feat: assign IM user account numbers

server/db/mysql/user_identity_schema.go

@@ -88,6 +88,9 @@ func ensureUserIdentitySchema(db *sqlx.DB) error {
 			return err
 		}
 	}
+	if err = ensureUserAccountNoSchema(ctx, conn); err != nil {
+		return err
+	}
 	if profilesExist {
 		if exists, err := identityColumnExists(ctx, conn, "im_user_profiles", "email"); err != nil {
 			return err
@@ -568,6 +571,39 @@ func identityCandidates(ctx context.Context, conn *sqlx.Conn, scoped bool, metho
 	return out, nil
 }
 
+func ensureUserAccountNoSchema(ctx context.Context, conn *sqlx.Conn) error {
+	if exists, err := identityColumnExists(ctx, conn, "im_users", "account_no"); err != nil {
+		return err
+	} else if !exists {
+		if _, err = conn.ExecContext(ctx, "ALTER TABLE im_users ADD COLUMN account_no INT UNSIGNED NOT NULL DEFAULT 0 AFTER id"); err != nil {
+			return err
+		}
+	}
+	var start int64 = 999
+	if err := conn.QueryRowContext(ctx, "SELECT GREATEST(COALESCE(MAX(account_no), 999), 999) FROM im_users WHERE account_no>0").Scan(&start); err != nil {
+		return err
+	}
+	if _, err := conn.ExecContext(ctx, `
+		UPDATE im_users AS u
+		JOIN (
+			SELECT ordered.id, (@im_user_account_no := @im_user_account_no + 1) AS next_no
+			FROM (SELECT id FROM im_users WHERE account_no=0 ORDER BY createdat, id) AS ordered
+			CROSS JOIN (SELECT @im_user_account_no := ?) AS vars
+		) AS seq ON seq.id=u.id
+		SET u.account_no=seq.next_no
+		WHERE u.account_no=0`, start); err != nil {
+		return err
+	}
+	if exists, err := identityIndexExists(ctx, conn, "im_users", "uk_im_users_account_no"); err != nil {
+		return err
+	} else if !exists {
+		if _, err = conn.ExecContext(ctx, "CREATE UNIQUE INDEX uk_im_users_account_no ON im_users(account_no)"); err != nil {
+			return fmt.Errorf("create unique user account number index: %w", err)
+		}
+	}
+	return nil
+}
+
 func identityTableExists(ctx context.Context, conn *sqlx.Conn, table string) (bool, error) {
 	var exists int
 	err := conn.QueryRowContext(ctx, `SELECT EXISTS(SELECT 1 FROM information_schema.tables