Simon Riggs <simon@xxxxxxxxxxxxxxx> írta: > Ordering by parent, child is fairly common but the variation you've got > here isn't that common. You'd need to make a case considering all the > alternatives; nobody will agree without a balanced case that includes > what is best for everyone. > > Your EXPLAIN looks edited. Have you also edited the sort costs? They > look slightly higher than we might expect. Please provide the full > normal EXPLAIN output. > > -- > Simon Riggs > 2ndQuadrant http://www.2ndQuadrant.com I've just inserted some newlines, so it's better to read than when my email-client wraps the lines automatically. Did not touch the information itself. But here is the normal output of EXPLAIN ANALYZE: EXPLAIN ANALYZE SELECT * FROM tparent JOIN tchild ON tchild.par_id = tparent.id WHERE tparent.ord BETWEEN 1 AND 4 ORDER BY tparent.ord, tchild.ord; QUERY PLAN ------------------------------------------------------------------------------------------- -------------------------------------------- Sort (cost=100000132.10..100000140.10 rows=8 width=16) (actual time=0.302..0.319 rows=9 loops=1) Sort Key: tparent.ord, tchild.ord -> Nested Loop (cost=0.00..84.10 rows=8 width=16) (actual time=0.181..0.267 rows=9 loops=1) -> Index Scan using par_uniq_ord on tparent (cost=0.00..20.40 rows=4 width=8) (actual time=0.100..0.109 rows=4 loops=1) Index Cond: ((ord >= 1) AND (ord <= 4)) -> Index Scan using chi_pkey_parid_ord on tchild (cost=0.00..9.93 rows=2 width=8) (actual time=0.020..0.026 rows=2 loops=4) Index Cond: (tchild.par_id = "outer".id) Total runtime: 0.412 ms (8 rows) The costs may be different because I've tuned the query planner's parameters. > Ordering by parent, child is fairly common but the variation you've got > here isn't that common. How else can you order by parent, child other than first ordering by a unique key of parent, then something in child? (Except for child.parent_id, child.something because this has all the information in child and can rely on a single multicolumn index.) Denes Daniel ------------------------------------------------------------------------ Olvasd az [origo]-t a mobilodon: mini magazinok a Mobizin-en ___________________________________________________ www.t-mobile.hu/mobizin ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
