From: PG Doc comments form <noreply@postgresql.org>
To: pgsql-docs@lists.postgresql.org
Cc: chris+postgresql@qwirx.com
Subject: Why can NUMERIC columns not use deduplication?
Date: Fri, 14 Jan 2022 13:57:59 +0000
Message-ID: <164216867903.23277.10737033258186320533@wrigleys.postgresql.org> (raw)
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/14/btree-implementation.html
Description:
"64.4.3. Deduplication" says:
"numeric cannot use deduplication. Numeric display scale must be preserved
among equal datums."
However I don't understand this. An equal datum is an equal datum regardless
of display scale, isn't it?
Even in the special case of a NUMERIC column with no precision or scale
(8.1.2), for example if a table has an index on a NUMERIC column, and some
rows have the value 8 in that column, and some have the value 8.0 (I think
these are different values/datums in this special case), I would not expect
all those index entries to be deduplicated into a single list, but I would
expect them to be deduplicated into two lists (one for the value 8, and one
for the value 8.0). Then again I am not familiar with the actual
implementation.
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Subject: Re: Why can NUMERIC columns not use deduplication?
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