in the table, until it is
          validated by using the VALIDATE CONSTRAINT option. See Notes
          below for more information about using the NOT VALID option.

          Although most forms of ADD table_constraint require an ACCESS
          EXCLUSIVE lock, ADD FOREIGN KEY requires only a SHARE ROW
          EXCLUSIVE lock. Note that ADD FOREIGN KEY also acquires a SHARE
          ROW EXCLUSIVE lock on the referenced table, in addition to the
          lock on the table on which the constraint is declared.

          Additional restrictions apply when unique or primary key
          constraints are added to partitioned tables; see CREATE TABLE.

   ADD table_constraint_using_index #
          This form adds a new PRIMARY KEY or UNIQUE constraint to a table
          based on an existing unique index. All the columns of the index
          will be included in the constraint.

          The index cannot have expression columns nor be a partial index.
          Also, it must be a b-tree index with default sort ordering.
          These restrictions ensure that the index is equivalent to one
          that would be built by a regular ADD PRIMARY KEY or ADD UNIQUE
          command.

          If PRIMARY KEY is specified, and the index's columns are not
          already marked NOT NULL, then this command will attempt to do
          ALTER COLUMN SET NOT NULL against each such column. That
          requires a full table scan to verify the column(s) contain no
          nulls. In all other cases, this is a fast operation.

          If a constraint name is provided then the index will be renamed
          to match the constraint name. Otherwise the constraint will be
          named the same as the index.

          After this command is executed, the index is “owned” by the
          constraint, in the same way as if the index had been built by a
          regular ADD PRIMARY KEY or ADD UNIQUE command. In particular,
          dropping the constraint will make the index disappear too.

          This form is not currently supported on partitioned tables.

Note

          Adding a constraint using an existing index can be helpful in
          situations where a new constraint needs to be added without
          blocking table updates for a long time. To do that, create the
          index using CREATE UNIQUE INDEX CONCURRENTLY, and then convert
          it to a constraint using this syntax. See the example below.

   ALTER CONSTRAINT #
          This form alters the attributes of a constraint that was
          previously created. Currently only foreign key constraints may
          be altered in this fashion, but see below.

   ALTER CONSTRAINT ... INHERIT
          ALTER CONSTRAINT ... NO INHERIT #
          These forms modify a inheritable constraint so that it becomes
          not inheritable, or vice-versa. Only not-null constraints may be
          altered in this fashion at present. In addition to changing the
          inheritability status of the constraint, in the case where a
          non-inheritable constraint is being marked inheritable, if the
          table has children, an equivalent constraint will be added to
          them. If marking an inheritable constraint as non-inheritable on
          a table with children, then the corresponding constraint on
          children will be marked as no longer inherited, but not removed.

   VALIDATE CONSTRAINT #
          This form validates a foreign key, check, or not-null constraint
          that was previously created as NOT VALID, by scanning the table
          to ensure there are no rows for which the constraint is not
          satisfied. If the constraint was set to NOT ENFORCED, an error
          is thrown. Nothing happens if the constraint is already marked
          valid. (See Notes below for an explanation of the usefulness of
          this command.)

          This command acquires a SHARE UPDATE EXCLUSIVE lock.

   DROP CONSTRAINT [ IF EXISTS ] #
          This form drops the specified constraint on a table, along with
          any index underlying the constraint. If IF EXISTS is specified
          and the constraint does not exist, no error is thrown. In this
          case a notice is issued instead.

   DISABLE/ENABLE [ REPLICA | ALWAYS ] TRIGGER #
          These forms configure the firing of trigger(s) belonging to the
          table. A disabled trigger is still known to the system, but is
          not executed when its triggering event occurs. (For a deferred
          trigger, the enable status is checked when the event occurs, not
          when the trigger function is actually executed.) One can disable
          or enable a single trigger specified by name, or all triggers on
          the table, or only user triggers (this option excludes
          internally generated constraint triggers, such as those that are
          used to implement foreign key constraints or deferrable
          uniqueness and exclusion constraints). Disabling or enabling
          internally generated constraint triggers requires superuser
          privileges; it should be done with caution since of course the
          integrity of the constraint cannot be guaranteed if the triggers
          are not executed.

