[jira] [Created] (ARROW-8901) [C++] Reduce number of take kernels

["Wes McKinney (Jira)" <ji...@apache.org>]

Wes McKinney created ARROW-8901:
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             Summary: [C++] Reduce number of take kernels
                 Key: ARROW-8901
                 URL: https://issues.apache.org/jira/browse/ARROW-8901
             Project: Apache Arrow
          Issue Type: Improvement
          Components: C++
            Reporter: Wes McKinney


After ARROW-8792 we can observe that we are generating 312 take kernels

{code}
In [1]: import pyarrow.compute as pc                                                                      

In [2]: reg = pc.function_registry()                                                                      

In [3]: reg.get_function('take')                                                                          
Out[3]: 
arrow.compute.Function
kind: vector
num_kernels: 312
{code}

You can see them all here: https://gist.github.com/wesm/c3085bf40fa2ee5e555204f8c65b4ad5

It's probably going to be sufficient to only support int16, int32, and int64 index types for almost all types and insert implicit casts (once we implement implicit-cast-insertion into the execution code) for other index types. If we determine that there is some performance hot path where we need to specialize for other index types, then we can always do that.

Additionally, we should be able to collapse the date/time kernels since we're just moving memory.



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