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https://issues.apache.org/jira/browse/CALCITE-604?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15107391#comment-15107391
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Julian Hyde commented on CALCITE-604:
-------------------------------------
While upgrading, if you get a stack like this:
{noformat}
java.lang.ExceptionInInitializerError
at
org.apache.calcite.rel.metadata.DefaultRelMetadataProvider.<init>(DefaultRelMetadataProvider.java:36)
at ...
Caused by: java.lang.ClassCastException:
org.apache.calcite.rel.metadata.RelMdSomething cannot be cast to
org.apache.calcite.rel.metadata.MetadataHandler
at
org.apache.calcite.rel.metadata.ReflectiveRelMetadataProvider.reflectiveSource(ReflectiveRelMetadataProvider.java:119)
at
org.apache.calcite.rel.metadata.ReflectiveRelMetadataProvider.reflectiveSource(ReflectiveRelMetadataProvider.java:107)
at
org.apache.calcite.rel.metadata.RelMdPopulationSize.<clinit>(RelMdPopulationSize.java:41)
... 33 more
{noformat}
you need to add {{implements MetadataHandler<BuiltinMetadata.Something>}} to
your provider (say {{RelMdPopulationSize}} needs to implement
{{MetadataHandler<BuiltinMetadata.PopulationSize>}}.
> Invoke metadata providers via MethodHandle rather than reflection
> -----------------------------------------------------------------
>
> Key: CALCITE-604
> URL: https://issues.apache.org/jira/browse/CALCITE-604
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
>
> JDK 1.7 introduced
> http://docs.oracle.com/javase/7/docs/api/java/lang/invoke/MethodHandle.html,
> a more efficient way to invoke methods. Access control etc. is done when the
> handle is created, not each invocation.
> Currently calls to metadata providers are dispatched via reflection
> (Method.invoke, see ReflectiveRelMetadataProvider, ChainedRelMetadataProvider
> and CachingInvocationHandler), and I suspect that planning a complex query
> (especially with tracing enabled) makes millions of calls. Moving to
> MethodHandle would improve performance.
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