feat: per-db add metrics (#20990)

* feat: per-db add metrics

* Add unit tests

superset/connectors/sqla/models.py

@@ -1932,7 +1932,10 @@ def fetch_metadata(self, commit: bool = True) -> MetadataResult:
         :return: Tuple with lists of added, removed and modified column names.
         """
         new_columns = self.external_metadata()
-        metrics = []
+        metrics = [
+            SqlMetric(**metric)
+            for metric in self.database.get_metrics(self.table_name, self.schema)
+        ]
         any_date_col = None
         db_engine_spec = self.db_engine_spec
 
@@ -1989,14 +1992,6 @@ def fetch_metadata(self, commit: bool = True) -> MetadataResult:
         columns.extend([col for col in old_columns if col.expression])
         self.columns = columns
 
-        metrics.append(
-            SqlMetric(
-                metric_name="count",
-                verbose_name="COUNT(*)",
-                metric_type="count",
-                expression="COUNT(*)",
-            )
-        )
         if not self.main_dttm_col:
             self.main_dttm_col = any_date_col
         self.add_missing_metrics(metrics)

superset/db_engine_specs/base.py

@@ -154,6 +154,21 @@ class LimitMethod:  # pylint: disable=too-few-public-methods
     FORCE_LIMIT = "force_limit"
 
 
+class MetricType(TypedDict, total=False):
+    """
+    Type for metrics return by `get_metrics`.
+    """
+
+    metric_name: str
+    expression: str
+    verbose_name: Optional[str]
+    metric_type: Optional[str]
+    description: Optional[str]
+    d3format: Optional[str]
+    warning_text: Optional[str]
+    extra: Optional[str]
+
+
 class BaseEngineSpec:  # pylint: disable=too-many-public-methods
     """Abstract class for database engine specific configurations
 
@@ -1054,6 +1069,26 @@ def get_columns(
         """
         return inspector.get_columns(table_name, schema)
 
+    @classmethod
+    def get_metrics(  # pylint: disable=unused-argument
+        cls,
+        database: "Database",
+        inspector: Inspector,
+        table_name: str,
+        schema: Optional[str],
+    ) -> List[MetricType]:
+        """
+        Get all metrics from a given schema and table.
+        """
+        return [
+            {
+                "metric_name": "count",
+                "verbose_name": "COUNT(*)",
+                "metric_type": "count",
+                "expression": "COUNT(*)",
+            }
+        ]
+
     @classmethod
     def where_latest_partition(  # pylint: disable=too-many-arguments,unused-argument
         cls,

superset/models/core.py

@@ -55,7 +55,7 @@
 
 from superset import app, db_engine_specs, is_feature_enabled
 from superset.databases.utils import make_url_safe
-from superset.db_engine_specs.base import TimeGrain
+from superset.db_engine_specs.base import MetricType, TimeGrain
 from superset.extensions import cache_manager, encrypted_field_factory, security_manager
 from superset.models.helpers import AuditMixinNullable, ImportExportMixin
 from superset.models.tags import FavStarUpdater
@@ -693,6 +693,13 @@ def get_columns(
     ) -> List[Dict[str, Any]]:
         return self.db_engine_spec.get_columns(self.inspector, table_name, schema)
 
+    def get_metrics(
+        self,
+        table_name: str,
+        schema: Optional[str] = None,
+    ) -> List[MetricType]:
+        return self.db_engine_spec.get_metrics(self, self.inspector, table_name, schema)
+
     def get_indexes(
         self, table_name: str, schema: Optional[str] = None
     ) -> List[Dict[str, Any]]:

tests/unit_tests/models/__init__.py

@@ -0,0 +1,16 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.

tests/unit_tests/models/core_test.py

@@ -0,0 +1,72 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+# pylint: disable=import-outside-toplevel
+
+from typing import List, Optional
+
+from pytest_mock import MockFixture
+from sqlalchemy.engine.reflection import Inspector
+
+
+def test_get_metrics(mocker: MockFixture) -> None:
+    """
+    Tests for ``get_metrics``.
+    """
+    from superset.db_engine_specs.base import MetricType
+    from superset.db_engine_specs.sqlite import SqliteEngineSpec
+    from superset.models.core import Database
+
+    database = Database(database_name="my_database", sqlalchemy_uri="sqlite://")
+    assert database.get_metrics("table") == [
+        {
+            "expression": "COUNT(*)",
+            "metric_name": "count",
+            "metric_type": "count",
+            "verbose_name": "COUNT(*)",
+        }
+    ]
+
+    class CustomSqliteEngineSpec(SqliteEngineSpec):
+        @classmethod
+        def get_metrics(
+            cls,
+            database: Database,
+            inspector: Inspector,
+            table_name: str,
+            schema: Optional[str],
+        ) -> List[MetricType]:
+            return [
+                {
+                    "expression": "COUNT(DISTINCT user_id)",
+                    "metric_name": "count_distinct_user_id",
+                    "metric_type": "count_distinct",
+                    "verbose_name": "COUNT(DISTINCT user_id)",
+                },
+            ]
+
+    database.get_db_engine_spec_for_backend = mocker.MagicMock(  # type: ignore
+        return_value=CustomSqliteEngineSpec
+    )
+    assert database.get_metrics("table") == [
+        {
+            "expression": "COUNT(DISTINCT user_id)",
+            "metric_name": "count_distinct_user_id",
+            "metric_type": "count_distinct",
+            "verbose_name": "COUNT(DISTINCT user_id)",
+        },
+    ]