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safe-migrations SKILL.md skillA

safe-migrations from sigistry/marketplace is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.

Install it, pinned

mdr add sigistry/marketplace/safe-migrations@git:20260826.571bc2f

Pins git:20260826.571bc2f in mdr.lock. Pin the fingerprint instead.

Audit grade: A, 17 of 17 checks passed
Kind: SKILL.md skill
Repository: sigistry/marketplace
Path: plugins/sql-safety-net/skills/safe-migrations/SKILL.md
Versions recorded: 3
Latest version: git:20260826.571bc2f, committed Aug 26, 2026
First version recorded: Jul 8, 2026
Size: 3,725 bytes
Repository stars: 3
License: MIT

This skill should be used when the user mentions "migration", "schema change", "zero downtime", "add column", "alter table", "add index", "lock", "expand contract", "backfill", "ALTER COLUMN", "NOT NULL", "CREATE INDEX", or rewriting a DDL change to avoid downtime. It provides the expand-contract (parallel-change) methodology and a per-dialect catalog of which DDL operations take blocking locks and their safe alternatives.

Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.

What the file says

# Safe Migrations

## Purpose
Provide a standardized, static methodology for turning a hazardous schema migration into a safe, reversible, zero-downtime change, without a database connection. The core idea: most outages come from a DDL statement that takes a long-held **ACCESS EXCLUSIVE** (Postgres) or table-copy (MySQL) lock and blocks all traffic while it rewrites the table. The fix is almost always the same shape, so this skill encodes it once.

## The Expand-Contract (Parallel-Change) Principle
Never change a schema object in place while the app runs. Instead, evolve in additive steps so old and new code both work at every moment:

1. **Expand**: add the new structure (nullable column, new index built concurrently, `NOT VALID` constraint) without touching existing behavior.
2. **Migrate**: backfill data in bounded batches; dual-write from the app so old and new stay consistent.
3. **Contract**: once all deploys read the new structure, remove the old one in a *later* deploy.

Each step is independently deployable and reversible. A rename or type change is never one migration, it is a sequence spanning multiple deploys.

## The Golden Rules
…

Read the whole file at its exact version.

How to install

The exact contents, by fingerprint

mdr add sigistry/marketplace/safe-migrations@sha256:6b398df31b22ab7e

The line at the top of this page pins the label git:20260826.571bc2f, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.

Badge

[![mdr](https://markdownregistry.com/badge/art_zxwmuz2zat5wko2s.svg)](https://markdownregistry.com/a/art_zxwmuz2zat5wko2s)

4 badge image fetches in 30 days. What the badge shows.

Versions

The registry has recorded 3 versions of this file, between Jul 8, 2026 and Aug 26, 2026, about one every 24 days.

version	committed	commit	size	audit
git:20260826.571bc2f latest	2026-08-26	571bc2f	3,725 B	A	view · diff
git:20260715.fcd8714	2026-07-15	fcd8714	3,725 B	A	view · diff
git:20260708.c0884a9	2026-07-08	c0884a9	3,752 B	A	view

Audit of the latest version

A 17 of 17 checks passed. Fixed automatic checks with no AI involved, so the same checks give the same answer every run.

pass: Frontmatter block present
pass: Frontmatter declares a name
pass: Frontmatter declares a description
pass: Size between 200 bytes and 200 KB (3725 bytes)
pass: No zero-width or bidi control characters
pass: No instruction hidden inside an HTML comment
pass: No link to an exfiltration or paste host
pass: No credential-shaped string
pass: No instruction to send local credentials anywhere
pass: No text hidden with inline styles
pass: No prompt-injection phrasing
pass: No curl or wget piped into a shell
pass: No recursive delete of root, home or parent
pass: No instruction to read or print local credentials
pass: No base64 blob over 200 characters
pass: No link to a raw IP address
pass: No script tag

Source

GitHub

sigistry/marketplace · 3 stars · license MIT · pushed 2026-11-06 · branch main

API

GET https://markdownregistry.com/api/v1/artifacts/art_zxwmuz2zat5wko2s
GET https://markdownregistry.com/api/v1/resolve?ref=sigistry/marketplace/safe-migrations
GET https://markdownregistry.com/api/v1/blob/6b398df31b22ab7ead035077ad4e910d8c312402beef2646d75ebdf50c7d050f

Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.

Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.

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