-- =============================================================================
-- drop_all_unique_indexes.sql
-- 去掉当前库所有非 PRIMARY 唯一索引的「唯一性」（改为同名普通 INDEX）
-- 流程：备份并删除外键 → UNIQUE 改 KEY → 恢复外键
-- 解决 Error 1553：Cannot drop index ... needed in a foreign key constraint
-- 可重复执行；唯一性请在业务代码中校验。
-- 请在 Navicat / DBeaver / MySQL Workbench 中整段执行（需要 DELIMITER）。
-- =============================================================================

SET @db := DATABASE();

-- ---------- 预览：将处理的唯一索引 ----------
SELECT
  TABLE_NAME,
  INDEX_NAME,
  GROUP_CONCAT(COLUMN_NAME ORDER BY SEQ_IN_INDEX) AS columns
FROM information_schema.STATISTICS
WHERE TABLE_SCHEMA = @db
  AND NON_UNIQUE = 0
  AND INDEX_NAME <> 'PRIMARY'
GROUP BY TABLE_NAME, INDEX_NAME
ORDER BY TABLE_NAME, INDEX_NAME;

-- ---------- 预览：库中物理外键（会临时删除再重建）----------
SELECT
  rc.CONSTRAINT_NAME,
  rc.TABLE_NAME,
  rc.REFERENCED_TABLE_NAME,
  rc.UPDATE_RULE,
  rc.DELETE_RULE
FROM information_schema.REFERENTIAL_CONSTRAINTS rc
WHERE rc.CONSTRAINT_SCHEMA = @db
ORDER BY rc.TABLE_NAME, rc.CONSTRAINT_NAME;

DROP PROCEDURE IF EXISTS `sp_drop_all_unique_indexes`;
DELIMITER $$
CREATE PROCEDURE `sp_drop_all_unique_indexes`()
BEGIN
  DECLARE done INT DEFAULT 0;
  DECLARE v_fk_name VARCHAR(128);
  DECLARE v_fk_table VARCHAR(128);
  DECLARE v_ref_table VARCHAR(128);
  DECLARE v_update VARCHAR(16);
  DECLARE v_delete VARCHAR(16);
  DECLARE v_cols TEXT;
  DECLARE v_ref_cols TEXT;
  DECLARE v_table VARCHAR(128);
  DECLARE v_index VARCHAR(128);
  DECLARE v_index_cols TEXT;
  DECLARE v_sql TEXT;

  -- 1) 备份当前库全部外键定义
  DROP TEMPORARY TABLE IF EXISTS `_tmp_fk_backup`;
  CREATE TEMPORARY TABLE `_tmp_fk_backup` (
    `id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    `constraint_name` VARCHAR(128) NOT NULL,
    `table_name` VARCHAR(128) NOT NULL,
    `column_names` TEXT NOT NULL,
    `ref_table_name` VARCHAR(128) NOT NULL,
    `ref_column_names` TEXT NOT NULL,
    `update_rule` VARCHAR(16) NOT NULL,
    `delete_rule` VARCHAR(16) NOT NULL
  );

  INSERT INTO `_tmp_fk_backup` (
    `constraint_name`, `table_name`, `column_names`,
    `ref_table_name`, `ref_column_names`, `update_rule`, `delete_rule`
  )
  SELECT
    kcu.CONSTRAINT_NAME,
    kcu.TABLE_NAME,
    GROUP_CONCAT(CONCAT('`', kcu.COLUMN_NAME, '`') ORDER BY kcu.ORDINAL_POSITION SEPARATOR ','),
    kcu.REFERENCED_TABLE_NAME,
    GROUP_CONCAT(CONCAT('`', kcu.REFERENCED_COLUMN_NAME, '`') ORDER BY kcu.ORDINAL_POSITION SEPARATOR ','),
    rc.UPDATE_RULE,
    rc.DELETE_RULE
  FROM information_schema.KEY_COLUMN_USAGE kcu
  INNER JOIN information_schema.REFERENTIAL_CONSTRAINTS rc
    ON rc.CONSTRAINT_SCHEMA = kcu.CONSTRAINT_SCHEMA
   AND rc.CONSTRAINT_NAME = kcu.CONSTRAINT_NAME
   AND rc.TABLE_NAME = kcu.TABLE_NAME
  WHERE kcu.TABLE_SCHEMA = DATABASE()
    AND kcu.REFERENCED_TABLE_NAME IS NOT NULL
  GROUP BY
    kcu.CONSTRAINT_NAME,
    kcu.TABLE_NAME,
    kcu.REFERENCED_TABLE_NAME,
    rc.UPDATE_RULE,
    rc.DELETE_RULE;

  -- 2) 删除全部外键（解除对唯一索引的占用）
  BEGIN
    DECLARE cur_fk_drop CURSOR FOR
      SELECT `constraint_name`, `table_name` FROM `_tmp_fk_backup` ORDER BY `id`;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
    SET done = 0;
    OPEN cur_fk_drop;
    fk_drop_loop: LOOP
      FETCH cur_fk_drop INTO v_fk_name, v_fk_table;
      IF done = 1 THEN
        LEAVE fk_drop_loop;
      END IF;
      SET v_sql = CONCAT('ALTER TABLE `', v_fk_table, '` DROP FOREIGN KEY `', v_fk_name, '`');
      SET @ddl := v_sql;
      PREPARE stmt FROM @ddl;
      EXECUTE stmt;
      DEALLOCATE PREPARE stmt;
    END LOOP;
    CLOSE cur_fk_drop;
  END;

