[GitHub] [arrow-datafusion] tustvold commented on a diff in pull request #5517: fix: cast literal to timestamp

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

tustvold commented on code in PR #5517:
URL: https://github.com/apache/arrow-datafusion/pull/5517#discussion_r1131237011


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datafusion/optimizer/src/unwrap_cast_in_comparison.rs:
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@@ -428,6 +452,36 @@ fn try_cast_literal_to_type(
     }
 }
 
+/// Cast a timestamp value from one unit to another
+fn cast_between_timestamp(from: DataType, to: DataType, value: i128) -> Option<i64> {

Review Comment:
   I think this has problematic overflow behaviour, I wonder if we can determine the scale factor and multiply or divide by this instead? This is what arrow-cast does - https://github.com/apache/arrow-rs/blob/master/arrow-cast/src/cast.rs#L1671
   
   Currently I think converting `i64::MAX / 1_000` to milliseconds from seconds will silently overflow, when in reality it shouldn't



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