[postgis-users] Partitioning spatial table
Markus Schaber
schabi at logix-tt.com
Tue Feb 21 02:55:32 PST 2006
Hi, David,
David Bitner wrote:
>>By "multi-index capabilities" I wonder if David is referring to
>>8.1's bitmap scans, which allow the planner to make use of disparate
>>indexes.
> Yep, that's exactly what I was referring to -- sorry for the lack of detail.
You would need both a GIST index and a btree index on the integer column.
However, in this case I think having partial indices is the more
efficient case, especially because there are only a few combinations of
queries, so we can "statically optimize" for them.
For such a bitmap scan, the query planner has to scan both indices to
create the bitmap in memory, and then access the table. With partial
indices, it only has to access a single index and no in-memory bitmap.
(The difference in planning time should be neglible, and can be
eliminated by using prepared statements.)
HTH,
Markus
--
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf. | Software Development GIS
Fight against software patents in EU! www.ffii.org www.nosoftwarepatents.org
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