  -- 3) 唯一索引 → 同名普通 INDEX（去掉唯一性，保留列与查询能力，便于外键重建）
  BEGIN
    DECLARE cur_uk CURSOR FOR
      SELECT
        s.TABLE_NAME,
        s.INDEX_NAME,
        GROUP_CONCAT(CONCAT('`', s.COLUMN_NAME, '`') ORDER BY s.SEQ_IN_INDEX SEPARATOR ',')
      FROM information_schema.STATISTICS s
      WHERE s.TABLE_SCHEMA = DATABASE()
        AND s.NON_UNIQUE = 0
        AND s.INDEX_NAME <> 'PRIMARY'
      GROUP BY s.TABLE_NAME, s.INDEX_NAME
      ORDER BY s.TABLE_NAME, s.INDEX_NAME;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
    SET done = 0;
    OPEN cur_uk;
    uk_loop: LOOP
      FETCH cur_uk INTO v_table, v_index, v_index_cols;
      IF done = 1 THEN
        LEAVE uk_loop;
      END IF;
      SET v_sql = CONCAT(
        'ALTER TABLE `', v_table, '` DROP INDEX `', v_index,
        '`, ADD INDEX `', v_index, '` (', v_index_cols, ')'
      );
      SET @ddl := v_sql;
      PREPARE stmt FROM @ddl;
      EXECUTE stmt;
      DEALLOCATE PREPARE stmt;
    END LOOP;
    CLOSE cur_uk;
  END;

  -- 4) 按备份重建外键
  --    若原外键引用的是「非主键唯一键」，去掉唯一性后 InnoDB 可能拒绝重建，将跳过并写入警告表
  DROP TEMPORARY TABLE IF EXISTS `_tmp_fk_restore_fail`;
  CREATE TEMPORARY TABLE `_tmp_fk_restore_fail` (
    `constraint_name` VARCHAR(128) NOT NULL,
    `table_name` VARCHAR(128) NOT NULL,
    `error_msg` TEXT
  );

  BEGIN
    DECLARE cur_fk_add CURSOR FOR
      SELECT
        `constraint_name`, `table_name`, `column_names`,
        `ref_table_name`, `ref_column_names`, `update_rule`, `delete_rule`
      FROM `_tmp_fk_backup`
      ORDER BY `id`;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
    DECLARE CONTINUE HANDLER FOR SQLEXCEPTION
    BEGIN
      GET DIAGNOSTICS CONDITION 1 @fk_err = MESSAGE_TEXT;
      INSERT INTO `_tmp_fk_restore_fail` (`constraint_name`, `table_name`, `error_msg`)
      VALUES (v_fk_name, v_fk_table, @fk_err);
    END;
    SET done = 0;
    OPEN cur_fk_add;
    fk_add_loop: LOOP
      FETCH cur_fk_add INTO
        v_fk_name, v_fk_table, v_cols, v_ref_table, v_ref_cols, v_update, v_delete;
      IF done = 1 THEN
        LEAVE fk_add_loop;
      END IF;
      SET v_sql = CONCAT(
        'ALTER TABLE `', v_fk_table,
        '` ADD CONSTRAINT `', v_fk_name,
        '` FOREIGN KEY (', v_cols,
        ') REFERENCES `', v_ref_table, '` (', v_ref_cols,
        ') ON UPDATE ', v_update,
        ' ON DELETE ', v_delete
      );
      SET @ddl := v_sql;
      PREPARE stmt FROM @ddl;
      EXECUTE stmt;
      DEALLOCATE PREPARE stmt;
    END LOOP;
    CLOSE cur_fk_add;
  END;

  -- 输出重建失败的外键（通常因引用侧不再是 UNIQUE/PRIMARY）
  SELECT * FROM `_tmp_fk_restore_fail`;

  DROP TEMPORARY TABLE IF EXISTS `_tmp_fk_backup`;
  DROP TEMPORARY TABLE IF EXISTS `_tmp_fk_restore_fail`;
END$$
DELIMITER ;

CALL `sp_drop_all_unique_indexes`();
DROP PROCEDURE IF EXISTS `sp_drop_all_unique_indexes`;

-- ---------- 校验：唯一索引应无结果（PRIMARY 除外）----------
SELECT
  TABLE_NAME,
  INDEX_NAME,
  GROUP_CONCAT(COLUMN_NAME ORDER BY SEQ_IN_INDEX) AS columns
FROM information_schema.STATISTICS
WHERE TABLE_SCHEMA = @db
  AND NON_UNIQUE = 0
  AND INDEX_NAME <> 'PRIMARY'
GROUP BY TABLE_NAME, INDEX_NAME
ORDER BY TABLE_NAME, INDEX_NAME;