Backends

Whoosh-NG supports pluggable storage backends through the Provider Architecture. The default backend stores data as files on disk, but you can use SQLite, PostgreSQL, S3, and more.

Built-in Backends

Backend	Class	Description
File (default)	FileBackend	Stores index as files on disk
SQLite	SQLiteBackend	Stores index in SQLite database
Memory	MemoryBackend	In-memory backend (testing only)

File Backend (Default)

from whoosh.index import create_in

# Uses FileBackend by default
ix = create_in("indexdir", schema)

Configuration

from whoosh.backends.file import FileBackend

backend = FileBackend(
    storage=FileStorage("indexdir"),
    compound=True  # Use compound files
)

SQLite Backend

from whoosh.backends.sqlite import SQLiteBackend
from whoosh.store.sqlite import SQLiteStorage

storage = SQLiteStorage("index.db")
backend = SQLiteBackend(storage=storage)

Advantages

• Single file index
• Better for transactional workloads
• Easier backups
• Supports concurrent reads

Disadvantages

• Slower for large indexes
• Limited by SQLite performance

Memory Backend

from whoosh.backends.memory import MemoryBackend

backend = MemoryBackend()
# Useful for testing

Custom Backend

Create a custom backend by subclassing Backend:

from whoosh.backends.abc import Backend

class MyBackend(Backend):
    def create(self):
        """Create a new segment."""
        pass

    def open(self):
        """Open existing segment."""
        pass

    def close(self):
        """Close the backend."""
        pass

    def commit(self):
        """Commit changes."""
        pass

Registering a Backend

from whoosh.registry import BackendRegistry

BackendRegistry.register("my_backend", MyBackend, "my_package")

Backend Selection

Choose a backend based on your use case:

Use Case	Recommended Backend
Small to medium indexes	File (default)
Single-file deployment	SQLite
Testing	Memory
Distributed systems	Object storage (S3, MinIO)
High concurrency	SQLite or custom

Best Practices

1. File backend for production: Most battle-tested
2. SQLite for single-file: Easier deployment
3. Memory for tests: Fast, no cleanup needed
4. Compound files: Enable for reduced file count
5. Backup strategy: File backend = copy directory; SQLite = copy file