          The trigger firing mechanism is also affected by the
          configuration variable session_replication_role. Simply enabled
          triggers (the default) will fire when the replication role is
          “origin” (the default) or “local”. Triggers configured as ENABLE
          REPLICA will only fire if the session is in “replica” mode, and
          triggers configured as ENABLE ALWAYS will fire regardless of the
          current replication role.

          The effect of this mechanism is that in the default
          configuration, triggers do not fire on replicas. This is useful
          because if a trigger is used on the origin to propagate data
          between tables, then the replication system will also replicate
          the propagated data; so the trigger should not fire a second
          time on the replica, because that would lead to duplication.
          However, if a trigger is used for another purpose such as
          creating external alerts, then it might be appropriate to set it
          to ENABLE ALWAYS so that it is also fired on replicas.

          When this command is applied to a partitioned table, the states
          of corresponding clone triggers in the partitions are updated
          too, unless ONLY is specified.

          This command acquires a SHARE ROW EXCLUSIVE lock.

   DISABLE/ENABLE [ REPLICA | ALWAYS ] RULE #
          These forms configure the firing of rewrite rules belonging to
          the table. A disabled rule is still known to the system, but is
          not applied during query rewriting. The semantics are as for
          disabled/enabled triggers. This configuration is ignored for ON
          SELECT rules, which are always applied in order to keep views
          working even if the current session is in a non-default
          replication role.

          The rule firing mechanism is also affected by the configuration
          variable session_replication_role, analogous to triggers as
          described above.

   DISABLE/ENABLE ROW LEVEL SECURITY #
          These forms control the application of row security policies
          belonging to the table. If enabled and no policies exist for the
          table, then a default-deny policy is applied. Note that policies
          can exist for a table even if row-level security is disabled. In
          this case, the policies will not be applied and the policies
          will be ignored. See also CREATE POLICY.

   NO FORCE/FORCE ROW LEVEL SECURITY #
          These forms control the application of row security policies
          belonging to the table when the user is the table owner. If
          enabled, row-level security policies will be applied when the
          user is the table owner. If disabled (the default) then
          row-level security will not be applied when the user is the
          table owner. See also CREATE POLICY.

   CLUSTER ON #
          This form selects the default index for future CLUSTER
          operations. It does not actually re-cluster the table.

          Changing cluster options acquires a SHARE UPDATE EXCLUSIVE lock.

   SET WITHOUT CLUSTER #
          This form removes the most recently used CLUSTER index
          specification from the table. This affects future cluster
          operations that don't specify an index.

          Changing cluster options acquires a SHARE UPDATE EXCLUSIVE lock.

   SET WITHOUT OIDS #
          Backward-compatible syntax for removing the oid system column.
          As oid system columns cannot be added anymore, this never has an
          effect.

   SET ACCESS METHOD #
          This form changes the access method of the table by rewriting it
          using the indicated access method; specifying DEFAULT selects
          the access method set as the default_table_access_method
          configuration parameter. See Chapter 62 for more information.

          When applied to a partitioned table, there is no data to
          rewrite, but partitions created afterwards will default to the
          given access method unless overridden by a USING clause.
          Specifying DEFAULT removes a previous value, causing future
          partitions to default to default_table_access_method.

   SET TABLESPACE #
          This form changes the table's tablespace to the specified
          tablespace and moves the data file(s) associated with the table
          to the new tablespace. Indexes on the table, if any, are not
          moved; but they can be moved separately with additional SET
          TABLESPACE commands. When applied to a partitioned table,
          nothing is moved, but any partitions created afterwards with
          CREATE TABLE PARTITION OF will use that tablespace, unless
          overridden by a TABLESPACE clause.

