Alexander Behm created IMPALA-6178:
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Summary: Heuristic for selecting the left-most table should
consider parallelism.
Key: IMPALA-6178
URL: https://issues.apache.org/jira/browse/IMPALA-6178
Project: IMPALA
Issue Type: Improvement
Components: Frontend
Affects Versions: Impala 2.10.0
Reporter: Alexander Behm
Priority: Critical
For each query block, Impala uses the estimated materialized size of tables as
a heuristic for choosing the left-most table in a series of joins.
Unfortunately, that heuristic does not factor in the number of hosts that
tables will execute on. The number of hosts of the left-most table dictates the
degree of inter-node parallelism.
To handle this tradeoff between parallelism and size we should use a heuristic
like the one in IMPALA-5612.
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