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Posted to dev@hive.apache.org by "Yongqiang He (JIRA)" <ji...@apache.org> on 2009/06/25 13:54:07 UTC
[jira] Updated: (HIVE-582) "SELECT count(1) as cnt from src x" not
working for column pruning
[ https://issues.apache.org/jira/browse/HIVE-582?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Yongqiang He updated HIVE-582:
------------------------------
Attachment: hive-582-2009-06-25.patch
> "SELECT count(1) as cnt from src x" not working for column pruning
> ------------------------------------------------------------------
>
> Key: HIVE-582
> URL: https://issues.apache.org/jira/browse/HIVE-582
> Project: Hadoop Hive
> Issue Type: Bug
> Reporter: Yongqiang He
> Assignee: Yongqiang He
> Attachments: hive-582-2009-06-25.patch
>
>
> The query "SELECT count(1) as cnt from src x" has some problems, even though nullgroup*.q passed in tests.
> Will check and solve it in this jira.
> A wrong plan sometimes can be generated due to some unknow factor:
> Wrong plan:
> {noformat}
> STAGE PLANS:
> Stage: Stage-1
> Map Reduce
> Alias -> Map Operator Tree:
> x
> Select Operator
> Reduce Output Operator
> sort order:
> tag: -1
> Reduce Operator Tree:
> Group By Operator
> aggregations:
> expr: count(VALUE._col0)
> mode: complete
> Select Operator
> expressions:
> expr: _col0
> type: bigint
> File Output Operator
> compressed: false
> GlobalTableId: 0
> table:
> input format: org.apache.hadoop.mapred.TextInputFormat
> output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat
> Stage: Stage-0
> Fetch Operator
> limit: -1
> {noformat}
> Without unknow factor, correct plan can be generated:
> {noformat}
> STAGE PLANS:
> Stage: Stage-1
> Map Reduce
> Alias -> Map Operator Tree:
> x
> Select Operator
> Group By Operator
> aggregations:
> expr: count(1)
> mode: hash
> Reduce Output Operator
> sort order:
> tag: -1
> value expressions:
> expr: _col0
> type: bigint
> Reduce Operator Tree:
> Group By Operator
> aggregations:
> expr: count(VALUE._col0)
> mode: mergepartial
> Select Operator
> expressions:
> expr: _col0
> type: bigint
> File Output Operator
> compressed: false
> GlobalTableId: 0
> table:
> input format: org.apache.hadoop.mapred.TextInputFormat
> output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat
> {noformat}
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