viktorluc-db commented on code in PR #47771:
URL: https://github.com/apache/spark/pull/47771#discussion_r1739767821
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common/unsafe/src/main/java/org/apache/spark/sql/catalyst/util/CollationAwareUTF8String.java:
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@@ -550,6 +549,152 @@ public static UTF8String toTitleCase(final UTF8String
target, final int collatio
BreakIterator.getWordInstance(locale)));
}
+ /**
+ * This 'HashMap' is introduced as a performance speedup. Since title-casing
a codepoint can
+ * result in more than a single codepoint, for correctness, we would use
+ * 'UCharacter.toTitleCase(String)' which returns a 'String'. If we use
+ * 'UCharacter.toTitleCase(int)' (the version of the same function which
converts a single
+ * codepoint to its title-case codepoint), it would be faster than the
previously mentioned
+ * version, but the problem here is that we don't handle when title-casing a
codepoint yields more
+ * than 1 codepoint. Since there are only 48 codepoints that are mapped to
more than 1 codepoint
+ * when title-cased, they are precalculated here, so that the faster
function for title-casing
+ * could be used in combination with this 'HashMap' in the method
'appendCodepointToTitleCase'.
+ */
+ private static final HashMap<Integer, String>
codepointOneToManyTitleCaseLookupTable =
+ new HashMap<>(){{
+ StringBuilder sb = new StringBuilder();
+ for (int i = Character.MIN_CODE_POINT; i <= Character.MAX_CODE_POINT; ++i)
{
+ sb.appendCodePoint(i);
+ String titleCase = UCharacter.toTitleCase(sb.toString(), null);
+ if (titleCase.codePointCount(0, titleCase.length()) > 1) {
+ put(i, titleCase);
+ }
+ sb.setLength(0);
+ }
+ }};
+
+ /**
+ * Title-casing a string using ICU case mappings. 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) {
Review Comment:
I agree.
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