Now let’s make this super clear with visuals and explanation, because this is a key concept in understanding FAISS and vector databases.

Question: When index create in database it will be named as index.faiss?

🧠 Short Answer

✅ Yes —
When you create and save a FAISS index to disk (using .save_local() or similar),
it gets stored as a binary file named

index.faiss

📦 Long Answer (With Visual Flow)

When you use FAISS (either directly or through LangChain / custom classes like FaissManager),
you typically create a vector index from document embeddings like this:

from langchain.vectorstores import FAISS

faiss_index = FAISS.from_texts(texts, embedding=embedding_function)
faiss_index.save_local("faiss_index")

💾 What Happens Internally

The save_local("faiss_index") method will create a folder named faiss_index
and store two files inside it:

📂 Resulting Directory Structure

faiss_index/
 ├── index.faiss      ←  binary file containing your vector embeddings
 ├── index.pkl        ←  Python pickle file storing metadata
 └── ingested_meta.json (optional) ← custom JSON file storing extra info

🔍 Example Explanation

When your custom function like _exists() checks this:

return (self.index_dir / "index.faiss").exists() and (self.index_dir / "index.pkl").exists()

It’s simply verifying:

“Hey, do I already have a complete FAISS index saved here?”

If both files exist, it means:

• The FAISS vector index has already been created.

• You can load it directly instead of recreating it from scratch.

🧩 How the name is decided

• The base name "index" is not automatic — it’s just a common convention used in FAISS-related code.

• You can name it anything you want if you control the saving logic.

Example:

faiss_index.save_local("my_vectors")

will create:

my_vectors/
 ├── index.faiss
 └── index.pkl

Here, even though the folder is named my_vectors,
the files inside are still named index.faiss and index.pkl.

Why?
Because LangChain’s FAISS wrapper internally uses these default filenames.

🧠 Summary Table

✅ So, conclusion is correct:

When  create and save a FAISS index to disk,
it creates a file named index.faiss (along with index.pkl) inside your index_dir.