Fix: Suppor forward-only changes of model kinds under certain circumstances

Author: izeigerman

sqlmesh/core/plan/builder.py

@@ -601,7 +601,7 @@ def _categorize_snapshots(
                 # If the model kind changes mark as breaking
                 if snapshot.is_model and snapshot.name in self._context_diff.modified_snapshots:
                     _, old = self._context_diff.modified_snapshots[snapshot.name]
-                    if old.model.kind.name != snapshot.model.kind.name:
+                    if _is_breaking_kind_change(old, snapshot):
                         category = SnapshotChangeCategory.BREAKING
 
                 snapshot.categorize_as(category)
@@ -765,8 +765,8 @@ def _is_forward_only_change(self, s_id: SnapshotId) -> bool:
         snapshot = self._context_diff.snapshots[s_id]
         if snapshot.name in self._context_diff.modified_snapshots:
             _, old = self._context_diff.modified_snapshots[snapshot.name]
-            # If the model kind has changed, then we should not consider this to be a forward-only change.
-            if snapshot.is_model and old.model.kind.name != snapshot.model.kind.name:
+            # If the model kind has changed in a breaking way, then we can't consider this to be a forward-only change.
+            if snapshot.is_model and _is_breaking_kind_change(old, snapshot):
                 return False
         return (
             snapshot.is_model
@@ -882,3 +882,16 @@ def _modified_and_added_snapshots(self) -> t.List[Snapshot]:
             if snapshot.name in self._context_diff.modified_snapshots
             or snapshot.snapshot_id in self._context_diff.added
         ]
+
+
+def _is_breaking_kind_change(old: Snapshot, new: Snapshot) -> bool:
+    if old.model.kind.name == new.model.kind.name:
+        # If the kind hasn't changed, then it's not a breaking change
+        return False
+    if not old.is_incremental or not new.is_incremental:
+        # If either is not incremental, then it's a breaking change
+        return True
+    if old.model.partitioned_by == new.model.partitioned_by:
+        # If the partitioning hasn't changed, then it's not a breaking change
+        return False
+    return True

sqlmesh/dbt/model.py

@@ -257,6 +257,13 @@ def model_kind(self, context: DbtContext) -> ModelKind:
                 if field_val is not None:
                     incremental_by_kind_kwargs[field] = field_val
 
+            disable_restatement = self.disable_restatement
+            if disable_restatement is None:
+                disable_restatement = (
+                    not self.full_refresh if self.full_refresh is not None else False
+                )
+            incremental_kind_kwargs["disable_restatement"] = disable_restatement
+
             if self.time_column:
                 strategy = self.incremental_strategy or target.default_incremental_strategy(
                     IncrementalByTimeRangeKind
@@ -270,20 +277,11 @@ def model_kind(self, context: DbtContext) -> ModelKind:
 
                 return IncrementalByTimeRangeKind(
                     time_column=self.time_column,
-                    disable_restatement=(
-                        self.disable_restatement if self.disable_restatement is not None else False
-                    ),
                     auto_restatement_intervals=self.auto_restatement_intervals,
                     **incremental_kind_kwargs,
                     **incremental_by_kind_kwargs,
                 )
 
-            disable_restatement = self.disable_restatement
-            if disable_restatement is None:
-                disable_restatement = (
-                    not self.full_refresh if self.full_refresh is not None else False
-                )
-
             if self.unique_key:
                 strategy = self.incremental_strategy or target.default_incremental_strategy(
                     IncrementalByUniqueKeyKind
@@ -309,7 +307,6 @@ def model_kind(self, context: DbtContext) -> ModelKind:
 
                 return IncrementalByUniqueKeyKind(
                     unique_key=self.unique_key,
-                    disable_restatement=disable_restatement,
                     **incremental_kind_kwargs,
                     **incremental_by_kind_kwargs,
                 )
@@ -319,7 +316,6 @@ def model_kind(self, context: DbtContext) -> ModelKind:
             )
             return IncrementalUnmanagedKind(
                 insert_overwrite=strategy in INCREMENTAL_BY_TIME_STRATEGIES,
-                disable_restatement=disable_restatement,
                 **incremental_kind_kwargs,
             )
         if materialization == Materialization.EPHEMERAL:

tests/core/test_plan.py

@@ -8,15 +8,17 @@
 from tests.core.test_table_diff import create_test_console
 import time_machine
 from pytest_mock.plugin import MockerFixture
-from sqlglot import parse_one
+from sqlglot import parse_one, exp
 
