pitrou commented on a change in pull request #6213:
URL: https://github.com/apache/arrow/pull/6213#discussion_r442423611
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File path: cpp/src/arrow/type.cc
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@@ -501,20 +501,35 @@ Status Decimal128Type::Make(int32_t precision, int32_t
scale,
// ----------------------------------------------------------------------
// Dictionary-encoded type
+Status DictionaryType::ValidateParameters(const DataType& index_type,
+ const DataType& value_type) {
+ const bool index_type_ok = is_integer(index_type.id()) &&
+ checked_cast<const
IntegerType&>(index_type).is_signed();
+ if (!index_type_ok) {
+ return Status::TypeError("Dictionary index type should be signed integer,
got ",
Review comment:
I'm not sure about the history (@wesm could tell more), but it's
specified here:
https://arrow.apache.org/docs/format/Columnar.html#dictionary-encoded-layout
> When a field is dictionary encoded, the values are represented by an array
of signed integers representing the index of the value in the dictionary.
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