PostgreSQL Create Index

How to Create an Index in PostgreSQL?

Indexes in databases are similar to the index in a book, which helps locate specific information quickly. In PostgreSQL, an index is a database object that provides a fast access path to data in a table. When you perform a query that involves a condition in the WHERE clause, without an index, the database needs to perform a sequential scan of the entire table to find matching rows. This can be very time-consuming, especially for large datasets. However, by creating an index on the column(s) used in the query condition, PostgreSQL can directly navigate to the relevant data, significantly speeding up the query.

The process of creating an index is known as indexing, and it is essential to design and implement indexes thoughtfully to achieve the desired performance improvements. Though indexes enhance read performance, they come with a cost of additional storage and slight overhead during write operations. Therefore, creating indexes should be done strategically based on the specific needs of the application and the types of queries executed.

Why do we Use the CREATE INDEX in PostgreSQL?

CREATE INDEX in PostgreSQL creates new indexes on tables, making data retrieval faster for specific queries. Indexes are particularly useful when you have large tables and frequently query the data based on certain columns. Without an index, the database would need to perform a full table scan each time you run a query with filtering conditions, resulting in slower performance.

Here are some key reasons why we use the CREATE INDEX in PostgreSQL:

1. Improved Query Performance:
   As mentioned earlier, indexes significantly speed up data retrieval by allowing the database to perform index scans instead of sequential scans.
2. Reduced Response Time:
   Queries that use indexed columns can return results much faster, leading to a more responsive application.
3. Optimized Sorting and Joining:
   Indexes can also improve the performance of sorting and joining operations in complex queries.
4. Efficient Searching:
   Indexes enable quick searching, especially when dealing with large datasets.
5. Support for Constraints:
   PostgreSQL indexes can support unique constraints and enforce uniqueness on a column or a group of columns.
6. Compatible with Multiple Data Types:
   PostgreSQL provides a wide range of data types, and indexes can be created on various data types, including numeric, text, date, and more.

Syntax of CREATE INDEX in PostgreSQL command

The syntax of the CREATE INDEX in PostgreSQL is as follows:

Parameters of CREATE INDEX in PostgreSQL

CREATE INDEX in PostgreSQL supports various parameters that allow you to customize the index creation process. Let's explore some essential parameters:

• UNIQUE:
  This parameter ensures the index enforces uniqueness on the indexed column(s).
• CONCURRENTLY:
  This parameter allows creating the index without locking the table, enabling concurrent operations.
• index_name:
  You can specify a custom name for the index using this parameter. Otherwise, PostgreSQL will generate a name automatically.
• USING method:
  You can select a specific index method with this parameter. PostgreSQL supports several methods, such as B-tree, Hash, GiST (Generalized Search Tree), GIN (Generalized Inverted Index), SP-GiST (Space-Partitioned Generalized Search Tree), and BRIN (Block Range INdex).
• column_name:
  This parameter specifies the name of the column(s) on which the index is created. Depending on your query requirements, you can create an index on a single column or multiple columns.
• operator_class:
  For certain data types, PostgreSQL allows you to specify an operator class to control the behavior of the index for that data type.
• ASC | DESC:
  This parameter lets you specify the sort order for the indexed column(s). ASC stands for ascending, and DESC stands for descending. The default is ASC if not specified.
• NULLS { FIRST | LAST }:
  With this parameter, you can define the sort order for NULL values in the indexed column(s).
• INCLUDE:
  Introduced in PostgreSQL 11, this parameter allows you to include non-key columns in the index. These columns are stored with the index and can improve index-only scans, where the data can be retrieved from the index itself without accessing the table.

You can tailor the index to suit your specific performance optimization needs using the appropriate combination of these parameters.

PostgreSQL CREATE INDEX Statement Example

Let's look at an example of creating an index in PostgreSQL. For this demonstration, we will consider a table called employees, and we want to create an index on the salary column to speed up salary-based queries.

Assuming we have the following employees table:

Now, let's create an index on the salary column:

The above command does not provide any direct output upon successful execution. If there are no errors, PostgreSQL will simply create the index silently. To verify that the index has been created successfully, you can use the following command:

The output of this command will show you the details of the employee's table, including the indexes associated with it. In this case, you should see an entry for the idx_employees_salary index under the "Indexes" section. The output might look something like this:

In this example, we named the index idx_employees_salary, and we are using the default index method (B-tree) for the salary column. With this index in place, any query involving filtering or sorting based on the salary column will be significantly faster.