Implement a non PS based dialect for PostGIS-ng
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Key: GEOT-2249
URL: http://jira.codehaus.org/browse/GEOT-2249
Project: GeoTools
Issue Type: Task
Components: data jdbc-ng
Affects Versions: 2.5.2
Reporter: Andrea Aime
Assignee: Andrea Aime
Fix For: 2.5.3
Some performance tests on PostGIS database show that a prepared statement based
dialect:
- does not help at all, performance wise, even the amounts of features
extracted is small (1000 out of 3 millions). The amount of data handled in the
typical GIS request is big enough to hide completely the advantage of not
having to make a query plan over and over (at least for PostGIS, for other
databases it may be different...)
- is a real disaster when all the features are read out in the typical WMS
request where a bbox filter is set anyways, as the database plans the query
just once based on the query "template" not knowing the bbox extent. Tests
shows that accessing all of the features of a 3million roads is at least twice
as slow than doing a sequential scan (the road chosen by the db when it can see
the bbox value prior to making the access plan). Thanks to Christian Mueller
for pointing this out a couple months ago (for DB2), it surely helped guess out
the cause of the slower performance of pg-ng compared to the old postgis db.
On the other side, ps based dialects are basically guaranteed against sql
injection attacks and on some dbms they may be faster when accessing small
amounts of data (Oracle for example is often cited as a database that lives and
dies by prepared statements).
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