Introduce TableLastModifiedMetadataBatch and implement BaseAdapter.ca…

…lculate_freshness_from_metadata_batch (#127)

.changes/unreleased/Features-20240325-180611.yaml

@@ -0,0 +1,6 @@
+kind: Features
+body: Introduce TableLastModifiedMetadataBatch and implement BaseAdapter.calculate_freshness_from_metadata_batch
+time: 2024-03-25T18:06:11.816163-04:00
+custom:
+  Author: michelleark
+  Issue: "138"

dbt/adapters/base/impl.py

@@ -1062,6 +1062,7 @@ def execute_macro(
         project: Optional[str] = None,
         context_override: Optional[Dict[str, Any]] = None,
         kwargs: Optional[Dict[str, Any]] = None,
+        needs_conn: bool = False,
     ) -> AttrDict:
         """Look macro_name up in the manifest and execute its results.
 
@@ -1074,6 +1075,10 @@ def execute_macro(
             execution context.
         :param kwargs: An optional dict of keyword args used to pass to the
             macro.
+        : param needs_conn: A boolean that indicates whether the specified macro
+            requires an open connection to execute. If needs_conn is True, a
+            connection is expected and opened if necessary. Otherwise (and by default),
+            no connection is expected prior to executing the macro.
         """
 
         if kwargs is None:
@@ -1106,6 +1111,10 @@ def execute_macro(
 
         macro_function = CallableMacroGenerator(macro, macro_context)
 
+        if needs_conn:
+            connection = self.connections.get_thread_connection()
+            self.connections.open(connection)
+
         with self.connections.exception_handler(f"macro {macro_name}"):
             result = macro_function(**kwargs)
         return result
@@ -1297,48 +1306,110 @@ def calculate_freshness(
         }
         return adapter_response, freshness
 
+    def calculate_freshness_from_metadata_batch(
+        self,
+        sources: List[BaseRelation],
+        macro_resolver: Optional[MacroResolverProtocol] = None,
+    ) -> Tuple[List[Optional[AdapterResponse]], Dict[BaseRelation, FreshnessResponse]]:
+        """
+        Given a list of sources (BaseRelations), calculate the metadata-based freshness in batch.
+        This method should _not_ execute a warehouse query per source, but rather batch up
+        the sources into as few requests as possible to minimize the number of roundtrips required
+        to compute metadata-based freshness for each input source.
+
+        :param sources: The list of sources to calculate metadata-based freshness for
+        :param macro_resolver: An optional macro_resolver to use for get_relation_last_modified
+        :return: a tuple where:
+            * the first element is a list of optional AdapterResponses indicating the response
+              for each request the method made to compute the freshness for the provided sources.
+            * the second element is a dictionary mapping an input source BaseRelation to a FreshnessResponse,
+              if it was possible to calculate a FreshnessResponse for the source.
+        """
+        # Track schema, identifiers of sources for lookup from batch query
+        schema_identifier_to_source = {
+            (
+                source.path.get_lowered_part(ComponentName.Schema),
+                source.path.get_lowered_part(ComponentName.Identifier),
+            ): source
+            for source in sources
+        }
+
+        # Group metadata sources by information schema -- one query per information schema will be necessary
+        sources_by_info_schema: Dict[InformationSchema, List[BaseRelation]] = self._get_catalog_relations_by_info_schema(sources)
+
+        freshness_responses: Dict[BaseRelation, FreshnessResponse] = {}
+        adapter_responses: List[Optional[AdapterResponse]] = []
+        for (
+            information_schema,
+            sources_for_information_schema,
+        ) in sources_by_info_schema.items():
+            result = self.execute_macro(
+                GET_RELATION_LAST_MODIFIED_MACRO_NAME,
+                kwargs={
+                    "information_schema": information_schema,
+                    "relations": sources_for_information_schema,
+                },
+                macro_resolver=macro_resolver,
+                needs_conn=True,
+            )
+            adapter_response, table = result.response, result.table  # type: ignore[attr-defined]
+            adapter_responses.append(adapter_response)
+
+            for row in table:
+                raw_relation, freshness_response = self._parse_freshness_row(row, table)
+                source_relation_for_result = schema_identifier_to_source[raw_relation]
+                freshness_responses[source_relation_for_result] = freshness_response
+
+        return adapter_responses, freshness_responses
+
     def calculate_freshness_from_metadata(
         self,
         source: BaseRelation,
         macro_resolver: Optional[MacroResolverProtocol] = None,
     ) -> Tuple[Optional[AdapterResponse], FreshnessResponse]:
-        kwargs: Dict[str, Any] = {
-            "information_schema": source.information_schema_only(),
-            "relations": [source],
-        }
-        result = self.execute_macro(
-            GET_RELATION_LAST_MODIFIED_MACRO_NAME,
-            kwargs=kwargs,
+        adapter_responses, freshness_responses = self.calculate_freshness_from_metadata_batch(
+            sources=[source],
             macro_resolver=macro_resolver,
         )
-        adapter_response, table = result.response, result.table  # type: ignore[attr-defined]
-
-        try:
-            from dbt_common.clients.agate_helper import get_column_value_uncased
+        adapter_response = adapter_responses[0] if adapter_responses else None
+        return adapter_response, freshness_responses[source]
 
