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Green_GoodERP18_FSJ_Standard/PostgreSQL/doc/postgresql/html/sql-altertable.html

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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>

  2. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>ALTER TABLE</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="sql-altersystem.html" title="ALTER SYSTEM" /><link rel="next" href="sql-altertablespace.html" title="ALTER TABLESPACE" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">ALTER TABLE</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-altersystem.html" title="ALTER SYSTEM">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><th width="60%" align="center">SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-altertablespace.html" title="ALTER TABLESPACE">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-ALTERTABLE"><div class="titlepage"></div><a id="id-1.9.3.35.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">ALTER TABLE</span></h2><p>ALTER TABLE — change the definition of a table</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">

  3. ALTER TABLE [ IF EXISTS ] [ ONLY ] <em class="replaceable"><code>name</code></em> [ * ]

  4.     <em class="replaceable"><code>action</code></em> [, ... ]

  5. ALTER TABLE [ IF EXISTS ] [ ONLY ] <em class="replaceable"><code>name</code></em> [ * ]

  6.     RENAME [ COLUMN ] <em class="replaceable"><code>column_name</code></em> TO <em class="replaceable"><code>new_column_name</code></em>

  7. ALTER TABLE [ IF EXISTS ] [ ONLY ] <em class="replaceable"><code>name</code></em> [ * ]

  8.     RENAME CONSTRAINT <em class="replaceable"><code>constraint_name</code></em> TO <em class="replaceable"><code>new_constraint_name</code></em>

  9. ALTER TABLE [ IF EXISTS ] <em class="replaceable"><code>name</code></em>

  10.     RENAME TO <em class="replaceable"><code>new_name</code></em>

  11. ALTER TABLE [ IF EXISTS ] <em class="replaceable"><code>name</code></em>

  12.     SET SCHEMA <em class="replaceable"><code>new_schema</code></em>

  13. ALTER TABLE ALL IN TABLESPACE <em class="replaceable"><code>name</code></em> [ OWNED BY <em class="replaceable"><code>role_name</code></em> [, ... ] ]

  14.     SET TABLESPACE <em class="replaceable"><code>new_tablespace</code></em> [ NOWAIT ]

  15. ALTER TABLE [ IF EXISTS ] <em class="replaceable"><code>name</code></em>

  16.     ATTACH PARTITION <em class="replaceable"><code>partition_name</code></em> { FOR VALUES <em class="replaceable"><code>partition_bound_spec</code></em> | DEFAULT }

  17. ALTER TABLE [ IF EXISTS ] <em class="replaceable"><code>name</code></em>

  18.     DETACH PARTITION <em class="replaceable"><code>partition_name</code></em>

  19. 

  20. <span class="phrase">where <em class="replaceable"><code>action</code></em> is one of:</span>

  21. 

  22.     ADD [ COLUMN ] [ IF NOT EXISTS ] <em class="replaceable"><code>column_name</code></em> <em class="replaceable"><code>data_type</code></em> [ COLLATE <em class="replaceable"><code>collation</code></em> ] [ <em class="replaceable"><code>column_constraint</code></em> [ ... ] ]

  23.     DROP [ COLUMN ] [ IF EXISTS ] <em class="replaceable"><code>column_name</code></em> [ RESTRICT | CASCADE ]

  24.     ALTER [ COLUMN ] <em class="replaceable"><code>column_name</code></em> [ SET DATA ] TYPE <em class="replaceable"><code>data_type</code></em> [ COLLATE <em class="replaceable"><code>collation</code></em> ] [ USING <em class="replaceable"><code>expression</code></em> ]

  25.     ALTER [ COLUMN ] <em class="replaceable"><code>column_name</code></em> SET DEFAULT <em class="replaceable"><code>expression</code></em>

  26.     ALTER [ COLUMN ] <em class="replaceable"><code>column_name</code></em> DROP DEFAULT

  27.     ALTER [ COLUMN ] <em class="replaceable"><code>column_name</code></em> { SET | DROP } NOT NULL

  28.     ALTER [ COLUMN ] <em class="replaceable"><code>column_name</code></em> ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( <em class="replaceable"><code>sequence_options</code></em> ) ]

  29.     ALTER [ COLUMN ] <em class="replaceable"><code>column_name</code></em> { SET GENERATED { ALWAYS | BY DEFAULT } | SET <em class="replaceable"><code>sequence_option</code></em> | RESTART [ [ WITH ] <em class="replaceable"><code>restart</code></em> ] } [...]

  30.     ALTER [ COLUMN ] <em class="replaceable"><code>column_name</code></em> DROP IDENTITY [ IF EXISTS ]

  31.     ALTER [ COLUMN ] <em class="replaceable"><code>column_name</code></em> SET STATISTICS <em class="replaceable"><code>integer</code></em>

  32.     ALTER [ COLUMN ] <em class="replaceable"><code>column_name</code></em> SET ( <em class="replaceable"><code>attribute_option</code></em> = <em class="replaceable"><code>value</code></em> [, ... ] )

  33.     ALTER [ COLUMN ] <em class="replaceable"><code>column_name</code></em> RESET ( <em class="replaceable"><code>attribute_option</code></em> [, ... ] )

  34.     ALTER [ COLUMN ] <em class="replaceable"><code>column_name</code></em> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }

  35.     ADD <em class="replaceable"><code>table_constraint</code></em> [ NOT VALID ]

  36.     ADD <em class="replaceable"><code>table_constraint_using_index</code></em>

  37.     ALTER CONSTRAINT <em class="replaceable"><code>constraint_name</code></em> [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]

  38.     VALIDATE CONSTRAINT <em class="replaceable"><code>constraint_name</code></em>

  39.     DROP CONSTRAINT [ IF EXISTS ]  <em class="replaceable"><code>constraint_name</code></em> [ RESTRICT | CASCADE ]

  40.     DISABLE TRIGGER [ <em class="replaceable"><code>trigger_name</code></em> | ALL | USER ]

  41.     ENABLE TRIGGER [ <em class="replaceable"><code>trigger_name</code></em> | ALL | USER ]

  42.     ENABLE REPLICA TRIGGER <em class="replaceable"><code>trigger_name</code></em>

  43.     ENABLE ALWAYS TRIGGER <em class="replaceable"><code>trigger_name</code></em>

  44.     DISABLE RULE <em class="replaceable"><code>rewrite_rule_name</code></em>

  45.     ENABLE RULE <em class="replaceable"><code>rewrite_rule_name</code></em>

  46.     ENABLE REPLICA RULE <em class="replaceable"><code>rewrite_rule_name</code></em>

  47.     ENABLE ALWAYS RULE <em class="replaceable"><code>rewrite_rule_name</code></em>

  48.     DISABLE ROW LEVEL SECURITY

  49.     ENABLE ROW LEVEL SECURITY

  50.     FORCE ROW LEVEL SECURITY

  51.     NO FORCE ROW LEVEL SECURITY

  52.     CLUSTER ON <em class="replaceable"><code>index_name</code></em>

  53.     SET WITHOUT CLUSTER

  54.     SET WITHOUT OIDS

  55.     SET TABLESPACE <em class="replaceable"><code>new_tablespace</code></em>

  56.     SET { LOGGED | UNLOGGED }

  57.     SET ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] )

  58.     RESET ( <em class="replaceable"><code>storage_parameter</code></em> [, ... ] )

  59.     INHERIT <em class="replaceable"><code>parent_table</code></em>

  60.     NO INHERIT <em class="replaceable"><code>parent_table</code></em>

  61.     OF <em class="replaceable"><code>type_name</code></em>

  62.     NOT OF

  63.     OWNER TO { <em class="replaceable"><code>new_owner</code></em> | CURRENT_USER | SESSION_USER }

  64.     REPLICA IDENTITY { DEFAULT | USING INDEX <em class="replaceable"><code>index_name</code></em> | FULL | NOTHING }

  65. 

  66. <span class="phrase">and <em class="replaceable"><code>partition_bound_spec</code></em> is:</span>

  67. 

  68. IN ( <em class="replaceable"><code>partition_bound_expr</code></em> [, ...] ) |

  69. FROM ( { <em class="replaceable"><code>partition_bound_expr</code></em> | MINVALUE | MAXVALUE } [, ...] )

  70.   TO ( { <em class="replaceable"><code>partition_bound_expr</code></em> | MINVALUE | MAXVALUE } [, ...] ) |

  71. WITH ( MODULUS <em class="replaceable"><code>numeric_literal</code></em>, REMAINDER <em class="replaceable"><code>numeric_literal</code></em> )

  72. 

  73. <span class="phrase">and <em class="replaceable"><code>column_constraint</code></em> is:</span>

  74. 

