kasakrisz opened a new pull request, #4272:
URL: https://github.com/apache/hive/pull/4272
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### What changes were proposed in this pull request?
`GenTezUtils.removeUnionOperators` tries to remove union operators from
union branches of the plan. I assume it is done because each branch has its own
Map vertex and the Union vertex takes the union of the result these.
Let's see the following query
```
SELECT NULL AS first_login_did
FROM tez_test_t5
LATERAL VIEW explode(split('0,6', ',')) gaps AS ads_h5_gap
UNION ALL
SELECT null as first_login_did
FROM tez_test_t1
UNION ALL
SELECT did AS first_login_did
FROM tez_test_t2
;
```
The plan before `removeUnionOperators`
```
TS[0]-LVF[1]-SEL[2] -LVJ[5]-SEL[6]-UNION[9]-SEL[12]-UNION[13]-FS[15]
-SEL[3]-UDTF[4]-LVJ[5]
TS[7]-SEL[8] -UNION[9]
TS[10]-SEL[11] -UNION[13]
```
The branch having lateral view has two sub branches from LVF (Lateral View
Forward op) to LVJ (Lateral View Join op).
The `removeUnionOperators` traverse the branches and it tries to remove the
UNION[9] operator twice. It fails the second time with the exception mentioned
in the jira.
### Why are the changes needed?
Fix issue mentioned above.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
```
mvn test -Dtest.output.overwrite -DskipSparkTests
-Dtest=TestMiniLlapLocalCliDriver -Dqfile=lateral_view_unionall.q -pl
itests/qtest -Pitests
```
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