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From Tom Hall <thattommyh...@gmail.com>
Subject Re: Sequence File Compression
Date Mon, 09 May 2011 17:19:55 GMT
Anyone have an idea on this?
Anyone using compression with sequence files successfully?

The wiki and Hadoop: the definitive guide suggest that the below is
correct so I am at a loss to explain what we are seeing.


Tom



On Fri, May 6, 2011 at 5:39 PM, Tom Hall <thattommyhall@gmail.com> wrote:
> I have read http://wiki.apache.org/hadoop/Hive/CompressedStorage and
> am trying to compress some of our tables. The only difference with the
> eg is that we have partitioned our tables.
>
>
> SET io.seqfile.compression.type=BLOCK;
> SET hive.exec.compress.output=true;
> SET mapred.output.compress=true;
> insert overwrite table keywords_lzo partition (dated = '2010-01-25',
> client = 'TESTCLIENT') select
> account,campaign,ad_group,keyword_id,keyword,match_type,status,first_page_bid,quality_score,distribution,max_cpc,destination_url,ad_group_status,campaign_status,currency_code,impressions,clicks,ctr,cpc,cost,avg_position,account_id,campaign_id,adgroup_id
> from keywords where dated = '2010-01-25' and client = 'TESTCLIENT';
>
>
>
> The keywords_lzo table was created by running:
>
> CREATE TABLE `keywords_lzo` (
>  `account` STRING,
>  `campaign` STRING,
>  `ad_group` STRING,
>  `keyword_id` STRING,
>  `keyword` STRING,
>  `match_type` STRING,
>  `status` STRING,
>  `first_page_bid` STRING,
>  `quality_score` FLOAT,
>  `distribution` STRING,
>  `max_cpc` FLOAT,
>  `destination_url` STRING,
>  `ad_group_status` STRING,
>  `campaign_status` STRING,
>  `currency_code` STRING,
>  `impressions` INT,
>  `clicks` INT,
>  `ctr` FLOAT,
>  `cpc` STRING,
>  `cost` FLOAT ,
>  `avg_position` FLOAT,
>  `account_id` STRING,
>  `campaign_id` STRING,
>  `adgroup_id` STRING
> )
> PARTITIONED BY (
> `dated` STRING,
> `client` STRING
> )
>
> ROW FORMAT DELIMITED
> FIELDS TERMINATED BY '\t'
> LINES TERMINATED BY '\n'
>
> STORED AS SEQUENCEFILE;
>
>
> The problem is that the output is 12 files totaling the same size as
> the input CSV (~750MB). With either LZO or GZIP I get the same
> behaviour. If I use TEXTFILE then I get the compression I would
> expect.
>
> I can see in the head of the file
> SEQ "org.apache.hadoop.io.BytesWritable org.apache.hadoop.io.Text �'org.apache.hadoop.io.compress.GzipCodec
> and it does look like garbage so something is happening but the total
> size is not reduced from the CSV
>
>
> Is the 12 output files significant? They are ~60M each and the blocksize is 64M
> I tried SET io.seqfile.compression.type=RECORD; also but still 12
> files and no reduction in size.
>
>
> Thanks,
> Tom
>

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