alamb opened a new issue #1160: URL: https://github.com/apache/arrow-datafusion/issues/1160
**Is your feature request related to a problem or challenge? Please describe what you are trying to do.** The constant folding and constant evaluation in https://github.com/apache/arrow-datafusion/blob/master/datafusion/src/optimizer/constant_folding.rs (and added to in https://github.com/apache/arrow-datafusion/pull/1153) can not fold certain types of expressions where it takes For example there is an expression like this in https://github.com/apache/arrow-datafusion/pull/1153 ``` now() < cast(to_timestamp(...) as int) + 5000000000 ``` It is entirely evaluateable at query time, however, as formulated in #1153 it will not be folded because it requires the constant evaluator to run after the simplifier (because the simplifier can fill in now()` and then the evaluator will fill in the rest). However, there are other types of exprs such as `(true or false) != col` which need to have the constant evaluator run before the simplifier to be fully simplified. It is a more general problem where running either the `Simplifier` or `ConstEvaluator` could allow a second pass of the other to proceed **Describe the solution you'd like** In general this is typically handled with some sort of 'fixed point' algorithm where there is a loop that runs the two passes until the Expr is not changed. It may also be possible to combine the Simplifier pass with the constant rewriter. **Describe alternatives you've considered** I think there are two possible approaches I can think if: 1. applying constant eval / simplifier in a loop until no changes are detected 2. Combining the `ConstantEval` and `Simplify` steps into a single pass **Additional context** https://github.com/apache/arrow-datafusion/pull/1153 -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
