1149 lines
44 KiB
Plaintext
1149 lines
44 KiB
Plaintext
<!--
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doc/src/sgml/ref/alter_table.sgml
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PostgreSQL documentation
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-->
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<refentry id="SQL-ALTERTABLE">
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<indexterm zone="sql-altertable">
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<primary>ALTER TABLE</primary>
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</indexterm>
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<refmeta>
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<refentrytitle>ALTER TABLE</refentrytitle>
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<manvolnum>7</manvolnum>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>ALTER TABLE</refname>
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<refpurpose>change the definition of a table</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<synopsis>
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ALTER TABLE [ IF EXISTS ] [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
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<replaceable class="PARAMETER">action</replaceable> [, ... ]
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ALTER TABLE [ IF EXISTS ] [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
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RENAME [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> TO <replaceable class="PARAMETER">new_column_name</replaceable>
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ALTER TABLE [ IF EXISTS ] [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
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RENAME CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> TO <replaceable class="PARAMETER">new_constraint_name</replaceable>
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ALTER TABLE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable>
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RENAME TO <replaceable class="PARAMETER">new_name</replaceable>
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ALTER TABLE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable>
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SET SCHEMA <replaceable class="PARAMETER">new_schema</replaceable>
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<phrase>where <replaceable class="PARAMETER">action</replaceable> is one of:</phrase>
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ADD [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> <replaceable class="PARAMETER">data_type</replaceable> [ COLLATE <replaceable class="PARAMETER">collation</replaceable> ] [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
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DROP [ COLUMN ] [ IF EXISTS ] <replaceable class="PARAMETER">column_name</replaceable> [ RESTRICT | CASCADE ]
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ALTER [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> [ SET DATA ] TYPE <replaceable class="PARAMETER">data_type</replaceable> [ COLLATE <replaceable class="PARAMETER">collation</replaceable> ] [ USING <replaceable class="PARAMETER">expression</replaceable> ]
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ALTER [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> SET DEFAULT <replaceable class="PARAMETER">expression</replaceable>
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ALTER [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> DROP DEFAULT
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ALTER [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> { SET | DROP } NOT NULL
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ALTER [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> SET STATISTICS <replaceable class="PARAMETER">integer</replaceable>
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ALTER [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> SET ( <replaceable class="PARAMETER">attribute_option</replaceable> = <replaceable class="PARAMETER">value</replaceable> [, ... ] )
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ALTER [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> RESET ( <replaceable class="PARAMETER">attribute_option</replaceable> [, ... ] )
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ALTER [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
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ADD <replaceable class="PARAMETER">table_constraint</replaceable> [ NOT VALID ]
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ADD <replaceable class="PARAMETER">table_constraint_using_index</replaceable>
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ALTER CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
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VALIDATE CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable>
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DROP CONSTRAINT [ IF EXISTS ] <replaceable class="PARAMETER">constraint_name</replaceable> [ RESTRICT | CASCADE ]
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DISABLE TRIGGER [ <replaceable class="PARAMETER">trigger_name</replaceable> | ALL | USER ]
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ENABLE TRIGGER [ <replaceable class="PARAMETER">trigger_name</replaceable> | ALL | USER ]
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ENABLE REPLICA TRIGGER <replaceable class="PARAMETER">trigger_name</replaceable>
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ENABLE ALWAYS TRIGGER <replaceable class="PARAMETER">trigger_name</replaceable>
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DISABLE RULE <replaceable class="PARAMETER">rewrite_rule_name</replaceable>
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ENABLE RULE <replaceable class="PARAMETER">rewrite_rule_name</replaceable>
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ENABLE REPLICA RULE <replaceable class="PARAMETER">rewrite_rule_name</replaceable>
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ENABLE ALWAYS RULE <replaceable class="PARAMETER">rewrite_rule_name</replaceable>
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CLUSTER ON <replaceable class="PARAMETER">index_name</replaceable>
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SET WITHOUT CLUSTER
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SET WITH OIDS
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SET WITHOUT OIDS
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SET ( <replaceable class="PARAMETER">storage_parameter</replaceable> = <replaceable class="PARAMETER">value</replaceable> [, ... ] )
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RESET ( <replaceable class="PARAMETER">storage_parameter</replaceable> [, ... ] )
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INHERIT <replaceable class="PARAMETER">parent_table</replaceable>
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NO INHERIT <replaceable class="PARAMETER">parent_table</replaceable>
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OF <replaceable class="PARAMETER">type_name</replaceable>
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NOT OF
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OWNER TO <replaceable class="PARAMETER">new_owner</replaceable>
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SET TABLESPACE <replaceable class="PARAMETER">new_tablespace</replaceable>
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REPLICA IDENTITY {DEFAULT | USING INDEX <replaceable class="PARAMETER">index_name</replaceable> | FULL | NOTHING}
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<phrase>and <replaceable class="PARAMETER">table_constraint_using_index</replaceable> is:</phrase>
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[ CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> ]
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{ UNIQUE | PRIMARY KEY } USING INDEX <replaceable class="PARAMETER">index_name</replaceable>
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[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
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</synopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<command>ALTER TABLE</command> changes the definition of an existing table.
