ankitsultana commented on code in PR #12392:
URL: https://github.com/apache/pinot/pull/12392#discussion_r1501214269
##########
pinot-common/src/main/java/org/apache/pinot/common/function/scalar/StringFunctions.java:
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@@ -570,6 +572,107 @@ public static String[] split(String input, String
delimiter, int limit) {
return StringUtils.splitByWholeSeparator(input, delimiter, limit);
}
+ /**
+ * @param input an input string for prefix strings generations.
+ * @param maxlength the max length of the prefix strings for the string.
+ * @return generate an array of prefix strings of the string that are
shorter than the specified length.
+ */
+ @ScalarFunction
+ public static String[] prefixes(String input, int maxlength) {
+ ObjectSet<String> prefixSet = new ObjectLinkedOpenHashSet<>();
+ for (int prefixLength = 1; prefixLength <= maxlength && prefixLength <=
input.length(); prefixLength++) {
+ prefixSet.add(input.substring(0, prefixLength));
+ }
+ return prefixSet.toArray(new String[0]);
+ }
+
+ /**
+ * @param input an input string for prefix strings generations.
+ * @param maxlength the max length of the prefix strings for the string.
+ * @param regexChar the character for regex matching to be added to prefix
strings generated. e.g. '^'
+ * @return generate an array of prefix matchers of the string that are
shorter than the specified length.
+ */
+ @ScalarFunction
+ public static String[] prefixMatchers(String input, int maxlength, String
regexChar) {
Review Comment:
sorry, I didn't understand what `regexChar` is for. We are simply prepending
the character to the strings right?
Can we then name this method: `uniquePrefixesWithPrefix(String input, int
maxLength, String prefix)` or similar?
My point being that this function itself is not tied to the fact that we are
going to use this for regex matching purposes.
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