community[patch]: ensure AstraDB createCollectionOptions are aligned …

…with py version (#5185)

* community[fix]: ensure AstraDB createCollectionOptions are aligned with py version

* fix

* fix

libs/langchain-community/src/vectorstores/astradb.ts

@@ -80,27 +80,34 @@ export class AstraDBVectorStore extends VectorStore {
     } = args;
     const dataAPIClient = new DataAPIClient(token, { caller: ["langchainjs"] });
     this.astraDBClient = dataAPIClient.db(endpoint, { namespace });
-    this.collectionName = collection;
-    this.collectionOptions = collectionOptions;
-    if (
-      !this.collectionOptions ||
-      this.collectionOptions.checkExists === undefined
-    ) {
-      this.collectionOptions = {
-        checkExists: false,
-        ...(this.collectionOptions || {}),
-      };
+    this.skipCollectionProvisioning = skipCollectionProvisioning ?? false;
+    if (this.skipCollectionProvisioning && collectionOptions) {
+      throw new Error(
+        "If 'skipCollectionProvisioning' has been set to true, 'collectionOptions' must not be defined"
+      );
     }
+    this.collectionName = collection;
+    this.collectionOptions =
+      AstraDBVectorStore.applyCollectionOptionsDefaults(collectionOptions);
     this.idKey = idKey ?? "_id";
     this.contentKey = contentKey ?? "text";
     this.batchSize = batchSize && batchSize <= 20 ? batchSize : 20;
     this.caller = new AsyncCaller(callerArgs);
-    this.skipCollectionProvisioning = skipCollectionProvisioning ?? false;
-    if (this.skipCollectionProvisioning && this.collectionOptions) {
-      throw new Error(
-        "If 'skipCollectionProvisioning' has been set to true, 'collectionOptions' must not be defined"
-      );
+  }
+
+  private static applyCollectionOptionsDefaults(
+    fromUser?: CreateCollectionOptions<any>
+  ): CreateCollectionOptions<any> {
+    const copy: CreateCollectionOptions<any> = fromUser ? { ...fromUser } : {};
+    if (copy.checkExists === undefined) {
+      copy.checkExists = false;
+    }
+    if (copy.indexing === undefined) {
+      // same default as langchain python AstraDBVectorStore.
+      // this enables to create the collection in python/ts and use it in ts/python with default options.
+      copy.indexing = { allow: ["metadata"] };
     }
+    return copy;
   }
 
   /**