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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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