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There are several subforms:
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<variablelist>
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<varlistentry>
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<term><literal>ADD COLUMN</literal></term>
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<listitem>
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<para>
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This form adds a new column to the table, using the same syntax as
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<xref linkend="SQL-CREATETABLE">.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>DROP COLUMN [ IF EXISTS ]</literal></term>
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<listitem>
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<para>
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This form drops a column from a table. Indexes and
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table constraints involving the column will be automatically
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dropped as well. You will need to say <literal>CASCADE</> if
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anything outside the table depends on the column, for example,
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foreign key references or views.
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If <literal>IF EXISTS</literal> is specified and the column
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does not exist, no error is thrown. In this case a notice
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is issued instead.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>IF EXISTS</literal></term>
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<listitem>
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<para>
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Do not throw an error if the table does not exist. A notice is issued
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in this case.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>SET DATA TYPE</literal></term>
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<listitem>
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<para>
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This form changes the type of a column of a table. Indexes and
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simple table constraints involving the column will be automatically
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converted to use the new column type by reparsing the originally
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supplied expression.
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The optional <literal>COLLATE</literal> clause specifies a collation
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for the new column; if omitted, the collation is the default for the
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new column type.
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The optional <literal>USING</literal>
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clause specifies how to compute the new column value from the old;
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if omitted, the default conversion is the same as an assignment
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cast from old data type to new. A <literal>USING</literal>
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clause must be provided if there is no implicit or assignment
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cast from old to new type.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>SET</literal>/<literal>DROP DEFAULT</literal></term>
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<listitem>
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<para>
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These forms set or remove the default value for a column.
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Default values only apply in subsequent <command>INSERT</command>
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or <command>UPDATE</> commands; they do not cause rows already in the
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table to change.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>SET</literal>/<literal>DROP NOT NULL</literal></term>
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<listitem>
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<para>
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These forms change whether a column is marked to allow null
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values or to reject null values. You can only use <literal>SET
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NOT NULL</> when the column contains no null values.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>SET STATISTICS</literal></term>
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<listitem>
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<para>
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This form
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sets the per-column statistics-gathering target for subsequent
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<xref linkend="sql-analyze"> operations.
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The target can be set in the range 0 to 10000; alternatively, set it
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to -1 to revert to using the system default statistics
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target (<xref linkend="guc-default-statistics-target">).
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For more information on the use of statistics by the
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<productname>PostgreSQL</productname> query planner, refer to
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<xref linkend="planner-stats">.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>SET ( <replaceable class="PARAMETER">attribute_option</replaceable> = <replaceable class="PARAMETER">value</replaceable> [, ... ] )</literal></term>
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<term><literal>RESET ( <replaceable class="PARAMETER">attribute_option</replaceable> [, ... ] )</literal></term>
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<listitem>
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<para>
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This form sets or resets per-attribute options. Currently, the only
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defined per-attribute options are <literal>n_distinct</> and
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<literal>n_distinct_inherited</>, which override the
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number-of-distinct-values estimates made by subsequent
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<xref linkend="sql-analyze">
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operations. <literal>n_distinct</> affects the statistics for the table
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itself, while <literal>n_distinct_inherited</> affects the statistics
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gathered for the table plus its inheritance children. When set to a
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positive value, <command>ANALYZE</> will assume that the column contains
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exactly the specified number of distinct nonnull values. When set to a
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negative value, which must be greater
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than or equal to -1, <command>ANALYZE</> will assume that the number of
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distinct nonnull values in the column is linear in the size of the
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table; the exact count is to be computed by multiplying the estimated
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table size by the absolute value of the given number. For example,
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a value of -1 implies that all values in the column are distinct, while
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a value of -0.5 implies that each value appears twice on the average.