          All tables in the current database in a tablespace can be moved
          by using the ALL IN TABLESPACE form, which will lock all tables
          to be moved first and then move each one. This form also
          supports OWNED BY, which will only move tables owned by the
          roles specified. If the NOWAIT option is specified then the
          command will fail if it is unable to acquire all of the locks
          required immediately. Note that system catalogs are not moved by
          this command; use ALTER DATABASE or explicit ALTER TABLE
          invocations instead if desired. The information_schema relations
          are not considered part of the system catalogs and will be
          moved. See also CREATE TABLESPACE.

   SET { LOGGED | UNLOGGED } #
          This form changes the table from unlogged to logged or
          vice-versa (see UNLOGGED). It cannot be applied to a temporary
          table.

          This also changes the persistence of any sequences linked to the
          table (for identity or serial columns). However, it is also
          possible to change the persistence of such sequences separately.

          This form is not supported for partitioned tables.

   SET ( storage_parameter [= value] [, ... ] ) #
          This form changes one or more storage parameters for the table.
          See Storage Parameters in the CREATE TABLE documentation for
          details on the available parameters. Note that the table
          contents will not be modified immediately by this command;
          depending on the parameter you might need to rewrite the table
          to get the desired effects. That can be done with VACUUM FULL,
          CLUSTER or one of the forms of ALTER TABLE that forces a table
          rewrite. For planner related parameters, changes will take
          effect from the next time the table is locked so currently
          executing queries will not be affected.

          SHARE UPDATE EXCLUSIVE lock will be taken for fillfactor, toast
          and autovacuum storage parameters, as well as the planner
          parameter parallel_workers.

   RESET ( storage_parameter [, ... ] ) #
          This form resets one or more storage parameters to their
          defaults. As with SET, a table rewrite might be needed to update
          the table entirely.

   INHERIT parent_table #
          This form adds the target table as a new child of the specified
          parent table. Subsequently, queries against the parent will
          include records of the target table. To be added as a child, the
          target table must already contain all the same columns as the
          parent (it could have additional columns, too). The columns must
          have matching data types.

          In addition, all CHECK and NOT NULL constraints on the parent
          must also exist on the child, except those marked
          non-inheritable (that is, created with ALTER TABLE ... ADD
          CONSTRAINT ... NO INHERIT), which are ignored. All child-table
          constraints matched must not be marked non-inheritable.
          Currently UNIQUE, PRIMARY KEY, and FOREIGN KEY constraints are
          not considered, but this might change in the future.

   NO INHERIT parent_table #
          This form removes the target table from the list of children of
          the specified parent table. Queries against the parent table
          will no longer include records drawn from the target table.

   OF type_name #
          This form links the table to a composite type as though CREATE
          TABLE OF had formed it. The table's list of column names and
          types must precisely match that of the composite type. The table
          must not inherit from any other table. These restrictions ensure
          that CREATE TABLE OF would permit an equivalent table
          definition.

   NOT OF #
          This form dissociates a typed table from its type.

   OWNER TO #
          This form changes the owner of the table, sequence, view,
          materialized view, or foreign table to the specified user.

   REPLICA IDENTITY #
          This form changes the information which is written to the
          write-ahead log to identify rows which are updated or deleted.
          In most cases, the old value of each column is only logged if it
          differs from the new value; however, if the old value is stored
          externally, it is always logged regardless of whether it
          changed. This option has no effect except when logical
          replication is in use.

        DEFAULT #
                Records the old values of the columns of the primary key.
                This is the default for non-system tables. When there is
                no primary key, the behavior is the same as NOTHING.

        USING INDEX index_name #
                Records the old values of the columns covered by the named
                index, that must be unique, not partial, not deferrable,
                and include only columns marked NOT NULL. If this index is
                dropped, the behavior is the same as NOTHING.

        FULL #
                Records the old values of all columns in the row.

        NOTHING #
                Records no information about the old row. This is the
                default for system tables.

   RENAME #
          The RENAME forms change the name of a table (or an index,
          sequence, view, materialized view, or foreign table), the name
          of an individual column in a table, or the name of a constraint
          of the table. When renaming a constraint that has an underlying
          index, the index is renamed as well. There is no effect on the
          stored data.

