Re: [PR] fix: bin coarse date_bin timestamps in i128 and restore ordering [datafusion]

["mhilton (via GitHub)" <gi...@apache.org>]

mhilton commented on code in PR #25815:
URL: https://github.com/apache/datafusion/pull/25815#discussion_r4153776681


##########
datafusion/functions/src/datetime/date_bin.rs:
##########
@@ -475,11 +562,31 @@ fn date_bin_timestamp_value<T: ArrowTimestampType>(
     value: i64,
     origin: i64,
     stride: i64,
-    stride_fn: BinFunction,
+    stride_fn: BinFunctions,
 ) -> Option<i64> {
     let scale = timestamp_scale::<T>();
-    scale_and_bin_to_nanos(value, scale, origin, stride, stride_fn)
-        .map(|binned| binned / scale)
+    match scale_and_bin_to_nanos(value, scale, origin, stride, stride_fn.narrow) {
+        Some(binned) => Some(binned / scale),
+        None => {
+            date_bin_timestamp_value_wide(value, scale, origin, stride, stride_fn.wide)
+        }
+    }
+}
+
+// Slow path for values whose i64 nanosecond computation overflows. Binning in
+// i128 means that only a result outside the source type's range becomes NULL,
+// instead of any value outside the i64 nanosecond range.

Review Comment:
   I wonder if it would be better to preserve the ordering here by converting to `i64::MIN` rather than `NULL`. Although that might be a technically wrong result I'm not sure that it's any less helpful than a `NULL`. We'd have to document that this is what `date_bin` does, but seeing as those dates are so far in the past I don't think it will cause a practical issue. Even when using nanoseconds we are discussing a time bin at some point in 1677. 



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