MongoDB Delete

Delete One Document

Remove the first document that matches your criteria

🔹 Delete by Name

import pymongo

client = pymongo.MongoClient("mongodb://localhost:27017/")
db = client["shop"]
products = db["products"]

# Delete one specific product by name
result = products.delete_one({"name": "Broken Widget"})

if result.deleted_count > 0:
    print("✅ Product deleted successfully")
else:
    print("❌ No product found to delete")

🔹 Delete by ID

# Delete one product by ID
product_id = "507f1f77bcf86cd799439011"
result = products.delete_one({"_id": product_id})

print(f"Documents deleted: {result.deleted_count}")

🔹 Safe Deletion with Check

# Safe deletion - check first
product_to_delete = products.find_one({"name": "Test Product"})
if product_to_delete:
    print(f"Found product: {product_to_delete['name']}")
    result = products.delete_one({"name": "Test Product"})
    print(f"Deleted: {result.deleted_count} document")
else:
    print("Product not found")

Delete Multiple Documents

Remove all documents that match your criteria

# Delete all products under $5
result = products.delete_many({"price": {"$lt": 5}})
print(f"Deleted {result.deleted_count} cheap products")

# Delete all out-of-stock items
result = products.delete_many({"stock": 0})
print(f"Deleted {result.deleted_count} out-of-stock items")

# Delete products from specific category
result = products.delete_many({"category": "discontinued"})
print(f"Deleted {result.deleted_count} discontinued products")

# Delete with multiple conditions
result = products.delete_many({
    "$and": [
        {"price": {"$lt": 10}},
        {"rating": {"$lt": 2}}
    ]
})
print(f"Deleted {result.deleted_count} cheap, low-rated products")

Safe Deletion Practices

Always verify what you're deleting before removing data

# Count documents before deleting
def safe_delete_many(collection, query):
    # First, see how many documents match
    count = collection.count_documents(query)
    
    if count == 0:
        print("No documents match the criteria")
        return
    
    print(f"Found {count} documents to delete")
    
    # Show a few examples
    examples = collection.find(query).limit(3)
    print("Examples of documents to be deleted:")
    for doc in examples:
        print(f"- {doc.get('name', 'Unknown')} (ID: {doc['_id']})")
    
    # Ask for confirmation (in real app, you'd get user input)
    confirm = True  # In real code: input("Delete these? (y/n): ").lower() == 'y'
    
    if confirm:
        result = collection.delete_many(query)
        print(f"✅ Deleted {result.deleted_count} documents")
    else:
        print("❌ Deletion cancelled")

# Example usage
safe_delete_many(products, {"price": {"$lt": 1}})

# Backup important data before deletion
def backup_before_delete(collection, query, backup_collection):
    # Find documents to delete
    docs_to_delete = list(collection.find(query))
    
    if docs_to_delete:
        # Backup to another collection
        backup_collection.insert_many(docs_to_delete)
        print(f"Backed up {len(docs_to_delete)} documents")
        
        # Now safe to delete
        result = collection.delete_many(query)
        print(f"Deleted {result.deleted_count} documents")
    else:
        print("No documents to delete")

# Create backup collection and use it
backup_products = db["products_backup"]
backup_before_delete(products, {"category": "old"}, backup_products)

Practical Delete Examples

Real-world deletion scenarios

# User account deletion
def delete_user_account(user_id):
    users = db["users"]
    
    # Check if user exists
    user = users.find_one({"_id": user_id})
    if not user:
        print("User not found")
        return False
    
    print(f"Deleting account for: {user['name']}")
    
    # Delete user's orders first
    orders = db["orders"]
    order_result = orders.delete_many({"user_id": user_id})
    print(f"Deleted {order_result.deleted_count} orders")
    
    # Delete user account
    user_result = users.delete_one({"_id": user_id})
    print(f"Deleted user account: {user_result.deleted_count}")
    
    return True

# Cleanup old data
def cleanup_old_logs():
    logs = db["logs"]
    
    # Delete logs older than 30 days
    from datetime import datetime, timedelta
    thirty_days_ago = datetime.now() - timedelta(days=30)
    
    result = logs.delete_many({
        "created_at": {"$lt": thirty_days_ago}
    })
    
    print(f"Cleaned up {result.deleted_count} old log entries")

# Remove duplicate products
def remove_duplicates():
    # Find products with same name
    pipeline = [
        {"$group": {
            "_id": "$name",
            "count": {"$sum": 1},
            "docs": {"$push": "$_id"}
        }},
        {"$match": {"count": {"$gt": 1}}}
    ]
    
    duplicates = list(products.aggregate(pipeline))
    
    for dup in duplicates:
        # Keep first, delete rest
        ids_to_delete = dup["docs"][1:]  # Skip first one
        result = products.delete_many({"_id": {"$in": ids_to_delete}})
        print(f"Removed {result.deleted_count} duplicates of '{dup['_id']}'")

# Run examples
delete_user_account("user123")
cleanup_old_logs()
remove_duplicates()