On 8/25/2011 1:21 PM, Ben Madin wrote:
Steve,
does this just apply to count(*), or is count(id) just as bad? I was
originally a MySQL user and count(*) could be very efficient there.
Best way to evaluate this is with explain. But yes both have the same
full table scan.
MySQL maintains row count as one of its tables stats so it just pulls
that from the stats metadata. If you just want an approximate row count,
there are some status based on the last analyze. If you use pgadmin3 you
can see in the table properties:
Rows (estimated) 1957620
This is one of the largest hurdles for MySQL users moving over to
postgresql because it is so obvious and in your face. But the things I
can do today with postgresql and with postgis, I could never do in MySQL.
-Steve
[snip history]
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