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From: "David G. Johnston" <david.g.johnston@gmail.com>
Date: Mon, 24 Jun 2024 06:35:54 -0700
Message-ID: <CAKFQuwbWg51wrQCNYe8J6V_KXoK5wQR3SERWKhCFwx6jx2OuOw@mail.gmail.com>
Subject: Re: Issue with pgstattuple on Sequences in PostgreSQL
To: Ayush Vatsa <ayushvatsa1810@gmail.com>
Cc: "pgsql-general@lists.postgresql.org" <pgsql-general@lists.postgresql.org>
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On Monday, June 24, 2024, Ayush Vatsa <ayushvatsa1810@gmail.com> wrote:
>
> I was recently exploring the pgstattuple code directory and found this
> piece of code: https://github.com/postgres/postgres/blob/master/contrib/
> pgstattuple/pgstattuple.c#L255-L259.
>
> It indicates that pgstattuple supports relations, toast tables,
> materialized views, and sequences.
> However, when I executed a query with a sequence, I encountered the
> following error:
>
> postgres=3D> CREATE SEQUENCE serial START 101;
> CREATE SEQUENCE
> postgres=3D> SELECT * FROM pgstattuple('serial');
> ERROR:  only heap AM is supported
> postgres=3D>
>
> It got stuck in this if condition - https://github.com/postgres/
> postgres/blob/master/contrib/pgstattuple/pgstattuple.c#L326-L329
>
>
> How can one use pgstattuple on sequences?
>

As-is?  Doesn=E2=80=99t look like you can.  I agree it=E2=80=99s a document=
ation bug that
this is the case with a brief explanation of why - sequences do not produce
dead tuples and do not behave like real tables aside from being able to be
selected from (i.e., no SQL update/delete command).

The code should produce an explicit error for that relkind as well.

David J.

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On Monday, June 24, 2024, Ayush Vatsa &lt;<a href=3D"mailto:ayushvatsa1810@=
gmail.com">ayushvatsa1810@gmail.com</a>&gt; wrote:<blockquote class=3D"gmai=
l_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left=
:1ex"><div dir=3D"ltr"><p>I was recently exploring the pgstattuple code dir=
ectory and found this piece of code: <a rel=3D"noreferrer" href=3D"https://=
github.com/postgres/postgres/blob/master/contrib/pgstattuple/pgstattuple.c#=
L255-L259" target=3D"_blank">https://github.com/postgres/<wbr>postgres/blob=
/master/contrib/<wbr>pgstattuple/pgstattuple.c#<wbr>L255-L259</a>.=C2=A0</p=
><p>It indicates that pgstattuple supports relations, toast tables, materia=
lized views, and sequences.<br>However, when I executed a query with a sequ=
ence, I encountered the following error:</p><p>postgres=3D&gt; CREATE SEQUE=
NCE serial START 101;<br>CREATE SEQUENCE<br>postgres=3D&gt; SELECT * FROM p=
gstattuple(&#39;serial&#39;);<br>ERROR: =C2=A0only heap AM is supported<br>=
postgres=3D&gt;</p><p>It got stuck in this if condition - <a href=3D"https:=
//github.com/postgres/postgres/blob/master/contrib/pgstattuple/pgstattuple.=
c#L326-L329" target=3D"_blank">https://github.com/postgres/<wbr>postgres/bl=
ob/master/contrib/<wbr>pgstattuple/pgstattuple.c#<wbr>L326-L329</a></p><p><=
br>How can one use pgstattuple on sequences?=C2=A0</p></div></blockquote><d=
iv><br></div><div>As-is?=C2=A0 Doesn=E2=80=99t look like you can.=C2=A0 I a=
gree it=E2=80=99s a documentation bug that this is the case with a brief ex=
planation of why - sequences do not produce dead tuples and do not behave l=
ike real tables aside from being able to be selected from (i.e., no SQL upd=
ate/delete command).</div><div><br></div><div>The code should produce an ex=
plicit error for that relkind as well.</div><div><br></div><div>David J.</d=
iv><div><br></div>

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