-- Tables affected: qt_configurations
-- recovery.not-started: safe to re-run; uses INFORMATION_SCHEMA check before DROP FOREIGN KEY
-- recovery.partial: no rollback needed; FK was dropped intentionally
-- recovery.completed: no action needed
-- verify: user_id column is still NOT NULL | SELECT 1 FROM information_schema.COLUMNS WHERE table_schema=DATABASE() AND table_name='qt_configurations' AND column_name='user_id' AND is_nullable='NO' HAVING COUNT(*)>0

-- Detach qt_configurations from qt_users (ownership is owner_username text)
-- Safe for MySQL 8+/MariaDB 10.2+ via INFORMATION_SCHEMA checks.

SET @fk_exists := (
    SELECT COUNT(*)
    FROM information_schema.TABLE_CONSTRAINTS
    WHERE CONSTRAINT_SCHEMA = DATABASE()
      AND TABLE_NAME = 'qt_configurations'
      AND CONSTRAINT_NAME = 'fk_qt_configurations_user'
      AND CONSTRAINT_TYPE = 'FOREIGN KEY'
);

SET @drop_fk_sql := IF(
    @fk_exists > 0,
    'ALTER TABLE qt_configurations DROP FOREIGN KEY fk_qt_configurations_user',
    'SELECT ''fk_qt_configurations_user not found, skip'' '
);
PREPARE stmt_drop_fk FROM @drop_fk_sql;
EXECUTE stmt_drop_fk;
DEALLOCATE PREPARE stmt_drop_fk;

-- user_id becomes optional legacy column (can stay NULL)
ALTER TABLE qt_configurations
    MODIFY COLUMN user_id BIGINT UNSIGNED NULL;