Re: 500x speed-down: Wrong query plan?

Alessandro Baretta <a(dot)baretta(at)barettadeit(dot)com> writes:
> Tom Lane wrote:
>> 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)

Well, there's your problem: 17697 rows estimated vs 0 actual. With a
closer row estimate it would've probably done the right thing for the
join problem.

How many rows are really in the table, anyway? Could we see the
pg_stats row for articolo.xdbs_modified?

regards, tom lane