deemoliu commented on code in PR #12392:
URL: https://github.com/apache/pinot/pull/12392#discussion_r1486774035
##########
pinot-common/src/main/java/org/apache/pinot/common/function/scalar/StringFunctions.java:
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@@ -570,6 +572,81 @@ 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 length 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 strings of the string that are
shorter than the specified length.
+ */
+ @ScalarFunction
+ public static String[] prefix(String input, int length, String regexChar) {
+ ObjectSet<String> prefixSet = new ObjectLinkedOpenHashSet<>();
+ for (int prefixLength = 1; prefixLength <= length && prefixLength <=
input.length(); prefixLength++) {
+ if (regexChar != null) {
+ prefixSet.add(regexChar + input.substring(0, prefixLength));
+ } else {
+ prefixSet.add(input.substring(0, prefixLength));
+ }
+ }
+ return prefixSet.toArray(new String[0]);
+ }
+
+ /**
+ * @param input an input string for suffix strings generations.
+ * @param length the max length of the suffix strings for the string.
+ * @param regexChar the character for regex matching to be added to suffix
strings generated. e.g. '$'
+ * @return generate an array of suffix strings of the string that are
shorter than the specified length.
+ */
+ @ScalarFunction
+ public static String[] suffix(String input, int length, String regexChar) {
+ ObjectSet<String> suffixSet = new ObjectLinkedOpenHashSet<>();
+ for (int suffixLength = 1; suffixLength <= length && suffixLength <=
input.length(); suffixLength++) {
+ if (regexChar != null) {
+ suffixSet.add(input.substring(input.length() - suffixLength) +
regexChar);
+ } else {
+ suffixSet.add(input.substring(input.length() - suffixLength));
+ }
+ }
+ return suffixSet.toArray(new String[0]);
+ }
+
+ /**
+ * @param input an input string for ngram generations.
+ * @param length the max length of the ngram for the string.
+ * @return generate an array of ngram of the string that length are exactly
matching the specified length.
+ */
+ @ScalarFunction
+ public static String[] ngram(String input, int length) {
Review Comment:
thanks for the review, this sounds good to me. i will rename it
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