Josh Kupershmidt <schmi...@gmail.com> writes:
> func.sgml still claims that a sequential scan is the only way to
> execute a SELECT COUNT(*) query. I think this note should just be
> removed from the current docs, given the existence of index-only
> scans; patch attached.
Well, it might need adjustment, but I don't think we should remove it
outright. The people who complain that COUNT(*) is not O(1) are still
going to be complaining. On tables that are not read-mostly, there's
no reason to expect that index-only scans will even provide a material
speed boost, let alone be close to free.
regards, tom lane
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