gh-ost
pg-online-schema-change
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gh-ost | pg-online-schema-change | |
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32 | 8 | |
11,934 | 82 | |
1.0% | - | |
7.4 | 3.6 | |
4 days ago | about 2 years ago | |
Go | Ruby | |
MIT License | MIT License |
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gh-ost
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How Modern SQL Databases Are Changing Web Development - #3 Better Developer Experience
I’ve been through multiple incidents where everything worked fine in the testing environment but ended up locking the production database for minutes when deployed. A category of open-source tools called OSC (Online Schema Change) exists to mitigate such pain, like gh-ost used by GitHub and OSC used by Meta. They work by creating a set of "ghost tables" to apply the migrations, copy over old data from the original tables, and catch up with new writes simultaneously. When all old data is migrated, you can trigger a cutover to make the "ghost tables" production. Check the post below for a great introduction and comparison:
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We migrated to SQL. Our biggest learning? Don't use Prisma
Sounds like it's basically explained in the gh-ost readme https://github.com/github/gh-ost#how
I think it amounts to "use views to decouple access to the table with a fixed interface" and "use triggers for migrating data between tables"
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Ask HN: Is PostgreSQL better than MySQL?
Gh-ost is the new hotness. Simple to use and lots of great features: https://github.com/github/gh-ost
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Changing column from longtext to mediumtext taking over 2 hours
As they have said it depends on the size of the table on disk and the number of rows, but an alter in production is not difficult to last from seconds to days. I don't know if you are doing the alter as is but try to check https://docs.percona.com/percona-toolkit/pt-online-schema-change.html or https://github.com/github/gh-ost , they usually simplify a lot the alters.
Not sure which version of MySQL you're using, but one approach would be to use a tool like pt-online-schema-change (from Percona) or g-host -- which will create a duplicate table and then swap it in place of the original table. It's a safer approach when operating in production environments. Here's a good comparison of the tools many people use https://planetscale.com/docs/learn/online-schema-change-tools-comparison
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Changing Tires at 100mph: A Guide to Zero Downtime Migrations
Actually I never tried but I was scared by the small print of GH not using RDS themselves [1] and Ghost relying on lower-level features that might be not easily available in RDS. Also I had the impression you have to setup a normal non-RDS replica attached to your RDS master?
MySQL has some robust tooling in this space. Some of the tools use triggers to copy to a new table. GitHub's gh-ost[1] is probably the state of the art, and uses the binary log stream to replicate the data.
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How Retool upgraded its 4 TB main application PostgreSQL database
https://github.com/github/gh-ost/issues/331#issuecomment-266...) it does become a little bit of a "you do not have google problems" type discussion.
(Perhaps you do have such problems, I don't know where you work! But 99%+ of companies don't have such problems and never will.)
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We lost 54k GitHub stars
GitHub doesn't use foreign keys[1], and there's likely many tables related to all the users, notifications, permissions, etc... that would need to be cleaned up. Without foreign keys they likely have some system process that does this instead of a simple `DELETE FROM` which cascades.
1. https://github.com/github/gh-ost/issues/331#issuecomment-266...
pg-online-schema-change
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pg-osc: Zero downtime non blocking schema changes in PostgreSQL
I wanted to share a new CLI tool (pg-osc) I built to make it easy and safe to perform schema changes and backfills in PostgreSQL.
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Zero-downtime schema migrations in Postgres using Reshape
This is very interesting, thanks for sharing. I had been noodling on the concept of zero downtime schema changes in postgres as well, and recently started https://github.com/shayonj/pg-online-schema-change. Its inspired by pg_repack and pt-online-schema-change (mysql).
I will give this a spin! Kudos
What are some alternatives?
doctrine-test-bundle - Symfony bundle to isolate your app's doctrine database tests and improve the test performance
pg-osc - Easy CLI tool for making zero downtime schema changes and backfills in PostgreSQL
reshape - An easy-to-use, zero-downtime schema migration tool for Postgres
squawk - 🐘 linter for PostgreSQL, focused on migrations
pg_squeeze - A PostgreSQL extension for automatic bloat cleanup
hub - A command-line tool that makes git easier to use with GitHub.
pg_party - ActiveRecord PostgreSQL Partitioning
Jenkins - Jenkins automation server
gormigrate - Minimalistic database migration helper for Gorm ORM
Large Hadron Migrator - Online MySQL schema migrations
gitlab