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* the doc should mention one particular aspect of partial indexes
@ 2021-01-18 17:07 PG Doc comments form <noreply@postgresql.org>
2021-01-18 20:39 ` Re: the doc should mention one particular aspect of partial indexes Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 1 reply; 3+ messages in thread
From: PG Doc comments form @ 2021-01-18 17:07 UTC (permalink / raw)
To: pgsql-docs@lists.postgresql.org; +Cc: chaodhib@gmail.com
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/10/sql-vacuum.html
Description:
Hi,
I think the documentation should mention one particular aspect of b-tree
partial indexes:
Say we have a row that satisfy a partial index's predicate. That row will be
referenced by the partial index. Say now that this row gets updated in such
a way that the updated row no longer satisfies the predicate. The entry of
that row in the index (more precisely, the row previous version) is still
kept in a leaf node of the b-tree until a VACUUM is issued on the index's
table.
So in short, an update on the index's predicate column results in no direct
change on the index whereas a change on an index column is reflected as soon
as the change has been committed. I think the documentation should mention
this specificity in some way since it can have impact in terms of index
design. I couldn't find a mention of this behavior anywhere in the doc.
Kind regards,
Chaouki Dhib
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: the doc should mention one particular aspect of partial indexes
2021-01-18 17:07 the doc should mention one particular aspect of partial indexes PG Doc comments form <noreply@postgresql.org>
@ 2021-01-18 20:39 ` Tom Lane <tgl@sss.pgh.pa.us>
2021-01-19 21:23 ` Re: the doc should mention one particular aspect of partial indexes Chaouki Dhib <chaodhib@gmail.com>
0 siblings, 1 reply; 3+ messages in thread
From: Tom Lane @ 2021-01-18 20:39 UTC (permalink / raw)
To: chaodhib@gmail.com; +Cc: pgsql-docs@lists.postgresql.org
PG Doc comments form <noreply@postgresql.org> writes:
> I think the documentation should mention one particular aspect of b-tree
> partial indexes:
> Say we have a row that satisfy a partial index's predicate. That row will be
> referenced by the partial index. Say now that this row gets updated in such
> a way that the updated row no longer satisfies the predicate. The entry of
> that row in the index (more precisely, the row previous version) is still
> kept in a leaf node of the b-tree until a VACUUM is issued on the index's
> table.
How is this different from the behavior for any other dead row version?
regards, tom lane
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: the doc should mention one particular aspect of partial indexes
2021-01-18 17:07 the doc should mention one particular aspect of partial indexes PG Doc comments form <noreply@postgresql.org>
2021-01-18 20:39 ` Re: the doc should mention one particular aspect of partial indexes Tom Lane <tgl@sss.pgh.pa.us>
@ 2021-01-19 21:23 ` Chaouki Dhib <chaodhib@gmail.com>
0 siblings, 0 replies; 3+ messages in thread
From: Chaouki Dhib @ 2021-01-19 21:23 UTC (permalink / raw)
To: Tom Lane <tgl@sss.pgh.pa.us>; +Cc: pgsql-docs@lists.postgresql.org
I guess it isn't. My apologies. This is something I ignored about PG
until now. Thank you for your reply.
Le lun. 18 janv. 2021 à 21:39, Tom Lane <tgl@sss.pgh.pa.us> a écrit :
>
> PG Doc comments form <noreply@postgresql.org> writes:
> > I think the documentation should mention one particular aspect of b-tree
> > partial indexes:
> > Say we have a row that satisfy a partial index's predicate. That row will be
> > referenced by the partial index. Say now that this row gets updated in such
> > a way that the updated row no longer satisfies the predicate. The entry of
> > that row in the index (more precisely, the row previous version) is still
> > kept in a leaf node of the b-tree until a VACUUM is issued on the index's
> > table.
>
> How is this different from the behavior for any other dead row version?
>
> regards, tom lane
^ permalink raw reply [nested|flat] 3+ messages in thread
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2021-01-18 17:07 the doc should mention one particular aspect of partial indexes PG Doc comments form <noreply@postgresql.org>
2021-01-18 20:39 ` Tom Lane <tgl@sss.pgh.pa.us>
2021-01-19 21:23 ` Chaouki Dhib <chaodhib@gmail.com>
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