On 2019/04/08 16:33, Pavel Stehule wrote:
po 8. 4. 2019 v 16:11 odesílatel Krzysztof Plocharz
<plocharz@xxxxxxxxxxxxxx <mailto:plocharz@xxxxxxxxxxxxxx>> napsal:
Hi
We have some very strange query planning problem. Long story short it
takes 67626.278ms just to plan. Query execution takes 12ms.
Query has 7 joins and 2 subselects.
It looks like the issue is not deterministic, sometimes is takes few ms
to plan the query.
One of the tables has 550,485,942 live tuples and 743,504,012 dead
tuples. Running ANALYZE on that tables solves the problem only
temporarily.
Question is how can we debug what is going on?
please check your indexes against bloating. Planner get min and max from
indexes and this operation is slow on bloat indexes.
Yes, we thought about this, there are over 700,000,000 dead tuples. But
as you said, it should not result in 67 second planning...
but 67 sec is really slow - it can be some other other problem - it is
real computer or virtual?
real, with pretty good specs: NVME drives, Six-Core AMD Opteron, 64GB of
ram. During testing system was mostly idle.
Best Regards,
Krzysztof Płocharz