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This can be useful when the size of the table changes over time, since
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the multiplication by the number of rows in the table is not performed
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until query planning time. Specify a value of 0 to revert to estimating
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the number of distinct values normally. For more information on the use
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of statistics by the <productname>PostgreSQL</productname> query
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planner, refer to <xref linkend="planner-stats">.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<indexterm>
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<primary>TOAST</primary>
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<secondary>per-column storage settings</secondary>
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</indexterm>
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<term><literal>SET STORAGE</literal></term>
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<listitem>
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<para>
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This form sets the storage mode for a column. This controls whether this
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column is held inline or in a secondary <acronym>TOAST</> table, and
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whether the data
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should be compressed or not. <literal>PLAIN</literal> must be used
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for fixed-length values such as <type>integer</type> and is
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inline, uncompressed. <literal>MAIN</literal> is for inline,
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compressible data. <literal>EXTERNAL</literal> is for external,
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uncompressed data, and <literal>EXTENDED</literal> is for external,
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compressed data. <literal>EXTENDED</literal> is the default for most
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data types that support non-<literal>PLAIN</literal> storage.
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Use of <literal>EXTERNAL</literal> will make substring operations on
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very large <type>text</type> and <type>bytea</type> values run faster,
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at the penalty of increased storage space. Note that
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<literal>SET STORAGE</> doesn't itself change anything in the table,
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it just sets the strategy to be pursued during future table updates.
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See <xref linkend="storage-toast"> for more information.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>ADD <replaceable class="PARAMETER">table_constraint</replaceable> [ NOT VALID ]</literal></term>
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<listitem>
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<para>
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This form adds a new constraint to a table using the same syntax as
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<xref linkend="SQL-CREATETABLE">, plus the option <literal>NOT
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VALID</literal>, which is currently only allowed for foreign key
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and CHECK constraints.
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If the constraint is marked <literal>NOT VALID</literal>, the
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potentially-lengthy initial check to verify that all rows in the table
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satisfy the constraint is skipped. The constraint will still be
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enforced against subsequent inserts or updates (that is, they'll fail
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unless there is a matching row in the referenced table, in the case
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of foreign keys; and they'll fail unless the new row matches the
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specified check constraints). But the
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database will not assume that the constraint holds for all rows in
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the table, until it is validated by using the <literal>VALIDATE
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CONSTRAINT</literal> option.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>ADD <replaceable class="PARAMETER">table_constraint_using_index</replaceable></literal></term>
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<listitem>
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<para>
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This form adds a new <literal>PRIMARY KEY</> or <literal>UNIQUE</>
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constraint to a table based on an existing unique index. All the
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columns of the index will be included in the constraint.
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</para>
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<para>
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The index cannot have expression columns nor be a partial index.
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Also, it must be a b-tree index with default sort ordering. These
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restrictions ensure that the index is equivalent to one that would be
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built by a regular <literal>ADD PRIMARY KEY</> or <literal>ADD UNIQUE</>
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command.
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</para>
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<para>
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If <literal>PRIMARY KEY</> is specified, and the index's columns are not
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already marked <literal>NOT NULL</>, then this command will attempt to
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do <literal>ALTER COLUMN SET NOT NULL</> against each such column.
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That requires a full table scan to verify the column(s) contain no
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nulls. In all other cases, this is a fast operation.
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</para>
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<para>
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If a constraint name is provided then the index will be renamed to match
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the constraint name. Otherwise the constraint will be named the same as
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the index.
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</para>
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<para>
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After this command is executed, the index is <quote>owned</> by the
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constraint, in the same way as if the index had been built by
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a regular <literal>ADD PRIMARY KEY</> or <literal>ADD UNIQUE</>
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command. In particular, dropping the constraint will make the index
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disappear too.
