diff options
Diffstat (limited to 'sql')
-rw-r--r-- | sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala | 37 | ||||
-rw-r--r-- | sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala | 40 |
2 files changed, 66 insertions, 11 deletions
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala b/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala index 03d9834d1d..ca6ae482eb 100644 --- a/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala +++ b/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala @@ -343,6 +343,43 @@ class DataFrame private[sql]( } /** + * Inner equi-join with another [[DataFrame]] using the given column. + * + * Different from other join functions, the join column will only appear once in the output, + * i.e. similar to SQL's `JOIN USING` syntax. + * + * {{{ + * // Joining df1 and df2 using the column "user_id" + * df1.join(df2, "user_id") + * }}} + * + * Note that if you perform a self-join using this function without aliasing the input + * [[DataFrame]]s, you will NOT be able to reference any columns after the join, since + * there is no way to disambiguate which side of the join you would like to reference. + * + * @param right Right side of the join operation. + * @param usingColumn Name of the column to join on. This column must exist on both sides. + * @group dfops + */ + def join(right: DataFrame, usingColumn: String): DataFrame = { + // Analyze the self join. The assumption is that the analyzer will disambiguate left vs right + // by creating a new instance for one of the branch. + val joined = sqlContext.executePlan( + Join(logicalPlan, right.logicalPlan, joinType = Inner, None)).analyzed.asInstanceOf[Join] + + // Project only one of the join column. + val joinedCol = joined.right.resolve(usingColumn) + Project( + joined.output.filterNot(_ == joinedCol), + Join( + joined.left, + joined.right, + joinType = Inner, + Some(EqualTo(joined.left.resolve(usingColumn), joined.right.resolve(usingColumn)))) + ) + } + + /** * Inner join with another [[DataFrame]], using the given join expression. * * {{{ diff --git a/sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala index b9b6a400ae..5ec06d448e 100644 --- a/sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala +++ b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala @@ -109,15 +109,6 @@ class DataFrameSuite extends QueryTest { assert(testData.head(2).head.schema === testData.schema) } - test("self join") { - val df1 = testData.select(testData("key")).as('df1) - val df2 = testData.select(testData("key")).as('df2) - - checkAnswer( - df1.join(df2, $"df1.key" === $"df2.key"), - sql("SELECT a.key, b.key FROM testData a JOIN testData b ON a.key = b.key").collect().toSeq) - } - test("simple explode") { val df = Seq(Tuple1("a b c"), Tuple1("d e")).toDF("words") @@ -127,8 +118,35 @@ class DataFrameSuite extends QueryTest { ) } - test("self join with aliases") { - val df = Seq(1,2,3).map(i => (i, i.toString)).toDF("int", "str") + test("join - join using") { + val df = Seq(1, 2, 3).map(i => (i, i.toString)).toDF("int", "str") + val df2 = Seq(1, 2, 3).map(i => (i, (i + 1).toString)).toDF("int", "str") + + checkAnswer( + df.join(df2, "int"), + Row(1, "1", "2") :: Row(2, "2", "3") :: Row(3, "3", "4") :: Nil) + } + + test("join - join using self join") { + val df = Seq(1, 2, 3).map(i => (i, i.toString)).toDF("int", "str") + + // self join + checkAnswer( + df.join(df, "int"), + Row(1, "1", "1") :: Row(2, "2", "2") :: Row(3, "3", "3") :: Nil) + } + + test("join - self join") { + val df1 = testData.select(testData("key")).as('df1) + val df2 = testData.select(testData("key")).as('df2) + + checkAnswer( + df1.join(df2, $"df1.key" === $"df2.key"), + sql("SELECT a.key, b.key FROM testData a JOIN testData b ON a.key = b.key").collect().toSeq) + } + + test("join - using aliases after self join") { + val df = Seq(1, 2, 3).map(i => (i, i.toString)).toDF("int", "str") checkAnswer( df.as('x).join(df.as('y), $"x.str" === $"y.str").groupBy("x.str").count(), Row("1", 1) :: Row("2", 1) :: Row("3", 1) :: Nil) |