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From "Roman Kondakov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (IGNITE-11756) SQL: implement a table row count statistics for the local queries
Date Fri, 24 May 2019 12:47:00 GMT

    [ https://issues.apache.org/jira/browse/IGNITE-11756?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16847524#comment-16847524
] 

Roman Kondakov commented on IGNITE-11756:
-----------------------------------------

[~amashenkov], [~Pavlukhin], patch is ready for merge. Tests look good. Code style is broken
in the master branch.

> SQL: implement a table row count statistics for the local queries
> -----------------------------------------------------------------
>
>                 Key: IGNITE-11756
>                 URL: https://issues.apache.org/jira/browse/IGNITE-11756
>             Project: Ignite
>          Issue Type: Improvement
>          Components: sql
>            Reporter: Roman Kondakov
>            Assignee: Roman Kondakov
>            Priority: Major
>          Time Spent: 1h
>  Remaining Estimate: 0h
>
> Row count statistics should help the H2 optimizer to select the better query execution
plan. Currently the row count supplied to H2 engine is hardcoded value == 10000 (see {{org.h2.index.Index#getRowCountApproximation}}). 
As a first step we can provide an actual table size in the case of local query. To prevent
counting size on each invocation we can cache row count value and invalidate it in some cases:
>  * Rebalancing
>  * Multiple updates (after the initial loading)
>  * On timeout (i.e. 1 minute)



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