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https://issues.apache.org/jira/browse/LENS-552?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15035616#comment-15035616
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Rajat Khandelwal commented on LENS-552:
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Sharing some of the thought process here:
Attaching class heirarchy of context classes.
We have single fact contexts: FactHQLContext and SingleFactHQLContext. Both
have exclusive use cases.
SingleFactHQLContext: Created directly, AST is used from CubeQueryContext
FactHQLContext: When a MultiFactHQLContext instance is made, ASTs are copied
from CubeQueryContext into CandidateFact instances and then FactHQLContext
instances are made over them.
Both work on ASTs, one picks AST from CubeQueryContext and the other picks from
CandidateFact.
I'll try to unify these.
The reason being that for multiple storage, right now we have
SingleFactMultiStorageHQLContext. From CubeQueryContext, SingleFactHQLContext
or SingleFactMultiStorageHQLContext are created depending on the requirement,
now I'd like to re-use that class from MultiFactHQLContext also. But
MultiFactHQLContext doesn't create SingleFactHQLContext, it crated
FactHQLContext. So I'd have to create another class say x such that
x:FactHQLContext :: SingleFactMultiStorageHQLContext:SingleFactHQLContext.
> Union support across storage tables in multi fact query
> -------------------------------------------------------
>
> Key: LENS-552
> URL: https://issues.apache.org/jira/browse/LENS-552
> Project: Apache Lens
> Issue Type: Improvement
> Components: cube
> Reporter: Sushil Mohanty
> Assignee: Rajat Khandelwal
> Attachments: Screen Shot 2015-12-02 at 3.57.14 PM.png
>
>
> We need to have support for union across storage tables of one/all facts
> tables taking part in multi fact query.
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