Re: DELETE query and indexes again

On Thu, Jul 23, 2020 at 5:11 PM Wells Oliver <wells.oliver@gmail.com> wrote:

This play_statistics table has 96,577,179 rows. Its PK is gid integer, guid uuid, cat text, name text, target integer.

Doing a EXPLAIN ANALYZE DELETE WHERE gid IN (SELECT DISTINCT gid FROM temptable) where there is one row in the temptable, I get this:

Delete on play_statistics (cost=1984.14..8037586.36 rows=3734075 width=34) (actual time=407093.859..407093.859 rows=0 loops=1)
-> Hash Join (cost=1984.14..8037586.36 rows=3734075 width=34) (actual time=407093.857..407093.857 rows=0 loops=1)
Hash Cond: (play_statistics.gid = "ANY_subquery".gid)
-> Seq Scan on play_statistics (cost=0.00..7781818.16 rows=96600516 width=10) (actual time=201.521..396052.101 rows=96556116 loops=1)
-> Hash (cost=1981.64..1981.64 rows=200 width=32) (actual time=13.020..13.020 rows=1 loops=1)
Buckets: 1024 Batches: 1 Memory Usage: 9kB
-> Subquery Scan on "ANY_subquery" (cost=1977.64..1981.64 rows=200 width=32) (actual time=13.012..13.013 rows=1 loops=1)
-> HashAggregate (cost=1977.64..1979.64 rows=200 width=4) (actual time=13.001..13.002 rows=1 loops=1)
Group Key: stats.gid
-> Seq Scan on stats (cost=0.00..1924.91 rows=21091 width=4) (actual time=0.028..9.244 rows=21091 loops=1)
Planning Time: 0.657 ms
JIT:
Functions: 15
Options: Inlining true, Optimization true, Expressions true, Deforming true
Timing: Generation 1.816 ms, Inlining 53.472 ms, Optimization 89.014 ms, Emission 58.759 ms, Total 203.060 ms
Execution Time: 407112.908 ms
(16 rows)

It takes 7 minutes to delete 21063 rows for one given gid value, which seems excessive given I think it should be using the PK index.

Anything I'm  missing here?

Your command text is over "temptable", but your plan is over "stats".  Is "temptable" a view?  

Cheers,

Jeff