What Data Structure Does Postgres Use?


Heather Bennett

PostgreSQL is a powerful and popular open-source relational database management system. When it comes to managing data efficiently, understanding the underlying data structure is essential. In this article, we will delve into the data structure that PostgreSQL uses to store and organize its data.

The Heap

At the core of PostgreSQL’s data storage lies the heap. The heap is a collection of pages that hold the actual table data. Each page can hold multiple rows, and each row represents a record in the table.

Within each page, rows are organized based on their physical location on disk. This organization optimizes disk I/O operations, making it faster to read and write data.


PostgreSQL relies heavily on B-trees for indexing. B-trees are balanced tree structures that allow efficient searching, insertion, and deletion of data.

Indexing plays a crucial role in database performance by providing quick access to specific records based on certain criteria. PostgreSQL uses B-trees to create indexes on columns or combinations of columns in tables.

B-trees maintain their balance by automatically redistributing keys when new ones are added or removed. This self-balancing property ensures that searches remain efficient even as the amount of data grows.

Hash Indexes

In addition to B-trees, PostgreSQL also supports hash indexes. Hash indexes use a hash function to map keys directly to their storage locations, enabling fast direct access.

This type of index is useful for equality-based searches but does not support range queries like B-trees do. Hash indexes work best for small lookup tables where there are frequent exact matches.


Gin (Generalized Inverted Index) is another indexing method used by PostgreSQL. This index type is designed for handling complex data types like arrays, full-text search, and geometric data.

GIN indexes break down the indexed values into smaller pieces and build an inverted index on those pieces. This allows for efficient searches on specific elements within the indexed values.

Hash Map

In PostgreSQL, hash maps are used for hash joins and hash aggregation. Hash joins allow efficient merging of two or more tables based on a common key, while hash aggregation performs grouping and aggregation operations.

Hash maps use a hash function to map keys to a specific bucket, where the corresponding data is stored. This enables quick access to related data during join or aggregation operations.


PostgreSQL utilizes various data structures like heaps, B-trees, hash indexes, Gin indexes, and hash maps to efficiently store and organize its data. Understanding these underlying structures can help developers optimize their database design and query performance.

Whether you are new to PostgreSQL or an experienced user, having knowledge of the data structure employed by this powerful database system is crucial for harnessing its full potential.

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