DB Migration Safety Reviewer

Name: DB Migration Safety Reviewer
Price: 15 USD
Availability: InStock
Author: Agensi

Review schema migrations for lock risk, data loss, backfill cost, and rolling-deploy breakage — get a verdict, safe rewrite, and deploy sequence.

$15

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You say

Database: PostgreSQL 15 Table size: not provided (production; estimate unknown) Deployment: rolling deploy (no maintenance window) Context: billing service; subscriptions table is hot path

Migration SQL

-- migration_2026_03_12_subscriptions.sql

ALTER TABLE subscriptions ADD COLUMN plan_tier TEXT NOT NULL;

CREATE INDEX idx_subscriptions_account_id ON subscriptions(account_id);

UPDATE subscriptions SET trial_ends_at = created_at + INTERVAL '14 days' WHERE trial_ends_at IS NULL;

ALTER TABLE subscriptions DROP COLUMN old_price_cents;

Your agent does

DB Migration Safety Review

1. Risk Summary

3. Risk Findings

MIG-01 CRITICAL lock — ADD plan_tier NOT NULL without DEFAULT → Add nullable/DEFAULT, backfill, then SET NOT NULL MIG-02 HIGH lock — CREATE INDEX blocks writes → CREATE INDEX CONCURRENTLY + verify valid MIG-03 HIGH backfill — Unbatched UPDATE on hot table → Batch 1k–10k with statement_timeout MIG-04 HIGH data-loss — DROP old_price_cents irreversible → Stop reading in code first; drop later

6. Deploy Sequence

Expand → Migrate → Contract (destructive last)

JSON: verdict "BLOCK", risk_score 0 Disclaimer: Review aid; not a substitute for staging tests, backups, or DBA review.

What you get

Prevent production downtime by catching long-running table locks before deploy.Ensure zero-downtime schema changes during rolling application deployments.Generate step-by-step safe execution plans for complex data backfills.Verify rollback feasibility and identify destructive operations lacking a path back.Pre-prod review before running a migration in CI/CDCheck whether CREATE INDEX / ALTER TABLE will lock a hot tablePlan safe backfills instead of one giant UPDATERolling-deploy expand → migrate → contract for breaking schema changesCatch ADD COLUMN NOT NULL without default before it fails in productionSecond pair of eyes for destructive drops / type changes

About this skill

The problem

Schema migrations are the quietest way to cause an outage: table locks, failed NOT NULL adds, irreversible drops, and rolling-deploy breaks when old pods still read a column you just removed. Generic “review this SQL” prompts miss database-specific lock behavior and rarely hand you a safe rewrite.

What it does

DB Migration Safety Reviewer is a production-safety review for DDL/DML migrations. It returns:

A Migration Risk Verdict: SAFE-TO-SHIP / SHIP-WITH-CAUTION / BLOCK
A deterministic Risk Score (0–100)
Severity-ranked findings across lock, data-loss, backfill, compatibility, and rollback
A safe-execution rewrite for every risky statement (e.g. CONCURRENTLY, batched backfill, expand-migrate-contract)
Rollback plan + rolling-deploy sequence
Pre-flight checklist + Migration Review JSON for CI/docs

Frameworks & tools

PostgreSQL, MySQL, and SQLite behavior differences
Five-dimension risk model + hard verdict gates
Common patterns: indexes, type changes, NOT NULL, FK validation, drops, large UPDATEs
Works from pasted SQL or migration files in your agent

Why this beats prompting it yourself

Database-aware rules (e.g. Postgres CONCURRENTLY vs MySQL online DDL tools)
Hard gates so CRITICAL issues force BLOCK — not a soft “maybe fine”
Safe rewrites, not only warnings
Rolling-deploy compatibility built into the plan
Assumes large tables when size is unknown (worst case) and labels assumptions
Read-only: never executes against your database

Use cases

Backend engineers shipping migrations under rolling deploys
DBAs reviewing lock and data-loss risk before a release
Teams adding indexes without a maintenance window
Destructive or backfill-heavy changes that need a staged plan

Known limitations

Cannot measure real lock duration or row counts without that input
Version-sensitive advice is sharper when you state the DB version
Not a substitute for staging tests, backups, or DBA review on high-risk production changes
Does not connect to or execute against any database