Add async methods to BaseStore (langchain-ai#16669)

- **Description:**

The BaseStore methods are currently blocking. Some implementations
(AstraDBStore, RedisStore) would benefit from having async methods.
Also once we have async methods for BaseStore, we can implement the
async `aembed_documents` in CacheBackedEmbeddings to cache the
embeddings asynchronously.

* adds async methods amget, amset, amedelete and ayield_keys to
BaseStore
  * implements the async methods for InMemoryStore
  * adds tests for InMemoryStore async methods

- **Twitter handle:** cbornet_

libs/core/langchain_core/stores.py

@@ -1,5 +1,17 @@
 from abc import ABC, abstractmethod
-from typing import Generic, Iterator, List, Optional, Sequence, Tuple, TypeVar, Union
+from typing import (
+    AsyncIterator,
+    Generic,
+    Iterator,
+    List,
+    Optional,
+    Sequence,
+    Tuple,
+    TypeVar,
+    Union,
+)
+
+from langchain_core.runnables import run_in_executor
 
 K = TypeVar("K")
 V = TypeVar("V")
@@ -20,6 +32,18 @@ def mget(self, keys: Sequence[K]) -> List[Optional[V]]:
             If a key is not found, the corresponding value will be None.
         """
 
+    async def amget(self, keys: Sequence[K]) -> List[Optional[V]]:
+        """Get the values associated with the given keys.
+
+        Args:
+            keys (Sequence[K]): A sequence of keys.
+
+        Returns:
+            A sequence of optional values associated with the keys.
+            If a key is not found, the corresponding value will be None.
+        """
+        return await run_in_executor(None, self.mget, keys)
+
     @abstractmethod
     def mset(self, key_value_pairs: Sequence[Tuple[K, V]]) -> None:
         """Set the values for the given keys.
@@ -28,6 +52,14 @@ def mset(self, key_value_pairs: Sequence[Tuple[K, V]]) -> None:
             key_value_pairs (Sequence[Tuple[K, V]]): A sequence of key-value pairs.
         """
 
+    async def amset(self, key_value_pairs: Sequence[Tuple[K, V]]) -> None:
+        """Set the values for the given keys.
+
+        Args:
+            key_value_pairs (Sequence[Tuple[K, V]]): A sequence of key-value pairs.
+        """
+        return await run_in_executor(None, self.mset, key_value_pairs)
+
     @abstractmethod
     def mdelete(self, keys: Sequence[K]) -> None:
         """Delete the given keys and their associated values.
@@ -36,6 +68,14 @@ def mdelete(self, keys: Sequence[K]) -> None:
             keys (Sequence[K]): A sequence of keys to delete.
         """
 
+    async def amdelete(self, keys: Sequence[K]) -> None:
+        """Delete the given keys and their associated values.
+
+        Args:
+            keys (Sequence[K]): A sequence of keys to delete.
+        """
+        return await run_in_executor(None, self.mdelete, keys)
+
     @abstractmethod
     def yield_keys(
         self, *, prefix: Optional[str] = None
@@ -52,5 +92,27 @@ def yield_keys(
             depending on what makes more sense for the given store.
         """
 
+    async def ayield_keys(
+        self, *, prefix: Optional[str] = None
+    ) -> Union[AsyncIterator[K], AsyncIterator[str]]:
+        """Get an iterator over keys that match the given prefix.
+
+        Args:
+            prefix (str): The prefix to match.
+
+        Returns:
+            Iterator[K | str]: An iterator over keys that match the given prefix.
+
+            This method is allowed to return an iterator over either K or str
+            depending on what makes more sense for the given store.
+        """
+        iterator = await run_in_executor(None, self.yield_keys, prefix=prefix)
+        done = object()
+        while True:
+            item = await run_in_executor(None, lambda it: next(it, done), iterator)
+            if item is done:
+                break
+            yield item
+
 
 ByteStore = BaseStore[str, bytes]

libs/langchain/langchain/storage/in_memory.py

@@ -5,6 +5,7 @@
 """
 from typing import (
     Any,
+    AsyncIterator,
     Dict,
     Generic,
     Iterator,
@@ -60,6 +61,18 @@ def mget(self, keys: Sequence[str]) -> List[Optional[V]]:
         """
         return [self.store.get(key) for key in keys]
 
+    async def amget(self, keys: Sequence[str]) -> List[Optional[V]]:
+        """Get the values associated with the given keys.
+
+        Args:
+            keys (Sequence[str]): A sequence of keys.
+
+        Returns:
+            A sequence of optional values associated with the keys.
+            If a key is not found, the corresponding value will be None.
+        """
+        return self.mget(keys)
+
     def mset(self, key_value_pairs: Sequence[Tuple[str, V]]) -> None:
         """Set the values for the given keys.
 