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</para>
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<note>
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<para>
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Adding a constraint using an existing index can be helpful in
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situations where a new constraint needs to be added without blocking
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table updates for a long time. To do that, create the index using
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<command>CREATE INDEX CONCURRENTLY</>, and then install it as an
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official constraint using this syntax. See the example below.
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</para>
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</note>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>ALTER CONSTRAINT</literal></term>
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<listitem>
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<para>
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This form alters the attributes of a constraint that was previously
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created. Currently only foreign key constraints may be altered.
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</para>
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</listitem>
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</varlistentry>
|
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<varlistentry>
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<term><literal>VALIDATE CONSTRAINT</literal></term>
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<listitem>
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<para>
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This form validates a foreign key or check constraint that was previously created
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as <literal>NOT VALID</literal>, by scanning the table to ensure there
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are no rows for which the constraint is not satisfied.
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Nothing happens if the constraint is already marked valid.
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</para>
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<para>
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Validation can be a long process on larger tables and currently requires
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an <literal>ACCESS EXCLUSIVE</literal> lock. The value of separating
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validation from initial creation is that you can defer validation to less
|
|
busy times, or can be used to give additional time to correct pre-existing
|
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errors while preventing new errors.
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</para>
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</listitem>
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</varlistentry>
|
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<varlistentry>
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<term><literal>DROP CONSTRAINT [ IF EXISTS ]</literal></term>
|
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<listitem>
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<para>
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This form drops the specified constraint on a table.
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|
If <literal>IF EXISTS</literal> is specified and the constraint
|
|
does not exist, no error is thrown. In this case a notice is issued instead.
|
|
</para>
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</listitem>
|
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</varlistentry>
|
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|
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<varlistentry>
|
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<term><literal>DISABLE</literal>/<literal>ENABLE [ REPLICA | ALWAYS ] TRIGGER</literal></term>
|
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<listitem>
|
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<para>
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These forms configure the firing of trigger(s) belonging to the table.
|
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A disabled trigger is still known to the system, but is not executed
|
|
when its triggering event occurs. For a deferred trigger, the enable
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|
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
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|
requires superuser privileges; it should be done with caution since
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of course the integrity of the constraint cannot be guaranteed if the
|
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triggers are not executed.
|
|
The trigger firing mechanism is also affected by the configuration
|
|
variable <xref linkend="guc-session-replication-role">. Simply enabled
|
|
triggers will fire when the replication role is <quote>origin</>
|
|
(the default) or <quote>local</>. Triggers configured as <literal>ENABLE
|
|
REPLICA</literal> will only fire if the session is in <quote>replica</>
|
|
mode, and triggers configured as <literal>ENABLE ALWAYS</literal> will
|
|
fire regardless of the current replication mode.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>DISABLE</literal>/<literal>ENABLE [ REPLICA | ALWAYS ] RULE</literal></term>
|
|
<listitem>
|
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<para>
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|
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 <literal>ON SELECT</literal> rules, which
|
|
are always applied in order to keep views working even if the current
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session is in a non-default replication role.
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|
</para>
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</listitem>
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</varlistentry>
|
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|
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<varlistentry>
|
|
<term><literal>CLUSTER ON</literal></term>
|
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<listitem>
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<para>
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This form selects the default index for future
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<xref linkend="SQL-CLUSTER">
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|
operations. It does not actually re-cluster the table.
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|
</para>
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</listitem>
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</varlistentry>
|
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|
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<varlistentry>
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<term><literal>SET WITHOUT CLUSTER</literal></term>
|
|
<listitem>
|
|
<para>
|
|
This form removes the most recently used
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<xref linkend="SQL-CLUSTER">
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|
index specification from the table. This affects
|
|
future cluster operations that don't specify an index.