   SET SCHEMA #
          This form moves the table into another schema. Associated
          indexes, constraints, and sequences owned by table columns are
          moved as well.

   ATTACH PARTITION partition_name { FOR VALUES partition_bound_spec |
          DEFAULT } #
          This form attaches an existing table (which might itself be
          partitioned) as a partition of the target table. The table can
          be attached as a partition for specific values using FOR VALUES
          or as a default partition by using DEFAULT. For each index in
          the target table, a corresponding one will be created in the
          attached table; or, if an equivalent index already exists, it
          will be attached to the target table's index, as if ALTER INDEX
          ATTACH PARTITION had been executed. Note that if the existing
          table is a foreign table, it is currently not allowed to attach
          the table as a partition of the target table if there are UNIQUE
          indexes on the target table. (See also CREATE FOREIGN TABLE.)
          For each user-defined row-level trigger that exists in the
          target table, a corresponding one is created in the attached
          table.

          A partition using FOR VALUES uses same syntax for
          partition_bound_spec as CREATE TABLE. The partition bound
          specification must correspond to the partitioning strategy and
          partition key of the target table. The table to be attached must
          have all the same columns as the target table and no more;
          moreover, the column types must also match. Also, it must have
          all the NOT NULL and CHECK constraints of the target table, not
          marked NO INHERIT. Currently FOREIGN KEY constraints are not
          considered. UNIQUE and PRIMARY KEY constraints from the parent
          table will be created in the partition, if they don't already
          exist.

          If the new partition is a regular table, a full table scan is
          performed to check that existing rows in the table do not
          violate the partition constraint. It is possible to avoid this
          scan by adding a valid CHECK constraint to the table that allows
          only rows satisfying the desired partition constraint before
          running this command. The CHECK constraint will be used to
          determine that the table need not be scanned to validate the
          partition constraint. This does not work, however, if any of the
          partition keys is an expression and the partition does not
          accept NULL values. If attaching a list partition that will not
          accept NULL values, also add a NOT NULL constraint to the
          partition key column, unless it's an expression.

          If the new partition is a foreign table, nothing is done to
          verify that all the rows in the foreign table obey the partition
          constraint. (See the discussion in CREATE FOREIGN TABLE about
          constraints on the foreign table.)

          When a table has a default partition, defining a new partition
          changes the partition constraint for the default partition. The
          default partition can't contain any rows that would need to be
          moved to the new partition, and will be scanned to verify that
          none are present. This scan, like the scan of the new partition,
          can be avoided if an appropriate CHECK constraint is present.
          Also like the scan of the new partition, it is always skipped
          when the default partition is a foreign table.

          Attaching a partition acquires a SHARE UPDATE EXCLUSIVE lock on
          the parent table, in addition to the ACCESS EXCLUSIVE locks on
          the table being attached and on the default partition (if any).

          Further locks must also be held on all sub-partitions if the
          table being attached is itself a partitioned table. Likewise if
          the default partition is itself a partitioned table. The locking
          of the sub-partitions can be avoided by adding a CHECK
          constraint as described in Section 5.12.2.2.

   DETACH PARTITION partition_name [ CONCURRENTLY | FINALIZE ] #
          This form detaches the specified partition of the target table.
          The detached partition continues to exist as a standalone table,
          but no longer has any ties to the table from which it was
          detached. Any indexes that were attached to the target table's
          indexes are detached. Any triggers that were created as clones
          of those in the target table are removed. SHARE lock is obtained
          on any tables that reference this partitioned table in foreign
          key constraints.

