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Postgres to MySQL Migration

1 post · Feb 2023 – Aug 2024

What this trail covers

PlanetScale offers robust database migration solutions, including zero-downtime migrations for terabyte and petabyte scale datasets. This is achieved through a process involving consistent, non-locking snapshots, continuous replication of changes from the old to the new system, data verification using VDiff, and a transparent cutover mechanism that buffers incoming queries. The platform leverages Vitess's VReplication and `MoveTables` workflow for these operations, and can also facilitate sharding as part of the migration. The process supports bidirectional cutovers and rollback capabilities, ensuring data integrity and minimal disruption. This capability extends to migrating from PostgreSQL to MySQL and vice-versa, handling data type differences and other schema complexities.

All PlanetScale trails
  1. Zero downtime migrations at petabyte scaleThis post details PlanetScale's zero-downtime migration process for large-scale databases, emphasizing the use of consistent, non-locking snapshots and continuous replication (VReplication) to keep the target database in sync with the source. It outlines a 7-step process including snapshotting, replication, verification (VDiff), pre-cutover traffic routing (Application->PlanetScale->OldDB), transparent cutover with query buffering, and optional rollback. The post highlights the performance implications of the pre-cutover routing and the benefits of PlanetScale Managed for minimizing network costs. It also notes that sharding is often a part of these large-scale migrations, leveraging Vitess's capabilities.
  2. Migrating from Postgres to MySQLThis post provides a detailed guide on migrating a database schema from PostgreSQL to MySQL. It outlines specific differences in data types such as VARCHAR (max length considerations), SERIAL (auto_increment and unsigned bigint), POINT (spatial data handling and ST_asText function), UUID (varchar(36) and UUID() function), and JSONB (using MySQL's JSON type). It also touches upon other migration factors like licensing, triggers, materialized views, ANSI/ISO SQL compliance, and table partitioning. The post uses a manual migration approach as an example and references PlanetScale's MySQL offering.