Simon Riggs <[EMAIL PROTECTED]> writes:
> [ ... a large amount of analysis based on exactly one test case ... ]
I think you are putting too much emphasis on fixing one case and not
enough on considering what may happen in other cases ...
In general, estimating n-distinct from a sample is just plain a hard
problem, and it's probably foolish to suppose we'll ever be able to
do it robustly. What we need is to minimize the impact when we get
it wrong. So I agree with the comment that we need to finish the
unfinished project of making HashAggregate tables expansible, but
I'm dubious about the rest of this.
regards, tom lane
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
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