emkornfield commented on code in PR #50916:
URL: https://github.com/apache/arrow/pull/50916#discussion_r3819117910
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cpp/src/parquet/statistics.cc:
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@@ -463,6 +463,56 @@ struct RebindLogical<Float16LogicalType> {
using c_type = DType::c_type;
};
+// Tag type for FLBA(12) timestamps.
+struct Flba12TimestampType {};
+
+// Max / min representable signed 96-bit two's-complement, little-endian.
+constexpr uint8_t kFlba12SignedMax[12] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F};
+constexpr uint8_t kFlba12SignedMin[12] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x80};
+
+template <>
+struct CompareHelper<Flba12TimestampType, /*is_signed=*/true> {
+ using T = FLBA;
+
+ // Seed for the running minimum is the maximum value; for the maximum, the
minimum
+ // value.
+ static T DefaultMin() { return T{kFlba12SignedMax}; }
+ static T DefaultMax() { return T{kFlba12SignedMin}; }
+
+ static T Coalesce(T val, T fallback) { return val.ptr == nullptr ? fallback
: val; }
+
+ // Signed little-endian comparison.
+ // Differing signs: negative (MSB >= 0x80) is smaller.
+ // Same sign: unsigned scan and comparison.
+ static inline bool Compare(int /*type_length*/, const T& a, const T& b) {
+ const bool a_neg = (a.ptr[11] & 0x80) != 0;
+ const bool b_neg = (b.ptr[11] & 0x80) != 0;
+ if (a_neg != b_neg) return a_neg;
+ for (int i = 11; i >= 0; --i) if (a.ptr[i] != b.ptr[i]) return a.ptr[i] <
b.ptr[i];
Review Comment:
do the two step integer comparison?
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