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From 冯宏华 <fenghong...@xiaomi.com>
Subject 答复: Finding the latest updated rows
Date Tue, 21 Jan 2014 12:23:38 GMT
seems such theme(encode timestamp in rowKey) works only for newly put rows, but not for updated
rows, since updated timestamp can't reflect in existing timestamp part of the rowkey. right?

no direct efficient way to achieve William's request for finding the latest updated (put new
row, or update only certain columns in some rows, etc) rows. maybe a reverved/special(can't
be used by user/application) row can help here: this row contains a single cell, the timestamp
is the latest put/updated timestamp and the value is the latest put/updated rowKey, each time
a put/update occurs, this reserved/special row is updated concurrently to record the put/updated
row as the value and together the latest put/update timestamp. but this need to resolve concurrent
writes from various different clients. it's ok if there is always a single client, otherwise
the write to the reserved row should be a special checkAndPut which compares the timestamp
to determine if to overwrite, such special checkAndPut introduces read for each write, hence
hurts performance and serializes writes from various clients by the reserved/special row...
________________________________________
发件人: Joshi, Rekha [Rekha_Joshi@intuit.com]
发送时间: 2014年1月21日 15:55
收件人: user@hbase.apache.org; hbase-user
主题: Re: Finding the latest updated rows

Hi Wiliam,

The timestamp part of rowkey schema design caters to this., usually
efficient but your SLA may differ.

http://hbase.apache.org/book.html#reverse.timestamp

http://hbase.apache.org/book.html#schema.casestudies

http://hbase.apache.org/book.html#timeseries


Thanks
Rekha

On 21/01/14 9:36 AM, "William Kang" <weliam.cloud@gmail.com> wrote:

>Hi,
>In HBase, the time stamp is set for each column, not for the entire row.
>If
>somehow I want to find the latest updated (put new row, or update only
>certain columns in some rows, etc) rows, is there an efficient way to do
>it?
>
>Many thanks.
>
>
>William

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