create index concurrently postgres with code examples

PostgreSQL offers a variety of indexing techniques to enable efficient querying of large datasets. One popular technique is creating indexes concurrently, which allows you to perform index creation without locking the database. This means that you can continue performing updates and queries during the index creation process, without experiencing any interruption.

In this article, we’ll explore the basics of creating indexes concurrently in PostgreSQL. We’ll start by discussing what concurrent index creation means and how it differs from regular index creation. Then, we’ll walk through the process of creating an index concurrently using some example code.

What is Concurrent Index Creation?

When you create an index in PostgreSQL, the database needs to build a data structure that allows for efficient searching of the indexed column. During this process, the table is locked, meaning that no other operations can be performed on it. This can cause problems if the table is in high demand or contains a large amount of data.

To avoid these problems, PostgreSQL provides the option to create indexes concurrently. This means that the index can be built while the table is still being updated and queried, without locking the table. The downside of concurrent index creation is that it can take longer to complete and may use more system resources.

Before we dive into the code, let’s first take a look at the syntax for creating indexes in PostgreSQL.

ON table_name (column_name);

The CONCURRENTLY keyword is optional. If included, it will trigger the creation of the index concurrently. However, concurrent index creation is not supported for all index types; only B-tree, GIN, and GiST indexes. Additionally, if your table is heavily updated, the overhead of concurrent index creation may outweigh the benefits of concurrent updates.

Creating an Index Concurrently

To create an index concurrently in PostgreSQL, you’ll need to follow these steps:

  1. Identify the table and column(s) that need indexing.
  2. Determine the type of index that would be most efficient (B-tree, GIN, or GiST).
  3. Write the SQL code for creating the index concurrently.
  4. Execute the code and observe the results.

Let’s work through an example using a simple database of users and their associated email addresses. For our purposes, we’ll assume that the table has already been created and has a significant amount of data.

Step 1: Identify the table and column(s) that require indexing

In our example, we’ll create an index for the email column in the users table. This will allow us to efficiently search for users based on their email addresses.

Step 2: Determine the type of index that would be most efficient

For our use case, we’ll use a B-tree index since it’s the most commonly used and efficient index type for single-column lookups.

Step 3: Write the SQL code for creating the index concurrently

We can create our index with the following SQL code:

ON users (email);

The CONCURRENTLY keyword tells PostgreSQL to perform the index creation concurrently. The name of the index (email_idx) is up to you, but it should be descriptive enough to identify the index’s purpose easily.

Step 4: Execute the code and observe the results

After running the code, PostgreSQL will start building the index concurrently, allowing the table to continue being updated and queried during the process. Depending on the size of the table, this may take some time.

Once the index has been created, you can use it in your queries to speed up searching for users based on their email addresses. For example:

FROM users
WHERE email = '';

Without the index, PostgreSQL would need to scan the entire users table to find users with the specified email address. With the index, PostgreSQL knows precisely which rows contain the information it needs, resulting in much quicker queries.

Final Thoughts

Concurrent index creation offers a useful option for creating indexes in PostgreSQL without interrupting other operations on your database. While it may take a little longer and use more system resources than non-concurrent index creation, the benefits of allowing the database to continue running during the creation process can outweigh the costs.

Remember that not all index types support concurrent creation, and the benefits of concurrent updates may not be worthwhile in all cases. However, when it is appropriate, concurrent index creation can help you maintain a high-performing database that can handle large amounts of data and high volumes of traffic.

In this article, we began by discussing how PostgreSQL's concurrent indexing feature allows you to build indexes on tables without locking the database. We also explained that concurrent indexing can be especially useful when you have large tables that need to be frequently updated and queried.

We then proceeded to explore the syntax for creating indexes in PostgreSQL, focusing on the CONCURRENTLY keyword that's used to request concurrent index creation. We also pointed out that not all index types support concurrent creation, and we emphasized the importance of choosing the right index type based on the specific requirements of your database.

Next, we provided a step-by-step approach to creating a B-tree index on a table containing users' email addresses. Finally, we explained how you can query the newly-created index to retrieve the data you require efficiently.

It's worth mentioning that PostgreSQL provides many other indexing options besides concurrent indexing that you should be aware of. For example, you might consider using partitioning, partial indexes, or expression indexes to optimize your database's performance. Some of these indexing techniques can be used in combination, depending on your application's requirements.

Furthermore, using indexes, whether concurrently or not, is just one way to speed up your database queries. There are other techniques you can use, such as optimizing SQL queries, caching, and using a load balancer, among others.

To sum up, PostgreSQL's concurrent indexing feature is an excellent tool for ensuring that you can create indexes on large tables without adversely impacting your application's performance. However, you should choose the right index type and combination of indexing techniques for your use case to ensure optimal database performance. Additionally, there are other ways to optimize database performance beyond indexing, so it's important to consider multiple strategies when designing a high-performing database.

Popular questions

  1. What is concurrent index creation in PostgreSQL?
    Answer: Concurrent index creation in PostgreSQL refers to the process of building an index while allowing the database to continue running without locking the data. It is useful when you have a large table that requires frequent updates and queries.

  2. Which index types support concurrent creation in PostgreSQL?
    Answer: Only B-tree, GIN, and GiST indexes support concurrent creation in PostgreSQL.

  3. When is concurrent index creation not the best option in PostgreSQL?
    Answer: Concurrent index creation may not be the best option when you have a small table with few updates or queries. The cost of concurrent creation may outweigh the benefits in such cases.

  4. What steps are required to create an index concurrently in PostgreSQL?
    Answer: To create an index concurrently in PostgreSQL, you need to identify the table and column that require indexing, determine the index type, write the SQL code, and execute it.

  5. Can you use concurrent indexing with other indexing techniques in PostgreSQL?
    Answer: Yes, you can use concurrent indexing with other techniques such as partitioning, partial indexes, or expression indexes to optimize your database performance.



My passion for coding started with my very first program in Java. The feeling of manipulating code to produce a desired output ignited a deep love for using software to solve practical problems. For me, software engineering is like solving a puzzle, and I am fully engaged in the process. As a Senior Software Engineer at PayPal, I am dedicated to soaking up as much knowledge and experience as possible in order to perfect my craft. I am constantly seeking to improve my skills and to stay up-to-date with the latest trends and technologies in the field. I have experience working with a diverse range of programming languages, including Ruby on Rails, Java, Python, Spark, Scala, Javascript, and Typescript. Despite my broad experience, I know there is always more to learn, more problems to solve, and more to build. I am eagerly looking forward to the next challenge and am committed to using my skills to create impactful solutions.

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