Am 29.08.2018 um 20:10 schrieb David:
On Wed, Aug 29, 2018 at 7:25 AM, Andreas Kretschmer
<andreas@xxxxxxxxxxxxxxx <mailto:andreas@xxxxxxxxxxxxxxx>> wrote:
Okay, other solution. The problem is the nested loop, we can
disable that:
test=*# set enable_nestloop to false;
Is it OK to keep this off permanently in production?
no, but you can switch off/on per session, for instance. and you can it
set to on after that query.
Nested Loop (cost=319.27..776.18 rows=1 width=196) (actual
time=3.156..334.963 rows=10000 loops=1)
Join Filter: (app.group_id = member_span.group_id)
-> Hash Join (cost=319.00..771.00 rows=12 width=104) (actual
time=3.100..14.040 rows=10000 loops=1)
Hm, also, it looks like one of the oddities of this query is that
PostgreSQL is severely underestimating the cardinality of the join.
ack, that's the main problem here, i think. It leads to the expensive
nested loop. Tbh, i don't have a better suggestion now besides the
workaround with setting nestloop to off.
Regards, Andreas
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