alamb commented on code in PR #9304:
URL: https://github.com/apache/arrow-datafusion/pull/9304#discussion_r1511896537
##########
datafusion/core/tests/user_defined/user_defined_scalar_functions.rs:
##########
@@ -514,6 +519,97 @@ async fn deregister_udf() -> Result<()> {
Ok(())
}
+#[derive(Debug)]
+struct CastToI64UDF {
+ signature: Signature,
+}
+
+impl CastToI64UDF {
+ fn new() -> Self {
+ Self {
+ signature: Signature::any(1, Volatility::Immutable),
+ }
+ }
+}
+
+impl ScalarUDFImpl for CastToI64UDF {
+ fn as_any(&self) -> &dyn Any {
+ self
+ }
+ fn name(&self) -> &str {
+ "cast_to_i64"
+ }
+ fn signature(&self) -> &Signature {
+ &self.signature
+ }
+ fn return_type(&self, _args: &[DataType]) -> Result<DataType> {
+ Ok(DataType::Int64)
+ }
+ // Wrap with Expr::Cast() to Int64
+ fn simplify(
+ &self,
+ mut args: Vec<Expr>,
+ info: &dyn SimplifyInfo,
+ ) -> Result<ExprSimplifyResult> {
+ // Note that Expr::cast_to requires an ExprSchema but simplify gets a
+ // SimplifyInfo so we have to replicate some of the casting logic here.
+ let source_type = info.get_data_type(&args[0])?;
+ if source_type == DataType::Int64 {
+ Ok(ExprSimplifyResult::Original(args))
+ } else {
+ // DataFusion should have ensured the function is called with just
a
+ // single argument
+ assert_eq!(args.len(), 1);
+ let e = args.pop().unwrap();
+ Ok(ExprSimplifyResult::Simplified(Expr::Cast(
+ datafusion_expr::Cast {
+ expr: Box::new(e),
+ data_type: DataType::Int64,
+ },
+ )))
+ }
+ }
+ // Casting should be done in `simplify`, so we just return the first
argument
+ fn invoke(&self, args: &[ColumnarValue]) -> Result<ColumnarValue> {
+ assert_eq!(args.len(), 1);
+ Ok(args.first().unwrap().clone())
Review Comment:
I think it is an excellent idea -- I did so in fea82cba9
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