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https://issues.apache.org/jira/browse/HIVE-26875?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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John Sherman resolved HIVE-26875.
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Resolution: Fixed
Committed to master
> 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
> Labels: pull-request-available
> Time Spent: 2h
> 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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