From: Tom Lane <tgl@sss.pgh.pa.us>
To: Guillaume Smet <guillaume.smet@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Question about Bitmap Heap Scan/BitmapAnd
Date: Tue, 13 Feb 2007 12:51:05 -0500
Message-ID: <1977.1171389065@sss.pgh.pa.us> (raw)
In-Reply-To: <1d4e0c10702130917x5b6ddaf7g540bfe1f7c93b728@mail.gmail.com>
References: <1d4e0c10702130832i35484abfmb229f5d0b4d9223b@mail.gmail.com>
<1285.1171385353@sss.pgh.pa.us>
<1d4e0c10702130917x5b6ddaf7g540bfe1f7c93b728@mail.gmail.com>
"Guillaume Smet" <guillaume.smet@gmail.com> writes:
> So the basic explanation is that it's in both lists due to the partial
> index and only qpqual keeps the condition? I would have expected the
> opposite but it doesn't change anything I suppose?
It gets the right answer, yes. I'm not sure if we could safely put the
condition into the recheck instead of the filter. The particular code
I showed you has to go the direction it does, because a condition in the
filter has to be checked even if the bitmap is not lossy. I seem to
recall concluding that we had to recheck partial-index conditions even
if the bitmap is not lossy, but I can't reconstruct my reasoning at the
moment.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, guillaume.smet@gmail.com
Subject: Re: Question about Bitmap Heap Scan/BitmapAnd
In-Reply-To: <1977.1171389065@sss.pgh.pa.us>
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