srowen commented on a change in pull request #26027: [SPARK-24540][SQL] Support
for multiple character delimiter in Spark CSV read
URL: https://github.com/apache/spark/pull/26027#discussion_r332032489
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/csv/CSVExprUtils.scala
##########
@@ -79,4 +82,48 @@ object CSVExprUtils {
throw new IllegalArgumentException(s"Delimiter cannot be more than one
character: $str")
}
}
+
+ /**
+ * Helper method that converts string representation of a character sequence
to actual
+ * delimiter characters. The input is processed in "chunks", and each chunk
is converted
+ * by calling [[CSVExprUtils.toChar()]]. A chunk is either:
+ * <ul>
+ * <li>a backslash followed by another character</li>
+ * <li>a non-backslash character by itself</li>
+ * </ul>
+ * , in that order of precedence. The result of the converting all chunks is
returned as
+ * a [[String]].
+ *
+ * <br/><br/>Examples:
+ * <ul><li>`\t` will result in a single tab character as the separator (same
as before)
+ * </li><li>`|||` will result in a sequence of three pipe characters as the
separator
+ * </li><li>`\\` will result in a single backslash as the separator (same as
before)
+ * </li><li>`\.` will result in an error (since a dot is not a character
that needs escaped)
+ * </li><li>`\\.` will result in a backslash, then dot, as the separator
character sequence
+ * </li><li>`.\t.` will result in a dot, then tab, then dot as the separator
character sequence
+ * </li>
+ * </ul>
+ *
+ * @param str the string representing the sequence of separator characters
+ * @return a [[String]] representing the multi-character delimiter
+ * @throws IllegalArgumentException if any of the individual input chunks
are illegal
+ */
+ def toDelimiterStr(str: String): String = {
+ var idx = 0
+
+ val delimiter = ListBuffer.empty[Char]
+
+ while (idx < str.length()) {
+ // if the current character is a backslash, check it plus the next char
+ // in order to use existing escape logic
+ val readAhead = if (str(idx) == '\\') 2 else 1
Review comment:
I was going to say, it's not worth it, because `toChar` doesn't support
general unicode syntax either, and it's Java/Scala syntax anyway, and `\0` is
the more natural way to say it. But `toChar` doesn't support `\0`. We could at
least special-case that in `toChar` as well instead, to support NULL as a
delimiter, rather than expand the logic here.
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