performance degradation after Redshift maintenance

Question

Our redshift cluster was recently upgraded to 1.0.69065 and we instantly noticed decreased performance for large queries. After investigating and determining no other changes were made we rolled back and saw instant improvements of up to 45%. I've deferred maintenance for now, but at some point we'll need to move forward with the update. Release notes don't mention any features we're heavily using.

Any pointers on what the cause may be or how to mitigate it?

Query Duration Graph

Any pointers on what the cause may be or how to mitigate it?

![Query Duration Graph](/media/postImages/original/IMRM-eRthxT7GakCeM-ZE5Qg)

iBehr · Accepted Answer

I would recommend opening a support case to determine if this is a known issue.  Perhaps there is post-upgrade integrity checks that run for a period or such.

Cross Ref:  https://repost.aws/questions/QU5L3c0MRASSCZx0euQzlyDA/after-a-redshift-s-maintenance-my-queries-are-too-slow

Riku_Kobayashi · Answer

Hello.

Is it possible to check something like "STL_ALERT_EVENT_LOG" to find queries that seem to be slow after the update?  
This table seems to record query information that may indicate a performance problem, so you may be able to find the query that is causing the problem.  
https://docs.aws.amazon.com/redshift/latest/dg/r_STL_ALERT_EVENT_LOG.html

performance degradation after Redshift maintenance

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