Re: Long running query in new production, not so long in old - Mailing list pgsql-admin

1. What vendor for the VMs?
2. Make sure memory and CPU are not overallocated in the hypervisor.
3. Evaluate the resource needs of the VM group/cluster to which it belongs.
4. Regarding VMWare, I dealt with a problem where the "cpu ready percentage" was too high (above 5-10%), which caused cpu cycle delays.
   

On Wed, 2019-03-27 at 19:27 -0400, Mark Steben wrote:

We are moving to a new VM environment (expedient) and have one query  that typically runs in 22 - 25
seconds in our old environment, but is running in about 1 hour, 20 minutes in our new.
I'd like some insight as to why the explain is showing shared buffer hits numbering over 113 milliion
in the new environment and only 445 thousand in the old.  I have sent the explains along with the
table descriptions, row counts, the one function that I know causes the bottleneck,  the query,
some relevant configuration settings in postgresql conf (identical in both environments)
and a listing from top in both environments, showing memory, shared memory, and cpu.

Everything seems to be identical or close, except for the shared buffer count in the explain.  
Any insight would be appreciated.

Slow plan:
->  Index Scan using emailrcpts_4columns on emailrcpts  (cost=0.56..119078.48 rows=5 width=29) (actual time=4873080.765..4873080.765 rows=0 loops=1)      Index Cond: ((cid = 1784539) AND (removed = false) AND (active = true) AND (bounce < 3))      Filter: ((NOT removed) AND active AND (email IS NOT NULL) AND (((fname IS NOT NULL) AND (length((fname)::text) <> 0)) OR ((lname IS NOT NULL) AND (length((lname)::text) <> 0))) AND
(number_of_sends(id, 30, 1) < 3) AND (lower(get_make(cid, (vin)::text, (make_purchased)::text)) = 'ohgoshnonotthebees!!!'::text) AND (NOT (SubPlan 1)))      Rows Removed by Filter: 19952      Buffers: shared hit=113768530 read=6244      SubPlan 1        ->  Limit  (cost=0.28..15.58 rows=1 width=0) (never executed)

Fast plan:
->  Index Scan using emailrcpts_4columns on emailrcpts  (cost=0.56..113162.26 rows=5 width=29) (actual time=21086.555..21086.555 rows=0 loops=1)      Index Cond: ((cid = 1784539) AND (removed = false) AND (active = true) AND (bounce < 3))      Filter: ((NOT removed) AND active AND (email IS NOT NULL) AND (((fname IS NOT NULL) AND (length((fname)::text) <> 0)) OR ((lname IS NOT NULL) AND (length((lname)::text) <> 0))) AND
(number_of_sends(id, 30, 1) < 3) AND (lower(get_make(cid, (vin)::text, (make_purchased)::text)) = 'ohgoshnonotthebees!!!'::text) AND (NOT (SubPlan 1)))      Rows Removed by Filter: 19952      Buffers: shared hit=445188 read=61756      SubPlan 1        ->  Limit  (cost=0.28..15.58 rows=1 width=0) (never executed)

Hmm. These are the ideas I can come up with:

1. There are many index tuples belonging to dead heap tuples.  Then re-running the query should produce way fewer buffer hits.  VACUUM would fix that issue.

2. The index is terribly fragmented.  REINDEX INDEX emailrcpts_4columns  would improve that one.

Yours,
Laurenz Albe