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https://issues.apache.org/jira/browse/YARN-5715?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15592348#comment-15592348
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Sangjin Lee commented on YARN-5715:
-----------------------------------
bq. Regarding Li's comment, we should have a constant like
DEFAULT_ENTITY_PREFIX irrespective of whether it is to be used by clients or
not. If it is intended to be used by clients, we should probably have it inside
TimelineEntity.
A constant in {{TimelineEntity}} sounds reasonable.
> 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
> Assignee: Rohith Sharma K S
> Priority: Critical
> Attachments: YARN-5715-YARN-5355.01.patch,
> YARN-5715-YARN-5355.02.patch, YARN-5715-YARN-5355.03.patch,
> YARN-5715-YARN-5355.04.patch
>
>
> 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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