maheshrajus opened a new pull request, #6916:
URL: https://github.com/apache/hive/pull/6916
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### What changes were proposed in this pull request?
- SharedWorkOptimizer: added removalLeavesWorkWithoutSink(...) and call it
from validPreConditions(). A merge
is skipped if deleting the duplicate's operators would leave a work with
no ReduceSink/FileSink.
- The check covers a deleted ReduceSink and also a deleted chain that ends
in one (e.g. SEL -> RS).
### Why are the changes needed?
When two identical table scans are merged, the operators that only fed the
duplicate scan are deleted.
Sometimes one of them is the only ReduceSink of a reducer, and all that
reducer has left is a dynamic
partition pruning (DPP) event branch. GenTezWork only starts a new vertex
at a sink, so that reducer never
gets its own vertex. Its mergepartial GroupBy ends up inside the upstream
Map vertex, and the query fails at
runtime with: **cannot find field key from [0:_col0, 1:_col1, 2:_col2]**
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
Newly added UT & qtests
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