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From Matei Zaharia <>
Subject Re: What's the lifecycle of an rdd? Can I control it?
Date Thu, 20 Mar 2014 02:35:43 GMT
Yes, Spark automatically removes old RDDs from the cache when you make new ones. Unpersist
forces it to remove them right away. In both cases though, note that Java doesn’t garbage-collect
the objects released until later.


On Mar 19, 2014, at 7:22 PM, Nicholas Chammas <> wrote:

> Related question: 
> If I keep creating new RDDs and cache()-ing them, does Spark automatically unpersist
the least recently used RDD when it runs out of memory? Or is an explicit unpersist the only
way to get rid of an RDD (barring the PR Tathagata mentioned)?
> Also, does unpersist()-ing an RDD immediately free up space, or just allow that space
to be reclaimed when needed?
> On Wed, Mar 19, 2014 at 7:01 PM, Tathagata Das <> wrote:
> Just a head's up, there is an active pull requeust that will automatically unpersist
RDDs that are not in reference/scope from the application any more. 
> TD
> On Wed, Mar 19, 2014 at 6:58 PM, hequn cheng <> wrote:
> persist and unpersist.
> unpersist:Mark the RDD as non-persistent, and remove all blocks for it from memory and
> 2014-03-19 16:40 GMT+08:00 林武康 <>:
> Hi, can any one tell me about the lifecycle of an rdd? I search through the official
website and still can't figure it out. Can I use an rdd in some stages and destroy it in order
to release memory because that no stages ahead will use this rdd any more. Is it possible?
> Thanks!
> Sincerely 
> Lin wukang

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