union of SchemaRDDs

[Daniel Mahler]

I would like to combine 2 parquet tables I have create.
I tried:

  sc.union(sqx.parquetFile(fileA), sqx.parquetFile(fileB))

but that just returns RDD[Row].
How do I combine them to get a SchemaRDD[Row]?

thanks
Daniel

Re: union of SchemaRDDs

[Matei Zaharia]

Try unionAll, which is a special method on SchemaRDDs that keeps the schema on 
the results.

Matei

 On Nov 1, 2014, at 3:57 PM, Daniel Mahler dmah...@gmail.com wrote:
 
 I would like to combine 2 parquet tables I have create.
 I tried:
 
   sc.union(sqx.parquetFile(fileA), sqx.parquetFile(fileB))
 
 but that just returns RDD[Row].
 How do I combine them to get a SchemaRDD[Row]?
 
 thanks
 Daniel


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Re: union of SchemaRDDs

[Daniel Mahler]

Thanks Matei. What does unionAll do if the input RDD schemas are not 100%
compatible. Does it take the union of the columns and generalize the types?

thanks
Daniel

On Sat, Nov 1, 2014 at 6:08 PM, Matei Zaharia matei.zaha...@gmail.com
wrote:

 Try unionAll, which is a special method on SchemaRDDs that keeps the
 schema on the results.

 Matei

  On Nov 1, 2014, at 3:57 PM, Daniel Mahler dmah...@gmail.com wrote:
 
  I would like to combine 2 parquet tables I have create.
  I tried:
 
sc.union(sqx.parquetFile(fileA), sqx.parquetFile(fileB))
 
  but that just returns RDD[Row].
  How do I combine them to get a SchemaRDD[Row]?
 
  thanks
  Daniel

Re: union of SchemaRDDs

[Matei Zaharia]

It does generalize types, but only on the intersection of the columns it seems. 
There might be a way to get the union of the columns too using HiveQL. Types 
generalize up with string being the most general.

Matei

 On Nov 1, 2014, at 6:22 PM, Daniel Mahler dmah...@gmail.com wrote:
 
 Thanks Matei. What does unionAll do if the input RDD schemas are not 100% 
 compatible. Does it take the union of the columns and generalize the types?
 
 thanks
 Daniel
 
 On Sat, Nov 1, 2014 at 6:08 PM, Matei Zaharia matei.zaha...@gmail.com 
 mailto:matei.zaha...@gmail.com wrote:
 Try unionAll, which is a special method on SchemaRDDs that keeps the schema 
 on the results.
 
 Matei
 
  On Nov 1, 2014, at 3:57 PM, Daniel Mahler dmah...@gmail.com 
  mailto:dmah...@gmail.com wrote:
 
  I would like to combine 2 parquet tables I have create.
  I tried:
 
sc.union(sqx.parquetFile(fileA), sqx.parquetFile(fileB))
 
  but that just returns RDD[Row].
  How do I combine them to get a SchemaRDD[Row]?
 
  thanks
  Daniel
 
 

Re: Shouldn't the UNION of SchemaRDDs produce SchemaRDD ?

[Michael Armbrust]

 * unionAll preserve duplicate v/s union that does not


This is true, if you want to eliminate duplicate items you should follow
the union with a distinct()


 * SQL union and unionAll result in same output format i.e. another SQL v/s
 different RDD types here.

* Understand the existing union contract issue. This may be a class
 hierarchy discussion for SchemaRDD, UnionRDD etc. ?


This is unfortunately going to be a limitation of the query DSL since it
extends standard RDDs.  It is not possible for us to return specialized
types from functions that are already defined in RDD (such as union) as the
base RDD class has a very opaque notion of schema, and at this point the
API for RDDs is very fixed.  If you use SQL however, you will always get
back SchemaRDDs.

Shouldn't the UNION of SchemaRDDs produce SchemaRDD ?

[Manoj Samel]

Hi,

I am trying SparkSQL based on the example on doc ...



val people =
sc.textFile(/data/spark/examples/src/main/resources/people.txt).map(_.split(,)).map(p
= Person(p(0), p(1).trim.toInt))


val olderThanTeans = people.where('age  19)
val youngerThanTeans = people.where('age  13)
val nonTeans = youngerThanTeans.union(olderThanTeans)

I can do a orderBy('age) on first two (which are SchemaRDD) but not on
third. The nonTeans is a UnionRDD that does not supports orderBy. This
seems different than the SQL behavior where results of 2 SQL unions is a
SQL itself with same functionality ...

Not clear why union of 2 SchemaRDDs does not produces a SchemaRDD 


Thanks,