pitrou commented on code in PR #54959:
URL: https://github.com/apache/arrow/pull/54959#discussion_r4380168859
##########
docs/source/format/Integration.rst:
##########
@@ -198,14 +198,19 @@ present if there are dictionary type fields in the schema.
"dictionary": {
"id": /* integer */,
"indexType": /* Type */,
- "isOrdered": /* boolean */
+ "isOrdered": /* boolean */,
+ "metadata" : /* Metadata */
Review Comment:
Perhaps make this `valueMetadata` to make it clear this metadata applies to
the dictionary values (as opposed to the `metadata` in the outer JSON object)?
##########
docs/source/format/Columnar.rst:
##########
@@ -1677,7 +1680,10 @@ Custom Application Metadata
We provide a ``custom_metadata`` field at three levels to provide a
mechanism for developers to pass application-specific metadata in
Arrow protocol messages. This includes ``Field``, ``Schema``, and
-``Message``.
+``Message``. The ``DictionaryEncoding`` of a dictionary-encoded ``Field``
Review Comment:
I'm not sure we need detail the specifics of
`DictionaryEncoding.custom_metadata` here, since they are described later in
the document.
##########
docs/source/format/Columnar.rst:
##########
@@ -1677,7 +1680,10 @@ Custom Application Metadata
We provide a ``custom_metadata`` field at three levels to provide a
Review Comment:
Well, four, now?
##########
docs/source/format/Columnar.rst:
##########
@@ -1732,6 +1738,55 @@ extension types:
metadata indicating the market trading calendar the data corresponds
to
+.. _format_metadata_extension_types_dictionary:
+
+Dictionary-encoded extension types
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+A dictionary-encoded field is serialized as a single ``Field`` whose data
Review Comment:
It would be nice to trim this down IMHO, I'm not sure Dictionary-encoded
extension types deserve five full paragraphs of explanations (looks
AI-generated?).
##########
docs/source/format/CDataInterface.rst:
##########
@@ -537,6 +537,14 @@ For dictionary-encoded arrays, the
:c:member:`ArrowSchema.format` string
encodes the *index* type. The dictionary *value* type can be read
from the :c:member:`ArrowSchema.dictionary` structure.
+The :c:member:`ArrowSchema.metadata` of the :c:member:`ArrowSchema.dictionary`
Review Comment:
I'm not sure this additional paragraph is extremely useful, given that this
is consistent with how other structure members work.
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