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|
</para>
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</listitem>
|
|
</varlistentry>
|
|
|
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<varlistentry>
|
|
<term><literal>SET WITH OIDS</literal></term>
|
|
<listitem>
|
|
<para>
|
|
This form adds an <literal>oid</literal> system column to the
|
|
table (see <xref linkend="ddl-system-columns">).
|
|
It does nothing if the table already has OIDs.
|
|
</para>
|
|
|
|
<para>
|
|
Note that this is not equivalent to <literal>ADD COLUMN oid oid</>;
|
|
that would add a normal column that happened to be named
|
|
<literal>oid</>, not a system column.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>SET WITHOUT OIDS</literal></term>
|
|
<listitem>
|
|
<para>
|
|
This form removes the <literal>oid</literal> system column from the
|
|
table. This is exactly equivalent to
|
|
<literal>DROP COLUMN oid RESTRICT</literal>,
|
|
except that it will not complain if there is already no
|
|
<literal>oid</literal> column.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>SET ( <replaceable class="PARAMETER">storage_parameter</replaceable> = <replaceable class="PARAMETER">value</replaceable> [, ... ] )</literal></term>
|
|
<listitem>
|
|
<para>
|
|
This form changes one or more storage parameters for the table. See
|
|
<xref linkend="SQL-CREATETABLE-storage-parameters"
|
|
endterm="SQL-CREATETABLE-storage-parameters-title">
|
|
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 <link linkend="SQL-VACUUM">VACUUM
|
|
FULL</>, <xref linkend="SQL-CLUSTER"> or one of the forms
|
|
of <command>ALTER TABLE</> that forces a table rewrite.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
While <command>CREATE TABLE</> allows <literal>OIDS</> to be specified
|
|
in the <literal>WITH (<replaceable
|
|
class="PARAMETER">storage_parameter</>)</literal> syntax,
|
|
<command>ALTER TABLE</> does not treat <literal>OIDS</> as a
|
|
storage parameter. Instead use the <literal>SET WITH OIDS</>
|
|
and <literal>SET WITHOUT OIDS</> forms to change OID status.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>RESET ( <replaceable class="PARAMETER">storage_parameter</replaceable> [, ... ] )</literal></term>
|
|
<listitem>
|
|
<para>
|
|
This form resets one or more storage parameters to their
|
|
defaults. As with <literal>SET</>, a table rewrite might be
|
|
needed to update the table entirely.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>INHERIT <replaceable class="PARAMETER">parent_table</replaceable></literal></term>
|
|
<listitem>
|
|
<para>
|
|
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,
|
|
and if they have <literal>NOT NULL</literal> constraints in the parent
|
|
then they must also have <literal>NOT NULL</literal> constraints in the
|
|
child.
|
|
</para>
|
|
|
|
<para>
|
|
There must also be matching child-table constraints for all
|
|
<literal>CHECK</literal> constraints of the parent, except those
|
|
marked non-inheritable (that is, created with <literal>ALTER TABLE ... ADD CONSTRAINT ... NO INHERIT</literal>)
|
|
in the parent, which are ignored; all child-table constraints matched
|
|
must not be marked non-inheritable.
|
|
Currently
|
|
<literal>UNIQUE</literal>, <literal>PRIMARY KEY</literal>, and
|
|
<literal>FOREIGN KEY</literal> constraints are not considered, but
|
|
this might change in the future.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>NO INHERIT <replaceable class="PARAMETER">parent_table</replaceable></literal></term>
|
|
<listitem>
|
|
<para>
|
|
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.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>OF <replaceable class="PARAMETER">type_name</replaceable></literal></term>
|
|
<listitem>
|
|
<para>
|
|
This form links the table to a composite type as though <command>CREATE
|
|
TABLE OF</> had formed it. The table's list of column names and types
|
|
must precisely match that of the composite type; the presence of
|
|
an <literal>oid</> system column is permitted to differ. The table must
|
|
not inherit from any other table. These restrictions ensure
|
|
that <command>CREATE TABLE OF</> would permit an equivalent table
|
|
definition.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>NOT OF</literal></term>
|
|
<listitem>
|
|
<para>
|
|
This form dissociates a typed table from its type.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>OWNER</literal></term>
|
|
<listitem>
|
|
<para>
|
|
This form changes the owner of the table, sequence, or view to the
|
|
specified user.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>SET TABLESPACE</literal></term>
|
|
<listitem>
|
|
<para>
|
|
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 <literal>SET TABLESPACE</literal> commands.
