[jira] [Updated] (IMPALA-10964) Add query option that limits skew query in runtime

["carolinchen (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-10964?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

carolinchen updated IMPALA-10964:
---------------------------------
    Fix Version/s:     (was: Impala 4.0.1)

> Add query option that limits skew query in runtime
> --------------------------------------------------
>
>                 Key: IMPALA-10964
>                 URL: https://issues.apache.org/jira/browse/IMPALA-10964
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>    Affects Versions: Impala 4.0.0
>            Reporter: carolinchen
>            Assignee: carolinchen
>            Priority: Major
>
> Reject queries that  skew value is too big when executing the query. 
> Query skew refers to the situation in which some nodes are significantly behind other nodes in the process of concurrent execution of SQL.
> There are two style skews:
> 1. Row skew, which may be caused by unreasonable sql or uneven task distributions.
> 2. Time skew, which may be caused by different capability by execnode.
> Query skew will cause two effects:
> 1. For the skew node may execute slowly,  which will slow down the query progress .
> 2. For the skew node may exhaust lots system resources( I/O, memory, rpc), which will
> affect other queries in the same host/ query pool.
> When the skew value reach unreasonale range,  will affect the cluster status and other running queries. This is a mechanism to protect the cluster from potentially harmful queries(eg: mem_limit).
> In our environment, the SKEW_LIMIT query option is added to limit skewed query.



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