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https://issues.apache.org/jira/browse/ARROW-6947?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17032835#comment-17032835
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Jorge commented on ARROW-6947:
------------------------------
[~andygrove], can I take a shoot at this?
My strategy to tackle this:
# add support for unary udfs
# support binary udfs
# add macro to support arbitrary argument udfs (I do not see an easy way to
implement variadic generics)
>From what I gathered, we need to
# Implement a new kernel (ala {{arrow::compute::kernels::arithmetic}}) to
execute a closure
# Implement a generic expression that implements {{PhysicalExpr}}
# Implement a {{FunctionProvider}} and add it to {{ExecutionContext}} (like
the attribute datasources)
# bits and pieces for integration (how the )
The design I was planning for the expression:
{code:java}
pub struct UnaryFunctionExpr<T, R>
where
T: ArrowPrimitiveType, // argument type
R: ArrowPrimitiveType, // return type
{
name: String,
/// name of the function
func:
Arc<dyn Fn(T::Native) -> arrow::error::Result<R::Native> + Sync + Send +
'static>,
arg: Arc<dyn PhysicalExpr>,
arg_type: DataType,
return_type: DataType,
}{code}
for the kernel:
{code:java}
pub fn unary_op<T, R>(
op: &dyn Fn(T::Native) -> Result<R::Native>,
arg: &PrimitiveArray<T>,
) -> Result<PrimitiveArray<R>>{code}
> [Rust] [DataFusion] Add support for scalar UDFs
> -----------------------------------------------
>
> Key: ARROW-6947
> URL: https://issues.apache.org/jira/browse/ARROW-6947
> Project: Apache Arrow
> Issue Type: New Feature
> Components: Rust, Rust - DataFusion
> Reporter: Andy Grove
> Assignee: Andy Grove
> Priority: Major
>
> As a user, I would like to be able to define my own functions and then use
> them in SQL statements.
>
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