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https://issues.apache.org/jira/browse/IMPALA-7969?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gabor Kaszab updated IMPALA-7969:
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Target Version: Impala 3.3.0 (was: Impala 3.2.0)
> Always admit trivial queries immediately
> ----------------------------------------
>
> Key: IMPALA-7969
> URL: https://issues.apache.org/jira/browse/IMPALA-7969
> Project: IMPALA
> Issue Type: Improvement
> Components: Backend
> Reporter: Tim Armstrong
> Assignee: Bikramjeet Vig
> Priority: Major
> Labels: admission-control
>
> Here are two common query types that consume minimal resources:
> * {{select ... from ... limit 0}}, which is used by some clients to determine
> column types
> * {{select <expr1>, <expr2>, <expr3>}}, which just evaluates some constant
> expressions on the coordinator
> Currently these queries get queued if there are existing queued queries or
> the number of queries limit is exceeded, which is inconvenient for use cases
> where latency is important. I think the planner should identify trivial
> queries and admission controller should admit immediately.
> Here's an initial thought on the definition of a trivial query:
> * Must have PLAN ROOT SINK as the root
> * Can contain UNION and EMPTYSET nodes only
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