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Posted to issues@spark.apache.org by "Sean Owen (JIRA)" <ji...@apache.org> on 2017/02/18 10:14:44 UTC
[jira] [Comment Edited] (SPARK-19655) select count(*) , requests 1
for each row
[ https://issues.apache.org/jira/browse/SPARK-19655?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15873087#comment-15873087 ]
Sean Owen edited comment on SPARK-19655 at 2/18/17 10:14 AM:
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What is the problem? selecting "1" _is_ an optimization, or at least, should make no difference at all. EDIT: I assume you mean count(1), but, if not, can you provide an example of which DB that affects? because of course that's not even an aggregate function then.
was (Author: srowen):
What is the problem? selecting "1" _is_ an optimization, or at least, should make no difference at all.
> select count(*) , requests 1 for each row
> -----------------------------------------
>
> Key: SPARK-19655
> URL: https://issues.apache.org/jira/browse/SPARK-19655
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.1.0
> Reporter: hosein
> Priority: Minor
>
> when I want query select count( * ) by JDBC and monitor queries in database side, I see spark requests: select 1 for destination table
> it means 1 for each row and it is not optimized
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