Re: Number of rows in a table

ron.l.johnson@cox.net (Ron Johnson) writes:
> Well yes, but in most other databases, there is a system table that
> stores the approximate number of records in each table, and querying
> that system table is a *lot* faster than sequentially reading a 100M
> row table.

That relation would be pg_class, the domain is called "reltuples."

It is only about as accurate as the last vacuum and/or analyze has
made it, so if you don't fairly regularly vacuum tables, the
approximation may not be very good.  (Which is an argument in favor of
vacuuming fairly often...)
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Christopher Browne
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