julianhyde commented on code in PR #3460:
URL: https://github.com/apache/calcite/pull/3460#discussion_r1369166613
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core/src/main/java/org/apache/calcite/runtime/SqlFunctions.java:
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@@ -603,6 +605,38 @@ public String regexpReplace(String s, String regex, String
replacement,
return Unsafe.regexpReplace(s, pattern, replacement, pos, occurrence);
}
+ /** SQL {@code REGEXP_REPLACE} function with 3 arguments with
+ * {@code \\} based indexing for capturing groups.
+ */
+ public String regexpReplaceNonDollarIndexed(String s, String regex,
+ String replacement) {
+ // Preprocessing to convert double-backslash based indexing for capturing
+ // groups into $ based indices recognized by java regex.
+
+ // Explicitly escaping any $ symbols coming from input
+ // to ignore them from being considered as capturing group index.
+ String indexedReplacement = replacement.replace("\\\\", "\\")
+ .replace("$", "\\$");
+
+ // Check each occurrence of escaped chars, convert \<n> integers into
+ // $<n> indices, keep \\ and \$, throw an error for any other invalid
escapes.
+ int lastOccIdx = 0;
+ while (lastOccIdx != -1) {
Review Comment:
The code to convert $-format to `\`-format can be a static utility method.
That utility method can be tested directly in `SqlFunctionsTest`.
You should add a (new) cache in `SqlRegexFunction`. Its type will be a
`LoadingCache<String, String>`. Don't worry that most instances of
`SqlRegexFunction` won't use this cache. The overhead of creating the cache is
small.
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