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https://issues.apache.org/jira/browse/HIVE-3005?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13269099#comment-13269099
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Carl Steinbach commented on HIVE-3005:
--------------------------------------
Executing a query that contains a "LIMIT 0" clause is a trick that some clients
(e.g. ODBC clients) employ in order to generate a result set without incurring
the cost of actually executing the query. Unfortunately, this trick doesn't
work with Hive:
{noformat}
hive> SELECT key FROM SRC LIMIT 0;
SELECT key FROM SRC LIMIT 0;
Total MapReduce jobs = 1
Launching Job 1 out of 1
Number of reduce tasks is set to 0 since there's no reduce operator
Execution log at:
/tmp/carl/carl_20120505182828_a5405bcb-c156-4572-b2d8-eda2cc199a14.log
Job running in-process (local Hadoop)
Hadoop job information for null: number of mappers: 0; number of reducers: 0
2012-05-05 18:28:35,999 null map = 100%, reduce = 0%
Ended Job = job_local_0001
Execution completed successfully
Mapred Local Task Succeeded . Convert the Join into MapJoin
OK
{noformat}
> Query containing "LIMIT 0" clause should skip execution phase
> -------------------------------------------------------------
>
> Key: HIVE-3005
> URL: https://issues.apache.org/jira/browse/HIVE-3005
> Project: Hive
> Issue Type: Improvement
> Components: Query Processor
> Reporter: Carl Steinbach
>
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