|
|
See also
|
|
<xref linkend="SQL-CREATETABLESPACE">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="SQL-CREATETABLE-REPLICA-IDENTITY">
|
|
<term><literal>REPLICA IDENTITY</literal></term>
|
|
<listitem>
|
|
<para>
|
|
This form changes the information which is written to the write-ahead log
|
|
to identify rows which are updated or deleted. This option has no effect
|
|
except when logical replication is in use. <literal>DEFAULT</> records the
|
|
old values of the columns of the primary key, if any. <literal>USING INDEX</>
|
|
records the old values of the columns covered by the named index, which
|
|
must be unique, not partial, not deferrable, and include only columns marked
|
|
<literal>NOT NULL</>. <literal>FULL</> records the old values of all columns
|
|
in the row. <literal>NOTHING</> records no information about the old row.
|
|
In all cases, no old values are logged unless at least one of the columns
|
|
that would be logged differs between the old and new versions of the row.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>RENAME</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The <literal>RENAME</literal> forms change the name of a table
|
|
(or an index, sequence, or view), the name of an individual column in
|
|
a table, or the name of a constraint of the table. There is no effect on the stored data.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>SET SCHEMA</literal></term>
|
|
<listitem>
|
|
<para>
|
|
This form moves the table into another schema. Associated indexes,
|
|
constraints, and sequences owned by table columns are moved as well.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</para>
|
|
|
|
<para>
|
|
All the actions except <literal>RENAME</literal> and <literal>SET SCHEMA</>
|
|
can be combined into
|
|
a list of multiple alterations to apply in parallel. 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.
|
|
</para>
|
|
|
|
<para>
|
|
You must own the table to use <command>ALTER TABLE</>.
|
|
To change the schema of a table, you must also have
|
|
<literal>CREATE</literal> privilege on the new schema.
|
|
To add the table as a new child of a parent table, you must own the
|
|
parent table as well.
|
|
To alter the owner, you must also be a direct or indirect member of the new
|
|
owning role, and that role must have <literal>CREATE</literal> 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 <literal>OF</literal>
|
|
clause, you must also have <literal>USAGE</literal> privilege on the data
|
|
type.
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Parameters</title>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">name</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
The name (optionally schema-qualified) of an existing table to
|
|
alter. If <literal>ONLY</> is specified before the table name, only
|
|
that table is altered. If <literal>ONLY</> is not specified, the table
|
|
and all its descendant tables (if any) are altered. Optionally,
|
|
<literal>*</> can be specified after the table name to explicitly
|
|
indicate that descendant tables are included.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">column_name</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Name of a new or existing column.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">new_column_name</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
New name for an existing column.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">new_name</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
New name for the table.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">type</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Data type of the new column, or new data type for an existing
|
|
column.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">table_constraint</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
New table constraint for the table.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">constraint_name</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Name of an existing constraint to drop.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>CASCADE</literal></term>
|
|
<listitem>
|
|
<para>
|
|
Automatically drop objects that depend on the dropped column
|
|
or constraint (for example, views referencing the column).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>RESTRICT</literal></term>
|
|
<listitem>
|
|
<para>
|
|
Refuse to drop the column or constraint if there are any dependent
|
|
objects. This is the default behavior.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">trigger_name</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Name of a single trigger to disable or enable.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>ALL</literal></term>
|
|
<listitem>
|
|
<para>
|
|
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.)
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>USER</literal></term>
|
|
<listitem>
|
|
<para>
|
|
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.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">index_name</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
The index name on which the table should be marked for clustering.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">storage_parameter</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
The name of a table storage parameter.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">value</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
The new value for a table storage parameter.
|
|
This might be a number or a word depending on the parameter.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">parent_table</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
A parent table to associate or de-associate with this table.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">new_owner</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
The user name of the new owner of the table.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">new_tablespace</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
The name of the tablespace to which the table will be moved.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable class="PARAMETER">new_schema</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
The name of the schema to which the table will be moved.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Notes</title>
|
|
|
|
<para>
|
|
The key word <literal>COLUMN</literal> is noise and can be omitted.
|
|
</para>
|
|
|
|
<para>
|
|
When a column is added with <literal>ADD COLUMN</literal>, all existing
|
|
rows in the table are initialized with the column's default value
|
|
(NULL if no <literal>DEFAULT</> clause is specified).
