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Posted to issues@calcite.apache.org by "James Starr (Jira)" <ji...@apache.org> on 2021/03/16 22:41:00 UTC
[jira] [Commented] (CALCITE-4539) Support pluggable metadata
handlers and caching
[ https://issues.apache.org/jira/browse/CALCITE-4539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17302960#comment-17302960 ]
James Starr commented on CALCITE-4539:
--------------------------------------
Relates to CALCITE-3901
> Support pluggable metadata handlers and caching
> -----------------------------------------------
>
> Key: CALCITE-4539
> URL: https://issues.apache.org/jira/browse/CALCITE-4539
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: James Starr
> Priority: Major
>
> Calcite janino backed metadata does not support all the functionality that the java reflection backed metadata system, such as customizing the cache to use soft refs or have a max size. Furthermore, the janino backed metadata provider has many opinion that other are not universally shared, such as lazy loading, requiring all rels to registered to a global singleton, use of thread locals. There is no easy way to currently override these opinions.
> Calcites metadata system should consist of 3 APIs: metadata consumer, metadata implementors, metadata behavior. The metadata consumer need to able to fetch the appropriate metadata and invalidate the cache. Currently this is all done through RelMetadataQuery with some very leaky abstractions. Metadata implementors create functions that extract the metadata for particular node types. These functions are registered via ReflectiveRelMetadataProvider and ChainedRelMetadataProvider. Attempting to configure the internal behavior does not currently have an api. Currently porptions of it a scattered through out various class and are frequently not extensible.
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