Can I turn an existing SurrealDB table into a RELATION table?

Existing table changed to TYPE RELATION

Warning: the statement succeeds, then writes fail, access changes, or the table is held up.

What happens

Observed on SurrealDB 3.0.2: after DEFINE TABLE OVERWRITE follows TYPE RELATION IN user OUT user, UPDATE of a record stored before fails with "Couldn't coerce value for field `in` of `follows:1`: Expected `record<user>` but found `NONE`".

Why it is dangerous on a populated table

SurrealDB checks a schema change against new writes, not the records already stored, so an empty table hides it: on a populated one every old record is a write waiting to fail, and whole-table work runs for the length of the table in one transaction.

Fires on

ALTER TABLE follows TYPE RELATION IN user OUT user;

The safe pattern

DEFINE TABLE follows_v2 TYPE RELATION IN user OUT user;
-- batched job: RELATE each (from, to) pair of follows into follows_v2

Fixtures

The rule ships with these files and the test suite runs them on every change: the first set must fire, the second must stay silent.

ALTER TABLE follows TYPE RELATION IN user OUT user;

DEFINE TABLE OVERWRITE follows TYPE RELATION FROM user TO user PERMISSIONS NONE;

ALTER TABLE follows TYPE NORMAL;

DEFINE TABLE follows TYPE RELATION IN user OUT user;

How to check locally

npx bolvrk check migration.surql --engine=surrealdb