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https://issues.apache.org/jira/browse/HBASE-17257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15734921#comment-15734921
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Ted Yu commented on HBASE-17257:
--------------------------------
I started looking at the patch.
For AliasEnabledTableMultiplexer#put() :
{code}
+ convertedPut = (Put) aliasManager.convertMutation(currentHtd, put);
+ } catch (IOException e) {
+ throw new IllegalStateException(e);
{code}
Looking at HTableMultiplexer, line 216:
{code}
} catch (IOException e) {
LOG.debug("Cannot process the put " + put, e);
}
return false;
{code}
I suggest using the same way of handling IOE.
{code}
+ /** Alias namespace name. */
+ public static final byte [] ALIAS_NAMESPACE_NAME =
Bytes.toBytes("hbase_alias");
{code}
Please use hbase namespace. Let us know if you see any error in tests after the
change.
{code}
+ public static final TableName ALIAS_TABLE_NAME =
+ valueOf(NamespaceDescriptor.ALIAS_NAMESPACE_NAME_STR,
"hbase_alias_table");
{code}
Considering above comment, "alias" or "column_alias" should suffice as table
name.
For AliasManager:
{code}
+ private static ByteBuffer aliasRowIdBuffer = ByteBuffer.allocate(128);
{code}
How is 128 determined ?
{code}
+ CAPACITY_FOR_ALIAS.put(1, Long.valueOf(Byte.MAX_VALUE) -
Long.valueOf(Byte.MIN_VALUE));
{code}
Why not using cast (to long) above ?
{code}
+ INVALID_ALIAS.put(1, new byte[]{Byte.MIN_VALUE});
{code}
Why does the invalid alias have the same value as initial value ?
Consider using postStartMaster() hook to create alias table.
Will post more comments after the patch is on review board.
> 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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