## Migrate Azure Database for PostgreSQL: Transactional workflows

Move PostgreSQL data from Azure Database for PostgreSQL to Ample, one component at a time. Destination verified on Ample: an optimistic version check and an event row written in the same transaction, a stale update rejected, and a history query over the application-owned events (history=2 conflict=rejected).

### Source procedure:
Take a logical backup with `pg_dump -Fc` from an allowed network or private endpoint. Not migrated automatically: Microsoft Entra authentication, zone-redundant HA and PITR have no equivalent on the managed database.

### Cutover:
Freeze writes with the user's go-ahead, take the final dump, restore, validate, redeploy with the managed DATABASE_URL, keep the Azure server until confirmed.

### Rollback:
Keep the source untouched until you confirm; nothing at the source is changed or deleted by this guide.

### Workflow Steps
1. **Inventory the source**  
   List what Azure Database for PostgreSQL provides beyond the component you are moving. Out of scope here: Microsoft Entra authentication, zone-redundant HA and PITR have no equivalent on the managed database.

2. **Source step 1**  
   Take a logical backup with `pg_dump -Fc` from an allowed network or private endpoint.

3. **Source step 2**  
   Check the engine major version, extensions and server parameters the app depends on.

4. **Source step 3**  
   Restore into a scratch managed database first and compare row counts.

5. **Provision and restore**  
   Deploy the app once so a managed PostgreSQL 16 database exists (or create one with `ample database create --engine postgres`), then restore the dump with pg_restore using its connection string; keep migrations idempotent.
   ```bash
   ample database create --name  --engine postgres
   ```

6. **Validate before cutover**  
   Run the app's own checks and, for data, compare counts and checksums; the example checks are the pattern self-tests (/p/transactional-workflows).

7. **Cut over**  
   Freeze writes with the user's go-ahead, take the final dump, restore, validate, redeploy with the managed DATABASE_URL, keep the Azure server until confirmed.

8. **Rollback**  
   Point DNS or configuration back to the source. The source was never modified; deletion is a separate, user-executed step after validation.

### Limitations
- Documentation only: nothing is executed automatically and no execution binding is offered.
- The source-side procedure is documented from Azure Database for PostgreSQL's standard tooling and was not executed in this catalog's evidence; the destination side was verified with the pattern fixture.
- No full source-product parity is claimed: Microsoft Entra authentication, zone-redundant HA and PITR have no equivalent on the managed database.
- Verified on the node-22 template at s-1vcpu-1gb; region, compliance and request-duration limits are unknown.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures on the managed side are not verified beyond the pattern checks.