Tom Lane wrote:
> <kynn(at)panix(dot)com> writes:
>> Limit (cost=19676.75..21327.99 rows=6000 width=84)
>> -> Hash Join (cost=19676.75..1062244.81 rows=3788315 width=84)
>> Hash Cond: (upper(("outer".id)::text) = upper(("inner".id)::text))
>> -> Seq Scan on huge_table h (cost=0.00..51292.43 rows=2525543 width=46)
>> -> Hash (cost=19676.00..19676.00 rows=300 width=38)
>> -> Seq Scan on tiny_table t (cost=0.00..19676.00 rows=300 width=38)
> Um, if huge_table is so much bigger than tiny_table, why are the cost
> estimates for seqscanning them only about 2.5x different? There's
> something wacko about your statistics, methinks.
This suggests that tiny_table is very wide (i.e a lot of columns
compared to huge_table), or else has thousands of dead tuples.
Do you want to post the descriptions for these tables?
If you are running 8.1.x, then the output of 'ANALYZE VERBOSE
tiny_table' is of interest too.
If you are running a pre-8.1 release, then lets see 'VACUUM VERBOSE
Note that after either of these, your plans may be altered (as ANALYZE
will recompute your stats for tiny_table, and VACUUM may truncate pages
full of dead tuples at the end of it)!
In response to
pgsql-performance by date
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