@@ -72,6 +85,17 @@ def mset(self, key_value_pairs: Sequence[Tuple[str, V]]) -> None:
         for key, value in key_value_pairs:
             self.store[key] = value
 
+    async def amset(self, key_value_pairs: Sequence[Tuple[str, V]]) -> None:
+        """Set the values for the given keys.
+
+        Args:
+            key_value_pairs (Sequence[Tuple[str, V]]): A sequence of key-value pairs.
+
+        Returns:
+            None
+        """
+        return self.mset(key_value_pairs)
+
     def mdelete(self, keys: Sequence[str]) -> None:
         """Delete the given keys and their associated values.
 
@@ -82,6 +106,14 @@ def mdelete(self, keys: Sequence[str]) -> None:
             if key in self.store:
                 del self.store[key]
 
+    async def amdelete(self, keys: Sequence[str]) -> None:
+        """Delete the given keys and their associated values.
+
+        Args:
+            keys (Sequence[str]): A sequence of keys to delete.
+        """
+        self.mdelete(keys)
+
     def yield_keys(self, prefix: Optional[str] = None) -> Iterator[str]:
         """Get an iterator over keys that match the given prefix.
 
@@ -98,6 +130,23 @@ def yield_keys(self, prefix: Optional[str] = None) -> Iterator[str]:
                 if key.startswith(prefix):
                     yield key
 
+    async def ayield_keys(self, prefix: Optional[str] = None) -> AsyncIterator[str]:
+        """Get an async iterator over keys that match the given prefix.
+
+        Args:
+            prefix (str, optional): The prefix to match. Defaults to None.
+
+        Returns:
+            AsyncIterator[str]: An async iterator over keys that match the given prefix.
+        """
+        if prefix is None:
+            for key in self.store.keys():
+                yield key
+        else:
+            for key in self.store.keys():
+                if key.startswith(prefix):
+                    yield key
+
 
 InMemoryStore = InMemoryBaseStore[Any]
 InMemoryByteStore = InMemoryBaseStore[bytes]

libs/langchain/tests/unit_tests/storage/test_in_memory.py

@@ -13,6 +13,18 @@ def test_mget() -> None:
     assert non_existent_value == [None]
 
 
+async def test_amget() -> None:
+    store = InMemoryStore()
+    await store.amset([("key1", "value1"), ("key2", "value2")])
+
+    values = await store.amget(["key1", "key2"])
+    assert values == ["value1", "value2"]
+
+    # Test non-existent key
+    non_existent_value = await store.amget(["key3"])
+    assert non_existent_value == [None]
+
+
 def test_mset() -> None:
     store = InMemoryStore()
     store.mset([("key1", "value1"), ("key2", "value2")])
@@ -21,6 +33,14 @@ def test_mset() -> None:
     assert values == ["value1", "value2"]
 
 
+async def test_amset() -> None:
+    store = InMemoryStore()
+    await store.amset([("key1", "value1"), ("key2", "value2")])
+
+    values = await store.amget(["key1", "key2"])
+    assert values == ["value1", "value2"]
+
+
 def test_mdelete() -> None:
     store = InMemoryStore()
     store.mset([("key1", "value1"), ("key2", "value2")])
@@ -34,6 +54,19 @@ def test_mdelete() -> None:
     store.mdelete(["key3"])  # No error should be raised
 
 
+async def test_amdelete() -> None:
+    store = InMemoryStore()
+    await store.amset([("key1", "value1"), ("key2", "value2")])
+
+    await store.amdelete(["key1"])
+
+    values = await store.amget(["key1", "key2"])
+    assert values == [None, "value2"]
+
+    # Test deleting non-existent key
+    await store.amdelete(["key3"])  # No error should be raised
+
+
 def test_yield_keys() -> None:
     store = InMemoryStore()
     store.mset([("key1", "value1"), ("key2", "value2"), ("key3", "value3")])
@@ -46,3 +79,17 @@ def test_yield_keys() -> None:
 
     keys_with_invalid_prefix = list(store.yield_keys(prefix="x"))
     assert keys_with_invalid_prefix == []
+
+
+async def test_ayield_keys() -> None:
+    store = InMemoryStore()
+    await store.amset([("key1", "value1"), ("key2", "value2"), ("key3", "value3")])
+
+    keys = [key async for key in store.ayield_keys()]
+    assert set(keys) == {"key1", "key2", "key3"}
+
+    keys_with_prefix = [key async for key in store.ayield_keys(prefix="key")]
+    assert set(keys_with_prefix) == {"key1", "key2", "key3"}
+
+    keys_with_invalid_prefix = [key async for key in store.ayield_keys(prefix="x")]
+    assert keys_with_invalid_prefix == []