Individual skill
postgres-database-migration
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-migration validation, and rollback planning.
skills/postgres-database-migration/SKILL.md
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- Last checked
- Nov 7, 2026
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- Repository last updated
- Nov 8, 2026
- License
- Apache-2.0
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SKILL.mdcore · 24,796 bytesSKILL.mdcore · 24,796 bytesSKILL.mdcore · 24,796 bytesreferences/backfill-strategies.mddoc · 2,389 bytesreferences/complete-example.mddoc · 2,091 bytesreferences/validation-queries.mddoc · 3,527 bytes
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# PostgreSQL Database Migrations
A 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.
## DDL Lock Reference
Every schema change acquires a lock. The critical question is: **does it block reads and writes, and for how long?**
### Fast, Non-Blocking Operations
These complete in milliseconds regardless of table size. They only hold a brief `AccessExclusiveLock` for the catalog update, not for data rewriting.
| Operation | Lock Level | Notes |
|-----------|-----------|-------|