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Posted to user@spark.apache.org by "Dai, Kevin" <yu...@ebay.com> on 2014/10/29 04:15:36 UTC
Use RDD like a Iterator
Hi, ALL
I have a RDD[T], can I use it like a iterator.
That means I can compute every element of this RDD lazily.
Best Regards,
Kevin.
RE: Use RDD like a Iterator
Posted by "Ganelin, Ilya" <Il...@capitalone.com>.
Would Rdd.map() do what you need? It will apply a function to every element of the rdd and return a resulting RDD.
-----Original Message-----
From: Zhan Zhang [zzhang@hortonworks.com<ma...@hortonworks.com>]
Sent: Tuesday, October 28, 2014 11:23 PM Eastern Standard Time
To: Dai, Kevin
Cc: user@spark.apache.org
Subject: Re: Use RDD like a Iterator
I think it is already lazily computed, or do you mean something else? Following is the signature of compute in RDD
def compute(split: Partition, context: TaskContext): Iterator[T]
Thanks.
Zhan Zhang
On Oct 28, 2014, at 8:15 PM, Dai, Kevin <yu...@ebay.com>> wrote:
Hi, ALL
I have a RDD[T], can I use it like a iterator.
That means I can compute every element of this RDD lazily.
Best Regards,
Kevin.
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Re: Use RDD like a Iterator
Posted by Zhan Zhang <zz...@hortonworks.com>.
I think it is already lazily computed, or do you mean something else? Following is the signature of compute in RDD
def compute(split: Partition, context: TaskContext): Iterator[T]
Thanks.
Zhan Zhang
On Oct 28, 2014, at 8:15 PM, Dai, Kevin <yu...@ebay.com> wrote:
> Hi, ALL
>
> I have a RDD[T], can I use it like a iterator.
> That means I can compute every element of this RDD lazily.
>
> Best Regards,
> Kevin.
--
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Re: Use RDD like a Iterator
Posted by Zhan Zhang <zz...@hortonworks.com>.
RDD.toLocalIterator return the partition one by one but with all elements in the partition, which is not lazy calculated. Given the design of spark, it is very hard to maintain the state of iterator across runJob.
def toLocalIterator: Iterator[T] = {
def collectPartition(p: Int): Array[T] = {
sc.runJob(this, (iter: Iterator[T]) => iter.toArray, Seq(p), allowLocal = false).head
}
(0 until partitions.length).iterator.flatMap(i => collectPartition(i))
}
Thanks.
Zhan Zhang
On Oct 29, 2014, at 3:43 AM, Yanbo Liang <ya...@gmail.com> wrote:
> RDD.toLocalIterator() is the suitable solution.
> But I doubt whether it conform with the design principle of spark and RDD.
> All RDD transform is lazily computed until it end with some actions.
>
> 2014-10-29 15:28 GMT+08:00 Sean Owen <so...@cloudera.com>:
> Call RDD.toLocalIterator()?
>
> https://spark.apache.org/docs/latest/api/java/org/apache/spark/rdd/RDD.html
>
> On Wed, Oct 29, 2014 at 4:15 AM, Dai, Kevin <yu...@ebay.com> wrote:
> > Hi, ALL
> >
> >
> >
> > I have a RDD[T], can I use it like a iterator.
> >
> > That means I can compute every element of this RDD lazily.
> >
> >
> >
> > Best Regards,
> >
> > Kevin.
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: user-unsubscribe@spark.apache.org
> For additional commands, e-mail: user-help@spark.apache.org
>
>
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which it is addressed and may contain information that is confidential,
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of this message is not the intended recipient, you are hereby notified that
any printing, copying, dissemination, distribution, disclosure or
forwarding of this communication is strictly prohibited. If you have
received this communication in error, please contact the sender immediately
and delete it from your system. Thank You.
Re: Use RDD like a Iterator
Posted by Yanbo Liang <ya...@gmail.com>.
RDD.toLocalIterator() is the suitable solution.
But I doubt whether it conform with the design principle of spark and RDD.
All RDD transform is lazily computed until it end with some actions.
2014-10-29 15:28 GMT+08:00 Sean Owen <so...@cloudera.com>:
> Call RDD.toLocalIterator()?
>
> https://spark.apache.org/docs/latest/api/java/org/apache/spark/rdd/RDD.html
>
> On Wed, Oct 29, 2014 at 4:15 AM, Dai, Kevin <yu...@ebay.com> wrote:
> > Hi, ALL
> >
> >
> >
> > I have a RDD[T], can I use it like a iterator.
> >
> > That means I can compute every element of this RDD lazily.
> >
> >
> >
> > Best Regards,
> >
> > Kevin.
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: user-unsubscribe@spark.apache.org
> For additional commands, e-mail: user-help@spark.apache.org
>
>
Re: Use RDD like a Iterator
Posted by Sean Owen <so...@cloudera.com>.
Call RDD.toLocalIterator()?
https://spark.apache.org/docs/latest/api/java/org/apache/spark/rdd/RDD.html
On Wed, Oct 29, 2014 at 4:15 AM, Dai, Kevin <yu...@ebay.com> wrote:
> Hi, ALL
>
>
>
> I have a RDD[T], can I use it like a iterator.
>
> That means I can compute every element of this RDD lazily.
>
>
>
> Best Regards,
>
> Kevin.
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