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How Does Incremental Sort Work?

Incremental Sort in PostgreSQL: A Developer’s Guide


Even though application developers are not expected to be familiar with all the inner workings of databases like PostgreSQL, it is essential to understand certain features that can significantly impact your application’s performance. One such feature is “incremental sort” in PostgreSQL, which can be a game-changer in optimizing your queries. 

What is Incremental Sort?

Incremental sort is a database optimization feature, introduced in PostgreSQL 13, that allows sorting to be done incrementally during the query execution process. Sorting is a common operation in database queries, often necessary when retrieving data in a specific order. PostgreSQL’s query planner uses incremental sort to improve query performance, particularly for large datasets. This feature is enabled by default in PostgreSQL 13 and above. 

How Does Incremental Sort Work?

When you execute a query that involves sorting, PostgreSQL traditionally performs a full sort of the entire dataset. However, with incremental sort, the database doesn’t have to sort the entire result set at once. Instead, it sorts smaller chunks of data, which are then merged together to produce the final sorted result.

Here’s a simplified example to illustrate the concept:

Traditional Sort

  1. Fetch all the data to be sorted into memory.
  2. Sort the entire dataset.
  3. Return the sorted result.

Incremental Sort

  1. Fetch a chunk of data.
  2. Sort that chunk.
  3. Fetch the next chunk and merge it with the sorted chunk.
  4. Continue until all data is sorted and merged.
  5. Return the final sorted result.

Benefits of Incremental Sort

1. Reduced Memory Usage 

Traditional sorting requires all data to be loaded into memory, which can be problematic for large datasets. Incremental sort, however, processes data in smaller chunks, reducing memory requirements.

2. Faster Query Execution

By sorting smaller portions of data at a time and merging them, incremental sort can lead to faster query execution, especially when dealing with large tables.

3. Better Resource Utilization

Since incremental sort uses less memory and CPU, it allows for better resource allocation within the database, preventing resource contention.

How can you use incremental sort? 

Using incremental sort in PostgreSQL doesn’t require any explicit action from the developer. It’s an internal optimization technique that the PostgreSQL query planner uses automatically when it deems it beneficial for a specific query. PostgreSQL’s query planner evaluates each query and determines the most efficient way to execute it, including whether to employ incremental sorting.

However, there are certain best practices you can follow to help PostgreSQL’s query planner make the right decisions and take advantage of incremental sort when appropriate. 

1. Write Optimized Queries 

Ensure that your SQL queries are well-structured and optimized. This includes using appropriate indexes, specifying clear sorting criteria, and avoiding unnecessary data fetching.

2. Maintain Proper Indexing

Properly indexing your database tables is crucial. PostgreSQL can use indexes to optimize sorting operations. Make sure your tables have indexes on columns commonly used for sorting.

3. Analyze Your Tables

Regularly run the ANALYZE command on your tables to update statistics. This helps the query planner make informed decisions about query execution plans.

4. Use ORDER BY Clause

When you want to sort query results, explicitly specify the ORDER BY clause in your SQL queries. This tells PostgreSQL how you want the data sorted, and it can help PostgreSQL’s query planner decide when to use incremental sort.

5. Consider LIMIT and OFFSET

If your query involves pagination, be mindful of how you use the LIMIT and OFFSET clauses. These can affect sorting performance, especially when dealing with large datasets.

6. Monitor Query Performance

Keep an eye on query performance using PostgreSQL’s built-in monitoring tools, such as EXPLAIN ANALYZE. This helps you understand how your queries are being executed and whether incremental sorting is being used effectively.

7. Database Version

Ensure you are using a reasonably recent version of PostgreSQL, as newer versions may have improved query planning and optimization features.

8. Hardware Resources

The effectiveness of incremental sort can also depend on the available hardware resources (CPU, memory, disk speed). Adequate hardware resources can enable PostgreSQL to make better use of incremental sort.


As an application developer, understanding PostgreSQL’s incremental sort can help you write more efficient queries and optimize the performance of your applications. By following these best practices and query optimization techniques, you can create an environment where PostgreSQL is more likely to employ incremental sort when it can enhance query performance. Remember that the database’s query planner is designed to make intelligent decisions, so focus on providing it with the necessary information and structure to do its job effectively.

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