Jinfeng Ni created DRILL-1044:
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Summary: Optimize logical boolean operator evaluation using
fast-success/fast-fail approach.
Key: DRILL-1044
URL: https://issues.apache.org/jira/browse/DRILL-1044
Project: Apache Drill
Issue Type: Improvement
Reporter: Jinfeng Ni
With short circuit evaluation supported for boolean and/or operators
(DRILL-937), we could further optimize boolean and/or operators by re-ordering
the evaluation sequence and choose to evaluate the cheapest test first.
For instance, consider we have the following expression :
really_slow_test ( ...) && slower_test ( ...) && fast_test ( ...)
If we choose to evaluate really_slow_test(() first, we will do such test for
every input. In contrast, if we choose do fast_test() first, we could skip the
evaluation of slower_test() and really_slow_test(), if some input fails at the
fast_test(). That is, performance would be better, if we transform the
expression into:
fast_test(..) && slower_test(...) && really_slow_test (....).
To add such support, we need do :
1. Change the boolean "and"/"or" so that it takes arbitrary number of
operands. ( Previously, "and"/"or" is processed as taking two operands) This
way, we could compare and sort all the operands under one single "and"/"or"
operator.
2. Assign a cost category to different functions/operators, to reflect the
rough estimation of each individual function/operator.
3. Re-order the operands based on the cumulative cost for evaluation.
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