got it, great thanks, Vishal, Ted and David
On Tue, Jan 19, 2016 at 1:10 PM, Vishal Maru <vzm...@gmail.com> wrote:
> 1. foreach doesn't expect any value from function being passed (in your
> func_foreach). so nothing happens. The return values are just lost. it's
> like calling a function without saving return value to another var.
> foreach also doesn't return anything so you don't get modified RDD (like
> map*).
> 2. RDD's are immutable. All transform functions (map*,groupBy*,reduceBy
> etc.) return new RDD.
> 3. Yes. It's just iterates through elements and calls the function being
> passed. That's it. It doesn't collect the values and don't return any new
> modified RDD.
>
>
> On Mon, Jan 18, 2016 at 11:10 PM, charles li <charles.up...@gmail.com>
> wrote:
>
>>
>> hi, great thanks to david and ted, I know that the content of RDD can be
>> returned to driver using 'collect' method.
>>
>> but my question is:
>>
>>
>> 1. cause we can write any code we like in the function put into
>> 'foreach', so what happened when we actually write a 'return' sentence in
>> the foreach function?
>> 2. as the photo shows bellow, the content of RDD doesn't change after
>> foreach function, why?
>> 3. I feel a little confused about the 'foreach' method, it should be an
>> 'action', right? cause it return nothing. or is there any best practice of
>> the 'foreach' funtion? or can some one put your code snippet when using
>> 'foreach' method in your application, that would be awesome.
>>
>>
>> great thanks again
>>
>>
>>
>>
>>
>> On Tue, Jan 19, 2016 at 11:44 AM, Ted Yu <yuzhih...@gmail.com> wrote:
>>
>>> Here is signature for foreach:
>>> def foreach(f: T => Unit): Unit = withScope {
>>>
>>> I don't think you can return element in the way shown in the snippet.
>>>
>>> On Mon, Jan 18, 2016 at 7:34 PM, charles li <charles.up...@gmail.com>
>>> wrote:
>>>
>>>> code snippet
>>>>
>>>>
>>>>
>>>> the 'print' actually print info on the worker node, but I feel confused
>>>> where the 'return' value
>>>> goes to. for I get nothing on the driver node.
>>>> --
>>>> *--------------------------------------*
>>>> a spark lover, a quant, a developer and a good man.
>>>>
>>>> http://github.com/litaotao
>>>>
>>>
>>>
>>
>>
>> --
>> *--------------------------------------*
>> a spark lover, a quant, a developer and a good man.
>>
>> http://github.com/litaotao
>>
>
>
--
*--------------------------------------*
a spark lover, a quant, a developer and a good man.
http://github.com/litaotao
