[
https://issues.apache.org/jira/browse/PIG-1590?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12905995#action_12905995
]
Ashutosh Chauhan commented on PIG-1590:
---
Also inner merge join on more then 2 then tables also translates into
POMergeCogroup + FE + Flatten. Here also it can be translated to use
POMergeJoin and enjoy the benefits which comes along with it. Though I suspect
it will introduce much more complexity in POMergeJoin then the case for left
outer merge join. So, may not be worth doing.
Use POMergeJoin for Left Outer Join when join using 'merge'
---
Key: PIG-1590
URL: https://issues.apache.org/jira/browse/PIG-1590
Project: Pig
Issue Type: Improvement
Components: impl
Affects Versions: 0.8.0
Reporter: Ashutosh Chauhan
Priority: Minor
C = join A by $0 left, B by $0 using 'merge';
will result in map-side sort merge join. Internally, it will translate to use
POMergeCogroup + ForEachFlatten. POMergeCogroup places quite a few
restrictions on its loaders (A and B in this case) which is cumbersome.
Currently, only Zebra is known to satisfy all those requirements. It will be
better to use POMergeJoin in this case, since it has far fewer requirements
on its loader. Importantly, it works with PigStorage. Plus, POMergeJoin will
be faster then POMergeCogroup + FE-Flatten.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
