paleolimbot commented on code in PR #43234:
URL: https://github.com/apache/arrow/pull/43234#discussion_r1681032624
##########
docs/source/format/CanonicalExtensions.rst:
##########
@@ -283,6 +283,28 @@ UUID
A specific UUID version is not required or guaranteed. This extension
represents
UUIDs as FixedSizeBinary(16) with big-endian notation and does not
interpret the bytes in any way.
+8-bit Boolean
+====
+
+Bool8 represents a boolean value using 1 byte (8 bits) to store each value
instead of only 1 bit as in
+the native Arrow Boolean type. Although less compact that the native
representation, Bool8 may have
+better zero-copy compatibility with various systems that also store booleans
using 1 byte.
+
+* Extension name: ``arrow.bool8``.
+
+* The storage type of this extension is ``Int8`` where:
+
+ * **false** is denoted by the value ``0``.
+ * **true** can be specified using any non-zero value.
Review Comment:
I believe bitpacking is another place where it's helpful to have only 0s and
1s (so that you can blindly bitshift the bytes).
> Producers SHOULD produce 0 or 1 values. Consumers MUST treat any non-zero
value as true and 0 as false.
I like this language! The point of this extension (I think) is to unlock
zero-copy for producers of systems that already use int8s for booleans. Unless
the MUST (0 or 1) is ubiquitous in existing implementations, we would force a
loop along the data on export (to check) or a copy (if any values were not zero
or one). (I think we're all on the same page about this!)
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