uros-db commented on code in PR #47771:
URL: https://github.com/apache/spark/pull/47771#discussion_r1719604498
##########
common/unsafe/src/main/java/org/apache/spark/sql/catalyst/util/CollationAwareUTF8String.java:
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@@ -1267,6 +1272,129 @@ public static UTF8String[] icuSplitSQL(final UTF8String
string, final UTF8String
return strings.toArray(new UTF8String[0]);
}
+ /**
+ * Title casing a string according to a new behaviour. Iterates over the
string and title cases
+ * the first character in each word, and lowercases every other character.
Handles lowercasing
+ * capital Greek letter sigma ('Σ') separately, taking into account if it
should be a small final
+ * Greek sigma ('ς') or small non-final Greek sigma ('σ'). Words are
separated by ASCII
+ * space(\u0020).
+ *
+ * @param target UTF8String to be title cased
+ * @return title cased target
+ */
+ public static UTF8String toTitleCaseICU(UTF8String target) {
+
+ // In the previous implementation, when UTF8String.toLowerCase() was
called, it implicitly did
+ // UTF8String validation(replacing invalid UTF-8 byte sequences with
Unicode replacement
+ // character U+FFFD), but now we have to do the validation manually.
+ target = target.makeValid();
+
+ // Building the title cased target with 'sb'.
+ StringBuilder sb = new StringBuilder();
+ // 'newWord' is true if the current character is the beginning of a word,
false otherwise.
+ boolean newWord = true;
+ // We are maintaining if the current character is preceded by a cased
letter.
+ // This is used when lowercasing capital Greek letter sigma ('Σ'), to
figure out if it should be
+ // lowercased into σ or ς.
+ boolean precededByCasedLetter = false;
+
+ // 'offset' is a byte offset in target's byte array pointing to the
beginning of the character
+ // that we need to process next.
+ int offset = 0;
+ int len = target.numBytes();
+
+ while(offset < len) {
+ // We will actually call 'codePointFrom()' 2 times for each character in
the worst case (once
+ // here, and once in 'followedByCasedLetter'). Example of a string where
we call it 2 times
+ // for almost every character is 'ΣΣΣΣΣ' (a string consisting only of
Greek capital sigma)
+ // and 'Σ`````' (a string consisting of a Greek capital sigma, followed
by case-ignorable
+ // characters).
+ int codepoint = target.codePointFrom(offset);
+ // Appending the correctly cased character onto 'sb'.
+ appendTitleCasedCodepoint(sb, codepoint, newWord, precededByCasedLetter,
target, offset);
+ // Updating 'newWord', 'precededByCasedLetter' and 'offset' to be ready
for the next character
+ // that we will process.
+ newWord = (codepoint == ASCII_SPACE_CODEPOINT);
+ if(!UCharacter.hasBinaryProperty(codepoint, UProperty.CASE_IGNORABLE)) {
+ precededByCasedLetter = UCharacter.hasBinaryProperty(codepoint,
UProperty.CASED);
+ }
+ offset += UTF8String.numBytesForFirstByte(target.getByte(offset));
+ }
+ return UTF8String.fromString(sb.toString());
+ }
+
+ private static void appendTitleCasedCodepoint(
+ StringBuilder sb,
+ int codepoint,
+ boolean isAfterAsciiSpace,
+ boolean precededByCasedLetter,
+ UTF8String target,
+ int offset) {
+ if(isAfterAsciiSpace) {
+ // Titlecasing a character if it is in the beginning of a new word.
+ sb.append(codepointToTitleString(codepoint));
+ return;
+ }
+ if(codepoint == CAPITAL_SIGMA) {
+ // Handling capital Greek letter sigma ('Σ').
+ appendLowerCasedGreekCapitalSigma(sb, precededByCasedLetter, target,
offset);
+ return;
+ }
+ // If it's not the beginning of a word, or a capital Greek letter sigma
('Σ'), we lowercase the
+ // character.
+ sb.append(
+ toLowerCase(UTF8String.fromString(new
String(Character.toChars(codepoint)))).toString());
+ }
Review Comment:
if I understand correctly, in any branch of this code, we will end up doing
`UTF8String.fromString(new String`
O(2n) string allocations per 1 string for UTF8_BINARY is quite a regression,
let's try to avoid it
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