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https://issues.apache.org/jira/browse/DRILL-7576?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17033137#comment-17033137
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ASF GitHub Bot commented on DRILL-7576:
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paul-rogers commented on pull request #1975: DRILL-7576: Fail fast for operator
errors
URL: https://github.com/apache/drill/pull/1975
Converts operators to fail with a UserException rather than using
the STOP iterator status. The result is clearer error messages
and simpler code.
## Description
Drill has long had two ways to indicate operator failures:
* By throwing an unchecked exception, preferably `UserException`.
* By setting the failed status on the operator and returning the `STOP`
iterator status.
Since the exception mechanism has been stable for several years, there is
little reason to use the complex mechanism involved with the `STOP` status.
Rather than write code to propagate `STOP` up the stack, we just let Java
unwind the stack for us.
This PR converts all places where we returned `STOP` status to instead throw
an exception. It also cleans up some lingering places where lower-level calls
threw generic exceptions to higher-level code. This PR catches the error as
close as possible to the source of the error to allow clearer, more focused
error messages.
One consequence of using exceptions to report errors is that there is no
longer any code to set the "failed" status for an operator. Mostly this doesn't
matter; no code (except `STOP` handling) uses that status. Except in one place:
the handy utility which dumps two batches on operator failure. That code relied
on the failure status. Since most errors didn't set the status, the batch dump
code did not actually work well.
Instead of having each operator catch the exception and mark itself failed.
this PR uses a more general solution. It compares the stack trace in the
exception with the list of operators to determine the leaf-most operator. This
must be the operator which failed. This operator, and its parent, are not those
dumped by the batch dump code.
## Documentation
This code is internal to Drill and is not user-visible.
## Testing
Added a new test for the stack trace analyzer. Reran all unit tests and
adjusted those that needed changes.
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> Fail fast in operators
> ----------------------
>
> Key: DRILL-7576
> URL: https://issues.apache.org/jira/browse/DRILL-7576
> Project: Apache Drill
> Issue Type: Improvement
> Affects Versions: 1.17.0
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Priority: Major
> Fix For: 1.18.0
>
>
> Continues to the work to clean up operators to "fail fast" by throwing an
> exception instead of using the more involved STOP status.
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