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From Chris Teoh <chris.t...@gmail.com>
Subject Re: Does explode lead to more usage of memory
Date Sun, 19 Jan 2020 02:03:07 GMT
I think it does mean more memory usage but consider how big your arrays
are. Think about your use case requirements and whether it makes sense to
use arrays. Also it may be preferable to explode if the arrays are very
large. I'd say exploding arrays will make the data more splittable, having
the array has benefit of avoiding a join and colocation of the children
items but does imply more memory pressure on each executor to read every
record in the array, requiring denser nodes.

I hope that helps.

On Sun, 19 Jan 2020, 7:50 am V0lleyBallJunki3, <venkatdabri@gmail.com>
wrote:

> I am using a dataframe and has structure like this :
>
> root
>  |-- orders: array (nullable = true)
>  |    |-- element: struct (containsNull = true)
>  |    |    |-- amount: double (nullable = true)
>  |    |    |-- id: string (nullable = true)
>  |-- user: string (nullable = true)
>  |-- language: string (nullable = true)
>
> Each user has multiple orders. Now if I explode orders like this:
>
> df.select($"user", explode($"orders").as("order")) . Each order element
> will
> become a row with a duplicated user and language. Was wondering if spark
> actually converts each order element into a single row in memory or it just
> logical. Because if a single user has 1000 orders  then wouldn't it lead to
> a lot more memory consumption since it is duplicating user and language a
> 1000 times (once for each order) in memory?
>
>
>
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