Riza Suminto created IMPALA-12192:
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Summary: Scan fragment parallelism is limited by its ScanNode cost.
Key: IMPALA-12192
URL: https://issues.apache.org/jira/browse/IMPALA-12192
Project: IMPALA
Issue Type: Bug
Components: Frontend
Reporter: Riza Suminto
Assignee: Riza Suminto
IMPALA-12091 implement processing cost for ScanNode. Scan fragment parallelism
is capped by this ScanNode cost, originally intended to prevent scanner
over-parallelization (small files problem).
However, there is a bug in the implementation where scan fragment parallelism
will always be limited solely by the ScanNode cost. If ScanNode is colocated
with other query node operator that have higher processing cost, Planner will
not scale it up beyond what is allowed by the ScanNode cost. Scan fragment
should be allowed to scale up, as long as it is within total processing cost of
the fragment and number of effective scan ranges.
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