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