          If CONCURRENTLY is specified, it runs using a reduced lock level
          to avoid blocking other sessions that might be accessing the
          partitioned table. In this mode, two transactions are used
          internally. During the first transaction, a SHARE UPDATE
          EXCLUSIVE lock is taken on both parent table and partition, and
          the partition is marked as undergoing detach; at that point, the
          transaction is committed and all other transactions using the
          partitioned table are waited for. Once all those transactions
          have completed, the second transaction acquires SHARE UPDATE
          EXCLUSIVE on the partitioned table and ACCESS EXCLUSIVE on the
          partition, and the detach process completes. A CHECK constraint
          that duplicates the partition constraint is added to the
          partition. CONCURRENTLY cannot be run in a transaction block and
          is not allowed if the partitioned table contains a default
          partition.

          If FINALIZE is specified, a previous DETACH CONCURRENTLY
          invocation that was canceled or interrupted is completed. At
          most one partition in a partitioned table can be pending detach
          at a time.

   All the forms of ALTER TABLE that act on a single table, except RENAME,
   SET SCHEMA, ATTACH PARTITION, and DETACH PARTITION can be combined into
   a list of multiple alterations to be applied together. For example, it
   is possible to add several columns and/or alter the type of several
   columns in a single command. This is particularly useful with large
   tables, since only one pass over the table need be made.

   You must own the table to use ALTER TABLE. To change the schema or
   tablespace of a table, you must also have CREATE privilege on the new
   schema or tablespace. To add the table as a new child of a parent
   table, you must own the parent table as well. Also, to attach a table
   as a new partition of the table, you must own the table being attached.
   To alter the owner, you must be able to SET ROLE to the new owning
   role, and that role must have CREATE privilege on the table's schema.
   (These restrictions enforce that altering the owner doesn't do anything
   you couldn't do by dropping and recreating the table. However, a
   superuser can alter ownership of any table anyway.) To add a column or
   alter a column type or use the OF clause, you must also have USAGE
   privilege on the data type.

Parameters

   IF EXISTS #
          Do not throw an error if the table does not exist. A notice is
          issued in this case.

   name #
          The name (optionally schema-qualified) of an existing table to
          alter. If ONLY is specified before the table name, only that
          table is altered. If ONLY is not specified, the table and all
          its descendant tables (if any) are altered. Optionally, * can be
          specified after the table name to explicitly indicate that
          descendant tables are included.

   column_name #
          Name of a new or existing column.

   new_column_name #
          New name for an existing column.

   new_name #
          New name for the table.

   data_type #
          Data type of the new column, or new data type for an existing
          column.

   table_constraint #
          New table constraint for the table.

   constraint_name #
          Name of a new or existing constraint.

   CASCADE #
          Automatically drop objects that depend on the dropped column or
          constraint (for example, views referencing the column), and in
          turn all objects that depend on those objects (see
          Section 5.15).

   RESTRICT #
          Refuse to drop the column or constraint if there are any
          dependent objects. This is the default behavior.

   trigger_name #
          Name of a single trigger to disable or enable.

   ALL #
          Disable or enable all triggers belonging to the table. (This
          requires superuser privilege if any of the triggers are
          internally generated constraint triggers, such as those that are
          used to implement foreign key constraints or deferrable
          uniqueness and exclusion constraints.)

   USER #
          Disable or enable all triggers belonging to the table except for
          internally generated constraint triggers, such as those that are
          used to implement foreign key constraints or deferrable
          uniqueness and exclusion constraints.

   index_name #
          The name of an existing index.

   storage_parameter #
          The name of a table storage parameter.

   value #
          The new value for a table storage parameter. This might be a
          number or a word depending on the parameter.

   parent_table #
          A parent table to associate or de-associate with this table.

   new_owner #
          The user name of the new owner of the table.

   new_access_method #
          The name of the access method to which the table will be
          converted.

   new_tablespace #
          The name of the tablespace to which the table will be moved.

   new_schema #
          The name of the schema to which the table will be moved.

   partition_name #
          The name of the table to attach as a new partition or to detach
          from this table.

   partition_bound_spec #
          The partition bound specification for a new partition. Refer to
          CREATE TABLE for more details on the syntax of the same.

Notes

   The key word COLUMN is noise and can be omitted.

