[GitHub] [arrow-datafusion] alamb commented on pull request #288: [Datafusion] NOW() function support

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alamb commented on pull request #288:
URL: https://github.com/apache/arrow-datafusion/pull/288#issuecomment-840101186


   > The stateful function seems needed at some point. I am not sure a stateful function would be needed here, at this moment, and might go a bit beyond the scope of this PR/feature(?).
   
   I agree with @Dandandan  -- I would like to get a basic implementation of now(). I feel @msathis had this PR really close but then the addition of `ExecutionProps` to all scalar functions has caused issues
   
   > Adding a node for node for timestamps (which can be used by current_date, NOW(), etc.) which only has access to the query start time seems like a more natural route to me for now. WDYT?
   
   Just to be clear, are you suggesting adding a new Expr variant, something like `Expr::now()`  that could be handled specially? 
   
   I guess I was hoping that part of the translation from Expr --> PhysicalExpr could somehow capture state that was available at plan time (e.g. `ExecutionProps`)  without having to change the signature of all scalar functions. Perhaps we could use a closure or something to capture this statel


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