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Re: Issue with pgstattuple on Sequences in PostgreSQL - Mailing list pgsql-general

From David G. Johnston
Subject Re: Issue with pgstattuple on Sequences in PostgreSQL
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Msg-id CAKFQuwbWg51wrQCNYe8J6V_KXoK5wQR3SERWKhCFwx6jx2OuOw@mail.gmail.com
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In response to Issue with pgstattuple on Sequences in PostgreSQL  (Ayush Vatsa <ayushvatsa1810@gmail.com>)
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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=> CREATE SEQUENCE serial START 101;
CREATE SEQUENCE
postgres=> SELECT * FROM pgstattuple('serial');
ERROR:  only heap AM is supported
postgres=>

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’t look like you can.  I agree it’s a documentation 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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