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Pig >> mail # dev >> Replicated join: is there a setting to make this better?


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Re: Replicated join: is there a setting to make this better?
Thanks Johnny. I am not sure how to post these images on mailing lists! :(
On Thu, Feb 21, 2013 at 6:30 PM, Johnny Zhang <[EMAIL PROTECTED]> wrote:

> Hi, Aniket:
> your image is blank :) not sure if this only happens to me though.
>
> Johnny
>
>
> On Thu, Feb 21, 2013 at 6:08 PM, Aniket Mokashi <[EMAIL PROTECTED]>
> wrote:
>
> > I think the email was filtered out. Resending.
> >
> >
> > ---------- Forwarded message ----------
> > From: Aniket Mokashi <[EMAIL PROTECTED]>
> > Date: Wed, Feb 20, 2013 at 1:18 PM
> > Subject: Replicated join: is there a setting to make this better?
> > To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> >
> >
> > Hi devs,
> >
> > I was looking into limitations of size/records for fragment replicated
> > join (map join) in pig. To test that I loaded a map (aka fragment) of
> longs
> > in an alias to join it with other alias which had few other columns.
> With a
> > map file of 50mb I saw GC Overheads on the mappers. I took a heap dump of
> > mapper to look into whats causing the GC Overheads and found that its the
> > memory footprint of fragment itself was high.
> >
> > [image: Inline image 1]
> >
> > Note, the hashmap was able to only load about 1.8 million records-
> > [image: Inline image 2]
> > Reason was that every map record has an overhead of about 1.5kb. Most of
> > it is part of retained heap, but it needs to be garbage collected.
> > [image: Inline image 3]
> >
> > So, it turns out-
> >
> > Size of heap required by a map join from above = 1.5 KB * Number of
> > records + Size of input (uncompressed databytearray)... (assuming the key
> > is a long).
> >
> > So, to run your replicated join, you need to satisfy following criteria:
> >
> > *1.5 KB * Number of records + Size of input (uncompressed) < estimated
> > free memory in the mapper (total heap - io.sort.mb - some minor constant
> > etc.)*
> >
> > Is that a right conclusion? Is there a setting/way to make this better?
> >
> > Thanks,
> >
> > Aniket
> >
> > *
> > *
> >
> >
> >
> > --
> > "...:::Aniket:::... Quetzalco@tl"
> >
>

--
"...:::Aniket:::... Quetzalco@tl"