   When a column is added with ADD COLUMN and a non-volatile DEFAULT is
   specified, the default value is evaluated at the time of the statement
   and the result stored in the table's metadata, where it will be
   returned when any existing rows are accessed. The value will be only
   applied when the table is rewritten, making the ALTER TABLE very fast
   even on large tables. If no column constraints are specified, NULL is
   used as the DEFAULT. In neither case is a rewrite of the table
   required.

   Adding a column with a volatile DEFAULT (e.g., clock_timestamp()), a
   stored generated column, an identity column, or a column with a domain
   data type that has constraints will cause the entire table and its
   indexes to be rewritten. Adding a virtual generated column never
   requires a rewrite.

   Changing the type of an existing column will normally cause the entire
   table and its indexes to be rewritten. As an exception, when changing
   the type of an existing column, if the USING clause does not change the
   column contents and the old type is either binary coercible to the new
   type or an unconstrained domain over the new type, a table rewrite is
   not needed. However, indexes will still be rebuilt unless the system
   can verify that the new index would be logically equivalent to the
   existing one. For example, if the collation for a column has been
   changed, an index rebuild is required because the new sort order might
   be different. However, in the absence of a collation change, a column
   can be changed from text to varchar (or vice versa) without rebuilding
   the indexes because these data types sort identically.

   Table and/or index rebuilds may take a significant amount of time for a
   large table, and will temporarily require as much as double the disk
   space.

   Adding a CHECK or NOT NULL constraint requires scanning the table to
   verify that existing rows meet the constraint, but does not require a
   table rewrite. If a CHECK constraint is added as NOT ENFORCED, no
   verification will be performed.

   Similarly, when attaching a new partition it may be scanned to verify
   that existing rows meet the partition constraint.

   The main reason for providing the option to specify multiple changes in
   a single ALTER TABLE is that multiple table scans or rewrites can
   thereby be combined into a single pass over the table.

   Scanning a large table to verify new foreign-key, check, or not-null
   constraints can take a long time, and other updates to the table are
   locked out until the ALTER TABLE ADD CONSTRAINT command is committed.
   The main purpose of the NOT VALID constraint option is to reduce the
   impact of adding a constraint on concurrent updates. With NOT VALID,
   the ADD CONSTRAINT command does not scan the table and can be committed
   immediately. After that, a VALIDATE CONSTRAINT command can be issued to
   verify that existing rows satisfy the constraint. The validation step
   does not need to lock out concurrent updates, since it knows that other
   transactions will be enforcing the constraint for rows that they insert
   or update; only pre-existing rows need to be checked. Hence, validation
   acquires only a SHARE UPDATE EXCLUSIVE lock on the table being altered.
   (If the constraint is a foreign key then a ROW SHARE lock is also
   required on the table referenced by the constraint.) In addition to
   improving concurrency, it can be useful to use NOT VALID and VALIDATE
   CONSTRAINT in cases where the table is known to contain pre-existing
   violations. Once the constraint is in place, no new violations can be
   inserted, and the existing problems can be corrected at leisure until
   VALIDATE CONSTRAINT finally succeeds.

   The DROP COLUMN form does not physically remove the column, but simply
   makes it invisible to SQL operations. Subsequent insert and update
   operations in the table will store a null value for the column. Thus,
   dropping a column is quick but it will not immediately reduce the
   on-disk size of your table, as the space occupied by the dropped column
   is not reclaimed. The space will be reclaimed over time as existing
   rows are updated.

   To force immediate reclamation of space occupied by a dropped column,
   you can execute one of the forms of ALTER TABLE that performs a rewrite
   of the whole table. This results in reconstructing each row with the
   dropped column replaced by a null value.

   The rewriting forms of ALTER TABLE are not MVCC-safe. After a table
   rewrite, the table will appear empty to concurrent transactions, if
   they are using a snapshot taken before the rewrite occurred. See
   Section 13.6 for more details.