  75. [ CONSTRAINT <em class="replaceable"><code>constraint_name</code></em> ]

  76. { NOT NULL |

  77.   NULL |

  78.   CHECK ( <em class="replaceable"><code>expression</code></em> ) [ NO INHERIT ] |

  79.   DEFAULT <em class="replaceable"><code>default_expr</code></em> |

  80.   GENERATED ALWAYS AS ( <em class="replaceable"><code>generation_expr</code></em> ) STORED |

  81.   GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( <em class="replaceable"><code>sequence_options</code></em> ) ] |

  82.   UNIQUE <em class="replaceable"><code>index_parameters</code></em> |

  83.   PRIMARY KEY <em class="replaceable"><code>index_parameters</code></em> |

  84.   REFERENCES <em class="replaceable"><code>reftable</code></em> [ ( <em class="replaceable"><code>refcolumn</code></em> ) ] [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ]

  85.     [ ON DELETE <em class="replaceable"><code>referential_action</code></em> ] [ ON UPDATE <em class="replaceable"><code>referential_action</code></em> ] }

  86. [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]

  87. 

  88. <span class="phrase">and <em class="replaceable"><code>table_constraint</code></em> is:</span>

  89. 

  90. [ CONSTRAINT <em class="replaceable"><code>constraint_name</code></em> ]

  91. { CHECK ( <em class="replaceable"><code>expression</code></em> ) [ NO INHERIT ] |

  92.   UNIQUE ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) <em class="replaceable"><code>index_parameters</code></em> |

  93.   PRIMARY KEY ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) <em class="replaceable"><code>index_parameters</code></em> |

  94.   EXCLUDE [ USING <em class="replaceable"><code>index_method</code></em> ] ( <em class="replaceable"><code>exclude_element</code></em> WITH <em class="replaceable"><code>operator</code></em> [, ... ] ) <em class="replaceable"><code>index_parameters</code></em> [ WHERE ( <em class="replaceable"><code>predicate</code></em> ) ] |

  95.   FOREIGN KEY ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) REFERENCES <em class="replaceable"><code>reftable</code></em> [ ( <em class="replaceable"><code>refcolumn</code></em> [, ... ] ) ]

  96.     [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE <em class="replaceable"><code>referential_action</code></em> ] [ ON UPDATE <em class="replaceable"><code>referential_action</code></em> ] }

  97. [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]

  98. 

  99. <span class="phrase">and <em class="replaceable"><code>table_constraint_using_index</code></em> is:</span>

  100. 

  101.     [ CONSTRAINT <em class="replaceable"><code>constraint_name</code></em> ]

  102.     { UNIQUE | PRIMARY KEY } USING INDEX <em class="replaceable"><code>index_name</code></em>

  103.     [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]

  104. 

  105. <span class="phrase"><em class="replaceable"><code>index_parameters</code></em> in <code class="literal">UNIQUE</code>, <code class="literal">PRIMARY KEY</code>, and <code class="literal">EXCLUDE</code> constraints are:</span>

  106. 

  107. [ INCLUDE ( <em class="replaceable"><code>column_name</code></em> [, ... ] ) ]

  108. [ WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] ) ]

  109. [ USING INDEX TABLESPACE <em class="replaceable"><code>tablespace_name</code></em> ]

  110. 

  111. <span class="phrase"><em class="replaceable"><code>exclude_element</code></em> in an <code class="literal">EXCLUDE</code> constraint is:</span>

  112. 

  113. { <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ <em class="replaceable"><code>opclass</code></em> ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ]

  114. </pre></div><div class="refsect1" id="id-1.9.3.35.5"><h2>Description</h2><p>

  115.    <code class="command">ALTER TABLE</code> changes the definition of an existing table.

  116.    There are several subforms described below. Note that the lock level required

  117.    may differ for each subform. An <code class="literal">ACCESS EXCLUSIVE</code> lock is

  118.    acquired unless explicitly noted. When multiple subcommands are given, the

  119.    lock acquired will be the strictest one required by any subcommand.

  120. 

  121.   </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">ADD COLUMN [ IF NOT EXISTS ]</code></span></dt><dd><p>

  122.       This form adds a new column to the table, using the same syntax as

  123.       <a class="xref" href="sql-createtable.html" title="CREATE TABLE"><span class="refentrytitle">CREATE TABLE</span></a>. If <code class="literal">IF NOT EXISTS</code>

  124.       is specified and a column already exists with this name,

  125.       no error is thrown.

  126.      </p></dd><dt><span class="term"><code class="literal">DROP COLUMN [ IF EXISTS ]</code></span></dt><dd><p>

  127.       This form drops a column from a table.  Indexes and

  128.       table constraints involving the column will be automatically

  129.       dropped as well.

  130.       Multivariate statistics referencing the dropped column will also be

  131.       removed if the removal of the column would cause the statistics to

  132.       contain data for only a single column.

  133.       You will need to say <code class="literal">CASCADE</code> if anything outside the table

  134.       depends on the column, for example, foreign key references or views.

  135.       If <code class="literal">IF EXISTS</code> is specified and the column

  136.       does not exist, no error is thrown. In this case a notice

  137.       is issued instead.

  138.      </p></dd><dt><span class="term"><code class="literal">SET DATA TYPE</code></span></dt><dd><p>

  139.       This form changes the type of a column of a table. Indexes and

  140.       simple table constraints involving the column will be automatically

  141.       converted to use the new column type by reparsing the originally

  142.       supplied expression.

  143.       The optional <code class="literal">COLLATE</code> clause specifies a collation

  144.       for the new column; if omitted, the collation is the default for the

  145.       new column type.

  146.       The optional <code class="literal">USING</code>

  147.       clause specifies how to compute the new column value from the old;

  148.       if omitted, the default conversion is the same as an assignment

  149.       cast from old data type to new.  A  <code class="literal">USING</code>

  150.       clause must be provided if there is no implicit or assignment

  151.       cast from old to new type.

  152.      </p></dd><dt><span class="term"><code class="literal">SET</code>/<code class="literal">DROP DEFAULT</code></span></dt><dd><p>

  153.       These forms set or remove the default value for a column.

  154.       Default values only apply in subsequent <code class="command">INSERT</code>

  155.       or <code class="command">UPDATE</code> commands; they do not cause rows already in the

  156.       table to change.

  157.      </p></dd><dt><span class="term"><code class="literal">SET</code>/<code class="literal">DROP NOT NULL</code></span></dt><dd><p>

  158.       These forms change whether a column is marked to allow null

  159.       values or to reject null values.

  160.      </p><p>

  161.       <code class="literal">SET NOT NULL</code> may only be applied to a column

  162.       provided none of the records in the table contain a

  163.       <code class="literal">NULL</code> value for the column.  Ordinarily this is

  164.       checked during the <code class="literal">ALTER TABLE</code> by scanning the

  165.       entire table; however, if a valid <code class="literal">CHECK</code> constraint is

  166.       found which proves no <code class="literal">NULL</code> can exist, then the

  167.       table scan is skipped.

  168.      </p><p>

  169.       If this table is a partition, one cannot perform <code class="literal">DROP NOT NULL</code>

  170.       on a column if it is marked <code class="literal">NOT NULL</code> in the parent

  171.       table.  To drop the <code class="literal">NOT NULL</code> constraint from all the

  172.       partitions, perform <code class="literal">DROP NOT NULL</code> on the parent

  173.       table.  Even if there is no <code class="literal">NOT NULL</code> constraint on the

  174.       parent, such a constraint can still be added to individual partitions,

  175.       if desired; that is, the children can disallow nulls even if the parent

  176.       allows them, but not the other way around.

  177.      </p></dd><dt><span class="term"><code class="literal">ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY</code><br /></span><span class="term"><code class="literal">SET GENERATED { ALWAYS | BY DEFAULT }</code><br /></span><span class="term"><code class="literal">DROP IDENTITY [ IF EXISTS ]</code></span></dt><dd><p>

  178.       These forms change whether a column is an identity column or change the

  179.       generation attribute of an existing identity column.

  180.       See <a class="xref" href="sql-createtable.html" title="CREATE TABLE"><span class="refentrytitle">CREATE TABLE</span></a> for details.

  181.      </p><p>

  182.       If <code class="literal">DROP IDENTITY IF EXISTS</code> is specified and the

  183.       column is not an identity column, no error is thrown.  In this case a

  184.       notice is issued instead.

  185.      </p></dd><dt><span class="term"><code class="literal">SET <em class="replaceable"><code>sequence_option</code></em></code><br /></span><span class="term"><code class="literal">RESTART</code></span></dt><dd><p>

  186.       These forms alter the sequence that underlies an existing identity

  187.       column.  <em class="replaceable"><code>sequence_option</code></em> is an option

  188.       supported by <a class="xref" href="sql-altersequence.html" title="ALTER SEQUENCE"><span class="refentrytitle">ALTER SEQUENCE</span></a> such

  189.       as <code class="literal">INCREMENT BY</code>.

