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https://issues.apache.org/jira/browse/AMBARI-19164?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sebastian Toader updated AMBARI-19164:
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Status: Patch Available (was: In Progress)
> Add PK to hostcomponentdesiredstate Table To Support FK Relationships
> ---------------------------------------------------------------------
>
> Key: AMBARI-19164
> URL: https://issues.apache.org/jira/browse/AMBARI-19164
> Project: Ambari
> Issue Type: Bug
> Components: ambari-server
> Reporter: Sebastian Toader
> Assignee: Sebastian Toader
> Priority: Critical
> Fix For: 2.5.0
>
> Attachments: AMBARI-19164.v1.patch
>
>
> The {{hostcomponentdesiredstate}} table currently uses a compound PK based
> off of the cluster ID, service name, host id and component name. There are
> several problems with this approach:
> * Primary Keys should be data that's not part of the business logic of the
> system and not subject to be changed potentially (as strings are).
> * Other tables referencing the {{hostcomponentdesiredstate}} table would now
> need knowledge of cluster/service/component/host in order to make the correct
> FK association. This leads to extra data being tracked as well as data
> duplication.
> * Some databases, such as SQL Server, have problems with the indexing of
> compound PKs and may lead to deadlocks when querying and updating
> concurrently.
> This table needs to be changed so that it uses a simple PK for referencing.
> FK relationships as they exist today can still be maintained as long as a
> {{UNIQUE}} constraint is placed on the table. We should:
> * Add a {{UNIQUE}} constraint to the former PK columns
> * Add an {{INDEX}} to the former PK columns
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