Spark Request Max Count

I'm a beginner on spark and I try to make a request allow me to retrieve the most visited web pages. My request is the following mostPopularWebPageDF = logDF.groupBy('webPage').agg

Solution 1:

In pyspark + sql:

logDF.registerTempTable("logDF")

mostPopularWebPageDF = sqlContext.sql("""select webPage, cntWebPage from (
                                            select webPage, count(*) as cntWebPage, max(count(*)) over () as maxcnt 
                                            from logDF 
                                            group by webPage) as tmp
                                            where tmp.cntWebPage = tmp.maxcnt""")

Maybe I can make it cleaner, but it works. I will try to optimize it.

My result:

webPage      cntWebPage
google.com   2

for dataset:

webPage    usersid
google.com 1
google.com 3
bing.com   10

Explanation: normal counting is done via grouping + count(*) function. Max of all these counts are calculated via window function, so for dataset above, immediate DataFrame /without dropping maxCount column/ is:

webPage    count  maxCount
google.com 2      2
bing.com   1      2

Then we select rows with count equal to maxCount

EDIT: I have deleted DSL version - it does not support window over () and ordering is changing result. Sorry for this bug. SQL version is correct