Pranav Yogi Lodha created IMPALA-14417:
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Summary: Query option for JDBC row count estimation
Key: IMPALA-14417
URL: https://issues.apache.org/jira/browse/IMPALA-14417
Project: IMPALA
Issue Type: New Feature
Reporter: Pranav Yogi Lodha
Currently, the JDBC external data source integration issues an additional
{{COUNT(*)}} query in the {{prepare()}} phase to estimate the number of rows in
a JDBC table. While this helps the planner choose a better parallelization
strategy for complex queries (e.g. joins or aggregations), it also introduces
an extra JDBC round trip.
To give users more control, we propose introducing a query option that enables
or disables row count estimation for JDBC tables. When enabled, Impala will
issue the {{COUNT(*)}} query during prepare. When disabled, Impala will skip
this step, avoiding the additional JDBC round trip.
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