MySQL to PostgreSQL Migration: A Practical Guide
Patch the MySQL dump by replacing backticks, AUTO_INCREMENT, TINYINT(1), DATETIME, and MySQL functions, then import into staging, resync SERIAL sequences, and audit queries for planner differences.
Patch the dump using sed or DBConverter, import into a staging database, run setval to resync SERIAL sequences, and run EXPLAIN ANALYZE on slow queries to adjust indexes.
Summary
Migrating a MySQL dump to PostgreSQL requires more than a simple copy because the two dialects differ in identifiers, auto‑increment syntax, data types, and functions. A typical MySQL dump uses backticks, AUTO_INCREMENT, TINYINT(1) for booleans, DATETIME, and MySQL‑specific functions like IFNULL and GROUP_CONCAT, all of which must be rewritten as double quotes, SERIAL or GENERATED ALWAYS AS IDENTITY, BOOLEAN, TIMESTAMP, COALESCE, STRING_AGG, and so on. The guide shows how to export cleanly with mysqldump flags, convert the dump with sed or a tool like DBConverter, import into a staging database, resync SERIAL sequences with setval, and audit queries with EXPLAIN ANALYZE to catch planner differences such as leading‑wildcard LIKE or strict GROUP BY rules. It also explains how to replace INSERT IGNORE and ON DUPLICATE KEY with ON CONFLICT DO NOTHING or DO UPDATE, and lists common import errors and their fixes. By following these steps you can avoid duplicate key errors, type mismatches, and missing indexes when moving a WordPress‑style schema from MySQL to PostgreSQL. The article also recommends testing the migrated schema against the existing test suite before promoting to production.
Key changes
- Backticks replaced with double quotes
- AUTO_INCREMENT converted to SERIAL or GENERATED ALWAYS AS IDENTITY
- TINYINT(1) mapped to BOOLEAN
- DATETIME changed to TIMESTAMP
- MySQL functions replaced with PostgreSQL equivalents (IFNULL→COALESCE, GROUP_CONCAT→STRING_AGG, LIMIT 10,20→LIMIT 10 OFFSET 20, RAND()→RANDOM())
- INSERT IGNORE/ON DUPLICATE KEY rewritten as ON CONFLICT DO NOTHING or DO UPDATE
- Resync SERIAL sequences with setval after import
- Audit queries with EXPLAIN ANALYZE to adjust indexes