aefb2e70e7
### What changes were proposed in this pull request? This PR adds a simple cost model and a mechanism to compare the costs of the before and after plans of each re-optimization in Adaptive Query Execution. Now the workflow of AQE re-optimization is changed to: If the cost of the plan after re-optimization is lower than or equal to that of the plan before re-optimization and the plan has been changed after re-optimization (if equal), the current physical plan will be updated to the plan after re-optimization, otherwise it will remain unchanged until the next re-optimization. ### Why are the changes needed? This new mechanism is to prevent regressions in Adaptive Query Execution caused by change of the plan introducing extra cost, in this PR specifically, change of SMJ to BHJ leading to extra `ShuffleExchangeExec`s. ### Does this PR introduce any user-facing change? No. ### How was this patch tested? Added UT. Closes #25456 from maryannxue/aqe-cost. Authored-by: maryannxue <maryannxue@apache.org> Signed-off-by: gatorsmile <gatorsmile@gmail.com> |
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