Reference: Alter System Statement

ALTER SYSTEM changes a server-wide configuration parameter and persists the new value across restarts. Instead of editing the configuration file by hand, you can write the value directly from a SQL session, and CedarDB stores it in the configuration file for you. Changes take effect the next time CedarDB starts.

Usage example:

ALTER SYSTEM SET buffersize = '8G';

The new value is only written to CedarDB’s configuration file and applies after the next restart. To inspect the current value of a setting, use SHOW.

To restore a setting to its default value and delete the explicitly set value from configuration file, use RESET:

ALTER SYSTEM RESET buffersize;

Like ALTER SYSTEM SET, this takes effect after the next restart.

When changes take effect

ALTER SYSTEM only changes the persisted value, but does not change the behavior of the running server. CedarDB reads its configuration once at startup, so a restart is required for any ALTER SYSTEM change to become active.

To change a setting for your current session without persisting it, use SET instead. SET applies immediately but is discarded when the session ends, whereas ALTER SYSTEM persists across restarts but does not affect running sessions.

Permissions

Only superusers can run ALTER SYSTEM, because it changes server-wide configuration.

PostgreSQL Differences

• ALTER SYSTEM writes to CedarDB’s configuration file (by default ~/.cedardb/config).
• All changes require a restart. CedarDB does not reload configuration live.