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From Nezih <>
Subject question about combining small input splits
Date Mon, 23 Nov 2015 21:24:01 GMT
Hi Spark Devs,
I tried getting an answer to my question in the user mailing list, but so
far couldn't. That's why I wanted to try the dev mailing list too in case
someone can help me.

I have a Hive table that has a lot of small parquet files and I am creating
a data frame out of it to do some processing, but since I have a large
number of splits/files my job creates a lot of tasks, which I don't want.
Basically what I want is the same functionality that Hive provides, that is,
to combine these small input splits into larger ones by specifying a max
split size setting. Is this currently possible with Spark?

I look at coalesce() but with coalesce I can only control the number of
output files not their sizes. And since the total input dataset size can
vary significantly in my case, I cannot just use a fixed partition count as
the size of each output file can get very large. I then looked for getting
the total input size from an rdd to come up with some heuristic to set the
partition count, but I couldn't find any ways to do it.

Any help is appreciated.



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