CODEWITHSUNDEEP
ruby-on-railspostgresqlactiverecord
Joe
Joe

Reputation: 47609

How to work with Rails ActiveRecord and Postgres incompatibility on a legacy project?

I am working with a project that has been running for a while against MySQL. There are migrations such as this:

add_index "things", ["one", "two", "three", "andevenmorelongnamedfields"]

Which causes an index named like this index_things_on_one_and_two_and_three_and_andevenmorelongnamedfields. This is OK for MySQL but too long for PostgreSQL.

This question recommends altering existing migrations.

add_index "things", ["one", "two", "three", "andevenmorelongnamedfields"], :name => "index_things_on_one_and_two_and_three_and_more"

That would solve it superficially.

However the codebase is already running against MySQL so changing past migrations would be a bad idea. I'm trying to install from scratch against PostgreSQL which (I think) means running all migrations?

I may have missed something here (I'm more familiar with Django), but am I correct in thinking that ActiveRecord isn't compatible with PostgreSQL in this specific instance?

How can I solve this (i.e. get it working with both Postgres and MySQL) without creating integrity problems for others?

Upvotes: 0

Views: 63

Answers (1)

Matt Jones
Matt Jones

Reputation: 544

One way would be to just create and run new migrations on the MySQL side that rename the indexes to something shorter. Then you can run rake db:schema:load on the Postgres side and shouldn't have a problem.

Also note the warning at the top of db/schema.rb:

Note that this schema.rb definition is the authoritative source for your database schema. If you need to create the application database on another system, you should be using db:schema:load, not running all the migrations from scratch. The latter is a flawed and unsustainable approach (the more migrations you'll amass, the slower it'll run and the greater likelihood for issues).

This is definitely an example of the "flawed and unsustainable" bit...

Upvotes: 1

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