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ALTER TABLE ... ALTER COLUMN ... DROP EXPRESSION

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Add an ALTER TABLE subcommand for dropping the generated property from
a column, per SQL standard.

Reviewed-by: Sergei Kornilov <sk@zsrv.org>
Discussion: https://www.postgresql.org/message-id/flat/2f7f1d9c-946e-0453-d841-4f38eb9d69b6%402ndquadrant.com
This commit is contained in:
Peter Eisentraut
2020-01-14 13:09:31 +01:00
parent d751ba5235
commit f595117e24
9 changed files with 326 additions and 4 deletions
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18
doc/src/sgml/ref/alter_table.sgml
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@ -46,6 +46,7 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET DEFAULT <replaceable class="parameter">expression</replaceable>
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> DROP DEFAULT
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> { SET | DROP } NOT NULL
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> DROP EXPRESSION [ IF EXISTS ]
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( <replaceable>sequence_options</replaceable> ) ]
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> { SET GENERATED { ALWAYS | BY DEFAULT } | SET <replaceable>sequence_option</replaceable> | RESTART [ [ WITH ] <replaceable class="parameter">restart</replaceable> ] } [...]
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> DROP IDENTITY [ IF EXISTS ]
@ -241,6 +242,23 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
</listitem>
</varlistentry>
<varlistentry>
<term><literal>DROP EXPRESSION [ IF EXISTS ]</literal></term>
<listitem>
<para>
This form turns a stored generated column into a normal base column.
Existing data in the columns is retained, but future changes will no
longer apply the generation expression.
</para>
<para>
If <literal>DROP EXPRESSION IF EXISTS</literal> is specified and the
column is not a stored generated column, no error is thrown. In this
case a notice is issued instead.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY</literal></term>
<term><literal>SET GENERATED { ALWAYS | BY DEFAULT }</literal></term>