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From "Daniel Vimont (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17257) Add column-aliasing capability to hbase-client
Date Thu, 15 Dec 2016 04:16:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15750330#comment-15750330

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
> 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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