From: | "Drouvot, Bertrand" <bdrouvot(at)amazon(dot)com> |
---|---|
To: | Hamid Akhtar <hamid(dot)akhtar(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Allow pageinspect's bt_page_stats function to return a set of rows instead of a single row |
Date: | 2022-06-27 08:09:42 |
Message-ID: | 6b05f7ca-78db-db95-8571-4d26bbc4fd9c@amazon.com |
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Lists: | pgsql-hackers |
Hi,
On 6/27/22 9:31 AM, Hamid Akhtar wrote:
>
> Hello Hackers,
>
> While working on one of my blogs on the B-Tree indexes
> <https://www.percona.com/blog/postgresql-14-b-tree-index-reduced-bloat-with-bottom-up-deletion/>,
> I needed to look at a range of B-Tree page statistics. So the goto
> solution was to use pageinspect. However, reviewing stats for multiple
> pages meant issuing multiple queries.
FWIW, I think you could also rely on generate_series()
> I felt that there's an opportunity for improvement in the extension by
> extending the API to output the statistics for multiple pages with a
> single query.
>
> That attached patch is based on the master branch. It makes the
> following changes to the pageinspect contrib module:
> - Updates bt_page_stats_internal function to accept 3 arguments
> instead of 2.
> - The function now uses SRF macros to return a set rather than a
> single row. The function call now requires specifying column names.
>
> The extension version is bumped to 1.11 (PAGEINSPECT_V1_11).
> To maintain backward compatibility, for versions below 1.11, the
> multi-call mechanism is ended to keep the old behavior consistent.
>
> Regression test cases for the module are updated as well as part of
> this change. Here is a subset of queries that are added to the
> btree.sql test case file for pageinspect.
>
> ----
> CREATE TABLE test2 AS (SELECT generate_series(1, 5000) AS col1);
> CREATE INDEX test2_col1_idx ON test2(col1);
> SELECT * FROM bt_page_stats('test2_col1_idx', 1, 2);
For example, this could be written as:
select * from
generate_series(1, 2) blkno ,
bt_page_stats('test2_col1_idx',blkno::int);
Or, if one wants to inspect to whole relation, something like:
select * from
generate_series(1, pg_relation_size('test2_col1_idx'::regclass::text) /
8192 - 1) blkno ,
bt_page_stats('test2_col1_idx',blkno::int);
Regards,
Bertrand
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