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https://issues.apache.org/jira/browse/IGNITE-10306?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vladimir Ozerov updated IGNITE-10306:
-------------------------------------
    Description: 
Currently subqueries are mostly not analyzed in any way. This makes our 
distributed execution plan more complex to analyze and execute. Moreover, we 
cannot extract partition information from such queries efficiently. We need to 
apply the simplest "JOIN conversion" optimization on early query analysis phase 
and try to transform our AST from subquery to join. 

This should be done before partition extraction, pushdowns and splitter. See 
[1] for more information.
Postgres implementation of subquery rewrites could be found here [2].

[1] 
https://cwiki.apache.org/confluence/display/IGNITE/IEP-24%3A+SQL+Partition+Pruning
[2] 
https://github.com/postgres/postgres/blob/master/src/backend/optimizer/prep/prepjointree.c

  was:
Currently subqueries are mostly not analyzed in any way. This makes our 
distributed execution plan more complex to analyze and execute. Moreover, we 
cannot extract partition information from such queries efficiently. We need to 
apply the simplest "JOIN conversion" optimization on early query analysis phase 
and try to transform our AST from subquery to join. 

This should be done before partition extraction, pushdowns and splitter. See 
[1] for more information.

[1] 
https://cwiki.apache.org/confluence/display/IGNITE/IEP-24%3A+SQL+Partition+Pruning


> SQL: Transform subqueries to JOINs when possible
> ------------------------------------------------
>
>                 Key: IGNITE-10306
>                 URL: https://issues.apache.org/jira/browse/IGNITE-10306
>             Project: Ignite
>          Issue Type: Task
>          Components: sql
>            Reporter: Vladimir Ozerov
>            Priority: Major
>              Labels: iep-24
>             Fix For: 2.8
>
>
> Currently subqueries are mostly not analyzed in any way. This makes our 
> distributed execution plan more complex to analyze and execute. Moreover, we 
> cannot extract partition information from such queries efficiently. We need 
> to apply the simplest "JOIN conversion" optimization on early query analysis 
> phase and try to transform our AST from subquery to join. 
> This should be done before partition extraction, pushdowns and splitter. See 
> [1] for more information.
> Postgres implementation of subquery rewrites could be found here [2].
> [1] 
> https://cwiki.apache.org/confluence/display/IGNITE/IEP-24%3A+SQL+Partition+Pruning
> [2] 
> https://github.com/postgres/postgres/blob/master/src/backend/optimizer/prep/prepjointree.c



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