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https://issues.apache.org/jira/browse/KYLIN-3249?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Shaofeng SHI reassigned KYLIN-3249:
-----------------------------------
Assignee: Shaofeng SHI
Fix Version/s: v2.6.0
> Default hybrid cube priority should be the same as of a regular cube
> --------------------------------------------------------------------
>
> Key: KYLIN-3249
> URL: https://issues.apache.org/jira/browse/KYLIN-3249
> Project: Kylin
> Issue Type: Bug
> Components: Query Engine
> Affects Versions: v2.2.0
> Environment: HDP 2.5.6, Kylin 2.2
> Reporter: Vsevolod Ostapenko
> Assignee: Shaofeng SHI
> Priority: Major
> Fix For: v2.6.0
>
>
> Hybrid cubes are assigned default priority lower than regular cubes, which
> leads to incorrect selection of a hybrid cube while a regular non-hybridized
> cube with lower cost is available.
> For example, model has a wide cube with full set of metrics and narrower cube
> with top-N entries for a subset of metrics.
> If wide cube is hybridized (due to a new metric addition), but top-N cube
> remains unchanged and non-hybridized, top-N cube will be no longer queried,
> causing query performance degradation.
> The issue can be tracked to the
> query/src/main/java/org/apache/kylin/query/routing/Candidate.java, where
> hybrid cubes are assigned priority 0, while regular cubes are assigned
> priority of 1.
> This unconditional priority assignment is incorrect as it only holds for
> cases when there is only one cube "flavor" in the model or when all the cubes
> of various "flavors" are hybridized at the same time.
> Simplest fix is to have hybrid priority to be the same as of a regular cube.
> Plus, as an enhancement to the cube selection algorithm a new rule can be
> implemented that will filter out regular candidate cubes that are included
> into candidate hybrid cubes.
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