revise mapping schema set; add docstrings

Author: themisvaltinos

sqlmesh/core/loader.py

@@ -77,10 +77,28 @@ def get_or_load_models(
 
     @abc.abstractmethod
     def put(self, models: t.List[Model], path: Path) -> bool:
+        """Store models in the cache associated with the given path.
+
+        Args:
+            models: List of models to cache
+            path: File path to associate with the cached models
+
+        Returns:
+            True if the models were successfully cached,
+            False otherwise (empty list, not a list, unsupported model types)
+        """
         pass
 
     @abc.abstractmethod
     def get(self, path: Path) -> t.List[Model]:
+        """Retrieve models from the cache for a given path.
+
+        Args:
+            path: File path to look up in the cache
+
+        Returns:
+            List of cached models associated with the path, an empty list if no cache entry exists
+        """
         pass
 
 

sqlmesh/core/model/definition.py

@@ -812,10 +812,8 @@ def convert_to_time_column(
         return exp.convert(time)
 
     def set_mapping_schema(self, schema: t.Dict) -> None:
-        # Make a shallow copy to avoid modifying the original in case they're the same
-        temp_schema = schema.copy()
         self.mapping_schema.clear()
-        self.mapping_schema.update(temp_schema)
+        self.mapping_schema.update(schema)
 
     def update_schema(self, schema: MappingSchema) -> None:
         """Updates the schema for this model's dependencies based on the given mapping schema."""

sqlmesh/core/model/schema.py

@@ -93,7 +93,8 @@ def process_models(completed_model: t.Optional[Model] = None) -> None:
                     model = models[fqn]
                     model._data_hash = data_hash
                     model._metadata_hash = metadata_hash
-                    model.set_mapping_schema(mapping_schema)
+                    if model.mapping_schema != mapping_schema:
+                        model.set_mapping_schema(mapping_schema)
                     optimized_query_cache.with_optimized_query(model, entry_name)
                     _update_schema_with_model(schema, model)
                     process_models(completed_model=model)