  190.      </p></dd><dt><span class="term"><code class="literal">SET STATISTICS</code></span></dt><dd><p>

  191.       This form

  192.       sets the per-column statistics-gathering target for subsequent

  193.       <a class="xref" href="sql-analyze.html" title="ANALYZE"><span class="refentrytitle">ANALYZE</span></a> operations.

  194.       The target can be set in the range 0 to 10000; alternatively, set it

  195.       to -1 to revert to using the system default statistics

  196.       target (<a class="xref" href="runtime-config-query.html#GUC-DEFAULT-STATISTICS-TARGET">default_statistics_target</a>).

  197.       For more information on the use of statistics by the

  198.       <span class="productname">PostgreSQL</span> query planner, refer to

  199.       <a class="xref" href="planner-stats.html" title="14.2. Statistics Used by the Planner">Section 14.2</a>.

  200.      </p><p>

  201.       <code class="literal">SET STATISTICS</code> acquires a

  202.       <code class="literal">SHARE UPDATE EXCLUSIVE</code> lock.

  203.      </p></dd><dt><span class="term"><code class="literal">SET ( <em class="replaceable"><code>attribute_option</code></em> = <em class="replaceable"><code>value</code></em> [, ... ] )</code><br /></span><span class="term"><code class="literal">RESET ( <em class="replaceable"><code>attribute_option</code></em> [, ... ] )</code></span></dt><dd><p>

  204.       This form sets or resets per-attribute options.  Currently, the only

  205.       defined per-attribute options are <code class="literal">n_distinct</code> and

  206.       <code class="literal">n_distinct_inherited</code>, which override the

  207.       number-of-distinct-values estimates made by subsequent

  208.       <a class="xref" href="sql-analyze.html" title="ANALYZE"><span class="refentrytitle">ANALYZE</span></a>

  209.       operations.  <code class="literal">n_distinct</code> affects the statistics for the table

  210.       itself, while <code class="literal">n_distinct_inherited</code> affects the statistics

  211.       gathered for the table plus its inheritance children.  When set to a

  212.       positive value, <code class="command">ANALYZE</code> will assume that the column contains

  213.       exactly the specified number of distinct nonnull values.  When set to a

  214.       negative value, which must be greater

  215.       than or equal to -1, <code class="command">ANALYZE</code> will assume that the number of

  216.       distinct nonnull values in the column is linear in the size of the

  217.       table; the exact count is to be computed by multiplying the estimated

  218.       table size by the absolute value of the given number.  For example,

  219.       a value of -1 implies that all values in the column are distinct, while

  220.       a value of -0.5 implies that each value appears twice on the average.

  221.       This can be useful when the size of the table changes over time, since

  222.       the multiplication by the number of rows in the table is not performed

  223.       until query planning time.  Specify a value of 0 to revert to estimating

  224.       the number of distinct values normally.  For more information on the use

  225.       of statistics by the <span class="productname">PostgreSQL</span> query

  226.       planner, refer to <a class="xref" href="planner-stats.html" title="14.2. Statistics Used by the Planner">Section 14.2</a>.

  227.      </p><p>

  228.       Changing per-attribute options acquires a

  229.       <code class="literal">SHARE UPDATE EXCLUSIVE</code> lock.

  230.      </p></dd><dt><span class="term">

  231.      <code class="literal">SET STORAGE</code>

  232.      <a id="id-1.9.3.35.5.2.3.10.1.2" class="indexterm"></a>

  233.     </span></dt><dd><p>

  234.       This form sets the storage mode for a column. This controls whether this

  235.       column is held inline or in a secondary <acronym class="acronym">TOAST</acronym> table, and

  236.       whether the data

  237.       should be compressed or not. <code class="literal">PLAIN</code> must be used

  238.       for fixed-length values such as <code class="type">integer</code> and is

  239.       inline, uncompressed. <code class="literal">MAIN</code> is for inline,

  240.       compressible data. <code class="literal">EXTERNAL</code> is for external,

  241.       uncompressed data, and <code class="literal">EXTENDED</code> is for external,

  242.       compressed data.  <code class="literal">EXTENDED</code> is the default for most

  243.       data types that support non-<code class="literal">PLAIN</code> storage.

  244.       Use of <code class="literal">EXTERNAL</code> will make substring operations on

  245.       very large <code class="type">text</code> and <code class="type">bytea</code> values run faster,

  246.       at the penalty of increased storage space.  Note that

  247.       <code class="literal">SET STORAGE</code> doesn't itself change anything in the table,

  248.       it just sets the strategy to be pursued during future table updates.

  249.       See <a class="xref" href="storage-toast.html" title="68.2. TOAST">Section 68.2</a> for more information.

  250.      </p></dd><dt><span class="term"><code class="literal">ADD <em class="replaceable"><code>table_constraint</code></em> [ NOT VALID ]</code></span></dt><dd><p>

  251.       This form adds a new constraint to a table using the same constraint

  252.       syntax as <a class="xref" href="sql-createtable.html" title="CREATE TABLE"><span class="refentrytitle">CREATE TABLE</span></a>, plus the option <code class="literal">NOT

  253.       VALID</code>, which is currently only allowed for foreign key

  254.       and CHECK constraints.

  255.      </p><p>

  256.       Normally, this form will cause a scan of the table to verify that all

  257.       existing rows in the table satisfy the new constraint.  But if

  258.       the <code class="literal">NOT VALID</code> option is used, this

  259.       potentially-lengthy scan is skipped.  The constraint will still be

  260.       enforced against subsequent inserts or updates (that is, they'll fail

  261.       unless there is a matching row in the referenced table, in the case

  262.       of foreign keys, or they'll fail unless the new row matches the

  263.       specified check condition).  But the

  264.       database will not assume that the constraint holds for all rows in

  265.       the table, until it is validated by using the <code class="literal">VALIDATE

  266.       CONSTRAINT</code> option.

  267.       See <a class="xref" href="sql-altertable.html#SQL-ALTERTABLE-NOTES" title="Notes">Notes</a> below for more information

  268.       about using the <code class="literal">NOT VALID</code> option.

  269.      </p><p>

  270.       Although most forms of <code class="literal">ADD

  271.       <em class="replaceable"><code>table_constraint</code></em></code>

  272.       require an <code class="literal">ACCESS EXCLUSIVE</code> lock, <code class="literal">ADD

  273.       FOREIGN KEY</code> requires only a <code class="literal">SHARE ROW

  274.       EXCLUSIVE</code> lock.  Note that <code class="literal">ADD FOREIGN KEY</code>

  275.       also acquires a <code class="literal">SHARE ROW EXCLUSIVE</code> lock on the

  276.       referenced table, in addition to the lock on the table on which the

  277.       constraint is declared.

  278.      </p><p>

  279.       Additional restrictions apply when unique or primary key constraints

  280.       are added to partitioned tables; see <a class="xref" href="sql-createtable.html" title="CREATE TABLE"><span class="refentrytitle">CREATE TABLE</span></a>.

  281.       Also, foreign key constraints on partitioned

  282.       tables may not be declared <code class="literal">NOT VALID</code> at present.

  283.      </p></dd><dt><span class="term"><code class="literal">ADD <em class="replaceable"><code>table_constraint_using_index</code></em></code></span></dt><dd><p>

  284.       This form adds a new <code class="literal">PRIMARY KEY</code> or <code class="literal">UNIQUE</code>

  285.       constraint to a table based on an existing unique index.  All the

  286.       columns of the index will be included in the constraint.

  287.      </p><p>

  288.       The index cannot have expression columns nor be a partial index.

  289.       Also, it must be a b-tree index with default sort ordering.  These

  290.       restrictions ensure that the index is equivalent to one that would be

  291.       built by a regular <code class="literal">ADD PRIMARY KEY</code> or <code class="literal">ADD UNIQUE</code>

  292.       command.

  293.      </p><p>

  294.       If <code class="literal">PRIMARY KEY</code> is specified, and the index's columns are not

  295.       already marked <code class="literal">NOT NULL</code>, then this command will attempt to

  296.       do <code class="literal">ALTER COLUMN SET NOT NULL</code> against each such column.

  297.       That requires a full table scan to verify the column(s) contain no

  298.       nulls.  In all other cases, this is a fast operation.

  299.      </p><p>

  300.       If a constraint name is provided then the index will be renamed to match

  301.       the constraint name.  Otherwise the constraint will be named the same as

  302.       the index.

