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help / color / mirror / Atom feedFrom: Bruce Momjian <[email protected]>
To: Peter Geoghegan <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Subject: Re: PG 18 release notes draft committed
Date: Wed, 17 Sep 2025 16:45:14 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAH2-Wzk1aYZpsXRP1iz7iBweg55dZPicPBUL50SmtzkF-Rm9ig@mail.gmail.com>
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On Wed, Sep 17, 2025 at 11:46:58AM -0400, Peter Geoghegan wrote:
> I suggest the following alternative, which has the merit of being a
> bit less verbose:
>
> "Skip scan allows B-Tree index scans to find the most efficient way of
> navigating through a multicolumn index when one or more of its columns
> initially lacks a = condition and comes before a column that is
> directly used by the query. Such an index scan can now be broken down
> into multiple "index searches" by generating an implementation level =
> condition on any underspecified columns. This allows the scan to skip
> over irrelevant sections of the index, though only when the generated
> = condition is on a column that has relatively few distinct values."
>
> Note that "index searches" is a term that now appears in EXPLAIN ANALYZE output.
I went with this text, which is more "aspirational" rather than
"proscriptive", and the right level of detail:
This allows multi-column btree indexes to be used in more cases
such as when there are no restrictions on the first or early
indexed columns (or they are non-equality ones), and there are
useful restrictions on later indexed columns.
--
Bruce Momjian <[email protected]> https://momjian.us
EDB https://enterprisedb.com
Do not let urgent matters crowd out time for investment in the future.
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Subject: Re: PG 18 release notes draft committed
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