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Date: Tue, 18 Jun 2013 21:10:21 +0000 (UTC)
From: "Enis Soztutar (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12635622.1362592237470.135300.1371589821833@arcas>
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References: <JIRA.12635622.1362592237470@arcas>
Subject: [jira] [Commented] (HBASE-8015) Support for Namespaces
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    [ https://issues.apache.org/jira/browse/HBASE-8015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13687200#comment-13687200 ] 

Enis Soztutar commented on HBASE-8015:
--------------------------------------

BTW regarding separator chars:
"\/:*?<>|"  NTFS does not allow these chars
"\/~"       Meaningful in ext/ntfs.
"-" and "_" cannot be used because they are legal in table names.
"#"         Comment in many SQL dialects, not compatible with URL encoding.
"$%&"       Used in shell scripts

This leaves: "!@^+=," if we disregard parenthesis chars. These also seem to work for HDFS. "," is our internal separator for region names and META naming. @ also seems good enough. Haven't tried these for znodes. 

It seems that we could not reach an agreement on which proposal to implement, where they are
1) use dot as separator, autogenerate namespaces on migration
2) use one of the candidate char's above as ns and table separator. 
3) In all places that require a table name, override with accepting namespace.

However, it seems that we definitely have to have an internal separator char and a deterministic way of encoding <ns,table> pair into a string and decoding it back. This is because we need to do this for znodes in zktable, tablelockmanager, etc as well as META. So, I think it is a matter of whether we want to expose the separator char between proposal 2 and 3. I am in favor of doing 2, since it will allow better interop with external tools, and the code changes needed for 3 is significant. 
                
> Support for Namespaces
> ----------------------
>
>                 Key: HBASE-8015
>                 URL: https://issues.apache.org/jira/browse/HBASE-8015
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Francis Liu
>            Assignee: Francis Liu
>         Attachments: HBASE-8015_draft_94.patch, Namespace Design.pdf
>
>


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