PostgreSQL: How to store images in database (and why you shouldn’t)

Introduction

Storing images in databases is a topic that often leads to heated debate among developers and database administrators. While PostgreSQL, a robust and scalable relational database system, provides mechanisms to store binaries including images, it may not always be the best strategy for managing image data. In this tutorial, we will explore the methods to store images directly in PostgreSQL using bytea and large object (lo) data types, and also discuss the reasons and alternatives to avoid such an approach.

Understanding The Data Types

In PostgreSQL, there are two primary data types suitable for storing binary data: bytea and large object (lo). The bytea data type allows you to store binary data up to a few MB in size directly in a table as a sequence of bytes. On the other hand, the large object system provides a way to store larger binary objects up to 2 GB in size.

CREATE TABLE image_table (
    id SERIAL PRIMARY KEY,
    name VARCHAR(255),
    image_data BYTEA
);

To insert an image into this table, one would typically have to first read the image into an application’s memory, then encode it to a bytea-compatible format, and finally insert it into the SQL command.

Inserting Images into PostgreSQL

INSERT INTO image_table (name, image_data)
VALUES ('MyImage', 'data goes here');

This pseudo-command shows the idea, but in a real environment, the image data would not be a simple text like ‘data goes here’.

Using Large Objects

To handle more extensive image data, you might consider using the Large Object feature offered by PostgreSQL.

BEGIN;
SELECT lo_create(0);

COMMIT;

This would create a new large object and the function would return a unique identifier which can be stored in an integer field.

However, storing images in a database comes with downsides such as increased database size, more complex backups, possible performance implications, and generally increased complexity in handling files.

Why You Shouldn’t Store Images In A Database

The practice of storing images or other binary files directly in databases is generally discouraged for several reasons. The most significant is that it negates the purpose of a file system, which is optimized to handle file storage and retrieval. Storing large objects in PostgreSQL also bloats the database, making it harder to maintain. It can also lead to slower performance because large files can be more efficiently served from a file system or a content delivery network (CDN).

Alternative approaches include using the filesystem to store the images and keeping only meta information, like the path to the image, in the database. Another modern approach is to use dedicated object storage services such as Amazon S3, Google Cloud Storage, or even PostgreSQL’s own foreign data wrapper to interface with these services.

Storing Image Path in PostgreSQL

CREATE TABLE image_path_table (
    id SERIAL PRIMARY KEY,
    name VARCHAR(255),
    image_path TEXT
);

This way, you reference the location of the image file within your database, but you can let your web server or a third-party service serve the image directly.

Conclusion

While PostgreSQL offers the technical capabilities to store binary data such as images, it is generally advisable to consider alternatives. Evaluating the pros and cons of database image storage versus using filesystems or object storage services is crucial. Leveraging PostgreSQL to manage image metadata and paths can provide the best of both worlds, combining robust data management with efficient image delivery.