presto-main/src/main/java/io/prestosql/metadata/MetadataManager.java/MetadataManager/resolveFunction
class MetadataManager:    @Override
    public ResolvedFunction resolveFunction(QualifiedName name, List<TypeSignatureProvider> parameterTypes)
    {
        return ResolvedFunction.fromQualifiedName(name)
                .orElseGet(() -> functions.resolveFunction(name, parameterTypes));
    }