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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2021/12/27 13:02:01 UTC
[GitHub] [arrow-datafusion] alamb opened a new issue #1493: Implement `power` function
alamb opened a new issue #1493:
URL: https://github.com/apache/arrow-datafusion/issues/1493
**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
We would like to compute a power function (like `2**4` = `2 * 2 * 2 * 2`) in datafusion
@matthewmturner asks for it here: https://github.com/apache/arrow-datafusion/issues/147#issuecomment-1001223018
**Describe the solution you'd like**
Implement the `power` function as described in https://www.postgresql.org/docs/14/functions-math.html
```
power ( a numeric, b numeric ) → numeric
power ( a double precision, b double precision ) → double precision
a raised to the power of b
power(9, 3) → 729
```
**Describe alternatives you've considered**
It may also be interesting to investigate adding support for `a**b` as another way to write the same thing
**Additional context**
This is probably a good ticket to learn about the datafusion codebase and its function implementations -- one could follow the example of one of the existing functions in
https://github.com/apache/arrow-datafusion/blob/master/datafusion/src/physical_plan/functions.rs
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[GitHub] [arrow-datafusion] matthewmturner commented on issue #1493: Implement `power` function
Posted by GitBox <gi...@apache.org>.
matthewmturner commented on issue #1493:
URL: https://github.com/apache/arrow-datafusion/issues/1493#issuecomment-1002220692
ill work on this
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[GitHub] [arrow-datafusion] matthewmturner commented on issue #1493: Implement `power` function
Posted by GitBox <gi...@apache.org>.
matthewmturner commented on issue #1493:
URL: https://github.com/apache/arrow-datafusion/issues/1493#issuecomment-1002767204
ive started looking into this and i think it makes sense to add `power` / `power_scalar` compute kernels to arrow first then expose it in `physical_plan/expressions/binary.rs` and `physical_plan/expressions/functions.rs`
@alamb ok with that?
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[GitHub] [arrow-datafusion] matthewmturner commented on issue #1493: Implement `power` function
Posted by GitBox <gi...@apache.org>.
matthewmturner commented on issue #1493:
URL: https://github.com/apache/arrow-datafusion/issues/1493#issuecomment-1003087297
@alamb ok happy to do that.
but just to show you where i was coming from, i saw both C++ (https://arrow.apache.org/docs/cpp/compute.html#arithmetic-functions) and arrow2 (https://github.com/jorgecarleitao/arrow2/blob/main/src/compute/arithmetics/basic/pow.rs) had kernels for power. so i thought we would want to do something similar and not have datafusion implement something that could / should be done downstream.
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[GitHub] [arrow-datafusion] alamb commented on issue #1493: Implement `power` function
Posted by GitBox <gi...@apache.org>.
alamb commented on issue #1493:
URL: https://github.com/apache/arrow-datafusion/issues/1493#issuecomment-1003192924
@matthewmturner -- I don't have a strong preference.
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[GitHub] [arrow-datafusion] alamb commented on issue #1493: Implement `power` function
Posted by GitBox <gi...@apache.org>.
alamb commented on issue #1493:
URL: https://github.com/apache/arrow-datafusion/issues/1493#issuecomment-1003005009
@matthewmturner I think `power` is more like a `function` rather than an `operator` -- so in that case I think you could just add `power` to `BuiltinScalarFunction` (and then fill in the implementation):
https://github.com/apache/arrow-datafusion/blob/5668be78a9ccbf5469e9e95ad070920ca5d105ba/datafusion/src/physical_plan/functions.rs
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