[
https://issues.apache.org/jira/browse/IMPALA-10566?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17430840#comment-17430840
]
Yuchen Fan commented on IMPALA-10566:
-------------------------------------
We encountered the same problem. Query result set may be empty or incorrect
when using default value of FETCH_ROWS_TIMEOUT_MS. So its default value should
be 0 or a larger enough value.
> 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.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
