>
>Hm, well, given that you are able to capture instances of the behavior
>in EXPLAIN ANALYZE, I'd suggest trying EXPLAIN (ANALYZE,BUFFERS).
>That will tell you the number of pages it found in shared buffers vs.
>having to read them. Now, a "read" just means we had to ask the kernel,
>not necessarily that the page came all the way from disk; if it's in
>the kernel's disk cache that won't be very much slower than a shared-
>buffers hit. Still, if the slowdowns are reliably seen only when a read
>occurred, I'd say that's good evidence.
Well, that was a good thought - but:
Nested Loop (cost=0.00..4.20 rows=1 width=185) (actual time=567.113..567.113 rows=0 loops=1)
Join Filter: (be.branding_id = b.branding_id)
Rows Removed by Join Filter: 1
Buffers: shared hit=4
-> Nested Loop (cost=0.00..3.19 rows=1 width=189) (actual time=567.081..567.092 rows=1 loops=1)
Join Filter: (s.setting_id = be.setting_id)
Rows Removed by Join Filter: 41
Buffers: shared hit=3
-> Seq Scan on branding_extension be (cost=0.00..1.00 rows=1 width=8) (actual time=0.011..0.012 rows=1 loops=1)
Buffers: shared hit=1
-> Seq Scan on setting s (cost=0.00..2.04 rows=42 width=185) (actual time=567.041..567.049 rows=42 loops=1)
Buffers: shared hit=2
-> Seq Scan on branding b (cost=0.00..1.01 rows=1 width=4) (actual time=0.007..0.009 rows=1 loops=1)
Filter: ((name)::text = 'crs'::text)
Rows Removed by Filter: 1
Buffers: shared hit=1
Total runtime: 567.185 ms
I ran it several times and there were no reads, just shared hits, even on slow executions.
It looks like it didn’t go out to the kernel for the data. I guess next steps would be to adjust the deadlock_timeout? If I’m reading the docs correctly, this doesn’t change how Postgres determines a deadlock, it just makes it check for them sooner?
Thanks,
Scott
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