Using Indexes to Improve Query Performance

Learn about how indexes can improve the performance of our database queries.

An index in a database is a data structure that allows faster data retrieval from a table. When we run a query, the database uses the index to quickly locate the requested information instead of scanning through every row in the table. PostgreSQL indexes can significantly improve our database queries’ speed and efficiency. They do this by storing a sorted list of values for a particular column, allowing faster data lookup and retrieval.

It’s important to note that creating an index does come at a cost—it takes up additional storage space and can slow down data insertion and updates. Therefore, it’s important to carefully assess the benefits of an index for a particular query before creating one.

Types of indexes

Types of indexes in PostgreSQL include B-tree, hash, GiST, and GIN.

  • B-Tree: This is the most commonly used type of index in PostgreSQL. It’s useful for supporting queries on a range of data values (e.g., WHERE x > 5 AND x < 10) and can also support partial matches (e.g., WHERE first_name LIKE 'Joh%'). PostgreSQL automatically creates a B-tree index on primary key columns.

  • Hash: This index type is best for equality matches (e.g., WHERE x = 5) and can’t support range queries or partial matches. Note that PostgreSQL automatically creates a Hash index on unique columns.

  • GiST: This stands for Generalized Search Tree. These indexes can support a variety of data types, including geometric shapes, network addresses, and text search documents.

  • GIN: This stands for Generalized Inverted Indexes. These are useful for indexing values in multiple rows, such as array values.

  • BRIN: This stands for Block Range Indexes. They’re a type of index that PostgreSQL can use to efficiently query very large tables by only examining a small number of “representative” blocks in the table rather than the entire table.

Creating an index

To create an index in PostgreSQL, we can use the CREATE INDEX statement, specifying the table and column (or columns) to be indexed. We can also specify options such as the index type and storage parameters.

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