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https://issues.apache.org/jira/browse/HIVE-7121?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14008377#comment-14008377
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Edward Capriolo commented on HIVE-7121:
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Does this effect bucketed tables? I think it does and then we can not just
change the hash code because that would break assumptions of what is in the
bucket. IE i create a bucket in hive 12, and in hive 13 different data would be
in the bucket.
I think this is why:
org.apache.hadoop.hive.cli.TestMinimrCliDriver.testCliDriver_infer_bucket_sort_num_buckets
org.apache.hadoop.hive.cli.TestMinimrCliDriver.testCliDriver_quotedid_smb
These tests are failing. If this is the case we need a way or recording the
hashcode in the metadata for the table.
> Use murmur hash to distribute HiveKey
> -------------------------------------
>
> Key: HIVE-7121
> URL: https://issues.apache.org/jira/browse/HIVE-7121
> Project: Hive
> Issue Type: Bug
> Components: Query Processor
> Reporter: Gopal V
> Assignee: Gopal V
> Attachments: HIVE-7121.1.patch, HIVE-7121.WIP.patch
>
>
> The current hashCode implementation produces poor parallelism when dealing
> with single integers or doubles.
> And for partitioned inserts into a 1 bucket table, there is a significant
> hotspot on Reducer #31.
> Removing the magic number 31 and using a more normal hash algorithm would
> help fix these hotspots.
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