Feature: on_update trigger

quixstreams/dataframe/dataframe.py

@@ -72,7 +72,7 @@
     TumblingCountWindowDefinition,
     TumblingTimeWindowDefinition,
 )
-from .windows.base import WindowOnLateCallback
+from .windows.base import WindowOnLateCallback, WindowOnUpdateCallback
 
 if typing.TYPE_CHECKING:
     from quixstreams.processing import ProcessingContext
@@ -1085,6 +1085,7 @@ def tumbling_window(
         grace_ms: Union[int, timedelta] = 0,
         name: Optional[str] = None,
         on_late: Optional[WindowOnLateCallback] = None,
+        on_update: Optional[WindowOnUpdateCallback] = None,
     ) -> TumblingTimeWindowDefinition:
         """
         Create a time-based tumbling window transformation on this StreamingDataFrame.
@@ -1151,6 +1152,10 @@ def tumbling_window(
             (default behavior).
             Otherwise, no message will be logged.
 
+        :param on_update: an optional callback to react on updated windows and
+            to expire them sooner. If the callback returns `True`, the window will be expired.
+            Default - `None`.
+
         :return: `TumblingTimeWindowDefinition` instance representing the tumbling window
             configuration.
             This object can be further configured with aggregation functions
@@ -1166,6 +1171,7 @@ def tumbling_window(
             dataframe=self,
             name=name,
             on_late=on_late,
+            on_update=on_update,
         )
 
     def tumbling_count_window(
@@ -1225,6 +1231,7 @@ def hopping_window(
         grace_ms: Union[int, timedelta] = 0,
         name: Optional[str] = None,
         on_late: Optional[WindowOnLateCallback] = None,
+        on_update: Optional[WindowOnUpdateCallback] = None,
     ) -> HoppingTimeWindowDefinition:
         """
         Create a time-based hopping window transformation on this StreamingDataFrame.
@@ -1302,6 +1309,10 @@ def hopping_window(
             (default behavior).
             Otherwise, no message will be logged.
 
+        :param on_update: an optional callback to react on updated windows and
+            to expire them sooner. If the callback returns `True`, the window will be expired.
+            Default - `None`.
+
         :return: `HoppingTimeWindowDefinition` instance representing the hopping
             window configuration.
             This object can be further configured with aggregation functions
@@ -1319,6 +1330,7 @@ def hopping_window(
             dataframe=self,
             name=name,
             on_late=on_late,
+            on_update=on_update,
         )
 
     def hopping_count_window(

quixstreams/dataframe/windows/base.py

@@ -34,6 +34,7 @@
 WindowResult: TypeAlias = dict[str, Any]
 WindowKeyResult: TypeAlias = tuple[Any, WindowResult]
 Message: TypeAlias = tuple[WindowResult, Any, int, Any]
+WindowOnUpdateCallback: TypeAlias = Callable[[Any, Any], bool]
 
 WindowAggregateFunc = Callable[[Any, Any], Any]
 

quixstreams/dataframe/windows/definitions.py

@@ -16,6 +16,7 @@
 from .base import (
     Window,
     WindowOnLateCallback,
+    WindowOnUpdateCallback,
 )
 from .count_based import (
     CountWindow,
@@ -54,11 +55,13 @@ def __init__(
         name: Optional[str],
         dataframe: "StreamingDataFrame",
         on_late: Optional[WindowOnLateCallback] = None,
+        on_update: Optional[WindowOnUpdateCallback] = None,
     ) -> None:
         super().__init__()
 
         self._name = name
         self._on_late = on_late
+        self._on_update = on_update
         self._dataframe = dataframe
 
     @abstractmethod
@@ -239,6 +242,7 @@ def __init__(
         name: Optional[str] = None,
         step_ms: Optional[int] = None,
         on_late: Optional[WindowOnLateCallback] = None,
+        on_update: Optional[WindowOnUpdateCallback] = None,
     ):
         if not isinstance(duration_ms, int):
             raise TypeError("Window size must be an integer")
@@ -253,7 +257,7 @@ def __init__(
                 f"got {step_ms}ms"
             )
 
-        super().__init__(name, dataframe, on_late)
+        super().__init__(name, dataframe, on_late, on_update)
 
         self._duration_ms = duration_ms
         self._grace_ms = grace_ms
@@ -281,6 +285,7 @@ def __init__(
         dataframe: "StreamingDataFrame",
         name: Optional[str] = None,
         on_late: Optional[WindowOnLateCallback] = None,
+        on_update: Optional[WindowOnUpdateCallback] = None,
     ):
         super().__init__(
             duration_ms=duration_ms,
@@ -289,6 +294,7 @@ def __init__(
             name=name,
             step_ms=step_ms,
             on_late=on_late,
+            on_update=on_update,
         )
 
     def _get_name(self, func_name: Optional[str]) -> str:
@@ -320,6 +326,7 @@ def _create_window(
             aggregators=aggregators or {},
             collectors=collectors or {},
             on_late=self._on_late,
+            on_update=self._on_update,
         )
 
 
@@ -331,6 +338,7 @@ def __init__(
         dataframe: "StreamingDataFrame",
         name: Optional[str] = None,
         on_late: Optional[WindowOnLateCallback] = None,
+        on_update: Optional[WindowOnUpdateCallback] = None,
     ):
         super().__init__(
             duration_ms=duration_ms,
@@ -339,6 +347,7 @@ def __init__(
             name=name,
             on_late=on_late,
         )
+        self._on_update = on_update
 
     def _get_name(self, func_name: Optional[str]) -> str:
         prefix = f"{self._name}_tumbling_window" if self._name else "tumbling_window"
@@ -368,6 +377,7 @@ def _create_window(
             aggregators=aggregators or {},
             collectors=collectors or {},
             on_late=self._on_late,
+            on_update=self._on_update,
         )
 
