[GitHub] [spark] cloud-fan commented on a change in pull request #32477: [SPARK-35348][SQL] Support the utils for escapse the regex for ANSI SQL: SIMILAR TO … ESCAPE syntax

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cloud-fan commented on a change in pull request #32477:
URL: https://github.com/apache/spark/pull/32477#discussion_r631990533



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/StringUtils.scala
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@@ -66,6 +67,52 @@ object StringUtils extends Logging {
     "(?s)" + out.result() // (?s) enables dotall mode, causing "." to match new lines
   }
 
+  /**
+   * Validate and convert SQL 'similar to' pattern to a Java regular expression.
+   *
+   * This function is similar to escapeLikeRegex, but there are some differences as follows:
+   * 1. If the escape character precedes the meta character for SIMILAR TO, the meta character
+   *    should convert to quote literal.
+   * 2. If '\' is not escape character, need convert to quote literal.
+   * 3. '.', '^' and '$' is not a meta character for SIMILAR TO,
+   *    so we need convert it to quote literal.
+   * 4. Avoid convert the characters of Java regular expression to quote literal.
+   * @param pattern the SQL pattern to convert
+   * @param escapeChar the escape character.
+   * @return the equivalent Java regular expression of the pattern for SIMILAR TO
+   */
+  def escapeSimilarRegex(pattern: String, escapeChar: Char): String = {

Review comment:
       Is it possible to share some code with `escapeLikeRegex`? It seems like the only difference is, let's say `escapeLikeRegex` produces `^the_regex`, and `escapeSimilarRegex` should produce `^the_regex$`




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