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From "Xing Shi (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5723) Simple Design of Secondary Index
Date Fri, 06 Apr 2012 04:09:22 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5723?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13248021#comment-13248021
] 

Xing Shi commented on HBASE-5723:
---------------------------------

Todd, 
    you mean the consistency of index table? Because the index table is also a HBase table,
so it will use the mvcc to ensure the consistency of the index table. 

Mainly there are 2 steps when do put.
Step1 : It will insert data into index table.
Step2 : It will insert data into primary table.

After step1, the client can read the index, but may be the step2 has not done. So client will
find there is no data are associated with the index, and it will read the old version index.
Here it is weak consistency, and at last the index and data will be eventual consistency except
as follows:.

If the step2 failed, we will not delete the new index´╝î the index is not correct(there is
no row in the primary table associated with this index by the rowkey, the value, and the same
timestamp) ant it is Weak consistency.

For these stale indices, we will not delete it forever(may be we can delete them by period
job to detect the not correct indice).
                
> Simple Design of Secondary Index
> --------------------------------
>
>                 Key: HBASE-5723
>                 URL: https://issues.apache.org/jira/browse/HBASE-5723
>             Project: HBase
>          Issue Type: New Feature
>          Components: coprocessors
>            Reporter: ShiXing
>            Priority: Minor
>         Attachments: Simple Design of HBase SecondaryIndex.pdf
>
>
> Use coprocessor to create index. And primary tables' compaction to purge the stale data.

> Attach file is the Design of the Seconday Index.

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