James Starr created CALCITE-4539:
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Summary: 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
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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