Re: [PERFORM] Big IN() clauses etc : feature proposal - Mailing list pgsql-hackers

> Does the time for commit change much if you leave out the analyze?

    Yes, when I don't ANALYZE the temp table, commit time changes from 30 ms
to about 15 ms ; but the queries get horrible plans (see below) :

    Fun thing is, the rowcount from a temp table (which is the problem here)
should be available without ANALYZE ; as the temp table is not concurrent,
it would be simple to inc/decrement a counter on INSERT/DELETE...

    I like the temp table approach : it can replace a large, complex query
with a batch of smaller and easier to optimize queries...

EXPLAIN ANALYZE SELECT a.* FROM tmp t, annonces_display a WHERE a.id=t.id
ORDER BY t.sort;
                                                                    QUERY
PLAN

-------------------------------------------------------------------------------------------------------------------------------------------------
  Sort  (cost=3689.88..3693.15 rows=1310 width=940) (actual
time=62.327..62.332 rows=85 loops=1)
    Sort Key: t.sort
    ->  Merge Join  (cost=90.93..3622.05 rows=1310 width=940) (actual
time=5.595..61.373 rows=85 loops=1)
          Merge Cond: ("outer".id = "inner".id)
          ->  Index Scan using annonces_pkey on annonces
(cost=0.00..3451.39 rows=10933 width=932) (actual time=0.012..6.620
rows=10916 loops=1)
          ->  Sort  (cost=90.93..94.20 rows=1310 width=12) (actual
time=0.098..0.105 rows=85 loops=1)
                Sort Key: t.id
                ->  Seq Scan on tmp t  (cost=0.00..23.10 rows=1310
width=12) (actual time=0.004..0.037 rows=85 loops=1)
  Total runtime: 62.593 ms

EXPLAIN ANALYZE SELECT * FROM contacts WHERE id IN (SELECT contact_id FROM
tmp);
                                                      QUERY PLAN
--------------------------------------------------------------------------------------------------------------------
  Hash Join  (cost=28.88..427.82 rows=200 width=336) (actual
time=0.156..5.019 rows=45 loops=1)
    Hash Cond: ("outer".id = "inner".contact_id)
    ->  Seq Scan on contacts  (cost=0.00..349.96 rows=9396 width=336)
(actual time=0.009..3.373 rows=9396 loops=1)
    ->  Hash  (cost=28.38..28.38 rows=200 width=4) (actual
time=0.082..0.082 rows=46 loops=1)
          ->  HashAggregate  (cost=26.38..28.38 rows=200 width=4) (actual
time=0.053..0.064 rows=46 loops=1)
                ->  Seq Scan on tmp  (cost=0.00..23.10 rows=1310 width=4)
(actual time=0.001..0.015 rows=85 loops=1)
  Total runtime: 5.092 ms

ANALYZE tmp;
ANALYZE
annonces=> EXPLAIN ANALYZE SELECT a.* FROM tmp t, annonces_display a WHERE
a.id=t.id ORDER BY t.sort;
                                                               QUERY PLAN

---------------------------------------------------------------------------------------------------------------------------------------
  Sort  (cost=508.63..508.84 rows=85 width=940) (actual time=1.830..1.832
rows=85 loops=1)
    Sort Key: t.sort
    ->  Nested Loop  (cost=0.00..505.91 rows=85 width=940) (actual
time=0.040..1.188 rows=85 loops=1)
          ->  Seq Scan on tmp t  (cost=0.00..1.85 rows=85 width=12) (actual
time=0.003..0.029 rows=85 loops=1)
          ->  Index Scan using annonces_pkey on annonces  (cost=0.00..5.89
rows=1 width=932) (actual time=0.003..0.004 rows=1 loops=85)
                Index Cond: (annonces.id = "outer".id)
  Total runtime: 2.053 ms
(7 lignes)

annonces=> EXPLAIN ANALYZE SELECT * FROM contacts WHERE id IN (SELECT
contact_id FROM tmp);
                                                            QUERY PLAN

---------------------------------------------------------------------------------------------------------------------------------
  Nested Loop  (cost=2.06..139.98 rows=36 width=336) (actual
time=0.072..0.274 rows=45 loops=1)
    ->  HashAggregate  (cost=2.06..2.51 rows=45 width=4) (actual
time=0.052..0.065 rows=46 loops=1)
          ->  Seq Scan on tmp  (cost=0.00..1.85 rows=85 width=4) (actual
time=0.003..0.016 rows=85 loops=1)
    ->  Index Scan using contacts_pkey on contacts  (cost=0.00..3.04 rows=1
width=336) (actual time=0.003..0.004 rows=1 loops=46)
          Index Cond: (contacts.id = "outer".contact_id)
  Total runtime: 0.341 ms