[jira] [Assigned] (IMPALA-10566) Change the default value of FETCH_ROWS_TIMEOUT_MS to 0

["Zoltán Borók-Nagy (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-10566?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Zoltán Borók-Nagy reassigned IMPALA-10566:
------------------------------------------

    Assignee: Zoltán Borók-Nagy

> Change the default value of FETCH_ROWS_TIMEOUT_MS to 0
> ------------------------------------------------------
>
>                 Key: IMPALA-10566
>                 URL: https://issues.apache.org/jira/browse/IMPALA-10566
>             Project: IMPALA
>          Issue Type: Bug
>          Components: Backend
>    Affects Versions: Impala 3.4.0
>            Reporter: Aman Sinha
>            Assignee: Zoltán Borók-Nagy
>            Priority: Major
>
> The current default value of FETCH_ROWS_TIMEOUT_MS is 10 secs.  This was done in IMPALA-7312 and IMPALA-8962 to introduce a non-blocking fetch() api behavior such that clients are not blocked indefinitely.  In some cases, especially with the supported JDBC/ODBC drivers, this can cause a regression by returning either empty or partial results to the client based on the following sequence:
> *     Client starts to fetch rows
> *     Impala is unable to produce rows in 10s. so to not make the client block, Impala returns an empty result set with hasMoreRows=true.
> *     Query’s state can be either RUNNING or FINISHED
> *     Client sees empty result set, ignores hasMoreRows=true
> *     Client closes the query thinking it got the whole result set
>  This issue was observed in internal testing and is also reported in the following JIRA:
> https://issues.apache.org/jira/browse/IMPALA-8962?focusedCommentId=17240474&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-17240474
> In contrast, impala-shell works correctly and does not have this partial results problem.
> Since this issue impacts various drivers, it is best to change the default value of FETCH_ROWS_TIMEOUT_MS to 0 to revert to the blocking behavior.  Users can opt-in by changing the value.  In the meantime, driver programs also need to be updated to allow the non-blocking fetch behavior.



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