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Posted to issues-all@impala.apache.org by "carolinchen (Jira)" <ji...@apache.org> on 2022/01/25 03:53:00 UTC
[jira] [Closed] (IMPALA-11082) Partition key scan optimization may return incorrect results when partition file have more than one block
[ https://issues.apache.org/jira/browse/IMPALA-11082?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
carolinchen closed IMPALA-11082.
--------------------------------
Resolution: Duplicate
> Partition key scan optimization may return incorrect results when partition file have more than one block
> ---------------------------------------------------------------------------------------------------------
>
> Key: IMPALA-11082
> URL: https://issues.apache.org/jira/browse/IMPALA-11082
> Project: IMPALA
> Issue Type: Bug
> Reporter: carolinchen
> Assignee: carolinchen
> Priority: Major
>
> In https://issues.apache.org/jira/browse/IMPALA-8834 will only generate one scan range for partition key's scan, but it may cause wrong result.
> In this case, when a file with more than one block.
> # The planner will only transforms the first block into TScanRange, which does not include footer.
> # The backend can't find the split with the footer, so that can neither parse the footer nor do the scan.
> so that the paritition key scan's result will be incorrect.
>
> see this snippet in HdfsScanNode.java:
>
> {code:java}
> private Pair<Boolean, Long> transformBlocksToScanRanges(
> FeFsPartition partition, FileDescriptor fileDesc,
> boolean fsHasBlocks, long scanRangeBytesLimit,
> Analyzer analyzer) {
> for (int i = 0; i < fileDesc.getNumFileBlocks(); ++i) {
> // Only generate one scan range for partition key scans.
> if (isPartitionKeyScan_) break;
> }
> }{code}
> In FE, if file with more than one block do partition key scan, transformBlocksToScanRanges will not include footer range.
>
> see this snippet in hdfs-scanner.cc:
>
> {code:java}
> /// Issue just the footer range for each file. This function is only used /// in parquet and orc scanners. We'll then parse the footer and pick out /// the columns we want.
> Status HdfsScanner::IssueFooterRanges(HdfsScanNodeBase* scan_node,
> const THdfsFileFormat::type& file_type,
> const std::vector<HdfsFileDesc*>& files) {
> // Try to find the split with the footer.
> ScanRange* footer_split = FindFooterSplit(files[i]);
> }{code}
> In BE, there no footer split won't add range to do the scan.
>
>
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