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https://issues.apache.org/jira/browse/IMPALA-11418?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daniel Becker updated IMPALA-11418:
-----------------------------------
Fix Version/s: (was: Impala 4.2.0)
Target Version: Impala 4.3.0
> Optimize select contant statement min memory reservation
> --------------------------------------------------------
>
> Key: IMPALA-11418
> URL: https://issues.apache.org/jira/browse/IMPALA-11418
> Project: IMPALA
> Issue Type: Improvement
> Components: Frontend
> Affects Versions: Impala 4.0.0, Impala 4.1.0
> Reporter: Xianqing He
> Assignee: Xianqing He
> Priority: Major
>
> If SPOOL_QUERY_RESULTS is true, then the ResourceProfile sets a min
> reservation in PlanRootSink.
> For the statement 'select 1', the min reservation is 4MB. It's no problem if
> the cluster has enough mem available within its process limit to execute the
> query. But if the host mem not available it will throw 'Failed to get minimum
> memory reservation'.
> Some connection pools use 'select 1' to check whether the connection is
> available. The check will fail if memory is oversubscribed.
> For this case we can set the min reservation to 0 to reduce failure when the
> memory is oversubscribed.
>
> {code:java}
> Query: explain select 1
> +--------------------------------------------------------+
> | Explain String |
> +--------------------------------------------------------+
> | Max Per-Host Resource Reservation: Memory=4MB Threads=1 |
> | Per-Host Resource Estimates: Memory=10MB |
> | Codegen disabled by planner |
> | |
> | PLAN-ROOT SINK |
> | | |
> | 00:UNION |
> | constant-operands=1 |
> | row-size=1B cardinality=1 |
> +--------------------------------------------------------+ {code}
>
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