|
|
If there is no <literal>DEFAULT</> clause, this is merely a metadata
|
|
change and does not require any immediate update of the table's data;
|
|
the added NULL values are supplied on readout, instead.
|
|
</para>
|
|
|
|
<para>
|
|
Adding a column with a <literal>DEFAULT</> clause or changing the type of
|
|
an existing column will require the entire table and its indexes to be
|
|
rewritten. As an exception when changing the type of an existing column,
|
|
if the <literal>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;
|
|
but any indexes on the affected columns must still be rebuilt. Adding or
|
|
removing a system <literal>oid</> column also requires rewriting the entire
|
|
table. 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.
|
|
</para>
|
|
|
|
<para>
|
|
Adding a <literal>CHECK</> or <literal>NOT NULL</> constraint requires
|
|
scanning the table to verify that existing rows meet the constraint.
|
|
</para>
|
|
|
|
<para>
|
|
The main reason for providing the option to specify multiple changes
|
|
in a single <command>ALTER TABLE</> is that multiple table scans or
|
|
rewrites can thereby be combined into a single pass over the table.
|
|
</para>
|
|
|
|
<para>
|
|
The <literal>DROP COLUMN</literal> 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. (These statements do
|
|
not apply when dropping the system <literal>oid</> column; that is done
|
|
with an immediate rewrite.)
|
|
</para>
|
|
|
|
<para>
|
|
To force an immediate rewrite of the table, you can use
|
|
<link linkend="SQL-VACUUM">VACUUM FULL</>, <xref linkend="SQL-CLUSTER">
|
|
or one of the forms of ALTER TABLE that forces a rewrite. This results in
|
|
no semantically-visible change in the table, but gets rid of
|
|
no-longer-useful data.
|
|
</para>
|
|
|
|
<para>
|
|
The <literal>USING</literal> option of <literal>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 <literal>SET DATA TYPE</>
|
|
syntax. Because of this flexibility, the <literal>USING</literal>
|
|
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, <literal>SET DATA TYPE</> might fail to convert the default even
|
|
though a <literal>USING</literal> clause is supplied. In such cases,
|
|
drop the default with <literal>DROP DEFAULT</>, perform the <literal>ALTER
|
|
TYPE</>, and then use <literal>SET DEFAULT</> to add a suitable new
|
|
default. Similar considerations apply to indexes and constraints involving
|
|
the column.
|
|
</para>
|
|
|
|
<para>
|
|
If a table has any descendant tables, it is not permitted to add,
|
|
rename, or change the type of a column, or rename an inherited constraint
|
|
in the parent table without doing
|
|
the same to the descendants. That is, <command>ALTER TABLE ONLY</command>
|
|
will be rejected. This ensures that the descendants always have
|
|
columns matching the parent.
|
|
</para>
|
|
|
|
<para>
|
|
A recursive <literal>DROP COLUMN</literal> 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 <literal>DROP
|
|
COLUMN</literal> (i.e., <command>ALTER TABLE ONLY ... DROP
|
|
COLUMN</command>) never removes any descendant columns, but
|
|
instead marks them as independently defined rather than inherited.
|
|
</para>
|
|
|
|
<para>
|
|
The <literal>TRIGGER</>, <literal>CLUSTER</>, <literal>OWNER</>,
|
|
and <literal>TABLESPACE</> actions never recurse to descendant tables;
|
|
that is, they always act as though <literal>ONLY</> were specified.
|
|
Adding a constraint recurses only for <literal>CHECK</> constraints
|
|
that are not marked <literal>NO INHERIT</>.
|
|
</para>
|
|
|
|
<para>
|
|
Changing any part of a system catalog table is not permitted.
|
|
</para>
|
|
|
|
<para>
|
|
Refer to <xref linkend="sql-createtable"> for a further description of valid
|
|
parameters. <xref linkend="ddl"> has further information on
|
|
inheritance.
