[ https://issues.apache.org/jira/browse/HIVE-17979?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Ashutosh Chauhan updated HIVE-17979: ------------------------------------ Status: Open (was: Patch Available) +1 > Tez: Improve ReduceRecordSource passDownKey copying > --------------------------------------------------- > > Key: HIVE-17979 > URL: https://issues.apache.org/jira/browse/HIVE-17979 > Project: Hive > Issue Type: Improvement > Affects Versions: 3.0.0 > Reporter: Gopal V > Assignee: Gopal V > Priority: Major > Attachments: HIVE-17979.1.patch, HIVE-17979.2.patch > > > Tez does not use a single Key stream for both sides of the join, so each > input gets its own ReduceRecordSource > {code} > sources[tag] = new ReduceRecordSource(); > {code} > And this means for each input stream, there's a deserialized key (because the > tag is not part of the Key byte stream), this means for a 2-table join there > are 2 ReduceRecordSource objects. > This means that the passDownKey is only an optimization when the Key, > List<Value> has more than 1 value in it. Otherwise the copy is entirely > wasted CPU cycles, because it deserializes the entire row to extract the key > and discards the row. -- This message was sent by Atlassian JIRA (v7.6.3#76005)