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Suddenly all queries moved to seq scan 4+ messages / 3 participants [nested] [flat]
* Suddenly all queries moved to seq scan @ 2024-11-20 10:50 Sreejith P <[email protected]> 0 siblings, 1 reply; 4+ messages in thread From: Sreejith P @ 2024-11-20 10:50 UTC (permalink / raw) To: [email protected] Hi, We are using PostgresQL 10 in our production database. We have around 890 req /s request on peak time. We have 1 primary and 4 slave databases as well in the same postgres cluster. 2 days back we applied some patches in the primary server and restarted. We didn't do anything on the secondary server. Next day, After 18 hours all our queries from secondary servers started taking too much time. queries were working in 2 sec started taking 80 seconds. Almost all queries behaved the same way. After half an hour of outage we restarted all db servers and system back to normal. Still we are not able to understand the root case. We couldn't find any error log or fatal errors. During the incident, in one of the read server disks was full. We couldn't see any replication lag or query cancellation due to replication. please help Regards Sreejith -- *Solutions for Care Anywhere* *dWise HealthCare IT Solutions Pvt. Ltd.* | www.lifetrenz.com <http://www.lifetrenz.com; *Disclaimer*: The information and attachments contained in this email are intended for exclusive use of the addressee(s) and may contain confidential or privileged information. If you are not the intended recipient, please notify the sender immediately and destroy all copies of this message and any attachments. The views expressed in this email are, unless otherwise stated, those of the author and not those of dWise HealthCare IT Solutions or its management. ^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Suddenly all queries moved to seq scan @ 2024-11-20 13:02 Daniel Gustafsson <[email protected]> parent: Sreejith P <[email protected]> 0 siblings, 2 replies; 4+ messages in thread From: Daniel Gustafsson @ 2024-11-20 13:02 UTC (permalink / raw) To: Sreejith P <[email protected]>; +Cc: [email protected] > On 20 Nov 2024, at 11:50, Sreejith P <[email protected]> wrote: > We are using PostgresQL 10 in our production database. We have around 890 req /s request on peak time. PostgreSQL 10 is well out of support and does not receive bugfixes or security fixes, you should plan a migration to a supported version sooner rather than later. > 2 days back we applied some patches in the primary server and restarted. We didn't do anything on the secondary server. Patches to the operating system, postgres, another application? > Next day, After 18 hours all our queries from secondary servers started taking too much time. queries were working in 2 sec started taking 80 seconds. Almost all queries behaved the same way. > > After half an hour of outage we restarted all db servers and system back to normal. > > Still we are not able to understand the root case. We couldn't find any error log or fatal errors. During the incident, in one of the read server disks was full. We couldn't see any replication lag or query cancellation due to replication. You say that all queries started doing sequential scans, is that an assumption from queries being slow or did you capture plans for the queries which be compared against "normal" production plans? -- Daniel Gustafsson ^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Suddenly all queries moved to seq scan @ 2024-11-20 13:21 Efrain J. Berdecia <[email protected]> parent: Daniel Gustafsson <[email protected]> 1 sibling, 0 replies; 4+ messages in thread From: Efrain J. Berdecia @ 2024-11-20 13:21 UTC (permalink / raw) To: Sreejith P <[email protected]>; Daniel Gustafsson <[email protected]>; +Cc: [email protected] <[email protected]> Make sure to run analyze on the entire database, possibly using vacuumdb would be faster. Also, check for invalid indexes. Efrain J. Berdecia On Wednesday, November 20, 2024 at 08:02:36 AM EST, Daniel Gustafsson <[email protected]> wrote: > On 20 Nov 2024, at 11:50, Sreejith P <[email protected]> wrote: > We are using PostgresQL 10 in our production database. We have around 890 req /s request on peak time. PostgreSQL 10 is well out of support and does not receive bugfixes or security fixes, you should plan a migration to a supported version sooner rather than later. > 2 days back we applied some patches in the primary server and restarted. We didn't do anything on the secondary server. Patches to the operating system, postgres, another application? > Next day, After 18 hours all our queries from secondary servers started taking too much time. queries were working in 2 sec started taking 80 seconds. Almost all queries behaved the same way. > > After half an hour of outage we restarted all db servers and system back to normal. > > Still we are not able to understand the root case. We couldn't find any error log or fatal errors. During the incident, in one of the read server disks was full. We couldn't see any replication lag or query cancellation due to replication. You say that all queries started doing sequential scans, is that an assumption from queries being slow or did you capture plans for the queries which be compared against "normal" production plans? -- Daniel Gustafsson ^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Suddenly all queries moved to seq scan @ 2024-11-20 14:08 Sreejith P <[email protected]> parent: Daniel Gustafsson <[email protected]> 1 sibling, 0 replies; 4+ messages in thread From: Sreejith P @ 2024-11-20 14:08 UTC (permalink / raw) To: Daniel Gustafsson <[email protected]>; +Cc: [email protected] > On 20 Nov 2024, at 6:32 PM, Daniel Gustafsson <[email protected]> wrote: > >> On 20 Nov 2024, at 11:50, Sreejith P <[email protected]> wrote: > >> We are using PostgresQL 10 in our production database. We have around 890 req /s request on peak time. > > PostgreSQL 10 is well out of support and does not receive bugfixes or security > fixes, you should plan a migration to a supported version sooner rather than > later. > >> 2 days back we applied some patches in the primary server and restarted. We didn't do anything on the secondary server. > > Patches to the operating system, postgres, another application? PostgreSQL Common 10.23-6 > >> Next day, After 18 hours all our queries from secondary servers started taking too much time. queries were working in 2 sec started taking 80 seconds. Almost all queries behaved the same way. >> >> After half an hour of outage we restarted all db servers and system back to normal. >> >> Still we are not able to understand the root case. We couldn't find any error log or fatal errors. During the incident, in one of the read server disks was full. We couldn't see any replication lag or query cancellation due to replication. > > You say that all queries started doing sequential scans, is that an assumption > from queries being slow or did you capture plans for the queries which be > compared against "normal" production plans?. Queries were taking 20 ms started taking 60 seconds. So have done SQL analyse to understand about query plan. There we found that query planner taking seq scan instead in index scan. I would like to add one ore point. A delete query were running in DB from 2 days for deleting around 80 million records. > > -- > Daniel Gustafsson > -- *Solutions for Care Anywhere* *dWise HealthCare IT Solutions Pvt. Ltd.* | www.lifetrenz.com <http://www.lifetrenz.com; *Disclaimer*: The information and attachments contained in this email are intended for exclusive use of the addressee(s) and may contain confidential or privileged information. If you are not the intended recipient, please notify the sender immediately and destroy all copies of this message and any attachments. The views expressed in this email are, unless otherwise stated, those of the author and not those of dWise HealthCare IT Solutions or its management. ^ permalink raw reply [nested|flat] 4+ messages in thread
end of thread, other threads:[~2024-11-20 14:08 UTC | newest] Thread overview: 4+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2024-11-20 10:50 Suddenly all queries moved to seq scan Sreejith P <[email protected]> 2024-11-20 13:02 ` Daniel Gustafsson <[email protected]> 2024-11-20 13:21 ` Efrain J. Berdecia <[email protected]> 2024-11-20 14:08 ` Sreejith P <[email protected]>
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