Simon Riggs <[EMAIL PROTECTED]> writes:
> My suggested hack for PostgreSQL is to have an option to *not* sample,
> just to scan the whole table and find n_distinct accurately.
> ...
> What price a single scan of a table, however large, when incorrect
> statistics could force scans and sorts to occur when they aren't
> actually needed ?

It's not just the scan --- you also have to sort, or something like
that, if you want to count distinct values.  I doubt anyone is really
going to consider this a feasible answer for large tables.

                        regards, tom lane

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