Fix: Check whether the expired snapshot is among previously finalized snapshots if the environment is not finalized

sqlmesh/core/state_sync/db/snapshot.py

@@ -185,7 +185,12 @@ def get_expired_snapshots(
         promoted_snapshot_ids = {
             snapshot.snapshot_id
             for environment in environments
-            for snapshot in environment.snapshots
+            for snapshot in (
+                environment.snapshots
+                if environment.finalized_ts is not None
+                # If the environment is not finalized, check both the current snapshots and the previous finalized snapshots
+                else [*environment.snapshots, *(environment.previous_finalized_snapshots or [])]
+            )
         }
 
         if promoted_snapshot_ids:

tests/core/state_sync/test_state_sync.py

@@ -1638,6 +1638,83 @@ def test_delete_expired_snapshots_promoted(
     assert not state_sync.get_snapshots(all_snapshots)
 
 
+def test_delete_expired_snapshots_previous_finalized_snapshots(
+    state_sync: EngineAdapterStateSync, make_snapshot: t.Callable
+):
+    """Test that expired snapshots are protected if they are part of previous finalized snapshots
+    in a non-finalized environment."""
+    now_ts = now_timestamp()
+
+    # Create an old snapshot that will be expired
+    old_snapshot = make_snapshot(
+        SqlModel(
+            name="a",
+            query=parse_one("select a, ds"),
+        ),
+    )
+    old_snapshot.ttl = "in 10 seconds"
+    old_snapshot.categorize_as(SnapshotChangeCategory.BREAKING)
+
+    # Create a new snapshot
+    new_snapshot = make_snapshot(
+        SqlModel(
+            name="a",
+            query=parse_one("select a, b, ds"),
+        ),
+    )
+    new_snapshot.categorize_as(SnapshotChangeCategory.BREAKING)
+
+    state_sync.push_snapshots([old_snapshot, new_snapshot])
+
+    # Promote the old snapshot to an environment and finalize it
+    env = Environment(
+        name="test_environment",
+        snapshots=[old_snapshot.table_info],
+        start_at="2022-01-01",
+        end_at="2022-01-01",
+        plan_id="test_plan_id",
+        previous_plan_id="test_plan_id",
+    )
+    state_sync.promote(env)
+    state_sync.finalize(env)
+
+    # Verify old snapshot is not cleaned up because it's in a finalized environment
+    assert not _get_cleanup_tasks(state_sync)
+
+    # Now promote the new snapshot to the same environment (this simulates a new plan)
+    # The environment will have previous_finalized_snapshots set to the old snapshot
+    # and will not be finalized yet
+    env = Environment(
+        name="test_environment",
+        snapshots=[new_snapshot.table_info],
+        previous_finalized_snapshots=[old_snapshot.table_info],
+        start_at="2022-01-01",
+        end_at="2022-01-01",
+        plan_id="new_plan_id",
+        previous_plan_id="test_plan_id",
+    )
+    state_sync.promote(env)
+
+    # Manually update the snapshots updated_ts to simulate expiration
+    state_sync.engine_adapter.execute(
+        f"UPDATE sqlmesh._snapshots SET updated_ts = {now_ts - 15000} WHERE name = '{old_snapshot.name}' AND identifier = '{old_snapshot.identifier}'"
+    )
+
+    # The old snapshot should still not be cleaned up because it's part of
+    # previous_finalized_snapshots in a non-finalized environment
+    assert not _get_cleanup_tasks(state_sync)
+    state_sync.delete_expired_snapshots(batch_range=ExpiredBatchRange.all_batch_range())
+    assert state_sync.snapshots_exist([old_snapshot.snapshot_id]) == {old_snapshot.snapshot_id}
+
+    # Once the environment is finalized, the expired snapshot should be removed successfully
+    state_sync.finalize(env)
+    assert _get_cleanup_tasks(state_sync) == [
+        SnapshotTableCleanupTask(snapshot=old_snapshot.table_info, dev_table_only=False),
+    ]
+    state_sync.delete_expired_snapshots(batch_range=ExpiredBatchRange.all_batch_range())
+    assert not state_sync.snapshots_exist([old_snapshot.snapshot_id])
+
+
 def test_delete_expired_snapshots_dev_table_cleanup_only(
     state_sync: EngineAdapterStateSync, make_snapshot: t.Callable
 ):