Base class for ResolverStrategy.

ResolverStrategy is used with tfx.dsl.Resolver to express the input resolution logic. Currently TFX supports the following builtin ResolverStrategy:

A resolver strategy defines a type behavior used for input selection. A resolver strategy subclass must override the resolve_artifacts() function which takes a Dict[str, List[Artifact]] as parameters and returns the resolved dict of the same type.



ResolverOp-like usage inside resolver_function.


Resolves artifacts from channels, optionally querying MLMD if needed.

In asynchronous execution mode, resolver classes may composed in sequence where the resolve_artifacts() result from the previous resolver instance would be passed to the next resolver instance's resolve_artifacts() inputs.

If resolve_artifacts() returns None, it is considered as "no inputs available", and the remaining resolvers will not be executed.

Also if resolve_artifacts() omits any key from the input_dict it will not be available from the downstream resolver instances. General recommendation is to preserve all keys in the input_dict unless you have specific reason.

store An MLMD MetadataStore.
input_dict The input_dict to resolve from.

If all entries has enough data after the resolving, returns the resolved input_dict. Otherise, return None.