func resourceAwsDbInstanceUpdate(d *schema.ResourceData, meta interface{}) error {
	conn := meta.(*AWSClient).rdsconn

	d.Partial(true)

	req := &rds.ModifyDBInstanceInput{
		ApplyImmediately:     aws.Bool(d.Get("apply_immediately").(bool)),
		DBInstanceIdentifier: aws.String(d.Id()),
	}
	d.SetPartial("apply_immediately")

	requestUpdate := false
	if d.HasChange("allocated_storage") {
		d.SetPartial("allocated_storage")
		req.AllocatedStorage = aws.Int64(int64(d.Get("allocated_storage").(int)))
		requestUpdate = true
	}
	if d.HasChange("allow_major_version_upgrade") {
		d.SetPartial("allow_major_version_upgrade")
		req.AllowMajorVersionUpgrade = aws.Bool(d.Get("allow_major_version_upgrade").(bool))
		requestUpdate = true
	}
	if d.HasChange("backup_retention_period") {
		d.SetPartial("backup_retention_period")
		req.BackupRetentionPeriod = aws.Int64(int64(d.Get("backup_retention_period").(int)))
		requestUpdate = true
	}
	if d.HasChange("copy_tags_to_snapshot") {
		d.SetPartial("copy_tags_to_snapshot")
		req.CopyTagsToSnapshot = aws.Bool(d.Get("copy_tags_to_snapshot").(bool))
		requestUpdate = true
	}
	if d.HasChange("instance_class") {
		d.SetPartial("instance_class")
		req.DBInstanceClass = aws.String(d.Get("instance_class").(string))
		requestUpdate = true
	}
	if d.HasChange("parameter_group_name") {
		d.SetPartial("parameter_group_name")
		req.DBParameterGroupName = aws.String(d.Get("parameter_group_name").(string))
		requestUpdate = true
	}
	if d.HasChange("engine_version") {
		d.SetPartial("engine_version")
		req.EngineVersion = aws.String(d.Get("engine_version").(string))
		requestUpdate = true
	}
	if d.HasChange("iops") {
		d.SetPartial("iops")
		req.Iops = aws.Int64(int64(d.Get("iops").(int)))
		requestUpdate = true
	}
	if d.HasChange("backup_window") {
		d.SetPartial("backup_window")
		req.PreferredBackupWindow = aws.String(d.Get("backup_window").(string))
		requestUpdate = true
	}
	if d.HasChange("maintenance_window") {
		d.SetPartial("maintenance_window")
		req.PreferredMaintenanceWindow = aws.String(d.Get("maintenance_window").(string))
		requestUpdate = true
	}
	if d.HasChange("password") {
		d.SetPartial("password")
		req.MasterUserPassword = aws.String(d.Get("password").(string))
		requestUpdate = true
	}
	if d.HasChange("multi_az") {
		d.SetPartial("multi_az")
		req.MultiAZ = aws.Bool(d.Get("multi_az").(bool))
		requestUpdate = true
	}
	if d.HasChange("publicly_accessible") {
		d.SetPartial("publicly_accessible")
		req.PubliclyAccessible = aws.Bool(d.Get("publicly_accessible").(bool))
		requestUpdate = true
	}
	if d.HasChange("storage_type") {
		d.SetPartial("storage_type")
		req.StorageType = aws.String(d.Get("storage_type").(string))
		requestUpdate = true
	}
	if d.HasChange("auto_minor_version_upgrade") {
		d.SetPartial("auto_minor_version_upgrade")
		req.AutoMinorVersionUpgrade = aws.Bool(d.Get("auto_minor_version_upgrade").(bool))
		requestUpdate = true
	}

	if d.HasChange("vpc_security_group_ids") {
		if attr := d.Get("vpc_security_group_ids").(*schema.Set); attr.Len() > 0 {
			var s []*string
			for _, v := range attr.List() {
				s = append(s, aws.String(v.(string)))
			}
			req.VpcSecurityGroupIds = s
		}
		requestUpdate = true
	}

	if d.HasChange("vpc_security_group_ids") {
		if attr := d.Get("security_group_names").(*schema.Set); attr.Len() > 0 {
			var s []*string
			for _, v := range attr.List() {
				s = append(s, aws.String(v.(string)))
			}
			req.DBSecurityGroups = s
		}
		requestUpdate = true
	}

	log.Printf("[DEBUG] Send DB Instance Modification request: %#v", requestUpdate)
	if requestUpdate {
		log.Printf("[DEBUG] DB Instance Modification request: %#v", req)
		_, err := conn.ModifyDBInstance(req)
		if err != nil {
			return fmt.Errorf("Error modifying DB Instance %s: %s", d.Id(), err)
		}
	}

