[Spark] Fix the inconsistencies in min/max Delta Log stats for special characters #3430
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Which Delta project/connector is this regarding?
Description
When truncating maxValue strings longer than 32 characters for statistics, it's crucial to ensure the final truncated string is lexicographically greater than or equal to the input string in UTF-8 encoded bytes.
Previously, we used the Unicode replacement character as the tieBreaker, comparing it directly against one byte of the next character at a time. This approach was insufficient because the tieBreaker could incorrectly win against the non-first bytes of other characters (e.g., � < 🌼 but � > the second byte of 🌼). We now compare one UTF-8 character (i.e. upto 2 Scala UTF-16 characters depending on surrogates) at a time to address this issue.
We also start using U+10FFFD i.e. character with highest Unicode code point as the tie-breaker now.
How was this patch tested?
UTs
Does this PR introduce any user-facing changes?
No