fix: replace deployment query broken into 2 queries

backend/controller/dal/dal.go

@@ -752,19 +752,21 @@ func (d *DAL) ReplaceDeployment(ctx context.Context, newDeploymentKey model.Depl
 	var replacedDeploymentKey optional.Option[model.DeploymentKey]
 	oldDeployment, err := tx.GetExistingDeploymentForModule(ctx, newDeployment.ModuleName)
 	if err == nil {
-		count, err := tx.ReplaceDeployment(ctx, oldDeployment.Key, newDeploymentKey, int32(minReplicas))
+		err = tx.SetDeploymentDesiredReplicas(ctx, oldDeployment.Key, 0)
 		if err != nil {
-			return fmt.Errorf("replace deployment failed to replace min replicas from %v to %v: %w", oldDeployment.Key, newDeploymentKey, dalerrs.TranslatePGError(err))
+			return fmt.Errorf("replace deployment failed to set old deployment replicas from %v to %v: %w", oldDeployment.Key, newDeploymentKey, dalerrs.TranslatePGError(err))
 		}
-		if count == 1 {
-			return fmt.Errorf("replace deployment failed: deployment already exists from %v to %v: %w", oldDeployment.Key, newDeploymentKey, ErrReplaceDeploymentAlreadyActive)
+		err = tx.SetDeploymentDesiredReplicas(ctx, newDeploymentKey, int32(minReplicas))
+		if err != nil {
+			return fmt.Errorf("replace deployment failed to set new deployment replicas from %v to %v: %w", oldDeployment.Key, newDeploymentKey, dalerrs.TranslatePGError(err))
 		}
 		err = d.deploymentWillDeactivate(ctx, tx, oldDeployment.Key)
 		if err != nil {
 			return fmt.Errorf("replace deployment failed willDeactivate trigger from %v to %v: %w", oldDeployment.Key, newDeploymentKey, dalerrs.TranslatePGError(err))
 		}
 		replacedDeploymentKey = optional.Some(oldDeployment.Key)
 	} else if !dalerrs.IsNotFound(err) {
+		// any error other than not found
 		return fmt.Errorf("replace deployment failed to get existing deployment for %v: %w", newDeploymentKey, dalerrs.TranslatePGError(err))
 	} else {
 		// Set the desired replicas for the new deployment

backend/controller/sql/queries.sql

@@ -41,18 +41,6 @@ RETURNING id;
 INSERT INTO deployment_artefacts (deployment_id, artefact_id, executable, path)
 VALUES ((SELECT id FROM deployments WHERE key = @key::deployment_key), $2, $3, $4);
 
--- name: ReplaceDeployment :one
-WITH update_container AS (
-    UPDATE deployments AS d
-        SET min_replicas = update_deployments.min_replicas
-        FROM (VALUES (sqlc.arg('old_deployment')::deployment_key, 0),
-                     (sqlc.arg('new_deployment')::deployment_key, sqlc.arg('min_replicas')::INT))
-            AS update_deployments(key, min_replicas)
-        WHERE d.key = update_deployments.key
-        RETURNING 1)
-SELECT COUNT(*)
-FROM update_container;
-
 -- name: GetDeployment :one
 SELECT sqlc.embed(d), m.language, m.name AS module_name, d.min_replicas
 FROM deployments d