feat(remove): add a remove_flow() method

docs/docs/core/flow_def.mdx

@@ -46,6 +46,22 @@ demo_flow = cocoindex.add_flow_def("DemoFlow", demo_flow_def)
 In both cases, `demo_flow` will be an object with `cocoindex.Flow` class type.
 See [Flow Running](/docs/core/flow_methods) for more details on it.
 
+Sometimes you no longer want to keep states of the flow in memory. We provide a `cocoindex.remove_flow()` method for this purpose:
+
+```python
+cocoindex.remove_flow(demo_flow)
+```
+
+After it's called, `demo_flow` becomes an invalid object, and you should not call any methods of it.
+
+:::note
+
+This only removes states of the flow from the current process, and it won't affect the persistent states.
+
+If you w
+
+:::
+
 </TabItem>
 </Tabs>
 

docs/docs/core/flow_methods.mdx

@@ -100,6 +100,14 @@ cocoindex.drop_all_flows(report_to_stdout=True)
 </TabItem>
 </Tabs>
 
+:::note
+
+After dropping the flow, the in-memory `cocoindex.Flow` instance is still valid, and you can call setup methods on it again.
+
+If you want to remove the flow from the current process, you can call `cocoindex.remove_flow(demo_flow)` to do so (see [related doc](/docs/core/flow_def#entry-point)).
+
+:::
+
 ## Build / update target data
 
 The major goal of a flow is to perform the transformations on source data and build / update data in the target.

python/cocoindex/__init__.py

@@ -11,7 +11,7 @@
 from .flow import flow_def
 from .flow import EvaluateAndDumpOptions, GeneratedField
 from .flow import FlowLiveUpdater, FlowLiveUpdaterOptions
-from .flow import add_flow_def
+from .flow import add_flow_def, remove_flow
 from .flow import update_all_flows_async, setup_all_flows, drop_all_flows
 from .lib import init, start_server, stop
 from .llm import LlmSpec, LlmApiType
@@ -54,6 +54,7 @@
     "FlowLiveUpdater",
     "FlowLiveUpdaterOptions",
     "add_flow_def",
+    "remove_flow",
     "update_all_flows_async",
     "setup_all_flows",
     "drop_all_flows",

python/cocoindex/flow.py

@@ -624,7 +624,7 @@ class Flow:
 
     _name: str
     _full_name: str
-    _lazy_engine_flow: Callable[[], _engine.Flow]
+    _lazy_engine_flow: Callable[[], _engine.Flow] | None
 
     def __init__(
         self, name: str, full_name: str, engine_flow_creator: Callable[[], _engine.Flow]
@@ -664,18 +664,18 @@ def build_tree(label: str, lines: list[Any]) -> Tree:
         return tree
 
     def _get_spec(self, verbose: bool = False) -> _engine.RenderedSpec:
-        return self._lazy_engine_flow().get_spec(
+        return self.internal_flow().get_spec(
             output_mode="verbose" if verbose else "concise"
         )
 
     def _get_schema(self) -> list[tuple[str, str, str]]:
-        return cast(list[tuple[str, str, str]], self._lazy_engine_flow().get_schema())
+        return cast(list[tuple[str, str, str]], self.internal_flow().get_schema())
 
     def __str__(self) -> str:
         return str(self._get_spec())
 
     def __repr__(self) -> str:
-        return repr(self._lazy_engine_flow())
+        return repr(self.internal_flow())
 
     @property
     def name(self) -> str:
@@ -715,12 +715,14 @@ def evaluate_and_dump(
         """
         Evaluate the flow and dump flow outputs to files.
         """
-        return self._lazy_engine_flow().evaluate_and_dump(dump_engine_object(options))
+        return self.internal_flow().evaluate_and_dump(dump_engine_object(options))
 
     def internal_flow(self) -> _engine.Flow:
         """
         Get the engine flow.
         """
+        if self._lazy_engine_flow is None:
+            raise RuntimeError(f"Flow {self.full_name} is already removed")
         return self._lazy_engine_flow()
 
     async def internal_flow_async(self) -> _engine.Flow:
@@ -731,27 +733,32 @@ async def internal_flow_async(self) -> _engine.Flow:
 