  303.      </p><p>

  304.       After this command is executed, the index is <span class="quote">“<span class="quote">owned</span>”</span> by the

  305.       constraint, in the same way as if the index had been built by

  306.       a regular <code class="literal">ADD PRIMARY KEY</code> or <code class="literal">ADD UNIQUE</code>

  307.       command.  In particular, dropping the constraint will make the index

  308.       disappear too.

  309.      </p><p>

  310.       This form is not currently supported on partitioned tables.

  311.      </p><div class="note"><h3 class="title">Note</h3><p>

  312.        Adding a constraint using an existing index can be helpful in

  313.        situations where a new constraint needs to be added without blocking

  314.        table updates for a long time.  To do that, create the index using

  315.        <code class="command">CREATE INDEX CONCURRENTLY</code>, and then install it as an

  316.        official constraint using this syntax.  See the example below.

  317.       </p></div></dd><dt><span class="term"><code class="literal">ALTER CONSTRAINT</code></span></dt><dd><p>

  318.       This form alters the attributes of a constraint that was previously

  319.       created. Currently only foreign key constraints may be altered.

  320.      </p></dd><dt><span class="term"><code class="literal">VALIDATE CONSTRAINT</code></span></dt><dd><p>

  321.       This form validates a foreign key or check constraint that was

  322.       previously created as <code class="literal">NOT VALID</code>, by scanning the

  323.       table to ensure there are no rows for which the constraint is not

  324.       satisfied.  Nothing happens if the constraint is already marked valid.

  325.       (See <a class="xref" href="sql-altertable.html#SQL-ALTERTABLE-NOTES" title="Notes">Notes</a> below for an explanation of the

  326.       usefulness of this command.)

  327.      </p></dd><dt><span class="term"><code class="literal">DROP CONSTRAINT [ IF EXISTS ]</code></span></dt><dd><p>

  328.       This form drops the specified constraint on a table, along with

  329.       any index underlying the constraint.

  330.       If <code class="literal">IF EXISTS</code> is specified and the constraint

  331.       does not exist, no error is thrown. In this case a notice is issued instead.

  332.      </p></dd><dt><span class="term"><code class="literal">DISABLE</code>/<code class="literal">ENABLE [ REPLICA | ALWAYS ] TRIGGER</code></span></dt><dd><p>

  333.       These forms configure the firing of trigger(s) belonging to the table.

  334.       A disabled trigger is still known to the system, but is not executed

  335.       when its triggering event occurs.  For a deferred trigger, the enable

  336.       status is checked when the event occurs, not when the trigger function

  337.       is actually executed.  One can disable or enable a single

  338.       trigger specified by name, or all triggers on the table, or only

  339.       user triggers (this option excludes internally generated constraint

  340.       triggers such as those that are used to implement foreign key

  341.       constraints or deferrable uniqueness and exclusion constraints).

  342.       Disabling or enabling internally generated constraint triggers

  343.       requires superuser privileges; it should be done with caution since

  344.       of course the integrity of the constraint cannot be guaranteed if the

  345.       triggers are not executed.

  346.      </p><p>

  347.       The trigger firing mechanism is also affected by the configuration

  348.       variable <a class="xref" href="runtime-config-client.html#GUC-SESSION-REPLICATION-ROLE">session_replication_role</a>. Simply enabled

  349.       triggers (the default) will fire when the replication role is <span class="quote">“<span class="quote">origin</span>”</span>

  350.       (the default) or <span class="quote">“<span class="quote">local</span>”</span>. Triggers configured as <code class="literal">ENABLE

  351.       REPLICA</code> will only fire if the session is in <span class="quote">“<span class="quote">replica</span>”</span>

  352.       mode, and triggers configured as <code class="literal">ENABLE ALWAYS</code> will

  353.       fire regardless of the current replication role.

  354.      </p><p>

  355.       The effect of this mechanism is that in the default configuration,

  356.       triggers do not fire on replicas.  This is useful because if a trigger

  357.       is used on the origin to propagate data between tables, then the

  358.       replication system will also replicate the propagated data, and the

  359.       trigger should not fire a second time on the replica, because that would

  360.       lead to duplication.  However, if a trigger is used for another purpose

  361.       such as creating external alerts, then it might be appropriate to set it

  362.       to <code class="literal">ENABLE ALWAYS</code> so that it is also fired on

  363.       replicas.

  364.      </p><p>

  365.       This command acquires a <code class="literal">SHARE ROW EXCLUSIVE</code> lock.

  366.      </p></dd><dt><span class="term"><code class="literal">DISABLE</code>/<code class="literal">ENABLE [ REPLICA | ALWAYS ] RULE</code></span></dt><dd><p>

  367.       These forms configure the firing of rewrite rules belonging to the table.

  368.       A disabled rule is still known to the system, but is not applied

  369.       during query rewriting. The semantics are as for disabled/enabled

  370.       triggers. This configuration is ignored for <code class="literal">ON SELECT</code> rules, which

  371.       are always applied in order to keep views working even if the current

  372.       session is in a non-default replication role.

  373.      </p><p>

  374.       The rule firing mechanism is also affected by the configuration variable

  375.       <a class="xref" href="runtime-config-client.html#GUC-SESSION-REPLICATION-ROLE">session_replication_role</a>, analogous to triggers as

  376.       described above.

  377.      </p></dd><dt><span class="term"><code class="literal">DISABLE</code>/<code class="literal">ENABLE ROW LEVEL SECURITY</code></span></dt><dd><p>

  378.       These forms control the application of row security policies belonging

  379.       to the table.  If enabled and no policies exist for the table, then a

  380.       default-deny policy is applied.  Note that policies can exist for a table

  381.       even if row level security is disabled - in this case, the policies will

  382.       NOT be applied and the policies will be ignored.

  383.       See also

  384.       <a class="xref" href="sql-createpolicy.html" title="CREATE POLICY"><span class="refentrytitle">CREATE POLICY</span></a>.

  385.      </p></dd><dt><span class="term"><code class="literal">NO FORCE</code>/<code class="literal">FORCE ROW LEVEL SECURITY</code></span></dt><dd><p>

  386.       These forms control the application of row security policies belonging

  387.       to the table when the user is the table owner.  If enabled, row level

  388.       security policies will be applied when the user is the table owner.  If

  389.       disabled (the default) then row level security will not be applied when

  390.       the user is the table owner.

  391.       See also

  392.       <a class="xref" href="sql-createpolicy.html" title="CREATE POLICY"><span class="refentrytitle">CREATE POLICY</span></a>.

  393.      </p></dd><dt><span class="term"><code class="literal">CLUSTER ON</code></span></dt><dd><p>

  394.       This form selects the default index for future

  395.       <a class="xref" href="sql-cluster.html" title="CLUSTER"><span class="refentrytitle">CLUSTER</span></a>

  396.       operations.  It does not actually re-cluster the table.

  397.      </p><p>

  398.       Changing cluster options acquires a <code class="literal">SHARE UPDATE EXCLUSIVE</code> lock.

  399.      </p></dd><dt><span class="term"><code class="literal">SET WITHOUT CLUSTER</code></span></dt><dd><p>

  400.       This form removes the most recently used

  401.       <a class="xref" href="sql-cluster.html" title="CLUSTER"><span class="refentrytitle">CLUSTER</span></a>

  402.       index specification from the table.  This affects

  403.       future cluster operations that don't specify an index.

  404.      </p><p>

  405.       Changing cluster options acquires a <code class="literal">SHARE UPDATE EXCLUSIVE</code> lock.

  406.      </p></dd><dt><span class="term"><code class="literal">SET WITHOUT OIDS</code></span></dt><dd><p>

  407.       Backward-compatible syntax for removing the <code class="literal">oid</code>

  408.       system column.  As <code class="literal">oid</code> system columns cannot be

  409.       added anymore, this never has an effect.

  410.      </p></dd><dt><span class="term"><code class="literal">SET TABLESPACE</code></span></dt><dd><p>

  411.       This form changes the table's tablespace to the specified tablespace and

  412.       moves the data file(s) associated with the table to the new tablespace.

  413.       Indexes on the table, if any, are not moved; but they can be moved

  414.       separately with additional <code class="literal">SET TABLESPACE</code> commands.

  415.       When applied to a partitioned table, nothing is moved, but any

  416.       partitions created afterwards with

  417.       <code class="command">CREATE TABLE PARTITION OF</code> will use that tablespace,

  418.       unless the <code class="literal">TABLESPACE</code> clause is used to override it.

