Schema management¶
PgDog inspects the database schema in order to automatically detect sharded and omnisharded tables. When new tables are added or existing tables are changed, PgDog's snapshot of the schema needs to be refreshed.
The open source edition supports refreshing the schema for single-node deployments only. The Enterprise edition takes care of synchronizing schema updates across multiple PgDog nodes, ensuring consistent configuration.
How it works¶
When a client executes a DDL command, e.g. CREATE TABLE, PgDog will send a notification to the control plane. The control plane will then trigger a schema reload across all registered PgDog nodes.
This process takes place in the background, so the schema snapshot across nodes is eventually consistent. This is sufficient for most applications, since migrations run as a separate process and application traffic doesn't use new tables for a considerable amount of time after the schema is changed. This gives PgDog ample time to refresh its schema snapshot.
Configuration¶
Schema reloading on DDL is enabled by default. This is configurable in pgdog.toml:
In the open source edition, this reloads the schema on the same node only, while in the Enterprise edition, this triggers a schema reload on all PgDog nodes part of the same deployment.