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Posted to issues-all@impala.apache.org by "Aman Sinha (Jira)" <ji...@apache.org> on 2021/03/09 02:39:00 UTC
[jira] [Commented] (IMPALA-8962) FETCH_ROWS_TIMEOUT_MS should apply
before rows are available
[ https://issues.apache.org/jira/browse/IMPALA-8962?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17297797#comment-17297797 ]
Aman Sinha commented on IMPALA-8962:
------------------------------------
[~guojingfeng] Thanks for reporting the issue with fetch_rows_timeout_ms. Based on internal investigation the empty results (or sometimes partial results) with the JDBC/ODBC driver is indeed a problem and we are pursuing this with the driver provider. In the meantime, it is best to set the value of fetch_rows_timeout_ms = 0. I will create a JIRA for reverting this to 0 since we cannot be sure what other drivers may be affected with the non-blocking mode.
> FETCH_ROWS_TIMEOUT_MS should apply before rows are available
> ------------------------------------------------------------
>
> Key: IMPALA-8962
> URL: https://issues.apache.org/jira/browse/IMPALA-8962
> Project: IMPALA
> Issue Type: Bug
> Components: Clients
> Reporter: Sahil Takiar
> Assignee: Sahil Takiar
> Priority: Major
> Fix For: Impala 3.4.0
>
>
> IMPALA-7312 added a fetch timeout controlled by the query option {{FETCH_ROWS_TIMEOUT_MS}}. The issue is that the timeout only applies after the *first* batch of rows are available. The issue is that both Beeswax and HS2 clients call {{request_state->BlockOnWait}} inside {{ImpalaServer::FetchInternal}}. The call to {{BlockOnWait}} blocks until rows are ready to be consumed via {{ClientRequestState::FetchRows}}.
> So clients can still end up blocking indefinitely waiting for the first row batch to appear.
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