gh-ost
pg_squeeze
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gh-ost | pg_squeeze | |
---|---|---|
32 | 2 | |
11,997 | 401 | |
1.0% | 2.3% | |
7.4 | 8.3 | |
11 days ago | about 2 months ago | |
Go | C | |
MIT License | GNU General Public License v3.0 or later |
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For example, an activity of 9.0 indicates that a project is amongst the top 10% of the most actively developed projects that we are tracking.
gh-ost
- "At GitHub we do not use foreign keys, ever, anywhere"
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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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My Green/blue AWS db deployment strategy for avoiding data loss due to table locks
If the performance of the db is a concern during migrations (locking, high cpu consumption for large writes) there are tools that can help and do similiar to what your describing but with the benefit that they are battle tested tools. This one spring to mind https://github.com/github/gh-ost there are other options as well and its worth reading the trade off docs
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Changing column from longtext to mediumtext taking over 2 hours
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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Ask HN: Do you use foreign Keys in Relational Databases
No, especially on large tables with billions of records. They make online schema changes impossible. More details: https://github.com/github/gh-ost/issues/331#issuecomment-266...
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Migrating a production database without any downtime
Tip #4: Consider slow-running migrations. Some tables can be so large that the traditional migration way is simply not a viable option for them. In such cases, you can consider embedding the data migration code right into your application, or use a special utility like GitHub's online schema migration for MySQL. A slow-running migration can work in production for days or even weeks. It gradually converts the data by small chunks, so you can carefully balance the load on the database while making sure that it doesn't cause slowness or downtime.
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How do you handle RDS schema migrations?
GitHub gh-ost
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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?
[1] https://github.com/github/gh-ost/blob/master/doc/rds.md
pg_squeeze
- Pg_squeeze: An extension to fix table bloat
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PlanetScale Is Now GA
> I am estimating that your database space isn't MySQL, which is just fine of course.
You are absolutely right :) My background is strongly on Postgres, you can see from my profile more information if you want to.
So yes, I apologize if some of my questions are not applying or become to obvious for cases that are MySQL-based. But for the most part, I believe principles of operation are the same.
> [other comments]
As mentioned, thank you very much for the detailed information. This completes the picture that I was looking for. I will definitely go in more detail for some of the links provided.
This principle of operation is not too different from something I proposed to a Postgres project some time ago (https://github.com/cybertec-postgresql/pg_squeeze/issues/18). This tool indeed is conceptually pretty similar. It's a shame that supporting schema changes is not part of their focus at this point. It wouldn't do throttling either, but it shouldn't be a difficult feature to add, I guess.
For other users here that may be interested in the Postgres world, there are two tools that perform similar operation (creating a shadow table and filling it in the background), but are both focused on rewriting the table to avoid bloat, rather than for doing a schema migration:
* pg_repack (https://reorg.github.io/pg_repack/): the most used one, relies on triggers
What are some alternatives?
pg-online-schema-change - Easy CLI tool for making zero downtime schema changes and backfills in PostgreSQL [Moved to: https://github.com/shayonj/pg-osc]
vitess - Vitess is a database clustering system for horizontal scaling of MySQL.
doctrine-test-bundle - Symfony bundle to isolate your app's doctrine database tests and improve the test performance
cstore_fdw - Columnar storage extension for Postgres built as a foreign data wrapper. Check out https://github.com/citusdata/citus for a modernized columnar storage implementation built as a table access method.
squawk - 🐘 linter for PostgreSQL, focused on migrations
tengo - Go La Tengo: a MySQL automation library
hub - A command-line tool that makes git easier to use with GitHub.
Jenkins - Jenkins automation server
reshape - An easy-to-use, zero-downtime schema migration tool for Postgres
gormigrate - Minimalistic database migration helper for Gorm ORM
Large Hadron Migrator - Online MySQL schema migrations
gitlab