-- Pending clarification state for the knowledge Q&A clarification loop. Additive and idempotent on MySQL 8.
-- The conversation row keeps at most one suspended clarification; it is resolved (answered,
-- given up or replaced by a new topic) on the next turn and never survives the 30-minute expiry.

SET @aihr_pending_conversation_exists := (
  SELECT COUNT(*)
    FROM information_schema.tables
   WHERE table_schema = DATABASE()
     AND table_name = 'aihr_knowledge_conversation'
);

SET @aihr_pending_clarification_exists := (
  SELECT COUNT(*)
    FROM information_schema.columns
   WHERE table_schema = DATABASE()
     AND table_name = 'aihr_knowledge_conversation'
     AND column_name = 'pending_clarification_json'
);
SET @aihr_pending_clarification_ddl := IF(
  @aihr_pending_conversation_exists = 1 AND @aihr_pending_clarification_exists = 0,
  'ALTER TABLE `aihr_knowledge_conversation` ADD COLUMN `pending_clarification_json` varchar(1000) DEFAULT NULL COMMENT ''挂起的澄清''',
  'SELECT 1'
);
PREPARE aihr_pending_clarification_stmt FROM @aihr_pending_clarification_ddl;
EXECUTE aihr_pending_clarification_stmt;
DEALLOCATE PREPARE aihr_pending_clarification_stmt;

SET @aihr_pending_conversation_exists := NULL;
SET @aihr_pending_clarification_exists := NULL;
SET @aihr_pending_clarification_ddl := NULL;