-            row = table[0]
-            last_modified_val = get_column_value_uncased("last_modified", row)
-            snapshotted_at_val = get_column_value_uncased("snapshotted_at", row)
-        except Exception:
-            raise MacroResultError(GET_RELATION_LAST_MODIFIED_MACRO_NAME, table)
-
-        if last_modified_val is None:
+    def _create_freshness_response(
+        self, last_modified: Optional[datetime], snapshotted_at: Optional[datetime]
+    ) -> FreshnessResponse:
+        if last_modified is None:
             # Interpret missing value as "infinitely long ago"
             max_loaded_at = datetime(1, 1, 1, 0, 0, 0, tzinfo=pytz.UTC)
         else:
-            max_loaded_at = _utc(last_modified_val, None, "last_modified")
-
-        snapshotted_at = _utc(snapshotted_at_val, None, "snapshotted_at")
+            max_loaded_at = _utc(last_modified, None, "last_modified")
 
+        snapshotted_at = _utc(snapshotted_at, None, "snapshotted_at")
         age = (snapshotted_at - max_loaded_at).total_seconds()
-
         freshness: FreshnessResponse = {
             "max_loaded_at": max_loaded_at,
             "snapshotted_at": snapshotted_at,
             "age": age,
         }
 
-        return adapter_response, freshness
+        return freshness
+
+    def _parse_freshness_row(self, row: "agate.Row", table: "agate.Table") -> Tuple[Any, FreshnessResponse]:
+        from dbt_common.clients.agate_helper import get_column_value_uncased
+
+        try:
+            last_modified_val = get_column_value_uncased("last_modified", row)
+            snapshotted_at_val = get_column_value_uncased("snapshotted_at", row)
+            identifier = get_column_value_uncased("identifier", row)
+            schema = get_column_value_uncased("schema", row)
+        except Exception:
+            raise MacroResultError(GET_RELATION_LAST_MODIFIED_MACRO_NAME, table)
+
+        freshness_response = self._create_freshness_response(
+            last_modified_val,
+            snapshotted_at_val
+        )
+        raw_relation = schema.lower().strip(), identifier.lower().strip()
+        return raw_relation, freshness_response
 
     def pre_model_hook(self, config: Mapping[str, Any]) -> Any:
         """A hook for running some operation before the model materialization

dbt/adapters/capability.py

@@ -13,6 +13,9 @@ class Capability(str, Enum):
     TableLastModifiedMetadata = "TableLastModifiedMetadata"
     """Indicates support for determining the time of the last table modification by querying database metadata."""
 
+    TableLastModifiedMetadataBatch = "TableLastModifiedMetadataBatch"
+    """Indicates support for performantly determining the time of the last table modification by querying database metadata in batch."""
+
 
 class Support(str, Enum):
     Unknown = "Unknown"