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https://issues.apache.org/jira/browse/IGNITE-6089?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vladimir Ozerov updated IGNITE-6089:
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Labels: performance sql-engine (was: performance)
> SQL: Improve query parallelism architecture
> -------------------------------------------
>
> Key: IGNITE-6089
> URL: https://issues.apache.org/jira/browse/IGNITE-6089
> Project: Ignite
> Issue Type: Task
> Components: sql
> Affects Versions: 2.1
> Reporter: Vladimir Ozerov
> Priority: Major
> Labels: performance, sql-engine
>
> Currently query parallelism implement with static split of all indexes
> (including PK) for cache. This approach has several major disadvantages:
> 1) It improves scans, but slows down index and range lookups
> 2) Tables with different DOP cannot be used in the same query
> We need to fix that. Proposed plan:
> 1) No more index splits, ever - there is one and only one index always
> 2) Use preliminary execution plan, statistics (IGNITE-6079), CPU cores count
> and CPU load to estimate whether query will benefit from parallelism.
> 3) if yes - split node-s single map query into several independent pieces.
> Splitting can be achieved in one of the following ways:
> 1) Partition-based: e.g. if node owns partitions A, B, C and D, then we can
> split it to two queries - one over (A, B), another over (C, D). This could be
> useful for pure scans (e.g. DWH)
> 2) Histogram-based: e.g. if we have a query {{SELECT ... WHERE salary > 50}},
> and we know salary distribution, we can split it into {{WHERE salary > 50 AND
> salary <= 200}} and {{WHERE salary > 200}}
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