# Introduction
This PR introduces the slow instance commands pattern, that allow
migrating data in prior of the schema migration, that would fail if not.
Slow instance commands runs after the fast instance commands and before
the workspace commands.
On twenty instance that do not has any active or suspended workspace the
data migration part is skipped but the migration still runs, especially
for fresh installs
We were previously hacking through typeorm transaction system to gain
such granularity using save points:
```ts
export class AddPayloadToCommandMenuItem1775129635528
implements MigrationInterface
{
name = 'AddPayloadToCommandMenuItem1775129635528';
public async up(queryRunner: QueryRunner): Promise<void> {
await queryRunner.query(
`ALTER TABLE "core"."commandMenuItem" ADD "payload" jsonb`,
);
const savepointName =
'sp_add_payload_check_constraint_to_command_menu_item';
try {
await queryRunner.query(`SAVEPOINT ${savepointName}`);
await addPayloadCheckConstraintToCommandMenuItem(queryRunner);
await queryRunner.query(`RELEASE SAVEPOINT ${savepointName}`);
} catch (e) {
try {
await queryRunner.query(`ROLLBACK TO SAVEPOINT ${savepointName}`);
await queryRunner.query(`RELEASE SAVEPOINT ${savepointName}`);
} catch (rollbackError) {
// oxlint-disable-next-line no-console
console.error(
'Failed to rollback to savepoint in AddPayloadToCommandMenuItem1775129635528',
rollbackError,
);
throw rollbackError;
}
// oxlint-disable-next-line no-console
console.error(
'Swallowing AddPayloadToCommandMenuItem1775129635528 error',
e,
);
}
}
```
It was afterwards re-applied within an workspace commands, it was hacky
and missleading for the self host having false positive in logs
## New pattern
Generate the slow instance command
```
npx nx database:migrate:generate twenty-server -- --name add-foo-bar-columns --type slow
```
```ts
import { DataSource, QueryRunner } from 'typeorm';
import { RegisteredInstanceCommand } from 'src/engine/core-modules/upgrade/decorators/registered-instance-command.decorator';
import { SlowInstanceCommand } from 'src/engine/core-modules/upgrade/interfaces/slow-instance-command.interface';
@RegisteredInstanceCommand('1.21.0', 1775640902366, { type: 'slow' })
export class AddPrastoinColToWorkspaceSlowInstanceCommand implements SlowInstanceCommand {
async runDataMigration(dataSource: DataSource): Promise<void> {
// TODO: implement data backfill before the DDL migration
}
public async up(queryRunner: QueryRunner): Promise<void> {
await queryRunner.query('ALTER TABLE "core"."workspace" ADD "prastoin" character varying');
}
public async down(queryRunner: QueryRunner): Promise<void> {
await queryRunner.query('ALTER TABLE "core"."workspace" DROP COLUMN "prastoin"');
}
}
```
### Why `run-instance-commands` and `upgrade` remain separate commands
These two commands serve fundamentally different purposes with
incompatible scoping semantics:
The run-instance-commands iterates over all the legacy typeorm and the
instance commands of all versions, used for database init and so on. we
could be centralizing both but the readability tradeoff isn't worth it
In the future thanks to the cross-version pattern we will be able to
centralize them but not right now
Please note that by default the `run-instance-commands` only run the
fast instance commands which is expected for our cloud prod CD
Paul Rastoin
85be463487