felipecrv commented on code in PR #43234:
URL: https://github.com/apache/arrow/pull/43234#discussion_r1681161336
##########
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:
When producing a `Bool8` array, integer values of any width MUST be
normalized into the `[0, 1]` range of `int8` values. `0` maps to `0` and every
other non-zero value maps to `1` (this is a very simple CPU operation).
A kernel consuming a `Bool8` array can assume values are in the `[0, 1]`
range, but to be robust against less strictly-conformant producers, it's
preferable to use `array[i] != 0` or `array[i] == 0` when converting the `int8`
value to `bool` instead of comparing against `1`.
Compute kernels that would benefit from the `[0, 1]` assumption can rely on
it and document that non-strictly conforming `Bool8` input may lead to bogus
output.
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