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@gmail.com> wrote: