alamb commented on code in PR #2636:
URL: https://github.com/apache/arrow-rs/pull/2636#discussion_r961692236
##########
arrow/src/array/cast.rs:
##########
@@ -53,6 +260,90 @@ where
.expect("Unable to downcast to primitive array")
}
+/// Downcast an [`Array`] to a [`DictionaryArray`] based on its [`DataType`],
accepts
+/// a number of subsequent patterns to match the data type
+///
+/// ```
+/// # use arrow::downcast_dict_array;
+/// # use arrow::array::Array;
+/// # use arrow::datatypes::DataType;
+/// # use arrow::array::as_string_array;
+///
+/// fn print_keys(array: &dyn Array) {
+/// downcast_dict_array!(
+/// array => {
+/// for v in array.keys() {
+/// println!("{:?}", v);
+/// }
+/// }
+/// t => println!("Unsupported datatype {}", t)
Review Comment:
I think it would be good to extend this example to show the String array as
well -- not only to document how to support other types, but also because the
StringArray is so common
##########
arrow/src/array/cast.rs:
##########
@@ -20,6 +20,213 @@
use crate::array::*;
use crate::datatypes::*;
+/// Downcast an [`Array`] to a [`PrimitiveArray`] based on its [`DataType`],
accepts
+/// a number of subsequent patterns to match the data type
+///
+/// ```
+/// # use arrow::downcast_primitive_array;
+/// # use arrow::array::Array;
+/// # use arrow::datatypes::DataType;
+/// # use arrow::array::as_string_array;
+///
+/// fn print_primitive(array: &dyn Array) {
+/// downcast_primitive_array!(
Review Comment:
❤️ that certainly will make the macros in code such as
https://github.com/apache/arrow-datafusion/blob/master/datafusion/physical-expr/src/expressions/binary.rs
easier to deal with ❤️
##########
arrow/src/compute/kernels/filter.rs:
##########
@@ -358,92 +336,12 @@ fn filter_array(values: &dyn Array, predicate:
&FilterPredicate) -> Result<Array
IterationStrategy::None => Ok(new_empty_array(values.data_type())),
IterationStrategy::All => Ok(make_array(values.data().slice(0,
predicate.count))),
// actually filter
- _ => match values.data_type() {
+ _ => downcast_primitive_array! {
+ values => Ok(Arc::new(filter_primitive(values, predicate))),
Review Comment:
👨🍳 👌
Very nice
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