On Wed, Oct 29, 2014 at 11:53 AM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> Jorge Arevalo <jorgearev...@libregis.org> writes: > > > This is the result of EXPLAIN ANALYZE > > > QUERY > > PLAN > > > ------------------------------------------------------------------------------------------------------------------------------------------------- > > Index Scan using table1_pkey on table1 (cost=67846.38..395773.45 > > rows=8419127 width=88) (actual time=7122.704..22670.680 rows=8419127 > > loops=1) > > InitPlan 2 (returns $1) > > -> Result (cost=67846.29..67846.29 rows=1 width=0) (actual > > time=7009.063..7009.065 rows=1 loops=1) > > InitPlan 1 (returns $0) > > -> Seq Scan on table2 p (cost=0.00..67846.29 rows=12689 > > width=20) (actual time=14.971..5069.840 rows=2537787 loops=1) > > Filter: (f3 = field7) > > Hm. If I'm reading that right, you're building an array containing > 2537787 entries, each of which is a composite datum containing two > columns of unmentioned datatypes. I suspect a big chunk of your > runtime is going into manipulating that array -- PG is not terribly > efficient with big arrays containing variable-width values. > > I'm also a bit confused as to why the planner is saying that the (SELECT > ARRAY(...)) bit is an InitPlan and not a SubPlan. That implies that > "field7" in the innermost WHERE clause is not a reference to table1 but a > reference to table2. Is that really what you meant? IOW, are you sure > this query is performing the right calculation in the first place? > > I thought the InitPlan was in place because the planner choose to execute the correlated subquery as a standalone query since it realizes that it is going to have to end up processing the entire table anyway due to the lack of a filter on the outer query. In effect executing "table1 JOIN (table2 subquery) ON (f3 = field7)". David J.
