[jira] [Created] (IMPALA-14417) Query option for JDBC row count estimation

["Pranav Yogi Lodha (Jira)" <ji...@apache.org>]

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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