Rails mysql structure.sql dump contains AUTO_INCREMENT

When rails generates a structure.sql dump for MySQL it contains the AUTO_INCREMENT value. Which is anoying because this is not something you want to happen.

CREATE TABLE `active_storage_variant_records` (
  `blob_id` bigint NOT NULL,
  `variation_digest` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `index_active_storage_variant_records_uniqueness` (`blob_id`,`variation_digest`),
  CONSTRAINT `fk_rails_993965df05` FOREIGN KEY (`blob_id`) REFERENCES `active_storage_blobs` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=471 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

Look at the part: AUTO_INCREMENT=471

After digging through the activerecord code, I saw I could sneak in a mysqldump option for the dump call. Yeah! 👍🏻

But there isn't such option 😕. It's an ancient BUG/Feature of mysql, which of course still isn't resolved in MySQL 8. https://bugs.mysql.com/bug.php?id=20786

Why would you like to dump the table structure (without data) with the AUTO_INCREMENT value!?

As a workaround it's possible to enhance the db:schema:dump task in a custom rake file (lib/tasks/remove_autoincrement_from_dump.rake).
So the AUTO_INCREMENT part is removed from it.

Rake::Task['db:schema:dump'].enhance do
  structure_sql_path = Rails.root.join("db/structure.sql")
  if File.exist?(structure_sql_path)
    sql = File.read(structure_sql_path)
    File.write(structure_sql_path, sql.gsub(/AUTO_INCREMENT=[0-9]+/, ""))


Rails generate both structure.sql and schema.rb

Default behaviour for rails is to generate a db/schema.rb when running migrations or dumping the database.

Schema.rb is great because it can be used for populating other database types and is used to populate the test database.
And I personally think it's great becaus of the vscode plugin Rails Schema which shows the database structure of your application in a sidebar (TIP, move this bar to the right panel).

The rake task db:migrate default behaviour is to invoke a db:schema:dump when migrating is done. By default this generates the schema.rb file.
This output of the generated file is used to popuplate the test-database..

But somethimes the db/schema.rb isn't good enough for popuplating the test database or using the file to generate the basic structure. Contraints are quirky.
(For example see previous article mysql json constraints).
To generate a native sql dump of the database structure, you can change the default structure to sql. Place the following line in your config/application.rb.

    config.active_record.schema_format = :sql

When enabling this dumps are generated to db/structure.sql.
But you loose the schema.rb dumps.

Here's a tip to work with structure.sql and just generate the schema.rb (for your lovely sidebar).

Create a file in lib/tasks/schema_dump.rb and enhance the dump task, so it also creates the schema.rb file.

Rake::Task['db:schema:dump'].enhance do
  File.open(Rails.root.join('db/schema.rb'), 'w') do |stream|
    ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, stream)

NOTE: structure.sql contains yet another MySQL bug. (See next article for workaround)
Tip: use postgresql !

Derailed benchmark not running on production environment

We're running a large rails application, with a lot of request.
Since our upgrade to FreeBSD 13 the live environment is leaking memory in our ruby on rails app.
(FreeBSD 12 version of the jail didn't leak)

This application uses an NFS mount to store (a lot) of client specific files.

Running derailed_benchmark live didn't work. (Pressing ctrl+t, I noticed there were a lof of NFS locks)

In the file

it adds '.' to the loadpath. Which causes the production environment to complete iterate over all directories. Which 'hangs', because we have a very big active-strorage directory.

Workaround is to remove the '.' file

#    %W{ . lib test config }.each do |file|
    %W{ lib test config }.each do |file|
      $LOAD_PATH << File.expand_path(file)

Ruby rbtrace ArgumentError: command is too long

(This code blow requires you to include rbtrace in your gems)

To make a stack dump of your running rubyprocess, you could use somthing like this:

bundle exec rbtrace -p $my_pid -e 'Thread.new{GC.start;require "objspace";io=File.open("/tmp/ruby-heap.dump", "w"); ObjectSpace.dump_all(output: io); io.close}'

Unfortunately on FreeBSD / Mac OS X this results in (ArgumentError: command is too long)

A workaround for this, is to simply put the code in ruby file, and just load it. For example:
/tmp/rbcode.rb. With the following content

Thread.new{GC.start;require "objspace";io=File.open("/tmp/ruby-heap.dump", "w"); ObjectSpace.dump_all(output: io); io.close}

Next you can use rbtrace lik this:

bundle exec rbtrace -p $my_pid -e 'load("/tmp/rbcode.rb")'