[SPARK-7321][SQL] Add Column expression for conditional statements (when/otherwise)
This builds on https://github.com/apache/spark/pull/5932 and should close https://github.com/apache/spark/pull/5932 as well.
As an example:
```python
df.select(when(df['age'] == 2, 3).otherwise(4).alias("age")).collect()
```
Author: Reynold Xin <rxin@databricks.com>
Author: kaka1992 <kaka_1992@163.com>
Closes #6072 from rxin/when-expr and squashes the following commits:
8f49201 [Reynold Xin] Throw exception if otherwise is applied twice.
0455eda [Reynold Xin] Reset run-tests.
bfb9d9f [Reynold Xin] Updated documentation and test cases.
762f6a5 [Reynold Xin] Merge pull request #5932 from kaka1992/IFCASE
95724c6 [kaka1992] Update
8218d0a [kaka1992] Update
801009e [kaka1992] Update
76d6346 [kaka1992] [SPARK-7321][SQL] Add Column expression for conditional statements (if, case)
(cherry picked from commit 97dee313f2
)
Signed-off-by: Reynold Xin <rxin@databricks.com>
This commit is contained in:
parent
bdd5db9f16
commit
219a9043ef
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@ -32,6 +32,8 @@ Important classes of Spark SQL and DataFrames:
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Aggregation methods, returned by :func:`DataFrame.groupBy`.
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- L{DataFrameNaFunctions}
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Methods for handling missing data (null values).
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- L{DataFrameStatFunctions}
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Methods for statistics functionality.
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- L{functions}
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List of built-in functions available for :class:`DataFrame`.
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- L{types}
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@ -1546,6 +1546,37 @@ class Column(object):
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"""
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return (self >= lowerBound) & (self <= upperBound)
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@ignore_unicode_prefix
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def when(self, condition, value):
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"""Evaluates a list of conditions and returns one of multiple possible result expressions.
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If :func:`Column.otherwise` is not invoked, None is returned for unmatched conditions.
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See :func:`pyspark.sql.functions.when` for example usage.
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:param condition: a boolean :class:`Column` expression.
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:param value: a literal value, or a :class:`Column` expression.
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"""
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sc = SparkContext._active_spark_context
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if not isinstance(condition, Column):
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raise TypeError("condition should be a Column")
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v = value._jc if isinstance(value, Column) else value
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jc = sc._jvm.functions.when(condition._jc, v)
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return Column(jc)
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@ignore_unicode_prefix
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def otherwise(self, value):
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"""Evaluates a list of conditions and returns one of multiple possible result expressions.
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If :func:`Column.otherwise` is not invoked, None is returned for unmatched conditions.
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See :func:`pyspark.sql.functions.when` for example usage.
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:param value: a literal value, or a :class:`Column` expression.
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"""
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v = value._jc if isinstance(value, Column) else value
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jc = self._jc.otherwise(value)
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return Column(jc)
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def __repr__(self):
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return 'Column<%s>' % self._jc.toString().encode('utf8')
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@ -32,13 +32,14 @@ from pyspark.sql.dataframe import Column, _to_java_column, _to_seq
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__all__ = [
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'approxCountDistinct',
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'coalesce',
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'countDistinct',
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'monotonicallyIncreasingId',
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'rand',
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'randn',
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'sparkPartitionId',
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'coalesce',
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'udf']
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'udf',
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'when']
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def _create_function(name, doc=""):
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@ -291,6 +292,27 @@ def struct(*cols):
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return Column(jc)
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def when(condition, value):
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"""Evaluates a list of conditions and returns one of multiple possible result expressions.
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If :func:`Column.otherwise` is not invoked, None is returned for unmatched conditions.
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:param condition: a boolean :class:`Column` expression.
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:param value: a literal value, or a :class:`Column` expression.
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>>> df.select(when(df['age'] == 2, 3).otherwise(4).alias("age")).collect()
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[Row(age=3), Row(age=4)]
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>>> df.select(when(df.age == 2, df.age + 1).alias("age")).collect()
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[Row(age=3), Row(age=None)]
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"""
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sc = SparkContext._active_spark_context
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if not isinstance(condition, Column):
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raise TypeError("condition should be a Column")
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v = value._jc if isinstance(value, Column) else value
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jc = sc._jvm.functions.when(condition._jc, v)
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return Column(jc)
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class UserDefinedFunction(object):
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"""
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User defined function in Python
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@ -327,6 +327,67 @@ class Column(protected[sql] val expr: Expression) extends Logging {
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*/
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def eqNullSafe(other: Any): Column = this <=> other
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/**
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* Evaluates a list of conditions and returns one of multiple possible result expressions.
