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Posted to issues@hive.apache.org by "Dmitriy Fingerman (Jira)" <ji...@apache.org> on 2022/09/26 13:47:00 UTC
[jira] [Resolved] (HIVE-26496) FetchOperator scans delete_delta folders multiple times causing slowness
[ https://issues.apache.org/jira/browse/HIVE-26496?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Dmitriy Fingerman resolved HIVE-26496.
--------------------------------------
Fix Version/s: 4.0.0-alpha-2
Resolution: Fixed
> FetchOperator scans delete_delta folders multiple times causing slowness
> ------------------------------------------------------------------------
>
> Key: HIVE-26496
> URL: https://issues.apache.org/jira/browse/HIVE-26496
> Project: Hive
> Issue Type: Bug
> Components: HiveServer2
> Reporter: Rajesh Balamohan
> Assignee: Dmitriy Fingerman
> Priority: Major
> Labels: pull-request-available
> Fix For: 4.0.0-alpha-2
>
> Time Spent: 12h
> Remaining Estimate: 0h
>
> FetchOperator scans way too many number of files/directories than needed.
> For e.g here is a layout of a table which had set of updates and deletes. There are set of "delta" and "delete_delta" folders which are created.
> {noformat}
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/base_0000001
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000002_0000002_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000003_0000003_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000004_0000004_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000005_0000005_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000006_0000006_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000007_0000007_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000008_0000008_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000009_0000009_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000010_0000010_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000011_0000011_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000012_0000012_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000013_0000013_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000014_0000014_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000015_0000015_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000016_0000016_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000017_0000017_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000018_0000018_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000019_0000019_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000020_0000020_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000021_0000021_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delete_delta_0000022_0000022_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000002_0000002_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000003_0000003_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000004_0000004_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000005_0000005_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000006_0000006_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000007_0000007_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000008_0000008_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000009_0000009_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000010_0000010_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000011_0000011_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000012_0000012_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000013_0000013_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000014_0000014_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000015_0000015_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000016_0000016_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000017_0000017_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000018_0000018_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000019_0000019_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000020_0000020_0000
> s3a://bucket-name/warehouse/tablespace/managed/hive/test.db/date_dim/delta_0000021_0000021_0000
> {noformat}
>
> When user runs *{color:#0747a6}{{select * from date_dim}}{color}* from beeline, FetchOperator tries to compute splits in "date_dim". This "base" and "delta" folders and computes 21 splits.
> However, for each of the 21 splits, it ends up loading entire "delete_delta" folders and scans unnecessarily. This increases the scan by "21 splits * 21 delete_delta folders" (i.e 1396) times. This makes the statement execution super slow, even when there is minimal dataset present in the table.
> It will be good to scan only relevant delete_delta folder in the split, instead of loading all delete_delta folders in every split.
>
> [https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/io/orc/OrcRawRecordMerger.java#L1142|https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/io/orc/OrcRawRecordMerger.java#L1142]
> [https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/io/orc/OrcRawRecordMerger.java#L1172|https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/io/orc/OrcRawRecordMerger.java#L1172]
>
> [https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/exec/FetchOperator.java#L402|https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/exec/FetchOperator.java#L402]
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