Re: count * performance issue

Greg Smith <gsmith@gregsmith.com> writes:
> I know when I'm playing with pgbench the primary key index on the big
> accounts table is 1/7 the size of the table, and when using that table
> heavily shared_buffers ends up being mostly filled with that index. The
> usage counts are so high on the index blocks relative to any section of
> the table itself that they're very sticky in memory.  And that's toy data;
> on some of the webapps people want these accurate counts for the ratio of
> index size to table data is even more exaggerated (think web forum).

Remember that our TOAST mechanism acts to limit the width of the
main-table row.

            regards, tom lane