zjw1111 commented on code in PR #222:
URL: https://github.com/apache/paimon-cpp/pull/222#discussion_r3842245326
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src/paimon/core/catalog/file_system_catalog.h:
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@@ -38,11 +39,17 @@ class FileSystem;
class Identifier;
class Logger;
-class FileSystemCatalog : public Catalog {
+class FileSystemCatalog : public Catalog, public FormatTableCatalog {
Review Comment:
This double-inheritance capability pattern still feels too implicit to us.
`Catalog` already exposes `GetFormatTable()`, while the actual override point
lives on a separate `FormatTableCatalog` and is discovered through
`dynamic_cast`. Catalog implementations therefore need to know about a second
orthogonal base class, and the extension point is not visible from the
`Catalog` interface itself; this also introduces an RTTI-based cross-cast.
We would prefer `LoadFormatTable()` (or a protected virtual hook used by
`GetFormatTable()`) to be a virtual function on `Catalog`, overridden directly
by `FileSystemCatalog` and `RestCatalog`, instead of introducing this parallel
interface. Since paimon-cpp is still in the 0.x stage and public API changes
are allowed, preserving the current vtable should not drive this design; the
explicit virtual contract seems like the simpler and more conventional API.
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