On Tue, 26 Apr 2005, Tom Lane wrote:
> Pavel Stehule <[EMAIL PROTECTED]> writes:
> > I tested bitmap scan and maybe I didnt find good examples, but with bitmap
> > scan is slower than hashjoin. Only when I use non otiptimized SELECT bps
> > was little bit faster. All my SELECTs are equal.
>
> Bitmap scans can't possibly be any faster for cases where the indexscan
> only fetches one row, which is true of all your test cases AFAICS.
yes, it's true. I found some selects where the benefit of bitmap scans is
more clearly. There is only one small problem - optimizer didn't
have to choose plan with bitmap scan in my examples.
Thank you for explication,
Regards
Pavel Stehule
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