  419.      </p><p>

  420.       All tables in the current database in a tablespace can be moved by using

  421.       the <code class="literal">ALL IN TABLESPACE</code> form, which will lock all tables

  422.       to be moved first and then move each one.  This form also supports

  423.       <code class="literal">OWNED BY</code>, which will only move tables owned by the

  424.       roles specified.  If the <code class="literal">NOWAIT</code> option is specified

  425.       then the command will fail if it is unable to acquire all of the locks

  426.       required immediately.  Note that system catalogs are not moved by this

  427.       command; use <code class="command">ALTER DATABASE</code> or explicit

  428.       <code class="command">ALTER TABLE</code> invocations instead if desired.  The

  429.       <code class="literal">information_schema</code> relations are not considered part

  430.       of the system catalogs and will be moved.

  431.       See also

  432.       <a class="xref" href="sql-createtablespace.html" title="CREATE TABLESPACE"><span class="refentrytitle">CREATE TABLESPACE</span></a>.

  433.      </p></dd><dt><span class="term"><code class="literal">SET { LOGGED | UNLOGGED }</code></span></dt><dd><p>

  434.       This form changes the table from unlogged to logged or vice-versa

  435.       (see <a class="xref" href="sql-createtable.html#SQL-CREATETABLE-UNLOGGED"><code class="literal">UNLOGGED</code></a>).  It cannot be applied

  436.       to a temporary table.

  437.      </p></dd><dt><span class="term"><code class="literal">SET ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] )</code></span></dt><dd><p>

  438.       This form changes one or more storage parameters for the table.  See

  439.       <a class="xref" href="sql-createtable.html#SQL-CREATETABLE-STORAGE-PARAMETERS" title="Storage Parameters">Storage Parameters</a>

  440.       for details on the available parameters.  Note that the table contents

  441.       will not be modified immediately by this command; depending on the

  442.       parameter you might need to rewrite the table to get the desired effects.

  443.       That can be done with <a class="link" href="sql-vacuum.html" title="VACUUM">VACUUM

  444.       FULL</a>, <a class="xref" href="sql-cluster.html" title="CLUSTER"><span class="refentrytitle">CLUSTER</span></a> or one of the forms

  445.       of <code class="command">ALTER TABLE</code> that forces a table rewrite.

  446.       For planner related parameters, changes will take effect from the next

  447.       time the table is locked so currently executing queries will not be

  448.       affected.

  449.      </p><p>

  450.       <code class="literal">SHARE UPDATE EXCLUSIVE</code> lock will be taken for

  451.       fillfactor, toast and autovacuum storage parameters, as well as the

  452.       planner parameter <code class="varname">parallel_workers</code>.

  453.      </p></dd><dt><span class="term"><code class="literal">RESET ( <em class="replaceable"><code>storage_parameter</code></em> [, ... ] )</code></span></dt><dd><p>

  454.       This form resets one or more storage parameters to their

  455.       defaults.  As with <code class="literal">SET</code>, a table rewrite might be

  456.       needed to update the table entirely.

  457.      </p></dd><dt><span class="term"><code class="literal">INHERIT <em class="replaceable"><code>parent_table</code></em></code></span></dt><dd><p>

  458.       This form adds the target table as a new child of the specified parent

  459.       table.  Subsequently, queries against the parent will include records

  460.       of the target table.  To be added as a child, the target table must

  461.       already contain all the same columns as the parent (it could have

  462.       additional columns, too).  The columns must have matching data types,

  463.       and if they have <code class="literal">NOT NULL</code> constraints in the parent

  464.       then they must also have <code class="literal">NOT NULL</code> constraints in the

  465.       child.

  466.      </p><p>

  467.       There must also be matching child-table constraints for all

  468.       <code class="literal">CHECK</code> constraints of the parent, except those

  469.       marked non-inheritable (that is, created with <code class="literal">ALTER TABLE ... ADD CONSTRAINT ... NO INHERIT</code>)

  470.       in the parent, which are ignored; all child-table constraints matched

  471.       must not be marked non-inheritable.

  472.       Currently

  473.       <code class="literal">UNIQUE</code>, <code class="literal">PRIMARY KEY</code>, and

  474.       <code class="literal">FOREIGN KEY</code> constraints are not considered, but

  475.       this might change in the future.

  476.      </p></dd><dt><span class="term"><code class="literal">NO INHERIT <em class="replaceable"><code>parent_table</code></em></code></span></dt><dd><p>

  477.       This form removes the target table from the list of children of the

  478.       specified parent table.

  479.       Queries against the parent table will no longer include records drawn

  480.       from the target table.

  481.      </p></dd><dt><span class="term"><code class="literal">OF <em class="replaceable"><code>type_name</code></em></code></span></dt><dd><p>

  482.       This form links the table to a composite type as though <code class="command">CREATE

  483.       TABLE OF</code> had formed it.  The table's list of column names and types

  484.       must precisely match that of the composite type.  The table must

  485.       not inherit from any other table.  These restrictions ensure

  486.       that <code class="command">CREATE TABLE OF</code> would permit an equivalent table

  487.       definition.

  488.      </p></dd><dt><span class="term"><code class="literal">NOT OF</code></span></dt><dd><p>

  489.       This form dissociates a typed table from its type.

  490.      </p></dd><dt><span class="term"><code class="literal">OWNER TO</code></span></dt><dd><p>

  491.       This form changes the owner of the table, sequence, view, materialized view,

  492.       or foreign table to the specified user.

  493.      </p></dd><dt id="SQL-CREATETABLE-REPLICA-IDENTITY"><span class="term"><code class="literal">REPLICA IDENTITY</code></span></dt><dd><p>

  494.       This form changes the information which is written to the write-ahead log

  495.       to identify rows which are updated or deleted.  This option has no effect

  496.       except when logical replication is in use.  <code class="literal">DEFAULT</code>

  497.       (the default for non-system tables) records the

  498.       old values of the columns of the primary key, if any.  <code class="literal">USING INDEX</code>

  499.       records the old values of the columns covered by the named index, which

  500.       must be unique, not partial, not deferrable, and include only columns marked

  501.       <code class="literal">NOT NULL</code>.  <code class="literal">FULL</code> records the old values of all columns

  502.       in the row.  <code class="literal">NOTHING</code> records no information about the old row.

  503.       (This is the default for system tables.)

  504.       In all cases, no old values are logged unless at least one of the columns

  505.       that would be logged differs between the old and new versions of the row.

  506.      </p></dd><dt><span class="term"><code class="literal">RENAME</code></span></dt><dd><p>

  507.       The <code class="literal">RENAME</code> forms change the name of a table

  508.       (or an index, sequence, view, materialized view, or foreign table), the

  509.       name of an individual column in a table, or the name of a constraint of

  510.       the table.  When renaming a constraint that has an underlying index,

  511.       the index is renamed as well.

  512.       There is no effect on the stored data.

  513.      </p></dd><dt><span class="term"><code class="literal">SET SCHEMA</code></span></dt><dd><p>

  514.       This form moves the table into another schema.  Associated indexes,

  515.       constraints, and sequences owned by table columns are moved as well.

  516.      </p></dd><dt id="SQL-ALTERTABLE-ATTACH-PARTITION"><span class="term"><code class="literal">ATTACH PARTITION <em class="replaceable"><code>partition_name</code></em> { FOR VALUES <em class="replaceable"><code>partition_bound_spec</code></em> | DEFAULT }</code></span></dt><dd><p>

  517.       This form attaches an existing table (which might itself be partitioned)

  518.       as a partition of the target table. The table can be attached

  519.       as a partition for specific values using <code class="literal">FOR VALUES</code>

  520.       or as a default partition by using <code class="literal">DEFAULT</code>.

  521.       For each index in the target table, a corresponding

  522.       one will be created in the attached table; or, if an equivalent

  523.       index already exists, it will be attached to the target table's index,

  524.       as if <code class="command">ALTER INDEX ATTACH PARTITION</code> had been executed.

  525.       Note that if the existing table is a foreign table, it is currently not

  526.       allowed to attach the table as a partition of the target table if there

  527.       are <code class="literal">UNIQUE</code> indexes on the target table.  (See also

  528.       <a class="xref" href="sql-createforeigntable.html" title="CREATE FOREIGN TABLE"><span class="refentrytitle">CREATE FOREIGN TABLE</span></a>.)  For each user-defined

  529.       row-level trigger that exists in the target table, a corresponding one

  530.       is created in the attached table.

  531.      </p><p>

  532.       A partition using <code class="literal">FOR VALUES</code> uses same syntax for

  533.       <em class="replaceable"><code>partition_bound_spec</code></em> as

  534.       <a class="xref" href="sql-createtable.html" title="CREATE TABLE"><span class="refentrytitle">CREATE TABLE</span></a>.  The partition bound specification

  535.       must correspond to the partitioning strategy and partition key of the

  536.       target table.  The table to be attached must have all the same columns

  537.       as the target table and no more; moreover, the column types must also

  538.       match.  Also, it must have all the <code class="literal">NOT NULL</code> and

  539.       <code class="literal">CHECK</code> constraints of the target table.  Currently

  540.       <code class="literal">FOREIGN KEY</code> constraints are not considered.