+from sqlmesh.core import dialect as d
 from sqlmesh.core.context import Context
 from sqlmesh.core.context_diff import ContextDiff
 from sqlmesh.core.environment import EnvironmentNamingInfo, EnvironmentStatements
 from sqlmesh.core.model import (
     ExternalModel,
     FullKind,
     IncrementalByTimeRangeKind,
+    IncrementalUnmanagedKind,
     SeedKind,
     SeedModel,
     SqlModel,
@@ -1724,6 +1726,60 @@ def test_forward_only_models_model_kind_changed(make_snapshot, mocker: MockerFix
     assert updated_snapshot.change_category == SnapshotChangeCategory.BREAKING
 
 
+@pytest.mark.parametrize(
+    "partitioned_by, expected_change_category",
+    [
+        ([], SnapshotChangeCategory.BREAKING),
+        ([d.parse_one("ds")], SnapshotChangeCategory.FORWARD_ONLY),
+    ],
+)
+def test_forward_only_models_model_kind_changed_to_incremental_by_time_range(
+    make_snapshot,
+    partitioned_by: t.List[exp.Expression],
+    expected_change_category: SnapshotChangeCategory,
+):
+    snapshot = make_snapshot(
+        SqlModel(
+            name="a",
+            query=parse_one("select 1, ds"),
+            kind=IncrementalUnmanagedKind(),
+            partitioned_by=partitioned_by,
+        )
+    )
+    snapshot.categorize_as(SnapshotChangeCategory.BREAKING)
+    updated_snapshot = make_snapshot(
+        SqlModel(
+            name="a",
+            query=parse_one("select 3, ds"),
+            kind=IncrementalByTimeRangeKind(time_column="ds", forward_only=True),
+        )
+    )
+    updated_snapshot.previous_versions = snapshot.all_versions
+
+    context_diff = ContextDiff(
+        environment="test_environment",
+        is_new_environment=True,
+        is_unfinalized_environment=False,
+        normalize_environment_name=True,
+        create_from="prod",
+        create_from_env_exists=True,
+        added=set(),
+        removed_snapshots={},
+        modified_snapshots={updated_snapshot.name: (updated_snapshot, snapshot)},
+        snapshots={updated_snapshot.snapshot_id: updated_snapshot},
+        new_snapshots={updated_snapshot.snapshot_id: updated_snapshot},
+        previous_plan_id=None,
+        previously_promoted_snapshot_ids=set(),
+        previous_finalized_snapshots=None,
+        previous_gateway_managed_virtual_layer=False,
+        gateway_managed_virtual_layer=False,
+        environment_statements=[],
+    )
+
+    PlanBuilder(context_diff, is_dev=True).build()
+    assert updated_snapshot.change_category == expected_change_category
+
+
 def test_indirectly_modified_forward_only_model(make_snapshot, mocker: MockerFixture):
     snapshot_a = make_snapshot(SqlModel(name="a", query=parse_one("select 1 as a, ds")))
     snapshot_a.categorize_as(SnapshotChangeCategory.BREAKING)

tests/dbt/test_transformation.py

@@ -244,6 +244,24 @@ def test_model_kind():
         time_column="foo", dialect="duckdb", forward_only=True, disable_restatement=False
     )
 
+    assert ModelConfig(
+        materialized=Materialization.INCREMENTAL,
+        time_column="foo",
+        incremental_strategy="merge",
+        full_refresh=True,
+    ).model_kind(context) == IncrementalByTimeRangeKind(
+        time_column="foo", dialect="duckdb", forward_only=True, disable_restatement=False
+    )
+
+    assert ModelConfig(
+        materialized=Materialization.INCREMENTAL,
+        time_column="foo",
+        incremental_strategy="merge",
+        full_refresh=False,
+    ).model_kind(context) == IncrementalByTimeRangeKind(
+        time_column="foo", dialect="duckdb", forward_only=True, disable_restatement=True
+    )
+
     assert ModelConfig(
         materialized=Materialization.INCREMENTAL,
         time_column="foo",