Mongodb iterate over large collection. Let's say I have 3 different collections. On occasion, I need to iterate through all the documents to prune data, do some other maintenance, etc. Let me know if you are interested and I can tell you our approach! Jul 23, 2025 · Cursors provide various methods for manipulating and accessing query results in MongoDB, making them essential for working with large datasets and complex queries. Jun 29, 2023 · Here’s an example of retrieving all documents from a collection: # Retrieve all documents from events collection documents = collection. For very large collections it’s not uncommon to take longer than that to process results and you get an exception half way through the iteration. TAILABLE ¶ The tailable cursor type. cursor. Prices are constantly changing, so I query a database that contains over 100,000 products every 10 minutes to filter to all products under $100 May 12, 2016 · I have a large collection of items with MongoDB (> 10m). Jan 26, 2025 · 1. log (++index) + " key: " + key_uid which logs 1 key: bB0KN 2 key: LOtOL 3 key: 51xJM 4 key: x9wFP 5 key: hcJKP 6 key: QZxnE . Dec 27, 2023 · Pymongo is a Python library that allows you to interact with MongoDB, a popular NoSQL database. A MongoDB deployment contains one or more databases, and each database contains one or more collections. In this article, we will explore how to retrieve all documents from a collection using Pymongo in Python 3. mongos> show collections collectionA collectionB collec Learn to retrieve data from a MongoDB collection using the . log err else console. A cursor is a server-side construct, how about a client-side cursor? May 25, 2018 · In this tutorial, we will show readers how to iterate the documents of a Mongo collection using the Java driver. Feb 11, 2020 · We have a platform and use Amazon SQS when we want to process each item of a collection without hurting the server. keys. Mar 28, 2012 · Sometimes you need to iterate over a large MongoDB collection. Jun 14, 2014 · I'm using mongojs and I'm trying to iterate over all elements in a collection index = 0 db. They are not closed when the last data is retrieved but are kept open and the cursor location marks the final Feb 2, 2024 · To get the above output, we read all data from the collection and use forEach() to iterate over every single document of the collection. To improve the performance of reading large collections you should try using RawBSONDocument: Dec 30, 2023 · Implementing these best practices and techniques leads to efficient interactions with large MongoDB collections, ensuring scalability and responsiveness in production environments. Jul 23, 2025 · Conclusion MongoDB cursors are essential for efficiently retrieving documents from the database, especially when dealing with large datasets. This article explains what a cursor is in MongoDB, how it works, and how to manually iterate over the results. Here's my question I've not been able to find a solution to. class pymongo. NET/C# Driver to access and manage MongoDB databases and collections. Tailable cursors are only for use with capped collections. NET. This tutorial covers the basics of MongoDB cursors and provides code examples for iterating over collections in both ascending and descending order. I use Repository interfaces to access data in collections. 5s. In this guide, we covered essential techniques such as manually iterating a cursor, using common Sep 21, 2016 · Using a generator to iterate over a large collection in Mongo Asked 8 years, 8 months ago Modified 8 years, 8 months ago Viewed 5k times cursor – Tools for iterating over MongoDB query results ¶ Cursor class to iterate over Mongo query results. In each collection, MongoDB stores data as documents that contain field-and-value pairs. You are iterating these properties and not the results in the cursor. items field from the collection. find({}, {uid: 1, _id: 0}). Learn how to iterate over a collection in MongoDB using Python. Sep 14, 2021 · iterate over large mongodb collection for purpose of updating schema Asked 3 years, 5 months ago Modified 3 years, 5 months ago Viewed 245 times Dec 1, 2016 · I am using PyMongo and trying to iterate over (10 millions) documents in my MongoDB collection and just extract a couple of keys: "name" and "address", then output them to . For some processing I need to iterate over all elements of collection. Access Cursor Contents Iteratively To iterate over the contents of a cursor, use a for loop, as shown in the following example. To learn how to create a free MongoDB Atlas cluster and load the sample datasets, see the Get Started with PyMongo tutorial. The biggest issue is that, by default, cursors timeout after 10 minutes of inactivity. 96 key: EeW6E 97 key: wqfmM 98 key: LIGHK 99 key: bjWTI 100 key: 2zNGE 101 key That is why you always get 49 as a result irrespective of whether you iterate an empty collection or a collection with more than 1000 records. Learn how to efficiently iterate over large MongoDB collections using Spring Data with examples and best practices. . I am using MongoDB in java project via spring-data. The code is in C# / . MongoDB organizes data in a hierarchical structure. NET/C# Driver with the `Find ()` method, including examples for finding single or multiple documents. To learn more about the document To iterate over the contents of a cursor, use a foreach loop inside a using block. I currently have a collection of ~50 documents (each around 1mb), where each document contains some metadata and an array of up to 10000 basic elements containing time, value. Select the Synchronous or Asynchronous tab to see the corresponding code: In this guide, you can learn how to use the . It provides a simple and intuitive way to perform various operations on MongoDB, including retrieving documents from a collection. Next, we use another forEach() to loop over every single field of the specified document. find() # Iterate over the documents for document in documents: Iterate over documents in a MongoDB cursor using `forEach ()` to apply a JavaScript function to each document. When iterating over queried cursor, getting each document takes up to 0. If you notice these enumerable properties, you can find hasNext, map, forEach functions as properties of the cursor. Installing I have a collection that is updated frequently and contains a large amount of data. Then, the third forEach() is used to iterate over the values of the fields. csv file. Use ToCursor and Process Documents Incrementally The MongoDB C# driver supports iterating over results with a cursor, which retrieves documents in batches from the server (default batch size is 101 documents). Nov 22, 2019 · I was wondering if it is possible to "split" a collection temporarily or create multiple cursors to iterate through the collection via parallel processing to speed up the time it takes to load my filters (Redis and Bloom Filter). Understanding how to iterate over a cursor and use its various methods allows developers to optimize query performance and manage data more effectively. forEach((err, key) => if err? console. The schema is essentially: { productType: Array, productName: Array, productPrice: Array } My users are concerned with finding products with prices lower than $100. CursorType ¶ NON_TAILABLE ¶ The standard cursor type. The following example retrieves documents from the restaurants collection in which the value of the name field is "Starbucks", then iterates over the results. Is that normal performance for larger files or is there something wrong? Aug 28, 2014 · First of, I'm quite new to mongodb. also, in. I can use fetchAll method of repository, but it always return ArrayList. futm xbk8 jlc rlocl 93i3r v2vlw h56yi kewf1p rd izm