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https://issues.apache.org/jira/browse/SPARK-19647?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15873490#comment-15873490
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wuchang commented on SPARK-19647:
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Hi , I don't think that it is just a question ,but also it maybe a quite
serious bug.But I am not sure.
> Spark query hive is extremelly slow even the result data is small
> -----------------------------------------------------------------
>
> Key: SPARK-19647
> URL: https://issues.apache.org/jira/browse/SPARK-19647
> Project: Spark
> Issue Type: Question
> Components: PySpark
> Affects Versions: 2.0.2
> Reporter: wuchang
> Priority: Critical
>
> I am using spark 2.0.0 to query hive table:
> my sql is:
> select * from app.abtestmsg_v limit 10
> Yes, I want to get the first 10 records from a view app.abtestmsg_v.
> When I run this sql in spark-shell,it is very fast, USE about 2 seconds .
> But then the problem comes when I try to implement this query by my python
> code.
> I am using Spark 2.0.0 and write a very simple pyspark program, code is:
> from pyspark.sql import HiveContext
> from pyspark.sql.functions import *
> import json
> hc = HiveContext(sc)
> hc.setConf("hive.exec.orc.split.strategy", "ETL")
> hc.setConf("hive.security.authorization.enabled",false)
> zj_sql = 'select * from app.abtestmsg_v limit 10'
> zj_df = hc.sql(zj_sql)
> zj_df.collect()
> From the info log , I find: although I use "limit 10" to tell spark that I
> just want the first 10 records , but spark still scan and read all files(in
> my case, the source data of this view contains 100 files and each file's size
> is about 1G) of the view , So , there are nearly 100 tasks , each task read a
> file , and all the task is executed serially. I use nearlly 15 minutes to
> finish these 100 tasks!!!!! but what I want is just to get the first 10
> records.
> So , I don't know what to do and what is wrong;
> Anybode could give me some suggestions?
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