	// separate request to promote a database
	if d.HasChange("replicate_source_db") {
		if d.Get("replicate_source_db").(string) == "" {
			// promote
			opts := rds.PromoteReadReplicaInput{
				DBInstanceIdentifier: aws.String(d.Id()),
			}
			attr := d.Get("backup_retention_period")
			opts.BackupRetentionPeriod = aws.Int64(int64(attr.(int)))
			if attr, ok := d.GetOk("backup_window"); ok {
				opts.PreferredBackupWindow = aws.String(attr.(string))
			}
			_, err := conn.PromoteReadReplica(&opts)
			if err != nil {
				return fmt.Errorf("Error promoting database: %#v", err)
			}
			d.Set("replicate_source_db", "")
		} else {
			return fmt.Errorf("cannot elect new source database for replication")
		}
	}

	if arn, err := buildRDSARN(d, meta); err == nil {
		if err := setTagsRDS(conn, d, arn); err != nil {
			return err
		} else {
			d.SetPartial("tags")
		}
	}
	d.Partial(false)

	return resourceAwsDbInstanceRead(d, meta)
}
func resourceAwsDbInstanceUpdate(d *schema.ResourceData, meta interface{}) error {
	conn := meta.(*AWSClient).rdsconn

	d.Partial(true)

	req := &rds.ModifyDBInstanceInput{
		ApplyImmediately:     aws.Bool(d.Get("apply_immediately").(bool)),
		DBInstanceIdentifier: aws.String(d.Id()),
	}
	d.SetPartial("apply_immediately")

	requestUpdate := false
	if d.HasChange("allocated_storage") || d.HasChange("iops") {
		d.SetPartial("allocated_storage")
		d.SetPartial("iops")
		req.Iops = aws.Int64(int64(d.Get("iops").(int)))
		req.AllocatedStorage = aws.Int64(int64(d.Get("allocated_storage").(int)))
		requestUpdate = true
	}
	if d.HasChange("allow_major_version_upgrade") {
		d.SetPartial("allow_major_version_upgrade")
		req.AllowMajorVersionUpgrade = aws.Bool(d.Get("allow_major_version_upgrade").(bool))
		requestUpdate = true
	}
	if d.HasChange("backup_retention_period") {
		d.SetPartial("backup_retention_period")
		req.BackupRetentionPeriod = aws.Int64(int64(d.Get("backup_retention_period").(int)))
		requestUpdate = true
	}
	if d.HasChange("copy_tags_to_snapshot") {
		d.SetPartial("copy_tags_to_snapshot")
		req.CopyTagsToSnapshot = aws.Bool(d.Get("copy_tags_to_snapshot").(bool))
		requestUpdate = true
	}
	if d.HasChange("instance_class") {
		d.SetPartial("instance_class")
		req.DBInstanceClass = aws.String(d.Get("instance_class").(string))
		requestUpdate = true
	}
	if d.HasChange("parameter_group_name") {
		d.SetPartial("parameter_group_name")
		req.DBParameterGroupName = aws.String(d.Get("parameter_group_name").(string))
		requestUpdate = true
	}
	if d.HasChange("engine_version") {
		d.SetPartial("engine_version")
		req.EngineVersion = aws.String(d.Get("engine_version").(string))
		requestUpdate = true
	}
	if d.HasChange("backup_window") {
		d.SetPartial("backup_window")
		req.PreferredBackupWindow = aws.String(d.Get("backup_window").(string))
		requestUpdate = true
	}
	if d.HasChange("maintenance_window") {
		d.SetPartial("maintenance_window")
		req.PreferredMaintenanceWindow = aws.String(d.Get("maintenance_window").(string))
		requestUpdate = true
	}
	if d.HasChange("password") {
		d.SetPartial("password")
		req.MasterUserPassword = aws.String(d.Get("password").(string))
		requestUpdate = true
	}
	if d.HasChange("multi_az") {
		d.SetPartial("multi_az")
		req.MultiAZ = aws.Bool(d.Get("multi_az").(bool))
		requestUpdate = true
	}
	if d.HasChange("publicly_accessible") {
		d.SetPartial("publicly_accessible")
		req.PubliclyAccessible = aws.Bool(d.Get("publicly_accessible").(bool))
		requestUpdate = true
	}
	if d.HasChange("storage_type") {
		d.SetPartial("storage_type")
		req.StorageType = aws.String(d.Get("storage_type").(string))
		requestUpdate = true

