Date: Wed, 17 Sep 2025 16:45:14 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Peter Geoghegan <pg@bowt.ie>
Cc: PostgreSQL-development <pgsql-hackers@lists.postgresql.org>
Subject: Re: PG 18 release notes draft committed
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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  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Do not let urgent matters crowd out time for investment in the future.