When we create a tmp table (SELECT INTO, CREATE TABLE AS) the planner won't know anything about its content after creating it.
Many people use temp tables heavy when the amount of data for a certain analysis has to be reduced significantly. Frequently the same tmp table is queried quite frequently. In order to speed those scenarios up it can be useful to vacuum those tmp tables so that the planner will find more clever joins.
Is it possible and does it make sense to generate those statistics on the fly (during CREATE TABLE AS)? Maybe we could have a GUC which tells the system whether to generate statistics or not.
test=# select * from test; id ---- 4 4 (2 rows)
test=# VACUUM test ; VACUUM
test=# explain select * from test ;
QUERY PLAN
----------------------------------------------------
Seq Scan on test (cost=0.00..1.02 rows=2 width=4)
(1 row)test=# select * into tmp from test;
SELECT
test=# explain select * from tmp;
QUERY PLAN
-------------------------------------------------------
Seq Scan on tmp (cost=0.00..20.00 rows=1000 width=4)
(1 row)
Best regards, Hans
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