[GitHub] [arrow-datafusion] jorgecarleitao commented on issue #251: Implement Postgres compatible `now()` function

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jorgecarleitao commented on issue #251:
URL: https://github.com/apache/arrow-datafusion/issues/251#issuecomment-833766100


   My two cents:
   
   I do not think that this issue is a "good first issue". Atm, functions are:
   
   1. stateless
   2. do not know what is the expected resulting size of the array (e.g. creating a function that filters currently works)
   
   Solving this issue requires both:
   
   * `now` is stateful because its value is stored after its first evaluation, like @returnString says
   * `now` requires knowing the output size of the array, which must be passed to when the record batch is passing through the stream
   
   This requires a (imo large) change in our internal workings.
   
   Note that another class of functions that is unlocked by this work are functions that return non-deterministic numbers (e.g. random numbers).
   
   
   
   


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