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* If otherwise is not defined at the end, null is returned for unmatched conditions.
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*
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* {{{
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* // Example: encoding gender string column into integer.
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*
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* // Scala:
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* people.select(when(people("gender") === "male", 0)
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* .when(people("gender") === "female", 1)
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* .otherwise(2))
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*
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* // Java:
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* people.select(when(col("gender").equalTo("male"), 0)
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* .when(col("gender").equalTo("female"), 1)
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* .otherwise(2))
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* }}}
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*
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* @group expr_ops
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*/
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def when(condition: Column, value: Any):Column = this.expr match {
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case CaseWhen(branches: Seq[Expression]) =>
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CaseWhen(branches ++ Seq(lit(condition).expr, lit(value).expr))
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case _ =>
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throw new IllegalArgumentException(
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"when() can only be applied on a Column previously generated by when() function")
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}
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/**
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* Evaluates a list of conditions and returns one of multiple possible result expressions.
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* If otherwise is not defined at the end, null is returned for unmatched conditions.
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*
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* {{{
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* // Example: encoding gender string column into integer.
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*
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* // Scala:
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* people.select(when(people("gender") === "male", 0)
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* .when(people("gender") === "female", 1)
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* .otherwise(2))
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*
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* // Java:
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* people.select(when(col("gender").equalTo("male"), 0)
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* .when(col("gender").equalTo("female"), 1)
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* .otherwise(2))
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* }}}
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*
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* @group expr_ops
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*/
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def otherwise(value: Any):Column = this.expr match {
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case CaseWhen(branches: Seq[Expression]) =>
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if (branches.size % 2 == 0) {
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CaseWhen(branches :+ lit(value).expr)
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} else {
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throw new IllegalArgumentException(
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"otherwise() can only be applied once on a Column previously generated by when()")
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}
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case _ =>
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throw new IllegalArgumentException(
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"otherwise() can only be applied on a Column previously generated by when()")
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}
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/**
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* True if the current column is between the lower bound and upper bound, inclusive.
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*
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@ -419,6 +419,30 @@ object functions {
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*/
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def not(e: Column): Column = !e
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/**
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* Evaluates a list of conditions and returns one of multiple possible result expressions.
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* If otherwise is not defined at the end, null is returned for unmatched conditions.
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*
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* {{{
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* // Example: encoding gender string column into integer.
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*
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* // Scala:
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* people.select(when(people("gender") === "male", 0)
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* .when(people("gender") === "female", 1)
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* .otherwise(2))
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*
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* // Java:
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* people.select(when(col("gender").equalTo("male"), 0)
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* .when(col("gender").equalTo("female"), 1)
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* .otherwise(2))
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* }}}
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*
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* @group normal_funcs
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*/
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def when(condition: Column, value: Any): Column = {
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CaseWhen(Seq(condition.expr, lit(value).expr))
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}
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/**
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* Generate a random column with i.i.d. samples from U[0.0, 1.0].
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*
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@ -255,6 +255,27 @@ class ColumnExpressionSuite extends QueryTest {
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Row(false, true) :: Row(true, false) :: Row(true, true) :: Nil)
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}
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test("SPARK-7321 when conditional statements") {
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val testData = (1 to 3).map(i => (i, i.toString)).toDF("key", "value")
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checkAnswer(
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testData.select(when($"key" === 1, -1).when($"key" === 2, -2).otherwise(0)),
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Seq(Row(-1), Row(-2), Row(0))
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)
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// Without the ending otherwise, return null for unmatched conditions.
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// Also test putting a non-literal value in the expression.
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checkAnswer(
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testData.select(when($"key" === 1, lit(0) - $"key").when($"key" === 2, -2)),
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Seq(Row(-1), Row(-2), Row(null))
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)
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// Test error handling for invalid expressions.
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intercept[IllegalArgumentException] { $"key".when($"key" === 1, -1) }
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intercept[IllegalArgumentException] { $"key".otherwise(-1) }
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intercept[IllegalArgumentException] { when($"key" === 1, -1).otherwise(-1).otherwise(-1) }
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}
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test("sqrt") {
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checkAnswer(
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testData.select(sqrt('key)).orderBy('key.asc),
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