README.md in strong_migrations-0.2.2 vs README.md in strong_migrations-0.2.3

@@ -14,11 +14,11 @@
 gem 'strong_migrations'
 ```
 
 ## How It Works
 
-Strong Migrations detects potentially dangerous operations in migrations, prevents them from running, and gives instructions on safer ways to do what you want.
+Strong Migrations detects potentially dangerous operations in migrations, prevents them from running by default, and provides instructions on safer ways to do what you want.
 
 ```
  __          __     _____ _______ _
  \ \        / /\   |_   _|__   __| |
   \ \  /\  / /  \    | |    | |  | |
@@ -43,10 +43,11 @@
 The following operations can cause downtime or errors:
 
 - adding a column with a non-null default value to an existing table
 - removing a column
 - changing the type of a column
+- setting a `NOT NULL` constraint with a default value
 - renaming a column
 - renaming a table
 - adding an index non-concurrently (Postgres only)
 - adding a `json` column to an existing table (Postgres only)
 
@@ -73,10 +74,12 @@
     remove_column :users, :some_column
   end
 end
 ```
 
+Don’t backfill existing rows in this migration, as it can cause downtime. See the next section for how to do it safely.
+
 ### Backfilling data
 
 To backfill data, use the Rails console or a separate migration with `disable_ddl_transaction!`. Avoid backfilling in a transaction, especially one that alters a table. See [this great article](https://wework.github.io/data/2015/11/05/add-columns-with-default-values-to-large-tables-in-rails-postgres/) on why.
 
 ```ruby
@@ -164,13 +167,13 @@
     add_index :users, :some_index, algorithm: :concurrently
   end
 end
 ```
 
-If you forget `disable_ddl_transaction!`, the migration will fail.
+If you forget `disable_ddl_transaction!`, the migration will fail. Also, note that indexes on new tables (those created in the same migration) don’t require this.
 
-Also, note that indexes on new tables (those created in the same migration) don’t require this.
+Check out [this gem](https://github.com/ankane/gindex) to quickly generate index migrations without memorizing the syntax.
 
 ### Adding a json column (Postgres)
 
 There’s no equality operator for the `json` column type, which causes issues for `SELECT DISTINCT` queries.
 
@@ -259,20 +262,24 @@
 StrongMigrations.auto_analyze = true
 ```
 
 ## Lock Timeout (Postgres)
 
-It’s a good idea to set a lock timeout for the database user that runs migrations. This way, if migrations can’t acquire a lock in a timely manner, other statements won’t be stuck behind it.
+It’s a good idea to set a lock timeout for the database user that runs migrations. This way, if migrations can’t acquire a lock in a timely manner, other statements won’t be stuck behind it. Here’s a great explanation of [how lock queues work](https://www.citusdata.com/blog/2018/02/15/when-postgresql-blocks/).
 
 ```sql
 ALTER ROLE myuser SET lock_timeout = '10s';
 ```
 
 There’s also [a gem](https://github.com/gocardless/activerecord-safer_migrations) you can use for this.
 
+## Bigint Primary Keys (Postgres & MySQL)
+
+Rails 5.1+ uses `bigint` for primary keys to keep you from running out of ids. To get this in earlier versions of Rails, check out [this gem](https://github.com/Shopify/rails-bigint-primarykey).
+
 ## Additional Reading
 
-- [Rails Migrations with No Downtime](http://pedro.herokuapp.com/past/2011/7/13/rails_migrations_with_no_downtime/)
+- [Rails Migrations with No Downtime](https://pedro.herokuapp.com/past/2011/7/13/rails_migrations_with_no_downtime/)
 - [Safe Operations For High Volume PostgreSQL](https://www.braintreepayments.com/blog/safe-operations-for-high-volume-postgresql/)
 
 ## Credits
 
 Thanks to Bob Remeika and David Waller for the [original code](https://github.com/foobarfighter/safe-migrations).