After a Redshift's Maintenance my queries are too slow

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It is possible to limit the negative effects of query performance after your cluster maintenance?Thanks

asked 2 years ago881 views
3 Answers
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There are some possible explanations to the behavior you're observing. For example, it is possible that a Redshift software upgrade forces an invalidation of your cluster's global query compile cache if the compile logic was changed as part of the release, but this is just one theory and I would be surprised if this happens with every software upgrade. The best course of action that I can recommend is to open a support ticket, so the AWS/Redshift support team can diagnose your cluster with you in real time.

AWS
asser_m
answered 2 years ago
AWS
EXPERT
reviewed 2 years ago
  • It could also just invalidate the result cache and the first execution of the query would be slower than subsequent runs.

  • No because the result cache is disabled for my user.I SET enable_result_cache_for_session TO OFF.

  • Do I need to activate the developer support plan to use AWS/Redshift support? Thanks

  • According to the website below, developer support is the first level of support available, but it can be month-to-month (i.e. no long term contracts needed). https://aws.amazon.com/premiumsupport/plans/

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These maintenances were done early Saturday morning : REDSHIFT-EVENT-3014 REDSHIFT-EVENT-3520 REDSHIFT-EVENT-3519 REDSHIFT-EVENT-2004 REDSHIFT-EVENT-2003 On Saturday during the day I connected to my reports and all queries were very slow. This happens after every amazon maintenance. I haven't tried to contact account support yet, I wanted to find out if this behavior was encountered by other users.

answered 2 years ago
  • Are all FIRST execution of a specific Query slow, and all subsequent runs go back to the execution time you are used to?

  • yes this is the behavior.

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Hello, to best answer your question, I think a few follow-up questions are needed. For example, you mention cluster maintenance (e.g. Redshift software upgrade), but am wondering if it is really automatic table maintenance that is being referred to (e.g. automatic sort key optimization). Also, is it all queries exhibiting a slow-down or just some queries? Have you tried reaching out to account support or your account solutions architect for help possibly examining your cluster with you in real time?

AWS
asser_m
answered 2 years ago

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