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Xuefu Zhang commented on HIVE-17486: ------------------------------------ [~lirui] The reason was briefly given at https://issues.apache.org/jira/browse/HIVE-8920?focusedCommentId=14260846&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14260846. I was dealing with the IOContext initialization issue. > Enable SharedWorkOptimizer in tez on HOS > ---------------------------------------- > > Key: HIVE-17486 > URL: https://issues.apache.org/jira/browse/HIVE-17486 > Project: Hive > Issue Type: Bug > Reporter: liyunzhang > Assignee: liyunzhang > Priority: Major > Attachments: scanshare.after.svg, scanshare.before.svg > > > in HIVE-16602, Implement shared scans with Tez. > Given a query plan, the goal is to identify scans on input tables that can be > merged so the data is read only once. Optimization will be carried out at the > physical level. In Hive on Spark, it caches the result of spark work if the > spark work is used by more than 1 child spark work. After sharedWorkOptimizer > is enabled in physical plan in HoS, the identical table scans are merged to 1 > table scan. This result of table scan will be used by more 1 child spark > work. Thus we need not do the same computation because of cache mechanism. -- This message was sent by Atlassian JIRA (v6.4.14#64029)