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Note that ALTER TABLE cannot alter generated stored columns 4+ messages / 3 participants [nested] [flat]
* Note that ALTER TABLE cannot alter generated stored columns @ 2021-05-30 13:25 Emre Hasegeli <[email protected]> 0 siblings, 2 replies; 4+ messages in thread From: Emre Hasegeli @ 2021-05-30 13:25 UTC (permalink / raw) To: pgsql-docs I was trying to change the generation expression of a generated stored column using ALTER TABLE. It took me a while before I figured SET GENERATED applies only to generated identity columns. I think it'd be useful to note this in the documentation with something like the attached. Attachments: [application/octet-stream] 0001-doc-Note-that-ALTER-TABLE-cannot-alter-generated-sto.patch (2.0K, 2-0001-doc-Note-that-ALTER-TABLE-cannot-alter-generated-sto.patch) download | inline diff: From 3d6fe7e6bb57081a9b7c3d5bcc23e5159ed65ba7 Mon Sep 17 00:00:00 2001 From: Emre Hasegeli <[email protected]> Date: Sun, 30 May 2021 16:11:30 +0300 Subject: [PATCH] doc: Note that ALTER TABLE cannot alter generated stored ALTER TABLE supports altering generated identity columns which could confuse the reader as they share syntax with generated stored columns. Clarify that a column cannot be turned into generated stored or generation expressions cannot be changed with a note. --- doc/src/sgml/ref/alter_table.sgml | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml index 939d3fe273..0e9846153e 100644 --- a/doc/src/sgml/ref/alter_table.sgml +++ b/doc/src/sgml/ref/alter_table.sgml @@ -251,20 +251,28 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM 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> + + <note> + <para> + Turning a column into generated or changing the generation expression + is currently not supported. To do that, use <command>DROP COLUMN</command> + and <command>CREATE COLUMN</command> with <command>GENERATED ALWAYS AS ( generation_expr ) STORED</command>. + </para> + </note> </listitem> </varlistentry> <varlistentry> <term><literal>ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY</literal></term> <term><literal>SET GENERATED { ALWAYS | BY DEFAULT }</literal></term> <term><literal>DROP IDENTITY [ IF EXISTS ]</literal></term> <listitem> <para> These forms change whether a column is an identity column or change the -- 2.30.1 (Apple Git-130) ^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Note that ALTER TABLE cannot alter generated stored columns @ 2021-05-31 05:42 Laurenz Albe <[email protected]> parent: Emre Hasegeli <[email protected]> 1 sibling, 0 replies; 4+ messages in thread From: Laurenz Albe @ 2021-05-31 05:42 UTC (permalink / raw) To: [email protected]; pgsql-docs On Sun, 2021-05-30 at 16:25 +0300, Emre Hasegeli wrote: > I was trying to change the generation expression of a generated stored > column using ALTER TABLE. It took me a while before I figured SET > GENERATED applies only to generated identity columns. I think it'd be > useful to note this in the documentation with something like the > attached. +1 Yours, Laurenz Albe ^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Note that ALTER TABLE cannot alter generated stored columns @ 2021-06-02 15:00 Peter Eisentraut <[email protected]> parent: Emre Hasegeli <[email protected]> 1 sibling, 1 reply; 4+ messages in thread From: Peter Eisentraut @ 2021-06-02 15:00 UTC (permalink / raw) To: [email protected]; pgsql-docs On 30.05.21 15:25, Emre Hasegeli wrote: > I was trying to change the generation expression of a generated stored > column using ALTER TABLE. It took me a while before I figured SET > GENERATED applies only to generated identity columns. I think it'd be > useful to note this in the documentation with something like the > attached. I don't follow why you put this documentation under ALTER TABLE ... DROP EXPRESSION. That action doesn't seem related to what you were hoping to do. ^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Note that ALTER TABLE cannot alter generated stored columns @ 2021-06-03 12:57 Emre Hasegeli <[email protected]> parent: Peter Eisentraut <[email protected]> 0 siblings, 0 replies; 4+ messages in thread From: Emre Hasegeli @ 2021-06-03 12:57 UTC (permalink / raw) To: Peter Eisentraut <[email protected]>; +Cc: pgsql-docs > I don't follow why you put this documentation under ALTER TABLE ... DROP > EXPRESSION. That action doesn't seem related to what you were hoping to do. I thought that's where it would be if we had ADD/SET EXPRESSION statements, just like the ADD/SET GENERATED statements just below. ^ permalink raw reply [nested|flat] 4+ messages in thread
end of thread, other threads:[~2021-06-03 12:57 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2021-05-30 13:25 Note that ALTER TABLE cannot alter generated stored columns Emre Hasegeli <[email protected]> 2021-05-31 05:42 ` Laurenz Albe <[email protected]> 2021-06-02 15:00 ` Peter Eisentraut <[email protected]> 2021-06-03 12:57 ` Emre Hasegeli <[email protected]>
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