     def setup(self, report_to_stdout: bool = False) -> None:
         """
-        Setup the flow.
+        Setup persistent backends of the flow.
         """
         execution_context.run(self.setup_async(report_to_stdout=report_to_stdout))
 
     async def setup_async(self, report_to_stdout: bool = False) -> None:
         """
-        Setup the flow. The async version.
+        Setup persistent backends of the flow. The async version.
         """
         await make_setup_bundle([self]).describe_and_apply_async(
             report_to_stdout=report_to_stdout
         )
 
     def drop(self, report_to_stdout: bool = False) -> None:
         """
-        Drop the flow.
+        Drop persistent backends of the flow.
+
+        The current instance is still valid after it's called.
+        For example, you can still call `setup()` after it, to setup the persistent backends again.
+
+        Call `cocoindex.remove_flow()` if you want to remove the flow from the current process.
         """
         execution_context.run(self.drop_async(report_to_stdout=report_to_stdout))
 
     async def drop_async(self, report_to_stdout: bool = False) -> None:
         """
-        Drop the flow. The async version.
+        Drop persistent backends of the flow. The async version.
         """
         await make_drop_bundle([self]).describe_and_apply_async(
             report_to_stdout=report_to_stdout
@@ -805,6 +812,19 @@ def add_flow_def(name: str, fl_def: Callable[[FlowBuilder, DataScope], None]) ->
     return fl
 
 
+def remove_flow(fl: Flow) -> None:
+    """
+    Remove a flow from the current process to free up resources.
+    After it's called, methods of the flow should no longer be called.
+
+    This will NOT touch the persistent backends of the flow.
+    """
+    _engine.remove_flow_context(fl.full_name)
+    fl._lazy_engine_flow = None  # pylint: disable=protected-access
+    with _flows_lock:
+        del _flows[fl.name]
+
+
 def flow_def(
     name: str | None = None,
 ) -> Callable[[Callable[[FlowBuilder, DataScope], None]], Flow]:

src/lib_context.rs

@@ -214,6 +214,11 @@ impl LibContext {
         Ok(flow_ctx)
     }
 
+    pub fn remove_flow_context(&self, flow_name: &str) {
+        let mut flows = self.flows.lock().unwrap();
+        flows.remove(flow_name);
+    }
+
     pub fn require_persistence_ctx(&self) -> Result<&PersistenceContext> {
         self.persistence_ctx
             .as_ref()
@@ -268,7 +273,7 @@ pub fn create_lib_context(settings: settings::Settings) -> Result<LibContext> {
     })
 }
 
-static LIB_CONTEXT: RwLock<Option<Arc<LibContext>>> = RwLock::new(None);
+pub static LIB_CONTEXT: RwLock<Option<Arc<LibContext>>> = RwLock::new(None);
 
 pub(crate) fn init_lib_context(settings: settings::Settings) -> Result<()> {
     let mut lib_context_locked = LIB_CONTEXT.write().unwrap();

src/py/mod.rs

@@ -462,6 +462,14 @@ fn make_drop_bundle(flow_names: Vec<String>) -> PyResult<SetupChangeBundle> {
     Ok(SetupChangeBundle(Arc::new(bundle)))
 }
 
+#[pyfunction]
+fn remove_flow_context(flow_name: String) {
+    let lib_context_locked = crate::lib_context::LIB_CONTEXT.read().unwrap();
+    if let Some(lib_context) = lib_context_locked.as_ref() {
+        lib_context.remove_flow_context(&flow_name)
+    }
+}
+
 #[pyfunction]
 fn add_auth_entry(key: String, value: Pythonized<serde_json::Value>) -> PyResult<()> {
     get_auth_registry()
@@ -493,6 +501,7 @@ fn cocoindex_engine(m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_function(wrap_pyfunction!(flow_names_with_setup_async, m)?)?;
     m.add_function(wrap_pyfunction!(make_setup_bundle, m)?)?;
     m.add_function(wrap_pyfunction!(make_drop_bundle, m)?)?;
+    m.add_function(wrap_pyfunction!(remove_flow_context, m)?)?;
     m.add_function(wrap_pyfunction!(add_auth_entry, m)?)?;
 
     m.add_class::<builder::flow_builder::FlowBuilder>()?;