[jira] [Commented] (CALCITE-2146) Errant CyclicMetadataException in multithreaded context

["Julian Hyde (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-2146?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16334696#comment-16334696 ] 

Julian Hyde commented on CALCITE-2146:
--------------------------------------

It was not designed to be thread-safe. A cluster is the state for preparing a query. We assume that only one thread is preparing a particular query at a time.

The solution to your problem, probably, is to copy a template into its own cluster when you start working on it as a mutable query.

 

> Errant CyclicMetadataException in multithreaded context
> -------------------------------------------------------
>
>                 Key: CALCITE-2146
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2146
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.15.0
>            Reporter: Paul Jackson
>            Assignee: Julian Hyde
>            Priority: Major
>
> The code that protects against cyclic metadata is not thread-safe. A typical stack trace looks like:
> {{Caused by: org.apache.calcite.rel.metadata.CyclicMetadataException}}
> {{ at org.apache.calcite.rel.metadata.CyclicMetadataException.<clinit>(CyclicMetadataException.java:28)}}
> {{  at GeneratedMetadataHandler_Collation.collations(Unknown Source)}}
> {{  at GeneratedMetadataHandler_Collation.collations_$(Unknown Source)}}
> {{  at GeneratedMetadataHandler_Collation.collations(Unknown Source)}}
> {{  at org.apache.calcite.rel.metadata.RelMetadataQuery.collations(RelMetadataQuery.java:563)}}
> {{  at org.apache.calcite.rel.metadata.RelMdCollation.collations(RelMdCollation.java:117)}}
> {{  at GeneratedMetadataHandler_Collation.collations_$(Unknown Source)}}
> {{  at GeneratedMetadataHandler_Collation.collations(Unknown Source)}}
> {{  at GeneratedMetadataHandler_Collation.collations_$(Unknown Source)}}
> {{  at GeneratedMetadataHandler_Collation.collations(Unknown Source)}}
> {{  at org.apache.calcite.rel.metadata.RelMetadataQuery.collations(RelMetadataQuery.java:563)}}
> {{  at org.apache.calcite.rel.metadata.RelMdCollation.project(RelMdCollation.java:207)}}
> {{  at org.apache.calcite.rel.logical.LogicalProject$1.get(LogicalProject.java:117)}}
> {{  at org.apache.calcite.rel.logical.LogicalProject$1.get(LogicalProject.java:115)}}
> {{ at org.apache.calcite.plan.RelTraitSet.replaceIfs(RelTraitSet.java:238)}}
> {{  at org.apache.calcite.rel.logical.LogicalProject.create(LogicalProject.java:113)}}
> {{  at org.apache.calcite.rel.logical.LogicalProject.create(LogicalProject.java:103)}}
> {{  at org.apache.calcite.rel.core.RelFactories$ProjectFactoryImpl.createProject(RelFactories.java:127)}}
> {{  at org.apache.calcite.tools.RelBuilder.project(RelBuilder.java:1064)}}
> Generally, the use case that causes this is one where we have a set of SQL templates represented as RelNodes, which we use as a starting point for queries. If different threads operate on the same RelNode, they may work on the same cluster, and therefore the same RelMetadataQuery instance, which contains a map instance that is used to detect Cyclic Metadata.



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