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https://issues.apache.org/jira/browse/HBASE-17257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15750330#comment-15750330
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Daniel Vimont commented on HBASE-17257:
---------------------------------------
Here is my summary of the progress on this task so far:
(1) *THE FIRST PATCH* encountered Jenkins pre-commit errors/failures due to the
following: new validation logic which included invocations of
Admin#getTableDescriptor (to determine whether a Table has any aliasEnabled
families) was causing errors/failures in existing Test modules in which the
Master server is incidentally or intentionally not available. This was resolved
by restructuring things such that Admin#getTableDescriptor calls are no longer
required to determine whether a user-table has any alias-enabled families
(replaced instead by a lookup by AliasManager to see whether row(s) exist for
the user-table in the alias-mapping table).
(2) *THE SECOND PATCH* encountered problems when some existing Test modules did
not receive the specific types of Exceptions they were expecting due to new
aliasing logic inappropriately catching them. Preparation of the third patch
also included several improvements/modifications recommended by Ted (listed in
his comments above).
(3) *THE THIRD PATCH* passed all Jenkins pre-commit testing, and its code was
posted to Review Board: https://reviews.apache.org/r/54635/
This leads me to produce a partial list of outstanding questions and
discussion-points regarding all of this, which I'll post as a separate comment.
> 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-v3.patch,
> HBASE-17257.patch
>
>
> Review Board link: https://reviews.apache.org/r/54635/
> 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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