I think the tricky part here is that the join condition is encoded in the
second data frame and not a direct value.
Assuming the second data frame (the tags) is small enough, you can collect it
(read it into memory) and then construct a "when" expression chain for each of
the possible tags , then all you need to do is select on data frame 1 (df1) (or
use "withColumn" to add the column) and provide the constructed "when" chain as
the new column value.
From a very high level, looking at your example data below, you would construct
the following expression from df2 (off course, in the real case, you would
construct the expression programmatically from the collected df2 data and not
hardcoded).
val e = when(expr("year = 1997 and model = 'E350'"), "1997_cars").
...
when(expr("year = 2015 and model = 'Volt'"), "2015_cars").
otherwise("unknown")
then you just need to add the new column to your input as:
df1.withColumn("tag", e)
I caveat this by saying that I have not tried the above (especially using
"expr" to evaluate partial sql expressions, but should work according to doc).
Sometimes, half the battle is just finding the right API. the
"when"/"otherwise" is documented under the "Column" class and
"withColumn"/"collect" are documented under "DataFrame".
--
Ali
On Feb 5, 2016, at 1:56 AM, Lohith Samaga M <lohith.sam...@mphasis.com> wrote:
> Hi,
> If you can also format the condition file as a csv file
> similar to the main file, then you can join the two dataframes and select
> only required columns.
>
> Best regards / Mit freundlichen Grüßen / Sincères salutations
> M. Lohith Samaga
>
> From: Divya Gehlot [mailto:divya.htco...@gmail.com]
> Sent: Friday, February 05, 2016 13.12
> To: user @spark
> Subject: pass one dataframe column value to another dataframe filter
> expression + Spark 1.5 + scala
>
> Hi,
> I have two input datasets
> First input dataset like as below :
>
> year,make,model,comment,blank
> "2012","Tesla","S","No comment",
> 1997,Ford,E350,"Go get one now they are going fast",
> 2015,Chevy,Volt
>
> Second Input dataset :
>
> TagId,condition
> 1997_cars,year = 1997 and model = 'E350'
> 2012_cars,year=2012 and model ='S'
> 2015_cars ,year=2015 and model = 'Volt'
>
> Now my requirement is read first data set and based on the filtering
> condition in second dataset need to tag rows of first input dataset by
> introducing a new column TagId to first input data set
> so the expected should look like :
>
> year,make,model,comment,blank,TagId
> "2012","Tesla","S","No comment",2012_cars
> 1997,Ford,E350,"Go get one now they are going fast",1997_cars
> 2015,Chevy,Volt, ,2015_cars
>
> I tried like :
>
> val sqlContext = new SQLContext(sc)
> val carsSchema = StructType(Seq(
> StructField("year", IntegerType, true),
> StructField("make", StringType, true),
> StructField("model", StringType, true),
> StructField("comment", StringType, true),
> StructField("blank", StringType, true)))
>
> val carTagsSchema = StructType(Seq(
> StructField("TagId", StringType, true),
> StructField("condition", StringType, true)))
>
>
> val dfcars =
> sqlContext.read.format("com.databricks.spark.csv").option("header", "true")
> .schema(carsSchema).load("/TestDivya/Spark/cars.csv")
> val dftags =
> sqlContext.read.format("com.databricks.spark.csv").option("header", "true")
> .schema(carTagsSchema).load("/TestDivya/Spark/CarTags.csv")
>
> val Amendeddf = dfcars.withColumn("TagId", dfcars("blank"))
> val cdtnval = dftags.select("condition")
> val df2=dfcars.filter(cdtnval)
> <console>:35: error: overloaded method value filter with alternatives:
> (conditionExpr: String)org.apache.spark.sql.DataFrame <and>
> (condition: org.apache.spark.sql.Column)org.apache.spark.sql.DataFrame
> cannot be applied to (org.apache.spark.sql.DataFrame)
> val df2=dfcars.filter(cdtnval)
>
> another way :
>
> val col = dftags.col("TagId")
> val finaldf = dfcars.withColumn("TagId", col)
> org.apache.spark.sql.AnalysisException: resolved attribute(s) TagId#5
> missing from comment#3,blank#4,model#2,make#1,year#0 in operator !Project
> [year#0,make#1,model#2,comment#3,blank#4,TagId#5 AS TagId#8];
>
> finaldf.write.format("com.databricks.spark.csv").option("header",
> "true").save("/TestDivya/Spark/carswithtags.csv")
>
>
> Would really appreciate if somebody give me pointers how can I pass the
> filter condition(second dataframe) to filter function of first dataframe.
> Or another solution .
> My apppologies for such a naive question as I am new to scala and Spark
>
> Thanks
>
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