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From jinfengni <...@git.apache.org>
Subject [GitHub] drill pull request: DRILL-3623: Use shorter query path for LIMIT 0...
Date Wed, 28 Oct 2015 22:13:41 GMT
Github user jinfengni commented on the pull request:

    The original approach (skipping the execution phase for limit 0 completely), actually
could potentially have issues in some cases, due to the difference in Calcite rule and Drill
execution rule, in terms of how type is determined.
    For example, sum(int) in calcite is resolved to be int, while in Drill execution, we changed
to bigint. Another case is implicit cast. Currently, there are some small differences between
Calcite and Drill execution. That means, if we skip the execution for limit 0, then types
which are resolved in Calcite could be different from the type if the query goes through Drill
execution. For BI tool like Tableau, that means the type returned from "limit 0" query and
type from a second query w/o "limit 0" could be different. 
    If we want to avoid the above issues, we have to detect all those cases, which are painful.
That's why Sudheesh and I are now more inclined to this new approach. 

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