-- IM file-message link msgid Snowflake compatibility migration.
-- Scope: the shared business database (for example meeting_im).
-- Fixes: im_filemsglinks.msgid was INT (max 2147483647) while message ids are
--        snowflake int64 values (~1.58e18), so every INSERT into the link table
--        failed with MySQL error 1264 "Out of range value for column 'msgid'".
--        Under Kafka persistence that failure retried forever and stalled the
--        consumer partition, blocking persistence for every message queued
--        behind it.
-- Notes: im_filemsglinks is a global (non tenant-sharded) table, but in
--        tenant-scoped-DB deployments every tenant database has its own copy —
--        run this script once per database.
--        Re-running is safe (MODIFY to the same shape is idempotent).
--        NOT REVERSIBLE: converting back to INT would truncate snowflake ids.
-- Review and back up before execution. This script does not replay dead letters.

-- 1. Preflight: confirm the live column shape before touching anything.
SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_TYPE, IS_NULLABLE
FROM information_schema.COLUMNS
WHERE TABLE_SCHEMA = DATABASE()
  AND TABLE_NAME = 'im_filemsglinks'
  AND COLUMN_NAME = 'msgid';

-- 2. Upgrade the column (keeps the nullable semantics of the original schema).
ALTER TABLE `im_filemsglinks`
  MODIFY COLUMN `msgid` BIGINT DEFAULT NULL;

-- 3. Post-check: this query must return zero rows.
SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_TYPE
FROM information_schema.COLUMNS
WHERE TABLE_SCHEMA = DATABASE()
  AND TABLE_NAME = 'im_filemsglinks'
  AND COLUMN_NAME = 'msgid'
  AND DATA_TYPE <> 'bigint';

-- 4. Observe pending recovery work caused by the overflow (and, before the
--    startup schema-contract check existed, by any other drift). Replay only
--    after the post-check passes and the referenced files still exist.
SELECT status, last_reason, COUNT(*) AS entry_count,
       MIN(created_at) AS first_created_at, MAX(created_at) AS last_created_at
FROM im_kafka_dead_letters
WHERE last_error LIKE '%Out of range value for column %'
   OR last_error LIKE '%file lifecycle enqueue failed: not found%'
GROUP BY status, last_reason
ORDER BY status, last_reason;