使用 Spark Scala 连接两个数据框

Question

I have this code :

   val o =    p_value.alias("d1").join(t_d.alias("d2"),
      (col("d1.origin_latitude")===col("d2.origin_latitude")&& 
      col("d1.origin_longitude")===col("d2.origin_longitude")),"left").
      filter(col("d2.origin_longitude").isNull)
   val c =    p_value2.alias("d3").join(o.alias("d4"),
      (col("d3.origin_latitude")===col("d4.origin_latitude") && 
       col("d3.origin_longitude")===col("d4.origin_longitude")),"left").
      filter(col("d3.origin_longitude").isNull)

I get this error :

Exception in thread "main" org.apache.spark.sql.AnalysisException: Reference 'd4.origin_latitude' is ambiguous, could be: d4.origin_latitude, d4.origin_latitude.;
at org.apache.spark.sql.catalyst.expressions.package$AttributeSeq.resolve(package.scala:240)
at org.apache.spark.sql.catalyst.plans.logical.LogicalPlan.resolveChildren(LogicalPlan.scala:101)

On this line

 (col("d3.origin_latitude")===col("d4.origin_latitude") && col("d3.origin_longitude")===col("d4.origin_longitude")),"left").

Any idea ?

Thank you .

Answer 1

You are aliasing DataFrame not columns, which is used to access/refer columns in that DataFrame . So the first join will result into another DataFrame having same column name twice ( origin_latitude as well as origin_longitude ). Once you try to access one of these columns in resultant DataFrame , you are going to get Ambiguity error.

So you need to make sure that DataFrame contains each column only once. You can rewrite the first join as below:

p_value
      .join(t_d, Seq("origin_latitude", "origin_longitude"), "left")
      .filter(t_d.col("t_d.origin_longitude").isNull)