[GitHub] [arrow-datafusion] tobyhede edited a comment on issue #1364: Documentation for using scalar functions with the the DataFrame API

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tobyhede edited a comment on issue #1364:
URL: https://github.com/apache/arrow-datafusion/issues/1364#issuecomment-980450411


   Thanks @xudong963. The core docs are very good, but don't seem to include any examples of using the scalar functions  `lower, upper, starts_with, etc` . I've been trying permutations with no luck.
   
   eg My assumption (based on the equality operators) was that something like this should work:
   ```
     .filter(col("some_col").starts_with(lit("alpha")))
   ```
   
   In the above, `starts_with` isn't found in the scope.
   
   I can do this:
   ```
   .filter(starts_with(lit("alpha")))
   ```
   But this fails at runtime saying:
   ```
   Error: Plan("Coercion from [Utf8] to the signature OneOf([Exact([Utf8, Utf8]), Exact([Utf8, LargeUtf8]), Exact([LargeUtf8, Utf8]), Exact([LargeUtf8, LargeUtf8])]) failed.")
   ```
          
   I know I am missing something a bit obvious :)
   


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