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https://issues.apache.org/jira/browse/BEAM-7049?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16932032#comment-16932032
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sridhar Reddy commented on BEAM-7049:
-------------------------------------
I noticed there is a change in behavior between union vs union all. The
following query works as expected with the code in the pull request
{{SELECT 1 }}{{UNION ALL
SELECT 2
UNION ALL
SELECT 3
UNION ALL
SELECT 4
UNION ALL
SELECT 5}}
{{}}
{{but the query}}
{{}}{{SELECT 1 }}{{UNION SELECT 2
UNION SELECT 3
UNION SELECT 4
UNION SELECT 5}}
{{}}
{{doesn't work as expected. It only uses 3 operands to give the result
}}{{[1,2,3] and skps 4 and 5. This behavior is observed with UnionMergeRule in
the right place. }}
{{I will do a couple of more tests with fresh clone to see if there is any
difference and update this Jira. }}{{}}
> Merge multiple input to one BeamUnionRel
> ----------------------------------------
>
> Key: BEAM-7049
> URL: https://issues.apache.org/jira/browse/BEAM-7049
> Project: Beam
> Issue Type: Improvement
> Components: dsl-sql
> Reporter: Rui Wang
> Assignee: sridhar Reddy
> Priority: Major
> Time Spent: 1h
> Remaining Estimate: 0h
>
> BeamUnionRel assumes inputs are two and rejects more. So `a UNION b UNION c`
> will have to be created as UNION(a, UNION(b, c)) and have two shuffles. If
> BeamUnionRel can handle multiple shuffles, we will have only one shuffle
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