[HBASE-8496] Implement tags and the internals of how a tag should look like - ASF JIRA

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Hadoop Flags:

Incompatible change, Reviewed
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Tags are additional metadata to be added with the KVs.
To enable the tags to be persisted in the HFiles, V3 version of HFile should be used.
<property>
      <name>hfile.format.version</name>
      <value>3</value>
  </property>
The tags has the below format
<2 byte tag length><1 byte type code><tag>
where <type> is the type of the tag, <tag> is a byte[] that has the tag data.
To add Tags using Puts
Put.add(byte[] family, byte [] qualifier, byte [] value, Tag[] tag)
Put.add(byte[] family, byte[] qualifier, long ts, byte[] value, Tag[] tag)
Can be used.
Note that even after changing the version to V3, the no-tag case will also be working fine as in V2 format.

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Tags are additional metadata to be added with the KVs. To enable the tags to be persisted in the HFiles, V3 version of HFile should be used. <property>       <name>hfile.format.version</name>       <value>3</value>   </property> The tags has the below format <2 byte tag length><1 byte type code><tag> where <type> is the type of the tag, <tag> is a byte[] that has the tag data. To add Tags using Puts Put.add(byte[] family, byte [] qualifier, byte [] value, Tag[] tag) Put.add(byte[] family, byte[] qualifier, long ts, byte[] value, Tag[] tag) Can be used. Note that even after changing the version to V3, the no-tag case will also be working fine as in V2 format.

The intent of this JIRA comes from ~~HBASE-7897~~.
This would help us to decide on the structure and format of how the tags should look like.

is related to

HBASE-7897 Add support for tags to Cell Interface

is required by

HBASE-6222 Add per-KeyValue Security

HBASE-7544 Transparent table/CF encryption

relates to

HBASE-9816 Address review comments in HBASE-8496

HBASE-9801 Change the default HFile version to V3

1.	Support Dictionary based Tag compression in HFiles	Resolved	Anoop Sam John
2.	Add client side support for Tags	Resolved	ramkrishna.s.vasudevan
3.	Support Tags in ImportTSV tool	Open	ramkrishna.s.vasudevan
4.	Optimization in HFile V3 when no tags are present in a file	Resolved	Anoop Sam John
5.	RPC side changes to have a different codec for server to client communication	Resolved	ramkrishna.s.vasudevan
6.	Add Tag dictionary in WAL compression	Resolved	Anoop Sam John
7.	HFileContext should adopt Builder pattern	Resolved	ramkrishna.s.vasudevan
8.	HStore should use HFileContext for holding the state therein rather than duplicating it	Open	ramkrishna.s.vasudevan
9.	HFileContext defaults can lead to inconsistency with expectations of HFile block header sizing between readers and writers	Resolved	ramkrishna.s.vasudevan

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