   The USING option of SET DATA TYPE can actually specify any expression
   involving the old values of the row; that is, it can refer to other
   columns as well as the one being converted. This allows very general
   conversions to be done with the SET DATA TYPE syntax. Because of this
   flexibility, the USING expression is not applied to the column's
   default value (if any); the result might not be a constant expression
   as required for a default. This means that when there is no implicit or
   assignment cast from old to new type, SET DATA TYPE might fail to
   convert the default even though a USING clause is supplied. In such
   cases, drop the default with DROP DEFAULT, perform the ALTER TYPE, and
   then use SET DEFAULT to add a suitable new default. Similar
   considerations apply to indexes and constraints involving the column.

   If a table has any descendant tables, it is not permitted to add,
   rename, or change the type of a column in the parent table without
   doing the same to the descendants. This ensures that the descendants
   always have columns matching the parent. Similarly, a CHECK constraint
   cannot be renamed in the parent without also renaming it in all
   descendants, so that CHECK constraints also match between the parent
   and its descendants. (That restriction does not apply to index-based
   constraints, however.) Also, because selecting from the parent also
   selects from its descendants, a constraint on the parent cannot be
   marked valid unless it is also marked valid for those descendants. In
   all of these cases, ALTER TABLE ONLY will be rejected.

   A recursive DROP COLUMN operation will remove a descendant table's
   column only if the descendant does not inherit that column from any
   other parents and never had an independent definition of the column. A
   nonrecursive DROP COLUMN (i.e., ALTER TABLE ONLY ... DROP COLUMN) never
   removes any descendant columns, but instead marks them as independently
   defined rather than inherited. A nonrecursive DROP COLUMN command will
   fail for a partitioned table, because all partitions of a table must
   have the same columns as the partitioning root.

   The actions for identity columns (ADD GENERATED, SET etc., DROP
   IDENTITY), as well as the actions CLUSTER, OWNER, and TABLESPACE never
   recurse to descendant tables; that is, they always act as though ONLY
   were specified. Actions affecting trigger states recurse to partitions
   of partitioned tables (unless ONLY is specified), but never to
   traditional-inheritance descendants. Adding a constraint recurses only
   for CHECK constraints that are not marked NO INHERIT.

   Changing any part of a system catalog table is not permitted.

   Refer to CREATE TABLE for a further description of valid parameters.
   Chapter 5 has further information on inheritance.

Examples

   To add a column of type varchar to a table:
ALTER TABLE distributors ADD COLUMN address varchar(30);

   That will cause all existing rows in the table to be filled with null
   values for the new column.

   To add a column with a non-null default:
ALTER TABLE measurements
  ADD COLUMN mtime timestamp with time zone DEFAULT now();

   Existing rows will be filled with the current time as the value of the
   new column, and then new rows will receive the time of their insertion.

   To add a column and fill it with a value different from the default to
   be used later:
ALTER TABLE transactions
  ADD COLUMN status varchar(30) DEFAULT 'old',
  ALTER COLUMN status SET default 'current';

   Existing rows will be filled with old, but then the default for
   subsequent commands will be current. The effects are the same as if the
   two sub-commands had been issued in separate ALTER TABLE commands.

   To drop a column from a table:
ALTER TABLE distributors DROP COLUMN address RESTRICT;

   To change the types of two existing columns in one operation:
ALTER TABLE distributors
    ALTER COLUMN address TYPE varchar(80),
    ALTER COLUMN name TYPE varchar(100);

   To change an integer column containing Unix timestamps to timestamp
   with time zone via a USING clause:
ALTER TABLE foo
    ALTER COLUMN foo_timestamp SET DATA TYPE timestamp with time zone
    USING
        timestamp with time zone 'epoch' + foo_timestamp * interval '1 second';

   The same, when the column has a default expression that won't
   automatically cast to the new data type:
ALTER TABLE foo
    ALTER COLUMN foo_timestamp DROP DEFAULT,
    ALTER COLUMN foo_timestamp TYPE timestamp with time zone
    USING
        timestamp with time zone 'epoch' + foo_timestamp * interval '1 second',
    ALTER COLUMN foo_timestamp SET DEFAULT now();

