Feat: Check freshness for mixed external & sqlmesh models

sqlmesh/core/context.py

@@ -154,6 +154,8 @@
     )
     from sqlmesh.core.snapshot import Node
 
+    from sqlmesh.core.snapshot.definition import Intervals
+
     ModelOrSnapshot = t.Union[str, Model, Snapshot]
     NodeOrSnapshot = t.Union[str, Model, StandaloneAudit, Snapshot]
 
@@ -276,6 +278,7 @@ def __init__(
         default_dialect: t.Optional[str] = None,
         default_catalog: t.Optional[str] = None,
         is_restatement: t.Optional[bool] = None,
+        parent_intervals: t.Optional[Intervals] = None,
         variables: t.Optional[t.Dict[str, t.Any]] = None,
         blueprint_variables: t.Optional[t.Dict[str, t.Any]] = None,
     ):
@@ -287,6 +290,7 @@ def __init__(
         self._variables = variables or {}
         self._blueprint_variables = blueprint_variables or {}
         self._is_restatement = is_restatement
+        self._parent_intervals = parent_intervals
 
     @property
     def default_dialect(self) -> t.Optional[str]:
@@ -315,6 +319,10 @@ def gateway(self) -> t.Optional[str]:
     def is_restatement(self) -> t.Optional[bool]:
         return self._is_restatement
 
+    @property
+    def parent_intervals(self) -> t.Optional[Intervals]:
+        return self._parent_intervals
+
     def var(self, var_name: str, default: t.Optional[t.Any] = None) -> t.Optional[t.Any]:
         """Returns a variable value."""
         return self._variables.get(var_name.lower(), default)

sqlmesh/core/scheduler.py

@@ -352,7 +352,7 @@ def batch_intervals(
             )
             for snapshot, intervals in merged_intervals.items()
         }
-        snapshot_batches = {}
+        snapshot_batches: t.Dict[Snapshot, Intervals] = {}
         all_unready_intervals: t.Dict[str, set[Interval]] = {}
         for snapshot_id in dag:
             if snapshot_id not in snapshot_intervals:
@@ -364,13 +364,22 @@ def batch_intervals(
 
             adapter = self.snapshot_evaluator.get_adapter(snapshot.model_gateway)
 
+            parent_intervals: Intervals = []
+            for parent_id in snapshot.parents:
+                parent_snapshot, _ = snapshot_intervals.get(parent_id, (None, []))
+                if not parent_snapshot or parent_snapshot.is_external:
+                    continue
+
+                parent_intervals.extend(snapshot_batches[parent_snapshot])
+
             context = ExecutionContext(
                 adapter,
                 self.snapshots_by_name,
                 deployability_index,
                 default_dialect=adapter.dialect,
                 default_catalog=self.default_catalog,
                 is_restatement=is_restatement,
+                parent_intervals=parent_intervals,
             )
 
             intervals = self._check_ready_intervals(

sqlmesh/core/signal.py

@@ -2,6 +2,7 @@
 
 import typing as t
 from sqlmesh.utils import UniqueKeyDict, registry_decorator
+from sqlmesh.utils.errors import MissingSourceError
 
 if t.TYPE_CHECKING:
     from sqlmesh.core.context import ExecutionContext
@@ -42,7 +43,16 @@ class signal(registry_decorator):
 
 
 @signal()
-def freshness(batch: DatetimeRanges, snapshot: Snapshot, context: ExecutionContext) -> bool:
+def freshness(
+    batch: DatetimeRanges,
+    snapshot: Snapshot,
+    context: ExecutionContext,
+) -> bool:
+    """
+    Implements model freshness as a signal, i.e it considers this model to be fresh if:
+    - Any upstream SQLMesh model has available intervals to compute i.e is fresh
+    - Any upstream external model has been altered since the last time the model was evaluated
+    """
     adapter = context.engine_adapter
     if context.is_restatement or not adapter.SUPPORTS_METADATA_TABLE_LAST_MODIFIED_TS:
         return True
@@ -54,24 +64,35 @@ def freshness(batch: DatetimeRanges, snapshot: Snapshot, context: ExecutionConte
         if deployability_index.is_deployable(snapshot)
         else snapshot.dev_last_altered_ts
     )
+
     if not last_altered_ts:
         return True
 
     parent_snapshots = {context.snapshots[p.name] for p in snapshot.parents}
-    if len(parent_snapshots) != len(snapshot.node.depends_on) or not all(
-        p.is_external for p in parent_snapshots
-    ):
-        # The mismatch can happen if e.g an external model is not registered in the project
+
+    upstream_parent_snapshots = {p for p in parent_snapshots if not p.is_external}
+    external_parents = snapshot.node.depends_on - {p.name for p in upstream_parent_snapshots}
+
+    if context.parent_intervals:
+        # At least one upstream sqlmesh model has intervals to compute (i.e is fresh),
+        # so the current model is considered fresh too
         return True
 
-    # Finding new data means that the upstream depedencies have been altered
-    # since the last time the model was evaluated
-    upstream_dep_has_new_data = any(
-        upstream_last_altered_ts > last_altered_ts
-        for upstream_last_altered_ts in adapter.get_table_last_modified_ts(
-            [p.name for p in parent_snapshots]
+    if external_parents:
+        external_last_altered_timestamps = adapter.get_table_last_modified_ts(
+            list(external_parents)
+        )
+
+        if len(external_last_altered_timestamps) != len(external_parents):
+            raise MissingSourceError(
+                f"Expected {len(external_parents)} sources to be present, but got {len(external_last_altered_timestamps)}."
+            )
+
+        # Finding new data means that the upstream depedencies have been altered
+        # since the last time the model was evaluated
+        return any(
+            external_last_altered_ts > last_altered_ts
+            for external_last_altered_ts in external_last_altered_timestamps
         )
-    )
 
-    # Returning true is a no-op, returning False nullifies the batch so the model will not be evaluated.
-    return upstream_dep_has_new_data
+    return False