[jira] [Closed] (DRILL-8388) CTAS sent over JDBC may be cancelled if query results are not fetched

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

     [ https://issues.apache.org/jira/browse/DRILL-8388?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

James Turton closed DRILL-8388.
-------------------------------
    Resolution: Information Provided

In addition to this issue itself, this has now been documented at https://drill.apache.org/docs/using-the-jdbc-driver/.

> CTAS sent over JDBC may be cancelled if query results are not fetched
> ---------------------------------------------------------------------
>
>                 Key: DRILL-8388
>                 URL: https://issues.apache.org/jira/browse/DRILL-8388
>             Project: Apache Drill
>          Issue Type: Task
>          Components: Client - JDBC, Storage - Writer
>    Affects Versions: 1.20.3
>            Reporter: James Turton
>            Assignee: James Turton
>            Priority: Minor
>             Fix For: Future
>
>
> When a JDBC client issues a CTAS statement then Drill will return a record for each completed writer fragment containing the number of records that fragment wrote. These records are returned in the usual streaming fashion as writer fragments complete, their order being unknowable in advance. If the client application immediately closes its clientside JDBC resources after its call to Statement.executeQuery has returned as follows
> {code:java}
> Statement ctasStatement = conn.createStatement();
> ResultSet ctasResults = ctasStatement.executeQuery(ctasQueryText);
> ctasResults.close();
> ctasStatement.close();
> {code}
> it may be that the CTAS statement is still executing, and that is then prematurely cancelled depending on good or bad luck with respect to timing.
> The cancellation of the CTAS statement is usually benign if it spawned only one writer fragment, but if it spawned more than one then it is likely that at least one writer will be interrupted before it has finished writing, resulting in incomplete or even corrupted output. Even in the benign case, such queries conclude in the CANCELLED state rather than the FINISHED state.
> To have CTAS queries reliably conclude completely, the JDBC client can wait for all of the writer fragments to complete before it closes its JDBC resources by scrolling through the ResultSet before closing it.
> {code:java}
> while (ctasResults.next());{code}
>  



--
This message was sent by Atlassian Jira
(v8.20.10#820010)