viirya commented on code in PR #3534:
URL: https://github.com/apache/arrow-rs/pull/3534#discussion_r1071516782
##########
arrow-schema/src/datatype.rs:
##########
@@ -242,6 +242,19 @@ pub enum DataType {
/// child fields may be respectively "entries", "key", and "value", but
this is
/// not enforced.
Map(Box<Field>, bool),
+
+ /// A run-end encoding (REE) array is a variation of run-length encoding
(RLE). These
+ /// encodings are well-suited for representing data containing sequences
of the
+ /// same value, called runs. Each run is represented as a value and an
integer giving
+ /// the index in the array where the run ends.
+ ///
+ /// A run-end encoded array has no buffers by itself, but has two child
arrays. The
+ /// first child array, called the run ends array, holds either 16, 32, or
64-bit
+ /// signed integers. The actual values of each run are held in the second
child array.
+ ///
+ /// These child arrays are prescribed the standard names of "run_ends" and
"values"
+ /// respectively.
+ RunEndEncodedType(Box<Field>, Box<Field>),
Review Comment:
Run-end encode type has child arrays with no buffers. Similar to `Struct`, I
treat it as two `Field`s. I think it makes sense for `values` to be `Field` as
it is possibly to be a dictionary. I remember it is necessary it to be a field
for IPC serialization on dictionary. `run-ends` is just primitive one, it could
be just `DataType`, I think.
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