[jira] [Work logged] (HIVE-26875) Transaction conflict retry loop only executes once

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-26875?focusedWorklogId=834940&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-834940 ]

ASF GitHub Bot logged work on HIVE-26875:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 20/Dec/22 22:45
            Start Date: 20/Dec/22 22:45
    Worklog Time Spent: 10m 
      Work Description: jfsii opened a new pull request, #3887:
URL: https://github.com/apache/hive/pull/3887

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   ### What changes were proposed in this pull request?
   The functional change is to not clear the query context completely when re-compiling the query.
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   ### Why are the changes needed?
   It is a bug that can cause duplicate records or other incorrect behavior.
   
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   ### Does this PR introduce _any_ user-facing change?
   No - except fixing the bug
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   ### How was this patch tested?
   Added test cases and tested on a 3 node cluster.
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Issue Time Tracking
-------------------

            Worklog Id:     (was: 834940)
    Remaining Estimate: 0h
            Time Spent: 10m

> Transaction conflict retry loop only executes once
> --------------------------------------------------
>
>                 Key: HIVE-26875
>                 URL: https://issues.apache.org/jira/browse/HIVE-26875
>             Project: Hive
>          Issue Type: Bug
>          Components: HiveServer2
>            Reporter: John Sherman
>            Assignee: John Sherman
>            Priority: Critical
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Currently the "conflict retry loop" only executes once.
> [https://github.com/apache/hive/blob/ab4c53de82d4aaa33706510441167f2df55df15e/ql/src/java/org/apache/hadoop/hive/ql/Driver.java#L264]
> The intent of this loop is to detect if a conflicting transaction has committed while we were waiting to acquire locks. If there is a conflicting transaction, it invalidates the snapshot, rolls-back the transaction, opens a new transaction and tries to re-acquire locks (and then recompile). It then checks again if a conflicting transaction has committed and if so, redoes the above steps again, up to HIVE_TXN_MAX_RETRYSNAPSHOT_COUNT times.
> However - isValidTxnState relies on getNonSharedLockedTable():
> [https://github.com/apache/hive/blob/ab4c53de82d4aaa33706510441167f2df55df15e/ql/src/java/org/apache/hadoop/hive/ql/DriverTxnHandler.java#L422]
> which does:
> {code:java}
>   private Set<String> getNonSharedLockedTables() {
>     if (CollectionUtils.isEmpty(driver.getContext().getHiveLocks())) {
>       return Collections.emptySet(); // Nothing to check
>     }{code}
> getHiveLocks gets populated by lockAndRespond... HOWEVER -
> compileInternal ends up calling compile which ends up calling preparForCompile which ends up calling prepareContext which ends up destroying the context with the information lockAndRespond populated. So when the loop executes after all of this, it will never detect a 2nd conflict because isValidTxnState will always return true (because it thinks there are no locked objects).
> This manifests as duplicate records being created during concurrent UPDATEs if a transaction get conflicted twice.



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