[postgis-users] Partitioning spatial table

[Markus Schaber]

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

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