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Examples</title>
|
|
|
|
<para>
|
|
To add a column of type <type>varchar</type> to a table:
|
|
<programlisting>
|
|
ALTER TABLE distributors ADD COLUMN address varchar(30);
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To drop a column from a table:
|
|
<programlisting>
|
|
ALTER TABLE distributors DROP COLUMN address RESTRICT;
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To change the types of two existing columns in one operation:
|
|
<programlisting>
|
|
ALTER TABLE distributors
|
|
ALTER COLUMN address TYPE varchar(80),
|
|
ALTER COLUMN name TYPE varchar(100);
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To change an integer column containing UNIX timestamps to <type>timestamp
|
|
with time zone</type> via a <literal>USING</literal> clause:
|
|
<programlisting>
|
|
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';
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The same, when the column has a default expression that won't automatically
|
|
cast to the new data type:
|
|
<programlisting>
|
|
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();
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To rename an existing column:
|
|
<programlisting>
|
|
ALTER TABLE distributors RENAME COLUMN address TO city;
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To rename an existing table:
|
|
<programlisting>
|
|
ALTER TABLE distributors RENAME TO suppliers;
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To rename an existing constraint:
|
|
<programlisting>
|
|
ALTER TABLE distributors RENAME CONSTRAINT zipchk TO zip_check;
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To add a not-null constraint to a column:
|
|
<programlisting>
|
|
ALTER TABLE distributors ALTER COLUMN street SET NOT NULL;
|
|
</programlisting>
|
|
To remove a not-null constraint from a column:
|
|
<programlisting>
|
|
ALTER TABLE distributors ALTER COLUMN street DROP NOT NULL;
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To add a check constraint to a table and all its children:
|
|
<programlisting>
|
|
ALTER TABLE distributors ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5);
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To add a check constraint only to a table and not to its children:
|
|
<programlisting>
|
|
ALTER TABLE distributors ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5) NO INHERIT;
|
|
</programlisting>
|
|
(The check constraint will not be inherited by future children, either.)
|
|
</para>
|
|
|
|
<para>
|
|
To remove a check constraint from a table and all its children:
|
|
<programlisting>
|
|
ALTER TABLE distributors DROP CONSTRAINT zipchk;
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To remove a check constraint from one table only:
|
|
<programlisting>
|
|
ALTER TABLE ONLY distributors DROP CONSTRAINT zipchk;
|
|
</programlisting>
|
|
(The check constraint remains in place for any child tables.)
|
|
</para>
|
|
|
|
<para>
|
|
To add a foreign key constraint to a table:
|
|
<programlisting>
|
|
ALTER TABLE distributors ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES addresses (address);
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To add a (multicolumn) unique constraint to a table:
|
|
<programlisting>
|
|
ALTER TABLE distributors ADD CONSTRAINT dist_id_zipcode_key UNIQUE (dist_id, zipcode);
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To add an automatically named primary key constraint to a table, noting
|
|
that a table can only ever have one primary key:
|
|
<programlisting>
|
|
ALTER TABLE distributors ADD PRIMARY KEY (dist_id);
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To move a table to a different tablespace:
|
|
<programlisting>
|
|
ALTER TABLE distributors SET TABLESPACE fasttablespace;
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To move a table to a different schema:
|
|
<programlisting>
|
|
ALTER TABLE myschema.distributors SET SCHEMA yourschema;
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To recreate a primary key constraint, without blocking updates while the
|
|
index is rebuilt:
|
|
<programlisting>
|
|
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;
|
|
</programlisting></para>
|
|
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Compatibility</title>
|
|
|
|
<para>
|
|
The forms <literal>ADD</literal> (without <literal>USING INDEX</literal>),
|
|
<literal>DROP</>, <literal>SET DEFAULT</>,
|
|
and <literal>SET DATA TYPE</literal> (without <literal>USING</literal>)
|
|
conform with the SQL standard. The other forms are
|
|
<productname>PostgreSQL</productname> extensions of the SQL standard.
|
|
Also, the ability to specify more than one manipulation in a single
|
|
<command>ALTER TABLE</> command is an extension.
|
|
</para>
|
|
|
|
<para>
|
|
<command>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.
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
|
|
<simplelist type="inline">
|
|
<member><xref linkend="sql-createtable"></member>
|
|
</simplelist>
|
|
</refsect1>
|
|
</refentry>
|