 
@@ -379,13 +389,20 @@ def __init__(
         dataframe: "StreamingDataFrame",
         name: Optional[str] = None,
         on_late: Optional[WindowOnLateCallback] = None,
+        on_update: Optional[WindowOnUpdateCallback] = None,
     ):
+        if on_update is not None:
+            raise ValueError(
+                "Sliding windows do not support the 'on_update' trigger callback. "
+                "Use tumbling or hopping windows instead."
+            )
         super().__init__(
             duration_ms=duration_ms,
             grace_ms=grace_ms,
             dataframe=dataframe,
             name=name,
             on_late=on_late,
+            on_update=on_update,
         )
 
     def _get_name(self, func_name: Optional[str]) -> str:
@@ -417,6 +434,7 @@ def _create_window(
             aggregators=aggregators or {},
             collectors=collectors or {},
             on_late=self._on_late,
+            on_update=self._on_update,
         )
 
 

quixstreams/dataframe/windows/time_based.py

@@ -11,6 +11,7 @@
     Window,
     WindowKeyResult,
     WindowOnLateCallback,
+    WindowOnUpdateCallback,
     get_window_ranges,
 )
 
@@ -46,6 +47,7 @@ def __init__(
         dataframe: "StreamingDataFrame",
         step_ms: Optional[int] = None,
         on_late: Optional[WindowOnLateCallback] = None,
+        on_update: Optional[WindowOnUpdateCallback] = None,
     ):
         super().__init__(
             name=name,
@@ -56,6 +58,7 @@ def __init__(
         self._grace_ms = grace_ms
         self._step_ms = step_ms
         self._on_late = on_late
+        self._on_update = on_update
 
         self._closing_strategy = ClosingStrategy.KEY
 
@@ -132,6 +135,7 @@ def process_window(
         state = transaction.as_state(prefix=key)
         duration_ms = self._duration_ms
         grace_ms = self._grace_ms
+        on_update = self._on_update
 
         collect = self.collect
         aggregate = self.aggregate
@@ -152,6 +156,7 @@ def process_window(
         max_expired_window_end = latest_timestamp - grace_ms
         max_expired_window_start = max_expired_window_end - duration_ms
         updated_windows: list[WindowKeyResult] = []
+        triggered_windows: list[WindowKeyResult] = []
         for start, end in ranges:
             if start <= max_expired_window_start:
                 late_by_ms = max_expired_window_end - timestamp_ms
@@ -169,18 +174,44 @@ def process_window(
             # since actual values are stored separately and combined into an array
             # during window expiration.
             aggregated = None
+
             if aggregate:
                 current_value = state.get_window(start, end)
                 if current_value is None:
                     current_value = self._initialize_value()
 
                 aggregated = self._aggregate_value(current_value, value, timestamp_ms)
-                updated_windows.append(
-                    (
-                        key,
-                        self._results(aggregated, [], start, end),
-                    )
-                )
+
+                if on_update and on_update(current_value, aggregated):
+                    # Get collected values for the result
+                    collected = []
+                    if collect:
+                        collected = state.get_from_collection(start, end)
+                        # Add the current value that's being collected
+                        collected.append(self._collect_value(value))
+
+                    result = self._results(aggregated, collected, start, end)
+                    triggered_windows.append((key, result))
+                    transaction.delete_window(start, end, prefix=key)
+                    # Note: We don't delete from collection here - normal expiration
+                    # will handle cleanup for both tumbling and hopping windows
+                    continue
+
+                result = self._results(aggregated, [], start, end)
+                updated_windows.append((key, result))
+            elif collect and on_update:
+                # For collect-only windows, get the old and new collected values
+                old_collected = state.get_from_collection(start, end)
+                new_collected = [*old_collected, self._collect_value(value)]
+
+                if on_update(old_collected, new_collected):
+                    result = self._results(None, new_collected, start, end)
+                    triggered_windows.append((key, result))
+                    transaction.delete_window(start, end, prefix=key)
+                    # Note: We don't delete from collection here - normal expiration
+                    # will handle cleanup for both tumbling and hopping windows
+                    continue
+
             state.update_window(start, end, value=aggregated, timestamp_ms=timestamp_ms)
 
         if collect:
@@ -198,7 +229,10 @@ def process_window(
                 key, state, max_expired_window_start, collect
             )
 
-        return updated_windows, expired_windows
+        # Combine triggered windows with time-expired windows
+        all_expired_windows = triggered_windows + list(expired_windows)
+
+        return updated_windows, iter(all_expired_windows)
 
     def expire_by_partition(
         self,

quixstreams/state/types.py

@@ -391,6 +391,16 @@ def expire_all_windows(
         """
         ...
 
+    def delete_window(self, start_ms: int, end_ms: int, prefix: bytes) -> None:
+        """
+        Delete a single window defined by start and end timestamps.
+
+        :param start_ms: start of the window in milliseconds
+        :param end_ms: end of the window in milliseconds
+        :param prefix: a key prefix
+        """
+        ...
+
     def delete_windows(
         self, max_start_time: int, delete_values: bool, prefix: bytes
     ) -> None: