[postgis-users] PERFORMANCE PROBLEMS II (More Data)
dblasby at refractions.net
Tue Mar 2 09:47:24 PST 2004
Alvaro Zabala wrote:
> My Java application is a JUMP plugin.
> Refraction's plugin es good, but it works downloading all features from
> database, to work with them in memory.
> We are working with massive datasets, and we need to execute one query
> by rectangle any time.
> (When changing zoom level, plugin execute a query by rectangle)
> I've made a query explain -to see if the query is using spatial index)
> and I get:
> "Index Scan using spt_index_muni on municipios (cost=0.00..5.95 rows=1
> It uses spatial index.
> May I improve the query execution time? How?
> My table only has 700 rows.
If your table only has 700 rows, it should be very quick. We do the
same thing on a table with 17,000,000 rows and the response time is <0.5
seconds for a medium-sized area (about 1,000 lines selected).
Doing this on a 700 row table should be instant - unless your individual
geometries are huge (>100,000 points).
If you do an
EXPLAIN ANALYSE <normal query>;
postgresql will give you execution time details as well as the plan.
The only reason your query would be slow is if you either have a
hopelessly tiny amount of memory or you machine is swamped doing other
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