-- Apply AFTER 2026_09_29_followup_audio.sql, BEFORE deploying delete-aware application code.
-- Re-runnable. Preserve original content SHA, upload binding, provider and all encrypted snapshots.
-- Rollback: leave these additive columns/index in place and disable deletion first.
-- Old application code must NOT be restored after tombstones exist: it exposes hidden tasks.
-- Restoring the old unique key is not generally possible after same-content reuploads.
SET @fa_db = DATABASE();
SET @fa_sql = IF((SELECT COUNT(*) FROM information_schema.COLUMNS WHERE TABLE_SCHEMA=@fa_db AND TABLE_NAME='zyt_followup_audio_task' AND COLUMN_NAME='active_slot')=0,
 'ALTER TABLE zyt_followup_audio_task ADD COLUMN active_slot BIGINT UNSIGNED NOT NULL DEFAULT 0, ADD COLUMN deleted_at BIGINT UNSIGNED NOT NULL DEFAULT 0, ADD COLUMN deleted_by BIGINT UNSIGNED NOT NULL DEFAULT 0, ADD COLUMN deletion_json TEXT NULL', 'SELECT 1');
PREPARE fa_stmt FROM @fa_sql;
EXECUTE fa_stmt;
DEALLOCATE PREPARE fa_stmt;
SET @fa_sql = IF((SELECT COUNT(*) FROM information_schema.STATISTICS WHERE TABLE_SCHEMA=@fa_db AND TABLE_NAME='zyt_followup_audio_task' AND INDEX_NAME='uk_content_profile' AND COLUMN_NAME='active_slot')=0,
 'ALTER TABLE zyt_followup_audio_task DROP INDEX uk_content_profile, ADD UNIQUE KEY uk_content_profile (diagnosis_id,sha256,model_key,active_slot)', 'SELECT 1');
PREPARE fa_stmt FROM @fa_sql;
EXECUTE fa_stmt;
DEALLOCATE PREPARE fa_stmt;