Skills for Real Engineers. Straight from my .agents directory.
39 skills
postgres-database-migration
Agent skill from
Use this skill for planning, testing, and safely executing PostgreSQL schema migrations — especially when working with production data or shared databases. **Trigger when user asks to:** - Test a schema migration before applying it to production - Add, remove, or rename columns safely on a live table - Change a column's data type without downtime - Add or drop indexes, constraints, or foreign keys on large tables - Understand which ALTER TABLE operations lock the table - Roll back a failed migration - Plan a zero-downtime migration strategy - Fork a database to test a migration safely **Keywords:** migration, schema change, ALTER TABLE, add column, drop column, rename column, change type, zero downtime, lock, AccessExclusiveLock, concurrent index, forking, rollback, backfill, deploy Covers: lock-level reference for every common DDL operation, safe migration patterns, fork-based testing, zero-downtime column changes, index creation, constraint addition, backfill strategies, pre/post-
How to install postgres-database-migration
install postgres-database-migration
# install the pg-aiguide pack with the skills CLI
npx skills add timescale/pg-aiguide# or add only this skill to Claude Code: copy the folder
skills/postgres-database-migration/
# into
~/.claude/skills/postgres-database-migration/ (all projects)
.claude/skills/postgres-database-migration/ (one project)
1# PostgreSQL Database Migrations23A schema migration that works on an empty dev database can fail, lock, or corrupt data on a production table with millions of rows. This guide covers how to assess risk, test against real data, and execute migrations safely.45## DDL Lock Reference67Every schema change acquires a lock. The critical question is: **does it block reads and writes, and for how long?**89### Fast, Non-Blocking Operations1011These complete in milliseconds regardless of table size. They only hold a brief `AccessExclusiveLock` for the catalog update, not for data rewriting.1213| Operation | Lock Level | Notes |14|-----------|-----------|-------|15| `ADD COLUMN` (nullable, no default) | `AccessExclusiveLock` (brief) | **Fast.** No table rewrite. Metadata-only change. |16| `ADD COLUMN ... DEFAULT x` (PG 11+) | `AccessExclusiveLock` (brief) | **Fast.** Non-volatile defaults stored in catalog, not backfilled. |17| `DROP COLUMN` | `AccessExclusiveLock` (brief) | **Fast.** Column marked invisible; space reclaimed by VACUUM over time. |18| `SET DEFAULT` / `DROP DEFAULT` | `AccessExclusiveLock` (brief) | Metadata change only. Does not touch existing rows. |19| `CREATE INDEX CONCURRENTLY` | `ShareUpdateExclusiveLock` | **Non-blocking.** Allows reads and writes during build. Slower than regular index creation. |20| `DROP INDEX CONCURRENTLY` | `ShareUpdateExclusiveLock` | **Non-blocking.** Waits for queries using the index to finish, then drops. No table-level exclusive lock. |21…
Excerpt shown under the repository's Apache-2.0 license.
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