| From: | Cherio <cherio(at)gmail(dot)com> |
|---|---|
| To: | Hellmuth Vargas <hivs77(at)gmail(dot)com> |
| Cc: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, Matt Zagrabelny <mzagrabe(at)d(dot)umn(dot)edu>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Rob Sargent <robjsargent(at)gmail(dot)com>, "pgsql-generallists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: count(*) vs count(id) |
| Date: | 2021-02-03 06:43:14 |
| Message-ID: | CAKHqFkKWVam7LyVM7bxDMXxsr4fZVbNuTG=rfHx07jpF5f6MMA@mail.gmail.com |
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| Lists: | pgsql-general |
I just ran a few practical tests on large (~14mil rows) tables that have
multiple indexes.
SELECT COUNT(id) forces PostgreSQL to use the primary key index.
SELECT COUNT(*) allows PostgreSQL to chose an index to use and it seems to
be choosing one of smaller size which leads to less IO and hence returns
the result faster.
On Tue, Feb 2, 2021 at 3:45 PM Hellmuth Vargas <hivs77(at)gmail(dot)com> wrote:
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