community[minor]: Improve InMemoryVectorStore with ability to persist to disk and filter on metadata. (#22186)

- **Description:** The InMemoryVectorStore is a nice and simple vector
store implementation for quick development and debugging. The current
implementation is quite limited in its functionalities. This PR extends
the functionalities by adding utility function to persist the vector
store to a json file and to load it from a json file. We choose the json
file format because it allows inspection of the database contents in a
text editor, which is great for debugging. Furthermore, it adds a
`filter` keyword that can be used to filter out documents on their
`page_content` or `metadata`.
- **Issue:** -
- **Dependencies:** -
- **Twitter handle:** @Vincent_Min

libs/community/langchain_community/vectorstores/inmemory.py

@@ -1,9 +1,12 @@
+import json
 import uuid
-from typing import Any, Dict, Iterable, List, Optional, Sequence, Tuple
+from pathlib import Path
+from typing import Any, Callable, Dict, Iterable, List, Optional, Sequence, Tuple
 
 import numpy as np
 from langchain_core.documents import Document
 from langchain_core.embeddings import Embeddings
+from langchain_core.load import dumpd, load
 from langchain_core.vectorstores import VectorStore
 
 from langchain_community.utils.math import cosine_similarity
@@ -64,22 +67,42 @@ class InMemoryVectorStore(VectorStore):
     ) -> List[str]:
         return self.add_texts(texts, metadatas, **kwargs)
 
+    def _similarity_search_with_score_by_vector(
+        self,
+        embedding: List[float],
+        k: int = 4,
+        filter: Optional[Callable[[Document], bool]] = None,
+        **kwargs: Any,
+    ) -> List[Tuple[Document, float, List[float]]]:
+        result = []
+        for doc in self.store.values():
+            vector = doc["vector"]
+            similarity = float(cosine_similarity([embedding], [vector]).item(0))
+            result.append(
+                (
+                    Document(page_content=doc["text"], metadata=doc["metadata"]),
+                    similarity,
+                    vector,
+                )
+            )
+        result.sort(key=lambda x: x[1], reverse=True)
+        if filter is not None:
+            result = [r for r in result if filter(r[0])]
+        return result[:k]
+
     def similarity_search_with_score_by_vector(
         self,
         embedding: List[float],
         k: int = 4,
+        filter: Optional[Callable[[Document], bool]] = None,
+        **kwargs: Any,
     ) -> List[Tuple[Document, float]]:
-        docs_with_similarity = []
-        for doc in self.store.values():
-            similarity = float(cosine_similarity([embedding], [doc["vector"]]).item(0))
-            docs_with_similarity.append(
-                (
-                    Document(page_content=doc["text"], metadata=doc["metadata"]),
-                    similarity,
-                )
+        return [
+            (doc, similarity)
+            for doc, similarity, _ in self._similarity_search_with_score_by_vector(
+                embedding=embedding, k=k, filter=filter, **kwargs
             )
-        docs_with_similarity.sort(key=lambda x: x[1], reverse=True)
-        return docs_with_similarity[:k]
+        ]
 
     def similarity_search_with_score(
         self,
@@ -91,6 +114,7 @@ class InMemoryVectorStore(VectorStore):
         docs = self.similarity_search_with_score_by_vector(
             embedding,
             k,
+            **kwargs,
         )
         return docs
 
@@ -108,6 +132,7 @@ class InMemoryVectorStore(VectorStore):
         docs_and_scores = self.similarity_search_with_score_by_vector(
             embedding,
             k,
+            **kwargs,
         )
         return [doc for doc, _ in docs_and_scores]
 
@@ -134,31 +159,19 @@ class InMemoryVectorStore(VectorStore):
         lambda_mult: float = 0.5,
         **kwargs: Any,
     ) -> List[Document]:
-        docs_with_similarity = []
-        for doc in self.store.values():
-            similarity = float(cosine_similarity([embedding], [doc["vector"]]).item(0))
-            docs_with_similarity.append(
-                (
-                    doc,
-                    similarity,
-                )
-            )
-        docs_with_similarity.sort(key=lambda x: x[1], reverse=True)
-        prefetch_hits = docs_with_similarity[:fetch_k]
+        prefetch_hits = self._similarity_search_with_score_by_vector(
+            embedding=embedding,
+            k=fetch_k,
+            **kwargs,
+        )
 
         mmr_chosen_indices = maximal_marginal_relevance(
             np.array(embedding, dtype=np.float32),
-            [doc["vector"] for doc, _ in prefetch_hits],
+            [vector for _, _, vector in prefetch_hits],
             k=k,
             lambda_mult=lambda_mult,
         )
-        return [
-            Document(
-                page_content=prefetch_hits[idx][0]["text"],
-                metadata=prefetch_hits[idx][0]["metadata"],
-            )
-            for idx in mmr_chosen_indices
-        ]
+        return [prefetch_hits[idx][0] for idx in mmr_chosen_indices]
 
     def max_marginal_relevance_search(
         self,
@@ -174,6 +187,7 @@ class InMemoryVectorStore(VectorStore):
             k,
             fetch_k,
             lambda_mult=lambda_mult,
+            **kwargs,
         )
 
     @classmethod
@@ -199,3 +213,20 @@ class InMemoryVectorStore(VectorStore):
         **kwargs: Any,
     ) -> "InMemoryVectorStore":
         return cls.from_texts(texts, embedding, metadatas, **kwargs)
+
+    @classmethod
+    def load(
+        cls, path: str, embedding: Embeddings, **kwargs: Any
+    ) -> "InMemoryVectorStore":
+        _path: Path = Path(path)
+        with _path.open("r") as f:
+            store = load(json.load(f))
+        vectorstore = cls(embedding=embedding, **kwargs)
+        vectorstore.store = store
+        return vectorstore
+
+    def dump(self, path: str) -> None:
+        _path: Path = Path(path)
+        _path.parent.mkdir(exist_ok=True, parents=True)
+        with _path.open("w") as f:
+            json.dump(dumpd(self.store), f, indent=2)

libs/community/tests/unit_tests/vectorstores/test_inmemory.py

@@ -1,3 +1,5 @@
+from pathlib import Path
+
 from langchain_core.documents import Document
 
 from langchain_community.vectorstores.inmemory import InMemoryVectorStore
@@ -44,3 +46,31 @@ async def test_inmemory_mmr() -> None:
     assert len(output) == len(texts)
     assert output[0] == Document(page_content="foo")
     assert output[1] == Document(page_content="foy")
+
+
+async def test_inmemory_dump_load(tmp_path: Path) -> None:
+    """Test end to end construction and search."""
+    embedding = ConsistentFakeEmbeddings()
+    store = await InMemoryVectorStore.afrom_texts(["foo", "bar", "baz"], embedding)
+    output = await store.asimilarity_search("foo", k=1)
+
+    test_file = str(tmp_path / "test.json")
+    store.dump(test_file)
+
+    loaded_store = InMemoryVectorStore.load(test_file, embedding)
+    loaded_output = await loaded_store.asimilarity_search("foo", k=1)
+
+    assert output == loaded_output
+
+
+async def test_inmemory_filter() -> None:
+    """Test end to end construction and search."""
+    store = await InMemoryVectorStore.afrom_texts(
+        ["foo", "bar"],
+        ConsistentFakeEmbeddings(),
+        [{"id": 1}, {"id": 2}],
+    )
+    output = await store.asimilarity_search(
+        "baz", filter=lambda doc: doc.metadata["id"] == 1
+    )
+    assert output == [Document(page_content="foo", metadata={"id": 1})]