Improve Cassandra vector store docs (#2903)

* Improve cassandra docs

* Update index name;

* improve code readability

* Fix formatting

docs/extras/modules/data_connection/vectorstores/integrations/cassandra.mdx

@@ -37,47 +37,43 @@ npm install cassandra-driver
 import { CassandraStore } from "langchain/vectorstores/cassandra";
 import { OpenAIEmbeddings } from "langchain/embeddings/openai";
 
-// text sample from Godel, Escher, Bach
+
+const config = {
+   cloud: {
+     secureConnectBundle: process.env.CASSANDRA_SCB as string,
+   },
+   credentials: {
+     username: "token",
+     password: process.env.CASSANDRA_TOKEN as string,
+   },
+   keyspace: "test",
+   dimensions: 1536,
+   table: "test",
+   primaryKey: {
+     name: "id",
+     type: "int",
+   },
+   metadataColumns: [
+     {
+       name: "name",
+       type: "text",
+     },
+   ],
+ };
+
 const vectorStore = await CassandraStore.fromTexts(
+  ["I am blue", "Green yellow purple", "Hello there hello"],
   [
-    "Tortoise: Labyrinth? Labyrinth? Could it Are we in the notorious Little\
-            Harmonic Labyrinth of the dreaded Majotaur?",
-    "Achilles: Yiikes! What is that?",
-    "Tortoise: They say-although I person never believed it myself-that an I\
-            Majotaur has created a tiny labyrinth sits in a pit in the middle of\
-            it, waiting innocent victims to get lost in its fears complexity.\
-            Then, when they wander and dazed into the center, he laughs and\
-            laughs at them-so hard, that he laughs them to death!",
-    "Achilles: Oh, no!",
-    "Tortoise: But it's only a myth. Courage, Achilles.",
+    { id: 2, name: "2" },
+    { id: 1, name: "1" },
+    { id: 3, name: "3" },
   ],
-  [{ id: 2 }, { id: 1 }, { id: 3 }, { id: 4 }, { id: 5 }],
   new OpenAIEmbeddings(),
-  {
-    collectionName: "goldel_escher_bach",
-  }
+  cassandraConfig
 );
 
-// or alternatively from docs
-const vectorStore = await CassandraStore.fromDocuments(docs, new OpenAIEmbeddings(), {
-  collectionName: "goldel_escher_bach",
-});
-
-const response = await vectorStore.similaritySearch("scared", 2);
-```
-
-## Query docs from existing collection
-
-```typescript
-import { CassandraStore } from "langchain/vectorstores/cassandra";
-import { OpenAIEmbeddings } from "langchain/embeddings/openai";
-
-const vectorStore = await CassandraStore.fromExistingCollection(
-  new OpenAIEmbeddings(),
-  {
-    collectionName: "goldel_escher_bach",
-  }
+const results = await vectorStore.similaritySearch(
+  "Green yellow purple",
+  1
 );
-
-const response = await vectorStore.similaritySearch("scared", 2);
-```
+```

langchain/src/vectorstores/cassandra.ts

@@ -195,7 +195,8 @@ export class CassandraStore extends VectorStore {
       vector VECTOR<FLOAT, ${this.dimensions}>
     );`);
 
-    await this.client.execute(`CREATE CUSTOM INDEX IF NOT EXISTS ann_index 
+    await this.client
+      .execute(`CREATE CUSTOM INDEX IF NOT EXISTS idx_vector_${this.table}
   ON ${this.keyspace}.${this.table}(vector) USING 'StorageAttachedIndex';`);
     this.isInitialized = true;
   }
@@ -218,9 +219,13 @@ export class CassandraStore extends VectorStore {
 
       const metadataColNames = Object.keys(document.metadata);
       const metadataVals = Object.values(document.metadata);
-      const query = `INSERT INTO ${this.keyspace}.${this.table} (vector, text${
-        metadataColNames.length > 0 ? ", " + metadataColNames.join(", ") : ""
-      }) VALUES ([${vector}], '${document.pageContent}'${
+      const metadataInsert =
+        metadataColNames.length > 0 ? ", " + metadataColNames.join(", ") : "";
+      const query = `INSERT INTO ${this.keyspace}.${
+        this.table
+      } (vector, text${metadataInsert}) VALUES ([${vector}], '${
+        document.pageContent
+      }'${
         metadataVals.length > 0
           ? ", " +
             metadataVals

langchain/src/vectorstores/tests/cassandra.int.test.ts

@@ -5,6 +5,7 @@ import { CassandraStore } from "../cassandra.js";
 import { OpenAIEmbeddings } from "../../embeddings/openai.js";
 import { Document } from "../../document.js";
 
+// yarn test:single /langchain/src/vectorstores/tests/cassandra.int.test.ts
 describe.skip("CassandraStore", () => {
   const cassandraConfig = {
     cloud: {