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https://issues.apache.org/jira/browse/HBASE-17257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15737893#comment-15737893
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Daniel Vimont commented on HBASE-17257:
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Thanks for your questions, Ted. This is the just the kind of discussion I was
hoping for.
Addressing your question -- I don't see any way around it: both read and write
access to any alias-enabled column-family would be completely incapacitated if
the hbase:alias table were to become unavailable. In more general terms, for
any application that is dependent upon constant read/write access to two or
more tables, if one table becomes unavailable, the application cannot keep
running.
This does relate to your first question above, about whether hbase:alias should
be made a traditional "system" table or not. My understanding is that system
(metadata) tables reside on the Master server, but my understanding also is
that even though the Master server may become totally unavailable, it is
expected that ("slave") Region Servers should be able to go on processing
standard read/write access to HBase tables. This suggests that the current
design for aliasing (in which the hbase:alias table resides as a "normal" HBase
table out on Region Server(s)) is the only way to go to maintain the read/write
viability of a cluster should the Master server become unavailable.
> Add column-aliasing capability to hbase-client
> ----------------------------------------------
>
> Key: HBASE-17257
> URL: https://issues.apache.org/jira/browse/HBASE-17257
> Project: HBase
> Issue Type: New Feature
> Components: Client
> Affects Versions: 2.0.0
> Reporter: Daniel Vimont
> Assignee: Daniel Vimont
> Labels: features
> Attachments: HBASE-17257-v2.patch, HBASE-17257.patch
>
>
> Column aliasing will provide the option for a 1, 2, or 4 byte alias value to
> be stored in each cell of an "alias enabled" column-family, in place of the
> full-length column-qualifier. Aliasing is intended to operate completely
> invisibly to the end-user developer, with absolutely no "awareness" of
> aliasing required to be coded into a front-end application. No new public
> hbase-client interfaces are to be introduced, and only a few new public
> methods should need to be added to existing interfaces, primarily to allow an
> administrator to designate that a new column-family is to be alias-enabled by
> setting its aliasSize attribute to 1, 2, or 4.
> To facilitate such functionality, new subclasses of HTable,
> BufferedMutatorImpl, and HTableMultiplexer are to be provided. The overriding
> methods of these new subclasses will invoke methods of the new AliasManager
> class to facilitate qualifier-to-alias conversions (for user-submitted Gets,
> Scans, and Mutations) and alias-to-qualifier conversions (for Results
> returned from HBase) for any Table that has one or more alias-enabled column
> families. All conversion logic will be encapsulated in the new AliasManager
> class, and all qualifier-to-alias mappings will be persisted in a new
> aliasMappingTable in a new, reserved namespace.
> An informal polling of HBase users at HBaseCon East and at the
> Strata/Hadoop-World conference in Sept. 2016 showed that Column Aliasing
> could be a popular enhancement to standard HBase functionality, due to the
> fact that full column-qualifiers are stored in each cell, and reducing this
> qualifier storage requirement down to 1, 2, or 4 bytes per cell could prove
> beneficial in terms of reduced storage and bandwidth needs. Aliasing is
> intended chiefly for column-families which are of the "narrow and tall"
> variety (i.e., that are designed to use relatively few distinct
> column-qualifiers throughout a large number of rows, throughout the lifespan
> of the column-family). A column-family that is set up with an alias-size of 1
> byte can contain up to 255 unique column-qualifiers; a 2 byte alias-size
> allows for up to 65,535 unique column-qualifiers; and a 4 byte alias-size
> allows for up to 4,294,967,295 unique column-qualifiers.
> Fuller specifications will be entered into the comments section below. Note
> that it may well not be viable to add aliasing support in the new "async"
> classes that appear to be currently under development.
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