PostgreSQL vs MySQL: Which Database Should You Choose for Your Application?

The Philosophical Difference

MySQL was built for speed and simplicity, prioritizing read-heavy workloads and ease of setup. It powers most of the web, such as WordPress, Drupal, and countless PHP applications.

PostgreSQL was built for correctness and extensibility, prioritizing ACID compliance, complex queries, and advanced data types. It’s chosen by enterprises when data integrity matters more than raw speed.

Performance Comparison

# MySQL Wins for Simple Read-Heavy Workloads

MySQL excels at simple SELECT queries with limited JOINs, web application read patterns, and high-throughput INSERT operations. For a typical WordPress site, MySQL’s query planner is highly optimized.

On a 4-core VPS with 8GB RAM, MySQL can handle 10,000+ simple SELECT queries per second with proper indexing.

# PostgreSQL Wins for Complex Queries

PostgreSQL’s query planner handles multi-table JOINs, subqueries, CTEs, window functions, and aggregations more efficiently. For queries involving 5+ table JOINs, PostgreSQL can be 2-3x faster.

# Write-Heavy Workloads: PostgreSQL’s MVCC Advantage

PostgreSQL uses MVCC more aggressively. Readers don’t block writers, writers don’t block readers. Better concurrency for mixed read/write workloads.

Data Types and Features

# PostgreSQL: Advanced Data Types

– JSONB: Binary JSON storage with indexing
– Arrays: Native array types eliminate junction tables
– Geometric Types: For GIS applications with PostGIS
– Custom Types: Define your own composite types and enums

# MySQL: Simpler Type System

Standard integers, decimals, dates, VARCHAR/TEXT, BLOB, and JSON (as of 5.7). Simpler but sufficient for most web applications.

Transaction Behavior

PostgreSQL enforces strict ACID compliance by default. Foreign key constraints always enforced, CHECK constraints work as expected.

MySQL’s InnoDB supports ACID but has historically allowed invalid dates, silent data truncation, and non-standard SQL behaviors. Strict mode tightens this.

Replication

MySQL: Primary-replica replication is dead simple, Group Replication offers multi-primary, Galera Cluster (MariaDB) provides synchronous multi-master.

PostgreSQL: Streaming replication, logical replication for specific tables, built-in failover with pg_auto_failover or Patroni.

Full-Text Search

PostgreSQL includes native full-text search with text search dictionaries, ranking, and phrase search. Not as feature-rich as Elasticsearch but eliminates a separate search service for many applications.

MySQL’s FULLTEXT indexes work for simple searches but lack advanced ranking and language-specific stemming.

When to Choose MySQL

Choose MySQL if you’re building a standard web application, your hosting environment dictates it, your workload is read-heavy with simple queries, you need battle-tested replication, or your team already knows MySQL.

When to Choose PostgreSQL

Choose PostgreSQL if data integrity is critical, you need complex queries, you want advanced features (JSONB, full-text search, geometric types), or you’re building a SaaS product with complex data relationships.

Migration Challenges

For simple schemas, migration tools exist. But you’ll face data type mismatches, different SQL dialects, and incompatible stored procedures. Plan for 2-4 weeks of work for medium-sized applications.

Which To Choose

Neither database is objectively better. MySQL’s simplicity and ubiquity make it the pragmatic choice for typical web applications. PostgreSQL’s advanced features and strictness make it ideal for applications where data is the core asset.

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