Tom Lane wrote:
Alessandro Baretta <[EMAIL PROTECTED]> writes:
Matteo Beccati wrote:
Are you sure that you recentrly ANALYZED the table "ubicazione"? If so,
try to increase statistics for the id_ente column.
No, this is not the problem. I increased the amount of statistics with ALTER
TABLE ... SET STATISTICS 1000, which is as much as I can have.
What Matteo wanted to know is if you'd done an ANALYZE afterward. ALTER
TABLE SET STATISTICS doesn't in itself update the statistics.
I probably forgot to mention that I have vacuum-analyze the after this
operation, and, since I did not manage to get the index to work, I
vacuum-analyzed several times more, just to be on the safe side.
What do you get from
EXPLAIN SELECT * FROM articolo WHERE articolo.xdbs_modified > '2006-01-08
18:25:00+01';
I'm curious to see how many rows the planner thinks this will produce,
and whether it will use the index or not.
dmd-freerp-1-alex=# EXPLAIN ANALYZE SELECT * FROM articolo WHERE
articolo.xdbs_modified > '2006-01-08 18:25:00+01';
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------------
Index Scan using articolo_modified_index on articolo (cost=0.00..3914.91
rows=17697 width=653) (actual time=0.032..0.032 rows=0 loops=1)
Index Cond: (xdbs_modified > '2006-01-08 18:25:00'::timestamp without time
zone)
Total runtime: 0.150 ms
(3 rows)
The planner gets tricked only by *SOME* join queries.
Also, I gather from the plan choices that the condition id_ente = 'dmd'
isn't very selective ... what fraction of the rows in each table
satisfy that?
In most situation, this condition selects all the tuples. "id_ente" selects the
"owner of the data". Since, in most situations, companies do not share a
database between them--although the application allows it--filtering according
to 'id_ente' is like to filtering at all. Yet, this field is used in the
indexes, so the condition ought to be specified in the queries anyhow.
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