Sorry, my code actually was

    df_one = df.select('col1', 'col2')
    df_two = df.select('col1', 'col3')

But in Spark 1.4.0 this does not seem to make any difference anyway and the problem is the same with both versions.


On 2015-04-21 17:04, ayan guha wrote:
your code should be

 df_one = df.select('col1', 'col2')
 df_two = df.select('col1', 'col3')

Your current code is generating a tupple, and of course df_1 and df_2 are
different, so join is yielding to cartesian.

Best
Ayan

On Wed, Apr 22, 2015 at 12:42 AM, Karlson <ksonsp...@siberie.de> wrote:

Hi,

can anyone confirm (and if so elaborate on) the following problem?

When I join two DataFrames that originate from the same source DataFrame, the resulting DF will explode to a huge number of rows. A quick example:

I load a DataFrame with n rows from disk:

    df = sql_context.parquetFile('data.parquet')

Then I create two DataFrames from that source.

    df_one = df.select(['col1', 'col2'])
    df_two = df.select(['col1', 'col3'])

Finally I want to (inner) join them back together:

    df_joined = df_one.join(df_two, df_one['col1'] == df_two['col2'],
'inner')

The key in col1 is unique. The resulting DataFrame should have n rows,
however it does have n*n rows.

That does not happen, when I load df_one and df_two from disk directly. I am on Spark 1.3.0, but this also happens on the current 1.4.0 snapshot.

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