  541.       <code class="literal">UNIQUE</code> and <code class="literal">PRIMARY KEY</code> constraints

  542.       from the parent table will be created in the partition, if they don't

  543.       already exist.

  544.       If any of the <code class="literal">CHECK</code> constraints of the table being

  545.       attached is marked <code class="literal">NO INHERIT</code>, the command will fail;

  546.       such constraints must be recreated without the

  547.       <code class="literal">NO INHERIT</code> clause.

  548.      </p><p>

  549.       If the new partition is a regular table, a full table scan is performed

  550.       to check that existing rows in the table do not violate the partition

  551.       constraint. It is possible to avoid this scan by adding a valid

  552.       <code class="literal">CHECK</code> constraint to the table that allows only

  553.       rows satisfying the desired partition constraint before running this

  554.       command. The <code class="literal">CHECK</code> constraint will be used to

  555.       determine that the table need not be scanned to validate the partition

  556.       constraint. This does not work, however, if any of the partition keys

  557.       is an expression and the partition does not accept

  558.       <code class="literal">NULL</code> values. If attaching a list partition that will

  559.       not accept <code class="literal">NULL</code> values, also add

  560.       <code class="literal">NOT NULL</code> constraint to the partition key column,

  561.       unless it's an expression.

  562.      </p><p>

  563.       If the new partition is a foreign table, nothing is done to verify

  564.       that all the rows in the foreign table obey the partition constraint.

  565.       (See the discussion in <a class="xref" href="sql-createforeigntable.html" title="CREATE FOREIGN TABLE"><span class="refentrytitle">CREATE FOREIGN TABLE</span></a> about

  566.       constraints on the foreign table.)

  567.      </p><p>

  568.       When a table has a default partition, defining a new partition changes

  569.       the partition constraint for the default partition. The default

  570.       partition can't contain any rows that would need to be moved to the new

  571.       partition, and will be scanned to verify that none are present. This

  572.       scan, like the scan of the new partition, can be avoided if an

  573.       appropriate <code class="literal">CHECK</code> constraint is present. Also like

  574.       the scan of the new partition, it is always skipped when the default

  575.       partition is a foreign table.

  576.      </p><p>

  577.       Attaching a partition acquires a

  578.       <code class="literal">SHARE UPDATE EXCLUSIVE</code> lock on the parent table,

  579.       in addition to <code class="literal">ACCESS EXCLUSIVE</code> locks on the table

  580.       to be attached and on the default partition (if any).

  581.      </p></dd><dt><span class="term"><code class="literal">DETACH PARTITION</code> <em class="replaceable"><code>partition_name</code></em></span></dt><dd><p>

  582.       This form detaches the specified partition of the target table.  The detached

  583.       partition continues to exist as a standalone table, but no longer has any

  584.       ties to the table from which it was detached.  Any indexes that were

  585.       attached to the target table's indexes are detached.  Any triggers that

  586.       were created as clones of those in the target table are removed.

  587.      </p></dd></dl></div><p>

  588.   </p><p>

  589.    All the forms of ALTER TABLE that act on a single table, except

  590.    <code class="literal">RENAME</code>, <code class="literal">SET SCHEMA</code>,

  591.    <code class="literal">ATTACH PARTITION</code>, and

  592.    <code class="literal">DETACH PARTITION</code> can be combined into

  593.    a list of multiple alterations to be applied together.  For example, it

  594.    is possible to add several columns and/or alter the type of several

  595.    columns in a single command.  This is particularly useful with large

  596.    tables, since only one pass over the table need be made.

  597.   </p><p>

  598.    You must own the table to use <code class="command">ALTER TABLE</code>.

  599.    To change the schema or tablespace of a table, you must also have

  600.    <code class="literal">CREATE</code> privilege on the new schema or tablespace.

  601.    To add the table as a new child of a parent table, you must own the parent

  602.    table as well.  Also, to attach a table as a new partition of the table,

  603.    you must own the table being attached.

  604.    To alter the owner, you must also be a direct or indirect member of the new

  605.    owning role, and that role must have <code class="literal">CREATE</code> privilege on

  606.    the table's schema.  (These restrictions enforce that altering the owner

  607.    doesn't do anything you couldn't do by dropping and recreating the table.

  608.    However, a superuser can alter ownership of any table anyway.)

  609.    To add a column or alter a column type or use the <code class="literal">OF</code>

  610.    clause, you must also have <code class="literal">USAGE</code> privilege on the data

  611.    type.

  612.   </p></div><div class="refsect1" id="id-1.9.3.35.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">IF EXISTS</code></span></dt><dd><p>

  613.         Do not throw an error if the table does not exist. A notice is issued

  614.         in this case.

  615.        </p></dd><dt><span class="term"><em class="replaceable"><code>name</code></em></span></dt><dd><p>

  616.         The name (optionally schema-qualified) of an existing table to

  617.         alter. If <code class="literal">ONLY</code> is specified before the table name, only

  618.         that table is altered. If <code class="literal">ONLY</code> is not specified, the table

  619.         and all its descendant tables (if any) are altered.  Optionally,

  620.         <code class="literal">*</code> can be specified after the table name to explicitly

  621.         indicate that descendant tables are included.

  622.        </p></dd><dt><span class="term"><em class="replaceable"><code>column_name</code></em></span></dt><dd><p>

  623.         Name of a new or existing column.

  624.        </p></dd><dt><span class="term"><em class="replaceable"><code>new_column_name</code></em></span></dt><dd><p>

  625.         New name for an existing column.

  626.        </p></dd><dt><span class="term"><em class="replaceable"><code>new_name</code></em></span></dt><dd><p>

  627.         New name for the table.

  628.        </p></dd><dt><span class="term"><em class="replaceable"><code>data_type</code></em></span></dt><dd><p>

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

  630.         column.

  631.        </p></dd><dt><span class="term"><em class="replaceable"><code>table_constraint</code></em></span></dt><dd><p>

  632.         New table constraint for the table.

  633.        </p></dd><dt><span class="term"><em class="replaceable"><code>constraint_name</code></em></span></dt><dd><p>

  634.         Name of a new or existing constraint.

  635.        </p></dd><dt><span class="term"><code class="literal">CASCADE</code></span></dt><dd><p>

  636.         Automatically drop objects that depend on the dropped column

  637.         or constraint (for example, views referencing the column),

  638.         and in turn all objects that depend on those objects

  639.         (see <a class="xref" href="ddl-depend.html" title="5.14. Dependency Tracking">Section 5.14</a>).

  640.        </p></dd><dt><span class="term"><code class="literal">RESTRICT</code></span></dt><dd><p>

  641.         Refuse to drop the column or constraint if there are any dependent

  642.         objects. This is the default behavior.

  643.        </p></dd><dt><span class="term"><em class="replaceable"><code>trigger_name</code></em></span></dt><dd><p>

  644.         Name of a single trigger to disable or enable.

  645.        </p></dd><dt><span class="term"><code class="literal">ALL</code></span></dt><dd><p>

  646.         Disable or enable all triggers belonging to the table.

  647.         (This requires superuser privilege if any of the triggers are

  648.         internally generated constraint triggers such as those that are used

  649.         to implement foreign key constraints or deferrable uniqueness and

  650.         exclusion constraints.)

  651.        </p></dd><dt><span class="term"><code class="literal">USER</code></span></dt><dd><p>

  652.         Disable or enable all triggers belonging to the table except for

  653.         internally generated constraint triggers such as those that are used

  654.         to implement foreign key constraints or deferrable uniqueness and

  655.         exclusion constraints.

  656.        </p></dd><dt><span class="term"><em class="replaceable"><code>index_name</code></em></span></dt><dd><p>

  657.         The name of an existing index.

  658.        </p></dd><dt><span class="term"><em class="replaceable"><code>storage_parameter</code></em></span></dt><dd><p>

  659.         The name of a table storage parameter.

  660.        </p></dd><dt><span class="term"><em class="replaceable"><code>value</code></em></span></dt><dd><p>

  661.         The new value for a table storage parameter.

  662.         This might be a number or a word depending on the parameter.

  663.        </p></dd><dt><span class="term"><em class="replaceable"><code>parent_table</code></em></span></dt><dd><p>

  664.         A parent table to associate or de-associate with this table.

  665.        </p></dd><dt><span class="term"><em class="replaceable"><code>new_owner</code></em></span></dt><dd><p>

  666.         The user name of the new owner of the table.

  667.        </p></dd><dt><span class="term"><em class="replaceable"><code>new_tablespace</code></em></span></dt><dd><p>

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

  669.        </p></dd><dt><span class="term"><em class="replaceable"><code>new_schema</code></em></span></dt><dd><p>

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

  671.        </p></dd><dt><span class="term"><em class="replaceable"><code>partition_name</code></em></span></dt><dd><p>

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

  673.        </p></dd><dt><span class="term"><em class="replaceable"><code>partition_bound_spec</code></em></span></dt><dd><p>

  674.         The partition bound specification for a new partition.  Refer to

  675.         <a class="xref" href="sql-createtable.html" title="CREATE TABLE"><span class="refentrytitle">CREATE TABLE</span></a> for more details on the syntax of the same.

