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https://issues.apache.org/jira/browse/HIVE-352?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12701837#action_12701837
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He Yongqiang commented on HIVE-352:
-----------------------------------
Thanks, Zheng.
>>0. Did you try that with hadoop 0.17.0? "ant -Dhadoop.version=0.17.0 test"
>>etc.
yes.
>>1. Can you add your tests to ant, or post the testing scripts so that
>>everybody can easily reproduce the test results that you have got?
I will do that with next patch
>>2. For DistributedFileSystem, how big is the cluster? Is the file (the file
>>size is small so it's clearly a single block) local?
The cluster is of six nodes. The file is not local. The test was run on my
local machine, and use HDFS.
>>3. It seems SequenceFile's compression is not as good as RCFile, although the
>>data is the same and also random. What is the exact record format in
>>sequencefile? Did you >>put delimitors or you put length of Strings?
yes, it has length of Strings.However, RCFile also has the length of strings
>>The approach of store compressed data at creation, and do bulk decompression
>>at reading is not practical because it's very easy to go out of memory.
Yes, I encountered Out of memory error. So i added some trick in
RCFile.Writer's append. Like
{noformat}
if ((columnBufferSize + (this.bufferedRecords * this.columnNumber * 2) >
COLUMNS_BUFFER_SIZE)
|| (this.bufferedRecords >= this.RECORD_INTERVAL)) {
flushRecords();
}
{noformat}
>>We've done BULK, and it showed great performance (1.6s to read and decompress
>>40MB local file), but I suspect the compression ratio will be lower than
>>NONBULK.
>>Can you compare the compression ratio of BULK and NONBULK, given different
>>buffer sizes and column numbers?
BULK and NONBULK( they mean decompress) are only for Read, they have nothing to
do with Write, so I guess it will not influence compression ratio.
> Make Hive support column based storage
> --------------------------------------
>
> Key: HIVE-352
> URL: https://issues.apache.org/jira/browse/HIVE-352
> Project: Hadoop Hive
> Issue Type: New Feature
> Reporter: He Yongqiang
> Assignee: He Yongqiang
> Attachments: 4-22 performace2.txt, 4-22 performance.txt, 4-22
> progress.txt, hive-352-2009-4-15.patch, hive-352-2009-4-16.patch,
> hive-352-2009-4-17.patch, hive-352-2009-4-19.patch,
> hive-352-2009-4-22-2.patch, hive-352-2009-4-22.patch,
> HIve-352-draft-2009-03-28.patch, Hive-352-draft-2009-03-30.patch
>
>
> column based storage has been proven a better storage layout for OLAP.
> Hive does a great job on raw row oriented storage. In this issue, we will
> enhance hive to support column based storage.
> Acctually we have done some work on column based storage on top of hdfs, i
> think it will need some review and refactoring to port it to Hive.
> Any thoughts?
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