-- =============================================
-- Education 模块 — Ticket #8 迁移回滚 (PostgreSQL)
-- 004-education-submit-report-rollback.sql
-- =============================================
--
-- WARNING: This file contains NO executable SQL.
-- Destructive rollback requires manual operator verification.
--
-- Manual rollback procedure (operator must execute):
-- 1. Verify no other tables depend on these tables:
--      SELECT
--          tc.table_name,
--          kcu.column_name,
--          ccu.table_name AS referenced_table_name
--      FROM information_schema.table_constraints AS tc
--      JOIN information_schema.key_column_usage AS kcu
--        ON tc.constraint_name = kcu.constraint_name
--      JOIN information_schema.constraint_column_usage AS ccu
--        ON ccu.constraint_name = tc.constraint_name
--      WHERE tc.constraint_type = 'FOREIGN KEY'
--        AND ccu.table_name IN ('education_submit_idempotency',
--             'education_practice_report', 'education_practice_report_detail')
--        AND ccu.table_catalog = current_database();
--    Result MUST be empty before proceeding.
--
-- 2. Verify columns are not referenced by application code:
--    Search codebase for 'correct_answer' / 'explanation' references in
--    education_practice_question to confirm no other consumers.
--
-- 3. Verify the tables contain only data from this migration:
--      SELECT COUNT(*) AS idempotency_count FROM education_submit_idempotency;
--      SELECT COUNT(*) AS report_count FROM education_practice_report;
--      SELECT COUNT(*) AS detail_count FROM education_practice_report_detail;
--    Operator must confirm these counts are acceptable to destroy.
--
-- 4. After verification, execute:
--      DROP TABLE IF EXISTS education_practice_report_detail;
--      DROP TABLE IF EXISTS education_practice_report;
--      DROP TABLE IF EXISTS education_submit_idempotency;
--      ALTER TABLE education_practice_question
--          DROP COLUMN correct_answer,
--          DROP COLUMN explanation;
--
-- DO NOT uncomment or execute the lines below without operator verification.
-- -- DROP TABLE IF EXISTS education_practice_report_detail;
-- -- DROP TABLE IF EXISTS education_practice_report;
-- -- DROP TABLE IF EXISTS education_submit_idempotency;
-- -- ALTER TABLE education_practice_question
-- --     DROP COLUMN correct_answer,
-- --     DROP COLUMN explanation;