  676.        </p></dd></dl></div></div><div class="refsect1" id="SQL-ALTERTABLE-NOTES"><h2>Notes</h2><p>

  677.     The key word <code class="literal">COLUMN</code> is noise and can be omitted.

  678.    </p><p>

  679.     When a column is added with <code class="literal">ADD COLUMN</code> and a

  680.     non-volatile <code class="literal">DEFAULT</code> is specified, the default is

  681.     evaluated at the time of the statement and the result stored in the

  682.     table's metadata.  That value will be used for the column for all existing

  683.     rows.  If no <code class="literal">DEFAULT</code> is specified, NULL is used.  In

  684.     neither case is a rewrite of the table required.

  685.    </p><p>

  686.     Adding a column with a volatile <code class="literal">DEFAULT</code> or

  687.     changing the type of an existing column will require the entire table and

  688.     its indexes to be rewritten. As an exception, when changing the type of an

  689.     existing column, if the <code class="literal">USING</code> clause does not change

  690.     the column contents and the old type is either binary coercible to the new

  691.     type or an unconstrained domain over the new type, a table rewrite is not

  692.     needed; but any indexes on the affected columns must still be rebuilt.

  693.     Table and/or index rebuilds may take a

  694.     significant amount of time for a large table; and will temporarily require

  695.     as much as double the disk space.

  696.    </p><p>

  697.     Adding a <code class="literal">CHECK</code> or <code class="literal">NOT NULL</code> constraint requires

  698.     scanning the table to verify that existing rows meet the constraint,

  699.     but does not require a table rewrite.

  700.    </p><p>

  701.     Similarly, when attaching a new partition it may be scanned to verify that

  702.     existing rows meet the partition constraint.

  703.    </p><p>

  704.     The main reason for providing the option to specify multiple changes

  705.     in a single <code class="command">ALTER TABLE</code> is that multiple table scans or

  706.     rewrites can thereby be combined into a single pass over the table.

  707.    </p><p>

  708.     Scanning a large table to verify a new foreign key or check constraint

  709.     can take a long time, and other updates to the table are locked out

  710.     until the <code class="command">ALTER TABLE ADD CONSTRAINT</code> command is

  711.     committed.  The main purpose of the <code class="literal">NOT VALID</code>

  712.     constraint option is to reduce the impact of adding a constraint on

  713.     concurrent updates.  With <code class="literal">NOT VALID</code>,

  714.     the <code class="command">ADD CONSTRAINT</code> command does not scan the table

  715.     and can be committed immediately.  After that, a <code class="literal">VALIDATE

  716.     CONSTRAINT</code> command can be issued to verify that existing rows

  717.     satisfy the constraint.  The validation step does not need to lock out

  718.     concurrent updates, since it knows that other transactions will be

  719.     enforcing the constraint for rows that they insert or update; only

  720.     pre-existing rows need to be checked.  Hence, validation acquires only

  721.     a <code class="literal">SHARE UPDATE EXCLUSIVE</code> lock on the table being

  722.     altered.  (If the constraint is a foreign key then a <code class="literal">ROW

  723.     SHARE</code> lock is also required on the table referenced by the

  724.     constraint.)  In addition to improving concurrency, it can be useful to

  725.     use <code class="literal">NOT VALID</code> and <code class="literal">VALIDATE

  726.     CONSTRAINT</code> in cases where the table is known to contain

  727.     pre-existing violations.  Once the constraint is in place, no new

  728.     violations can be inserted, and the existing problems can be corrected

  729.     at leisure until <code class="literal">VALIDATE CONSTRAINT</code> finally

  730.     succeeds.

  731.    </p><p>

  732.     The <code class="literal">DROP COLUMN</code> form does not physically remove

  733.     the column, but simply makes it invisible to SQL operations.  Subsequent

  734.     insert and update operations in the table will store a null value for the

  735.     column. Thus, dropping a column is quick but it will not immediately

  736.     reduce the on-disk size of your table, as the space occupied

  737.     by the dropped column is not reclaimed.  The space will be

  738.     reclaimed over time as existing rows are updated.

  739.    </p><p>

  740.     To force immediate reclamation of space occupied by a dropped column,

  741.     you can execute one of the forms of <code class="command">ALTER TABLE</code> that

  742.     performs a rewrite of the whole table.  This results in reconstructing

  743.     each row with the dropped column replaced by a null value.

  744.    </p><p>

  745.     The rewriting forms of <code class="command">ALTER TABLE</code> are not MVCC-safe.

  746.     After a table rewrite, the table will appear empty to concurrent

  747.     transactions, if they are using a snapshot taken before the rewrite

  748.     occurred.  See <a class="xref" href="mvcc-caveats.html" title="13.5. Caveats">Section 13.5</a> for more details.

  749.    </p><p>

  750.     The <code class="literal">USING</code> option of <code class="literal">SET DATA TYPE</code> can actually

  751.     specify any expression involving the old values of the row; that is, it

  752.     can refer to other columns as well as the one being converted.  This allows

  753.     very general conversions to be done with the <code class="literal">SET DATA TYPE</code>

  754.     syntax.  Because of this flexibility, the <code class="literal">USING</code>

  755.     expression is not applied to the column's default value (if any); the

  756.     result might not be a constant expression as required for a default.

  757.     This means that when there is no implicit or assignment cast from old to

  758.     new type, <code class="literal">SET DATA TYPE</code> might fail to convert the default even

  759.     though a <code class="literal">USING</code> clause is supplied.  In such cases,

  760.     drop the default with <code class="literal">DROP DEFAULT</code>, perform the <code class="literal">ALTER

  761.     TYPE</code>, and then use <code class="literal">SET DEFAULT</code> to add a suitable new

  762.     default.  Similar considerations apply to indexes and constraints involving

  763.     the column.

  764.    </p><p>

  765.     If a table has any descendant tables, it is not permitted to add,

  766.     rename, or change the type of a column in the parent table without doing

  767.     the same to the descendants.  This ensures that the descendants always

  768.     have columns matching the parent.  Similarly, a <code class="literal">CHECK</code>

  769.     constraint cannot be renamed in the parent without also renaming it in

  770.     all descendants, so that <code class="literal">CHECK</code> constraints also match

  771.     between the parent and its descendants.  (That restriction does not apply

  772.     to index-based constraints, however.)

  773.     Also, because selecting from the parent also selects from its descendants,

  774.     a constraint on the parent cannot be marked valid unless it is also marked

  775.     valid for those descendants.  In all of these cases, <code class="command">ALTER TABLE

  776.     ONLY</code> will be rejected.

  777.    </p><p>

  778.     A recursive <code class="literal">DROP COLUMN</code> operation will remove a

  779.     descendant table's column only if the descendant does not inherit

  780.     that column from any other parents and never had an independent

  781.     definition of the column.  A nonrecursive <code class="literal">DROP

  782.     COLUMN</code> (i.e., <code class="command">ALTER TABLE ONLY ... DROP

  783.     COLUMN</code>) never removes any descendant columns, but

  784.     instead marks them as independently defined rather than inherited.

  785.     A nonrecursive <code class="literal">DROP COLUMN</code> command will fail for a

  786.     partitioned table, because all partitions of a table must have the same

  787.     columns as the partitioning root.

  788.    </p><p>

  789.     The actions for identity columns (<code class="literal">ADD

  790.     GENERATED</code>, <code class="literal">SET</code> etc., <code class="literal">DROP

  791.     IDENTITY</code>), as well as the actions

  792.     <code class="literal">TRIGGER</code>, <code class="literal">CLUSTER</code>, <code class="literal">OWNER</code>,

  793.     and <code class="literal">TABLESPACE</code> never recurse to descendant tables;

  794.     that is, they always act as though <code class="literal">ONLY</code> were specified.

  795.     Adding a constraint recurses only for <code class="literal">CHECK</code> constraints

  796.     that are not marked <code class="literal">NO INHERIT</code>.

