Better feature detection mechanism for adapters.

core/dbt/adapters/base/impl.py

@@ -162,6 +162,14 @@ def submit(self, compiled_code: str) -> Any:
         raise NotImplementedError("PythonJobHelper submit function is not implemented yet")
 
 
+class AdapterFeature(str, Enum):
+    """Enumeration of optional adapter features which can be probed using BaseAdapter.has_feature()"""
+
+    CatalogByRelations = "GetCatalogByRelations"
+    """Flags support for retrieving catalog information using a list of relations, rather than always retrieving all
+    the relations in a schema """
+
+
 class BaseAdapter(metaclass=AdapterMeta):
     """The BaseAdapter provides an abstract base class for adapters.
 
@@ -223,8 +231,6 @@ class BaseAdapter(metaclass=AdapterMeta):
         ConstraintType.foreign_key: ConstraintSupport.ENFORCED,
     }
 
-    CATALOG_BY_RELATION_SUPPORT = False
-
     def __init__(self, config) -> None:
         self.config = config
         self.cache = RelationsCache()
@@ -1141,7 +1147,7 @@ def get_catalog(self, manifest: Manifest) -> Tuple[agate.Table, List[Exception]]
         with executor(self.config) as tpe:
             futures: List[Future[agate.Table]] = []
             relation_count = len(self._get_catalog_relations(manifest))
-            if relation_count <= 100 and self.CATALOG_BY_RELATION_SUPPORT:
+            if relation_count <= 100 and self.has_feature(AdapterFeature.CatalogByRelations):
                 relations_by_schema = self._get_catalog_relations_by_info_schema(manifest)
                 for info_schema in relations_by_schema:
                     name = ".".join([str(info_schema.database), "information_schema"])
@@ -1495,6 +1501,12 @@ def render_model_constraint(cls, constraint: ModelLevelConstraint) -> Optional[s
         else:
             return None
 
+    def has_feature(self, feature: AdapterFeature) -> bool:
+        # The base adapter implementation does not implement any optional
+        # features, so always return false. Adapters which wish to provide
+        # optional features will have to override this function.
+        return False
+
 
 COLUMNS_EQUAL_SQL = """
 with diff_count as (

plugins/postgres/dbt/adapters/postgres/impl.py

@@ -3,7 +3,7 @@
 from typing import Optional, Set, List, Any
 
 from dbt.adapters.base.meta import available
-from dbt.adapters.base.impl import AdapterConfig, ConstraintSupport
+from dbt.adapters.base.impl import AdapterConfig, AdapterFeature, ConstraintSupport
 from dbt.adapters.sql import SQLAdapter
 from dbt.adapters.postgres import PostgresConnectionManager
 from dbt.adapters.postgres.column import PostgresColumn
@@ -75,6 +75,8 @@ class PostgresAdapter(SQLAdapter):
 
     CATALOG_BY_RELATION_SUPPORT = True
 
+    SUPPORTED_FEATURES: Set[AdapterFeature] = frozenset(AdapterFeature.CatalogByRelations)
+
     @classmethod
     def date_function(cls):
         return "now()"
@@ -145,3 +147,6 @@ def valid_incremental_strategies(self):
 
     def debug_query(self):
         self.execute("select 1 as id")
+
+    def has_feature(self, feature: AdapterFeature) -> bool:
+        return feature in self.SUPPORTED_FEATURES