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Pig, mail # user - problems with .gz


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William Oberman 2013-06-07, 21:10
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Niels Basjes 2013-06-08, 05:23
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William Oberman 2013-06-08, 12:00
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William Oberman 2013-06-10, 16:06
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Alan Crosswell 2013-06-10, 16:41
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Alan Crosswell 2013-06-10, 20:27
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Niels Basjes 2013-06-10, 20:38
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Jonathan Coveney 2013-06-11, 12:46
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William Oberman 2013-06-12, 20:16
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Jonathan Coveney 2013-06-12, 21:09
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Re: problems with .gz
William Oberman 2013-06-10, 17:12
I'm using gzip as I had a huge S3 bucket of uncompressed files, and
s3distcp only supported {gz, lzo, snappy}.

I haven't ever done this, but can I mix/match files?  My backup processes
add files to these buckets, so I could upload new files as *.bz.  But then
I'd have some files as *.gz, and others as *.bz.

will
On Mon, Jun 10, 2013 at 12:41 PM, Alan Crosswell <[EMAIL PROTECTED]> wrote:

> Suggest that if you have a choice, you use bzip2 compression instead of
> gzip as bzip2 is block-based and Pig can split reading a large bzipped file
> across multiple mappers while gzip can't be split that way.
>
>
> On Mon, Jun 10, 2013 at 12:06 PM, William Oberman
> <[EMAIL PROTECTED]>wrote:
>
> > I still don't fully understand (and am still debugging), but I have a
> > "problem file" and a theory.
> >
> > The file has a "corrupt line" that is a huge block of null characters
> > followed by a "\n" (other lines are json followed by "\n").  I'm thinking
> > that's a problem with my cassandra -> s3 process, but is out of scope for
> > this thread....  I wrote scripts to examine the file directly, and if I
> > stop counting at the weird line, I get the "gz" count.   If I count all
> > lines (e.g. don't fail at the corrupt line) I get the "uncompressed"
> count.
> >
> > I don't know how to debug hadoop/pig quite as well, though I'm trying
> now.
> >  But, my working theory is that some combination of pig/hadoop aborts
> > processing the gz stream on a null character, but keeps chugging on a
> > non-gz stream.  Does that sound familiar?
> >
> > will
> >
> >
> > On Sat, Jun 8, 2013 at 8:00 AM, William Oberman <
> [EMAIL PROTECTED]
> > >wrote:
> >
> > > They are all *.gz, I confirmed that first :-)
> > >
> > >
> > > On Saturday, June 8, 2013, Niels Basjes wrote:
> > >
> > >> What are the exact filenames you used?
> > >> The decompression of input files is based on the filename extention.
> > >>
> > >> Niels
> > >> On Jun 7, 2013 11:11 PM, "William Oberman" <[EMAIL PROTECTED]>
> > >> wrote:
> > >>
> > >> > I'm using pig 0.11.2.
> > >> >
> > >> > I had been processing ASCII files of json with schema:
> (key:chararray,
> > >> > columns:bag {column:tuple (timeUUID:chararray, value:chararray,
> > >> > timestamp:long)})
> > >> > For what it's worth, this is cassandra data, at a fairly low level.
> > >> >
> > >> > But, this was getting big, so I compressed it all with gzip (my
> "ETL"
> > >> > process is already chunking the data into 1GB parts, making the .gz
> > >> files
> > >> > ~100MB).
> > >> >
> > >> > As a sanity check, I decided to do a quick check of pre/post, and
> the
> > >> > numbers aren't matching.  Then I've done a lot of messing around
> > trying
> > >> to
> > >> > figure out why and I'm getting more and more puzzled.
> > >> >
> > >> > My "quick check" was to get an overall count.  It looked like
> > (assuming
> > >> A
> > >> > is a LOAD given the schema above):
> > >> > -------
> > >> > allGrp = GROUP A ALL;
> > >> > aCount = FOREACH allGrp GENERATE group, COUNT(A);
> > >> > DUMP aCount;
> > >> > -------
> > >> >
> > >> > Basically the original data returned a number GREATER than the
> > >> compressed
> > >> > data number (not by a lot, but still...).
> > >> >
> > >> > Then I uncompressed all of the compressed files, and did a size
> check
> > of
> > >> > original vs. uncompressed.  They were the same.  Then I "quick
> > checked"
> > >> the
> > >> > uncompressed, and the count of that was == original!  So, the way in
> > >> which
> > >> > pig processes the gzip'ed data is actually somehow different.
> > >> >
> > >> > Then I tried to see if there are nulls floating around, so I loaded
> > >> "orig"
> > >> > and "comp" and tried to catch the "missing keys" with outer joins:
> > >> > -----------
> > >> > joined = JOIN orig by key LEFT OUTER, comp BY key;
> > >> > filtered = FILTER joined BY (comp::key is null);
> > >> > -----------
> > >> > And filtered was empty!  I then tried the reverse (which makes no
> > sense
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Alan Crosswell 2013-06-10, 18:02