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From "Sangjin Lee (JIRA)" <j...@apache.org>
Subject [jira] [Created] (YARN-5715) introduce entity prefix for return and sort order
Date Thu, 06 Oct 2016 22:41:20 GMT
Sangjin Lee created YARN-5715:

             Summary: introduce entity prefix for return and sort order
                 Key: YARN-5715
                 URL: https://issues.apache.org/jira/browse/YARN-5715
             Project: Hadoop YARN
          Issue Type: Sub-task
          Components: timelineserver
            Reporter: Sangjin Lee
            Priority: Critical

While looking into YARN-5585, we have come across the need to provide a sort order different
than the current entity id order. The current entity id order returns entities strictly in
the lexicographical order, and as such it returns the earliest entities first. This may not
be the most natural return order. A more natural return/sort order would be from the most
recent entities.

To solve this, we would like to add what we call the "entity prefix" in the row key for the
entity table. It is a number (long) that can be easily provided by the client on write. In
the row key, it would be added before the entity id itself.

The entity prefix would be considered mandatory. On all writes (including updates) the correct
entity prefix should be set by the client so that the correct row key is used. The entity
prefix needs to be unique only within the scope of the application and the entity type.

For queries that return a list of entities, the prefix values will be returned along with
the entity id's. Queries that specify the prefix and the id should be returned quickly using
the row key. If the query omits the prefix but specifies the id (query by id), the query may
be less efficient.

This JIRA should add the entity prefix to the entity API and add its handling to the schema
and the write path. The read path will be addressed in YARN-5585.

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