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help / color / mirror / Atom feedFrom: Dimitrios Apostolou <[email protected]>
To: David Rowley <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: [email protected]
Subject: Re: SELECT DISTINCT chooses parallel seqscan instead of indexscan on huge table with 1000 partitions
Date: Tue, 14 May 2024 20:26:20 +0200 (CEST)
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I have forgotten to mention that I have enable_partitionwise_aggregate=on
in the global settings since the beginning. According to the docs:
> Enables or disables the query planner's use of partitionwise grouping or
> aggregation, which allows grouping or aggregation on partitioned tables
> to be performed separately for each partition.
Reading that, I'd expect to see a separate DISTINCT->LIMIT 10 on every
partition, and then it would be up to independent plans to decide whether
each partition follows a parallel or a serial plan.
Not sure if this plan was checked but rejected because of cost.
Dimitris
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Subject: Re: SELECT DISTINCT chooses parallel seqscan instead of indexscan on huge table with 1000 partitions
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