   To rename an existing column:
ALTER TABLE distributors RENAME COLUMN address TO city;

   To rename an existing table:
ALTER TABLE distributors RENAME TO suppliers;

   To rename an existing constraint:
ALTER TABLE distributors RENAME CONSTRAINT zipchk TO zip_check;

   To add a not-null constraint to a column:
ALTER TABLE distributors ALTER COLUMN street SET NOT NULL;

   To remove a not-null constraint from a column:
ALTER TABLE distributors ALTER COLUMN street DROP NOT NULL;

   To add a check constraint to a table and all its children:
ALTER TABLE distributors ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5);

   To add a check constraint only to a table and not to its children:
ALTER TABLE distributors ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5)
NO INHERIT;

   (The check constraint will not be inherited by future children,
   either.)

   To remove a check constraint from a table and all its children:
ALTER TABLE distributors DROP CONSTRAINT zipchk;

   To remove a check constraint from one table only:
ALTER TABLE ONLY distributors DROP CONSTRAINT zipchk;

   (The check constraint remains in place for any child tables.)

   To add a foreign key constraint to a table:
ALTER TABLE distributors ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES
addresses (address);

   To add a foreign key constraint to a table with the least impact on
   other work:
ALTER TABLE distributors ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES
addresses (address) NOT VALID;
ALTER TABLE distributors VALIDATE CONSTRAINT distfk;

   To add a (multicolumn) unique constraint to a table:
ALTER TABLE distributors ADD CONSTRAINT dist_id_zipcode_key UNIQUE (dist_id, zip
code);

   To add an automatically named primary key constraint to a table, noting
   that a table can only ever have one primary key:
ALTER TABLE distributors ADD PRIMARY KEY (dist_id);

   To move a table to a different tablespace:
ALTER TABLE distributors SET TABLESPACE fasttablespace;

   To move a table to a different schema:
ALTER TABLE myschema.distributors SET SCHEMA yourschema;

   To recreate a primary key constraint, without blocking updates while
   the index is rebuilt:
CREATE UNIQUE INDEX CONCURRENTLY dist_id_temp_idx ON distributors (dist_id);
ALTER TABLE distributors DROP CONSTRAINT distributors_pkey,
    ADD CONSTRAINT distributors_pkey PRIMARY KEY USING INDEX dist_id_temp_idx;

   To attach a partition to a range-partitioned table:
ALTER TABLE measurement
    ATTACH PARTITION measurement_y2016m07 FOR VALUES FROM ('2016-07-01') TO ('20
16-08-01');

   To attach a partition to a list-partitioned table:
ALTER TABLE cities
    ATTACH PARTITION cities_ab FOR VALUES IN ('a', 'b');

   To attach a partition to a hash-partitioned table:
ALTER TABLE orders
    ATTACH PARTITION orders_p4 FOR VALUES WITH (MODULUS 4, REMAINDER 3);

   To attach a default partition to a partitioned table:
ALTER TABLE cities
    ATTACH PARTITION cities_partdef DEFAULT;

   To detach a partition from a partitioned table:
ALTER TABLE measurement
    DETACH PARTITION measurement_y2015m12;

Compatibility

   The forms ADD [COLUMN], DROP [COLUMN], DROP IDENTITY, RESTART, SET
   DEFAULT, SET DATA TYPE (without USING), SET GENERATED, and SET
   sequence_option conform with the SQL standard. The form ADD
   table_constraint conforms with the SQL standard when the USING INDEX
   and NOT VALID clauses are omitted and the constraint type is one of
   CHECK, UNIQUE, PRIMARY KEY, or REFERENCES. The other forms are
   PostgreSQL extensions of the SQL standard. Also, the ability to specify
   more than one manipulation in a single ALTER TABLE command is an
   extension.

   ALTER TABLE DROP COLUMN can be used to drop the only column of a table,
   leaving a zero-column table. This is an extension of SQL, which
   disallows zero-column tables.

See Also

   CREATE TABLE