Curious- Is geqo_threshold still set to 12? Is increasing join_collapse_limit to be higher than geqo_threshold going to have a noticeable impact?
The disk sorts are the killer as Justin says. I wonder how it performs with that increased significantly. Is the storage SSD or traditional hard disks? *Michael Lewis* On Fri, Feb 22, 2019 at 8:54 AM Justin Pryzby <pry...@telsasoft.com> wrote: > On Fri, Feb 22, 2019 at 04:14:05PM +0100, kimaidou wrote: > > Explain shows that the GROUP AGGREGATE and needed sort kill the > performance. > > Do you have any hint how to optimize this ? > > https://explain.depesz.com/s/6nf > > This is writing 2GB tempfile, perhaps the query would benefit from larger > work_mem: > |Sort (cost=3,014,498.66..3,016,923.15 rows=969,796 width=1,818) (actual > time=21,745.193..22,446.561 rows=1,212,419 loops=1) > | Sort Method: external sort Disk: 1782200kB > | Buffers: shared hit=5882951, temp read=230958 written=230958 > > This is apparently joining without indices: > |Nested Loop Left Join (cost=1.76..360,977.37 rows=321,583 width=1,404) > (actual time=0.080..1,953.007 rows=321,849 loops=1) > | Join Filter: (tgc1.groupe_nom = t.group1_inpn) > | Rows Removed by Join Filter: 965547 > | Buffers: shared hit=1486327 > > This perhaps should have an index on tgc2.groupe_type ? > |Index Scan using t_group_categorie_pkey on taxon.t_group_categorie tgc2 > (cost=0.14..0.42 rows=1 width=28) (actual time=0.002..0.002 rows=1 > loops=321,849) > | Index Cond: (tgc2.groupe_nom = t.group2_inpn) > | Filter: (tgc2.groupe_type = 'group2_inpn'::text) > | Buffers: shared hit=643687 > > This would perhaps benefit from an index on tv.cd_ref ? > |Index Scan using taxref_consolide_non_filtre_cd_nom_idx on > taxon.taxref_consolide_non_filtre tv (cost=0.42..0.63 rows=1 width=94) > (actual time=0.002..0.002 rows=1 loops=690,785) > | Index Cond: (tv.cd_nom = t.cd_ref) > | Filter: (tv.cd_nom = tv.cd_ref) > | Buffers: shared hit=2764875 > > I don't think it's causing a significant fraction of the issue, but for > some > reason this is overestimating rowcount by 2000. Do you need to VACUUM > ANALYZE > the table ? > |Seq Scan on occtax.personne p_1 (cost=0.00..78.04 ROWS=2,204 width=56) > (actual time=0.011..0.011 ROWS=1 loops=1) > > Justin > >
