[GitHub] [spark] cloud-fan commented on a change in pull request #29891: [SPARK-30796][SQL] Add parameter position for REGEXP_REPLACE

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cloud-fan commented on a change in pull request #29891:
URL: https://github.com/apache/spark/pull/29891#discussion_r504720050



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/regexpExpressions.scala
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@@ -318,16 +320,46 @@ case class StringSplit(str: Expression, regex: Expression, limit: Expression)
  */
 // scalastyle:off line.size.limit
 @ExpressionDescription(
-  usage = "_FUNC_(str, regexp, rep) - Replaces all substrings of `str` that match `regexp` with `rep`.",
+  usage = "_FUNC_(str, regexp, rep[, position]) - Replaces all substrings of `str` that match `regexp` with `rep`.",
+  arguments = """
+    Arguments:
+      * str - a string expression to search for a regular expression pattern match.
+      * regexp - a string representing a regular expression. The regex string should be a
+          Java regular expression.
+
+          Since Spark 2.0, string literals (including regex patterns) are unescaped in our SQL
+          parser. For example, to match "\abc", a regular expression for `regexp` can be
+          "^\\abc$".
+
+          There is a SQL config 'spark.sql.parser.escapedStringLiterals' that can be used to
+          fallback to the Spark 1.6 behavior regarding string literal parsing. For example,
+          if the config is enabled, the `regexp` that can match "\abc" is "^\abc$".
+      * rep - a string expression to replace matched substrings.
+      * position - a positive integer expression that indicates the position within `str` to begin searching.

Review comment:
       `a positive integer literal`




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