From: PG Doc comments form <noreply@postgresql.org>
To: pgsql-docs@lists.postgresql.org
Cc: chaodhib@gmail.com
Subject: the doc should mention one particular aspect of partial indexes
Date: Mon, 18 Jan 2021 17:07:42 +0000
Message-ID: <161098966261.468.431083803607667410@wrigleys.postgresql.org> (raw)
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
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Subject: Re: the doc should mention one particular aspect of partial indexes
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