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* Note that ALTER TABLE cannot alter generated stored columns
@ 2021-05-30 13:25 Emre Hasegeli <[email protected]>
2021-05-31 05:42 ` Re: Note that ALTER TABLE cannot alter generated stored columns Laurenz Albe <[email protected]>
2021-06-02 15:00 ` Re: Note that ALTER TABLE cannot alter generated stored columns Peter Eisentraut <[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
2021-05-30 13:25 Note that ALTER TABLE cannot alter generated stored columns Emre Hasegeli <[email protected]>
@ 2021-05-31 05:42 ` Laurenz Albe <[email protected]>
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
2021-05-30 13:25 Note that ALTER TABLE cannot alter generated stored columns Emre Hasegeli <[email protected]>
@ 2021-06-02 15:00 ` Peter Eisentraut <[email protected]>
2021-06-03 12:57 ` Re: Note that ALTER TABLE cannot alter generated stored columns 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
2021-05-30 13:25 Note that ALTER TABLE cannot alter generated stored columns Emre Hasegeli <[email protected]>
2021-06-02 15:00 ` Re: Note that ALTER TABLE cannot alter generated stored columns Peter Eisentraut <[email protected]>
@ 2021-06-03 12:57 ` Emre Hasegeli <[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)
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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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