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Peter Vary commented on HIVE-26150: ----------------------------------- [~asolimando]: I am trying to find out if fixing this issue would cause performance improvements when reading tables where we have delete deltas present. We have two ways to read the delete deltas: - [SortMergedDeleteEventRegistry |https://github.com/apache/hive/blob/a29810ce97a726fc70aecb53ebd648c3237106c4/ql/src/java/org/apache/hadoop/hive/ql/io/orc/VectorizedOrcAcidRowBatchReader.java#L1228] - [ColumnizedDeleteEventRegistry |https://github.com/apache/hive/blob/a29810ce97a726fc70aecb53ebd648c3237106c4/ql/src/java/org/apache/hadoop/hive/ql/io/orc/VectorizedOrcAcidRowBatchReader.java#L1383] IIRC the ColumnizedDeleteEventRegistry creates its own readers and SortMergedDeleteEventRegistry uses OrcRawRecordMerger, so I would guess that the normal reads would be effected with this inefficiency when SortMergedDeleteEventRegistry is used, but I would like this to be confirmed. Thanks, Peter > OrcRawRecordMerger reads each row twice > --------------------------------------- > > Key: HIVE-26150 > URL: https://issues.apache.org/jira/browse/HIVE-26150 > Project: Hive > Issue Type: Bug > Components: ORC, Transactions > Affects Versions: 4.0.0-alpha-2 > Reporter: Alessandro Solimando > Priority: Major > > OrcRawRecordMerger reads each row twice, the issue does not surface since the > merger is only used with the parameter "collapseEvents" as true, which > filters out one of the two rows. > collapseEvents true and false should produce the same result, since in > current acid implementation, each event has a distinct rowid, so two > identical rows cannot be there, this is the case only for the bug. > In order to reproduce the issue, it is sufficient to set the second parameter > to false > [here|https://github.com/apache/hive/blob/61d4ff2be48b20df9fd24692c372ee9c2606babe/ql/src/java/org/apache/hadoop/hive/ql/io/orc/OrcInputFormat.java#L2103-L2106], > and run tests in TestOrcRawRecordMerger and observe two tests failing: > {code:bash} > mvn test -Dtest=TestOrcRawRecordMerger -pl ql > {code} > {noformat} > [INFO] Results: > [INFO] > [ERROR] Failures: > [ERROR] TestOrcRawRecordMerger.testRecordReaderNewBaseAndDelta:1332 Found > unexpected row: (0,ignore.1) > [ERROR] TestOrcRawRecordMerger.testRecordReaderOldBaseAndDelta:1208 Found > unexpected row: (0,ignore.1) > {noformat} -- This message was sent by Atlassian Jira (v8.20.7#820007)