bitmap scan and explain analyze
I noticed that explain analyze emits a little bit funny reslut for
bitmap scans:
BitmapOr (cost=157.36..157.36 rows=18894 width=0) (actual time=9.406..9.406 rows=0 loops=1)
Why actual rows=0?
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Tatsuo Ishii
Tatsuo Ishii <t-ishii@sra.co.jp> writes:
Why actual rows=0?
I couldn't think of any reasonably cheap way to count the actual rows
(especially in the presence of lossy bitmaps), so I just punted.
regards, tom lane
Why actual rows=0?
I couldn't think of any reasonably cheap way to count the actual rows
(especially in the presence of lossy bitmaps), so I just punted.
I see.
BTW is it possible to let BitmapHeapScan fetch tuples by TID order? It
would make heap acccess in sequential manner and would boost disk
access performance.
--
Tatsuo Ishii
Tatsuo Ishii <t-ishii@sra.co.jp> writes:
BTW is it possible to let BitmapHeapScan fetch tuples by TID order?
It already does ...
regards, tom lane