panbingkun commented on code in PR #41169:
URL: https://github.com/apache/spark/pull/41169#discussion_r1196188986
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala:
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@@ -2134,30 +2134,145 @@ case class OctetLength(child: Expression)
* A function that return the Levenshtein distance between the two given
strings.
*/
@ExpressionDescription(
- usage = "_FUNC_(str1, str2) - Returns the Levenshtein distance between the
two given strings.",
+ usage = """
+ _FUNC_(str1, str2) - Returns the Levenshtein distance between the two
given strings.
+ If threshold is set and distance more than it, return -1.""",
examples = """
Examples:
> SELECT _FUNC_('kitten', 'sitting');
3
+ > SELECT _FUNC_('kitten', 'sitting', 2);
+ -1
""",
since = "1.5.0",
group = "string_funcs")
-case class Levenshtein(left: Expression, right: Expression) extends
BinaryExpression
- with ImplicitCastInputTypes with NullIntolerant {
+case class Levenshtein(
+ left: Expression,
+ right: Expression,
+ threshold: Option[Expression] = None)
+ extends Expression
Review Comment:
1.If we extend TernaryExpression, then threshold expression will not be
optional, just like the implementation logic of `Substring`. When the threshold
value is not passed in, we will set a default value for it: Integer.MAX_ Value,
the levenshteinDistance algorithm in UTF8String, only one reserved -
levenshteinDistance(UTF8String other, int threshold)
But it seems that `org.apache.commons.text.similarity.LevenshteinDistance`
did not do this, it retained two - `limitedCompare` & `unlimitedCompare`.
https://github.com/apache/commons-text/blob/master/src/main/java/org/apache/commons/text/similarity/LevenshteinDistance.java
Are we really going to do this?
2.Additionally, I am referring to the implementation of
[`ArrayJoin`](https://github.com/apache/spark/blob/d44e073f0cdaf16028a4854e79db200a4e39a6fe/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala#L1824-L1854)
in spark
3.UT referring to
https://github.com/apache/commons-text/blob/master/src/test/java/org/apache/commons/text/similarity/LevenshteinDistanceTest.java#L76-L138
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