From 0578ff9681edbaab4ae68f67272dc3d4d890d53b Mon Sep 17 00:00:00 2001
From: Sean Owen <sowen@cloudera.com>
Date: Wed, 10 Aug 2016 10:14:43 +0100
Subject: [PATCH] [SPARK-16324][SQL] regexp_extract should doc that it returns
empty string when match fails
## What changes were proposed in this pull request?
Doc that regexp_extract returns empty string when regex or group does not match
## How was this patch tested?
Jenkins test, with a few new test cases
Author: Sean Owen <sowen@cloudera.com>
Closes #14525 from srowen/SPARK-16324.
---
python/pyspark/sql/functions.py | 6 +++++-
.../src/main/scala/org/apache/spark/sql/functions.scala | 3 ++-
.../scala/org/apache/spark/sql/StringFunctionsSuite.scala | 4 ++++
3 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/python/pyspark/sql/functions.py b/python/pyspark/sql/functions.py
index 8a01805ec8..4ea83e24bb 100644
--- a/python/pyspark/sql/functions.py
+++ b/python/pyspark/sql/functions.py
@@ -1440,11 +1440,15 @@ def split(str, pattern):
@ignore_unicode_prefix
@since(1.5)
def regexp_extract(str, pattern, idx):
- """Extract a specific(idx) group identified by a java regex, from the specified string column.
+ """Extract a specific group matched by a Java regex, from the specified string column.
+ If the regex did not match, or the specified group did not match, an empty string is returned.
>>> df = spark.createDataFrame([('100-200',)], ['str'])
>>> df.select(regexp_extract('str', '(\d+)-(\d+)', 1).alias('d')).collect()
[Row(d=u'100')]
+ >>> df = spark.createDataFrame([('foo',)], ['str'])
+ >>> df.select(regexp_extract('str', '(\d+)', 1).alias('d')).collect()
+ [Row(d=u'')]
>>> df = spark.createDataFrame([('aaaac',)], ['str'])
>>> df.select(regexp_extract('str', '(a+)(b)?(c)', 2).alias('d')).collect()
[Row(d=u'')]
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/functions.scala b/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
index 81f6ed75e6..18e736ab69 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
@@ -2175,7 +2175,8 @@ object functions {
def ltrim(e: Column): Column = withExpr {StringTrimLeft(e.expr) }
/**
- * Extract a specific(idx) group identified by a java regex, from the specified string column.
+ * Extract a specific group matched by a Java regex, from the specified string column.
+ * If the regex did not match, or the specified group did not match, an empty string is returned.
*
* @group string_funcs
* @since 1.5.0
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/StringFunctionsSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/StringFunctionsSuite.scala
index 64b4718538..1cc77464b9 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/StringFunctionsSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/StringFunctionsSuite.scala
@@ -96,6 +96,10 @@ class StringFunctionsSuite extends QueryTest with SharedSQLContext {
test("non-matching optional group") {
val df = Seq(Tuple1("aaaac")).toDF("s")
+ checkAnswer(
+ df.select(regexp_extract($"s", "(foo)", 1)),
+ Row("")
+ )
checkAnswer(
df.select(regexp_extract($"s", "(a+)(b)?(c)", 2)),
Row("")
--
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