Tom Lane wrote:
<kynn@xxxxxxxxx> 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
tiny_table'.
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)!