  797.    </p><p>

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

  799.    </p><p>

  800.     Refer to <a class="xref" href="sql-createtable.html" title="CREATE TABLE"><span class="refentrytitle">CREATE TABLE</span></a> for a further description of valid

  801.     parameters. <a class="xref" href="ddl.html" title="Chapter 5. Data Definition">Chapter 5</a> has further information on

  802.     inheritance.

  803.    </p></div><div class="refsect1" id="id-1.9.3.35.8"><h2>Examples</h2><p>

  804.    To add a column of type <code class="type">varchar</code> to a table:

  805. </p><pre class="programlisting">

  806. ALTER TABLE distributors ADD COLUMN address varchar(30);

  807. </pre><p>

  808.   </p><p>

  809.    To drop a column from a table:

  810. </p><pre class="programlisting">

  811. ALTER TABLE distributors DROP COLUMN address RESTRICT;

  812. </pre><p>

  813.   </p><p>

  814.    To change the types of two existing columns in one operation:

  815. </p><pre class="programlisting">

  816. ALTER TABLE distributors

  817.     ALTER COLUMN address TYPE varchar(80),

  818.     ALTER COLUMN name TYPE varchar(100);

  819. </pre><p>

  820.   </p><p>

  821.    To change an integer column containing Unix timestamps to <code class="type">timestamp

  822.    with time zone</code> via a <code class="literal">USING</code> clause:

  823. </p><pre class="programlisting">

  824. ALTER TABLE foo

  825.     ALTER COLUMN foo_timestamp SET DATA TYPE timestamp with time zone

  826.     USING

  827.         timestamp with time zone 'epoch' + foo_timestamp * interval '1 second';

  828. </pre><p>

  829.   </p><p>

  830.    The same, when the column has a default expression that won't automatically

  831.    cast to the new data type:

  832. </p><pre class="programlisting">

  833. ALTER TABLE foo

  834.     ALTER COLUMN foo_timestamp DROP DEFAULT,

  835.     ALTER COLUMN foo_timestamp TYPE timestamp with time zone

  836.     USING

  837.         timestamp with time zone 'epoch' + foo_timestamp * interval '1 second',

  838.     ALTER COLUMN foo_timestamp SET DEFAULT now();

  839. </pre><p>

  840.   </p><p>

  841.    To rename an existing column:

  842. </p><pre class="programlisting">

  843. ALTER TABLE distributors RENAME COLUMN address TO city;

  844. </pre><p>

  845.   </p><p>

  846.    To rename an existing table:

  847. </p><pre class="programlisting">

  848. ALTER TABLE distributors RENAME TO suppliers;

  849. </pre><p>

  850.   </p><p>

  851.    To rename an existing constraint:

  852. </p><pre class="programlisting">

  853. ALTER TABLE distributors RENAME CONSTRAINT zipchk TO zip_check;

  854. </pre><p>

  855.   </p><p>

  856.    To add a not-null constraint to a column:

  857. </p><pre class="programlisting">

  858. ALTER TABLE distributors ALTER COLUMN street SET NOT NULL;

  859. </pre><p>

  860.    To remove a not-null constraint from a column:

  861. </p><pre class="programlisting">

  862. ALTER TABLE distributors ALTER COLUMN street DROP NOT NULL;

  863. </pre><p>

  864.   </p><p>

  865.    To add a check constraint to a table and all its children:

  866. </p><pre class="programlisting">

  867. ALTER TABLE distributors ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5);

  868. </pre><p>

  869.   </p><p>

  870.    To add a check constraint only to a table and not to its children:

  871. </p><pre class="programlisting">

  872. ALTER TABLE distributors ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5) NO INHERIT;

  873. </pre><p>

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

  875.   </p><p>

  876.    To remove a check constraint from a table and all its children:

  877. </p><pre class="programlisting">

  878. ALTER TABLE distributors DROP CONSTRAINT zipchk;

  879. </pre><p>

  880.   </p><p>

  881.    To remove a check constraint from one table only:

  882. </p><pre class="programlisting">

  883. ALTER TABLE ONLY distributors DROP CONSTRAINT zipchk;

  884. </pre><p>

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

  886.   </p><p>

  887.    To add a foreign key constraint to a table:

  888. </p><pre class="programlisting">

  889. ALTER TABLE distributors ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES addresses (address);

  890. </pre><p>

  891.   </p><p>

  892.    To add a foreign key constraint to a table with the least impact on other work:

  893. </p><pre class="programlisting">

  894. ALTER TABLE distributors ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES addresses (address) NOT VALID;

  895. ALTER TABLE distributors VALIDATE CONSTRAINT distfk;

  896. </pre><p>

  897.   </p><p>

  898.    To add a (multicolumn) unique constraint to a table:

  899. </p><pre class="programlisting">

  900. ALTER TABLE distributors ADD CONSTRAINT dist_id_zipcode_key UNIQUE (dist_id, zipcode);

  901. </pre><p>

  902.   </p><p>

  903.    To add an automatically named primary key constraint to a table, noting

  904.    that a table can only ever have one primary key:

  905. </p><pre class="programlisting">

  906. ALTER TABLE distributors ADD PRIMARY KEY (dist_id);

  907. </pre><p>

  908.   </p><p>

  909.    To move a table to a different tablespace:

  910. </p><pre class="programlisting">

  911. ALTER TABLE distributors SET TABLESPACE fasttablespace;

  912. </pre><p>

  913.   </p><p>

  914.    To move a table to a different schema:

  915. </p><pre class="programlisting">

  916. ALTER TABLE myschema.distributors SET SCHEMA yourschema;

  917. </pre><p>

  918.   </p><p>

  919.    To recreate a primary key constraint, without blocking updates while the

  920.    index is rebuilt:

  921. </p><pre class="programlisting">

  922. CREATE UNIQUE INDEX CONCURRENTLY dist_id_temp_idx ON distributors (dist_id);

  923. ALTER TABLE distributors DROP CONSTRAINT distributors_pkey,

  924.     ADD CONSTRAINT distributors_pkey PRIMARY KEY USING INDEX dist_id_temp_idx;

  925. </pre><p>

  926.    To attach a partition to a range-partitioned table:

  927. </p><pre class="programlisting">

  928. ALTER TABLE measurement

  929.     ATTACH PARTITION measurement_y2016m07 FOR VALUES FROM ('2016-07-01') TO ('2016-08-01');

  930. </pre><p>

  931.    To attach a partition to a list-partitioned table:

  932. </p><pre class="programlisting">

  933. ALTER TABLE cities

  934.     ATTACH PARTITION cities_ab FOR VALUES IN ('a', 'b');

  935. </pre><p>

  936.    To attach a partition to a hash-partitioned table:

  937. </p><pre class="programlisting">

  938. ALTER TABLE orders

  939.     ATTACH PARTITION orders_p4 FOR VALUES WITH (MODULUS 4, REMAINDER 3);

  940. </pre><p>

  941.    To attach a default partition to a partitioned table:

  942. </p><pre class="programlisting">

  943. ALTER TABLE cities

  944.     ATTACH PARTITION cities_partdef DEFAULT;

  945. </pre><p>

  946.    To detach a partition from a partitioned table:

  947. </p><pre class="programlisting">

  948. ALTER TABLE measurement

  949.     DETACH PARTITION measurement_y2015m12;

  950. </pre></div><div class="refsect1" id="id-1.9.3.35.9"><h2>Compatibility</h2><p>

  951.    The forms <code class="literal">ADD</code> (without <code class="literal">USING INDEX</code>),

  952.    <code class="literal">DROP [COLUMN]</code>, <code class="literal">DROP IDENTITY</code>, <code class="literal">RESTART</code>,

  953.    <code class="literal">SET DEFAULT</code>, <code class="literal">SET DATA TYPE</code> (without <code class="literal">USING</code>),

  954.    <code class="literal">SET GENERATED</code>, and <code class="literal">SET <em class="replaceable"><code>sequence_option</code></em></code>

  955.    conform with the SQL standard.  The other forms are

  956.    <span class="productname">PostgreSQL</span> extensions of the SQL standard.

  957.    Also, the ability to specify more than one manipulation in a single

  958.    <code class="command">ALTER TABLE</code> command is an extension.

  959.   </p><p>

  960.    <code class="command">ALTER TABLE DROP COLUMN</code> can be used to drop the only

  961.    column of a table, leaving a zero-column table.  This is an

  962.    extension of SQL, which disallows zero-column tables.

  963.   </p></div><div class="refsect1" id="id-1.9.3.35.10"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-createtable.html" title="CREATE TABLE"><span class="refentrytitle">CREATE TABLE</span></a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-altersystem.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql-commands.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sql-altertablespace.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">ALTER SYSTEM </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> ALTER TABLESPACE</td></tr></table></div></body></html>
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