		if *req.StorageType == "io1" {
			req.Iops = aws.Int64(int64(d.Get("iops").(int)))
		}
	}
	if d.HasChange("auto_minor_version_upgrade") {
		d.SetPartial("auto_minor_version_upgrade")
		req.AutoMinorVersionUpgrade = aws.Bool(d.Get("auto_minor_version_upgrade").(bool))
		requestUpdate = true
	}

	if d.HasChange("monitoring_role_arn") {
		d.SetPartial("monitoring_role_arn")
		req.MonitoringRoleArn = aws.String(d.Get("monitoring_role_arn").(string))
		requestUpdate = true
	}

	if d.HasChange("monitoring_interval") {
		d.SetPartial("monitoring_interval")
		req.MonitoringInterval = aws.Int64(int64(d.Get("monitoring_interval").(int)))
		requestUpdate = true
	}

	if d.HasChange("vpc_security_group_ids") {
		if attr := d.Get("vpc_security_group_ids").(*schema.Set); attr.Len() > 0 {
			var s []*string
			for _, v := range attr.List() {
				s = append(s, aws.String(v.(string)))
			}
			req.VpcSecurityGroupIds = s
		}
		requestUpdate = true
	}

	if d.HasChange("security_group_names") {
		if attr := d.Get("security_group_names").(*schema.Set); attr.Len() > 0 {
			var s []*string
			for _, v := range attr.List() {
				s = append(s, aws.String(v.(string)))
			}
			req.DBSecurityGroups = s
		}
		requestUpdate = true
	}

	if d.HasChange("option_group_name") {
		d.SetPartial("option_group_name")
		req.OptionGroupName = aws.String(d.Get("option_group_name").(string))
		requestUpdate = true
	}

	if d.HasChange("port") {
		d.SetPartial("port")
		req.DBPortNumber = aws.Int64(int64(d.Get("port").(int)))
		requestUpdate = true
	}

	log.Printf("[DEBUG] Send DB Instance Modification request: %t", requestUpdate)
	if requestUpdate {
		log.Printf("[DEBUG] DB Instance Modification request: %s", req)
		_, err := conn.ModifyDBInstance(req)
		if err != nil {
			return fmt.Errorf("Error modifying DB Instance %s: %s", d.Id(), err)
		}

		log.Println("[INFO] Waiting for DB Instance to be available")

		stateConf := &resource.StateChangeConf{
			Pending: []string{"creating", "backing-up", "modifying", "resetting-master-credentials",
				"maintenance", "renaming", "rebooting", "upgrading"},
			Target:     []string{"available"},
			Refresh:    resourceAwsDbInstanceStateRefreshFunc(d, meta),
			Timeout:    80 * time.Minute,
			MinTimeout: 10 * time.Second,
			Delay:      30 * time.Second, // Wait 30 secs before starting
		}

		// Wait, catching any errors
		_, dbStateErr := stateConf.WaitForState()
		if dbStateErr != nil {
			return dbStateErr
		}
	}

	// separate request to promote a database
	if d.HasChange("replicate_source_db") {
		if d.Get("replicate_source_db").(string) == "" {
			// promote
			opts := rds.PromoteReadReplicaInput{
				DBInstanceIdentifier: aws.String(d.Id()),
			}
			attr := d.Get("backup_retention_period")
			opts.BackupRetentionPeriod = aws.Int64(int64(attr.(int)))
			if attr, ok := d.GetOk("backup_window"); ok {
				opts.PreferredBackupWindow = aws.String(attr.(string))
			}
			_, err := conn.PromoteReadReplica(&opts)
			if err != nil {
				return fmt.Errorf("Error promoting database: %#v", err)
			}
			d.Set("replicate_source_db", "")
		} else {
			return fmt.Errorf("cannot elect new source database for replication")
		}
	}

	if arn, err := buildRDSARN(d.Id(), meta.(*AWSClient).accountid, meta.(*AWSClient).region); err == nil {
		if err := setTagsRDS(conn, d, arn); err != nil {
			return err
		} else {
			d.SetPartial("tags")
		}
	}
	d.Partial(false)

	return resourceAwsDbInstanceRead(d, meta)
}