what does rake db:schema:cache:dump exactly do? is it safe to be ran in production?

user_15067600 0
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Rails has an issue with big schemas where it becomes slower over time as the app grows, to fix this issue the schema_cache file was introduced and is enabled by default, it get updated with every migration.

We can create and update the file manually using rake db:schema:cache:dump.

Finally my questions:

  1. What query does it actually run inside the db?
  2. Does it lock the db while performing the query?
  3. Finally is it safe to be ran in production?

Thank you

ruby-on-rails mysql
2 Answers

After logging my DB and running the command, it turns out it just runs

show full fields table_name

against all the tables in the schema.

user_150676000

The command can be executed in production and it creates a db/schema_cache.yml. Mainly it serializes data related to schema into this file. Generally in a prod environment with multiple servers, this file would be shared across to avoid db calls for

show full fields

This query is run by rails framework on boot of servers and with this file the requests would decline and the yml file would serve this.

user_5999890
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