etseidl commented on code in PR #12978:
URL: https://github.com/apache/datafusion/pull/12978#discussion_r1880659932
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datafusion/core/src/physical_optimizer/pruning.rs:
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@@ -3443,6 +3583,425 @@ mod tests {
);
}
+ #[test]
+ fn test_increment_utf8() {
+ // Basic ASCII
+ assert_eq!(increment_utf8("abc").unwrap(), "abd");
+ assert_eq!(increment_utf8("abz").unwrap(), "ab{");
+
+ // Test around ASCII 127 (DEL)
+ assert_eq!(increment_utf8("~").unwrap(), "\u{7f}"); // 126 -> 127
+ assert_eq!(increment_utf8("\u{7f}").unwrap(), "\u{80}"); // 127 -> 128
+
+ // Test 2-byte UTF-8 sequences
+ assert_eq!(increment_utf8("ß").unwrap(), "à"); // U+00DF -> U+00E0
+
+ // Test 3-byte UTF-8 sequences
+ assert_eq!(increment_utf8("℣").unwrap(), "ℤ"); // U+2123 -> U+2124
+
+ // Test at UTF-8 boundaries
+ assert_eq!(increment_utf8("\u{7FF}").unwrap(), "\u{800}"); // 2-byte
to 3-byte boundary
+ assert_eq!(increment_utf8("\u{FFFF}").unwrap(), "\u{10000}"); //
3-byte to 4-byte boundary
+
+ // Test that if we can't increment we return None
+ assert!(increment_utf8("").is_none());
+ assert!(increment_utf8("\u{10FFFF}").is_none()); // U+10FFFF is the
max code point
+
+ // Test that if we can't increment the last character we do the
previous one and truncate
+ assert_eq!(increment_utf8("a\u{10FFFF}").unwrap(), "b");
+
+ // Test surrogate pair range (0xD800..=0xDFFF)
+ assert_eq!(increment_utf8("a\u{D7FF}").unwrap(), "b");
+ assert!(increment_utf8("\u{D7FF}").is_none());
Review Comment:
This is an interesting case. While trying to patch up parquet-rs, I found
that a byte-byte-byte approach will actually wind up incrementing `U+D7FF` to
`U+E000` (which is private use, but still a valid character).
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