Can't we set up proper codecs for sequence files. Ashish ________________________________________ From: Josh Ferguson [EMAIL PROTECTED] Sent: Tuesday, December 02, 2008 1:37 AM To: [email protected] Subject: Re: Compression
I'm not sure, from their wiki: Compressed Input Compressed files are difficult to process in parallel, since they cannot, in general, be split into fragments and independently decompressed. However, if the compression is block-oriented (e.g. bz2), the splitting and parallel processing is easy to do. Pig has inbuilt support for processing .bz2 files in parallel (.gz support is coming soon). If the input file name extension is .bz2, Pig decompresses the file on the fly and passes the decompressed input stream to your load function. For example, A = LOAD 'input.bz2' USING myLoad(); Multiple instances of myLoad() (as dictated by the degree of parallelism) will be created and each will be given a fragment of the *decompressed* version of input.bz2 to process. On Dec 2, 2008, at 1:32 AM, Zheng Shao wrote: Can you give a little more details? For example, you tried a single .bz file as input, and the pig job has 2 or more mappers? I didn't know bz2 was splittable. Zheng On Tue, Dec 2, 2008 at 1:18 AM, Josh Ferguson <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> wrote: It is splittable because of how the compression uses blocks, Pig does this out of the box. Josh On Dec 2, 2008, at 1:14 AM, Zheng Shao wrote: It shouldn't be a problem for Hive to support it (by defining your own input/output file format that does the decompression on the flyer), but we won't be able to parallelize the execution as we do with uncompressed text files, and sequence files, since bz2 compression is not splittable. -- Yours, Zheng
