Move DatabaseAlreadyExists detection to DB adapter

Previously it was the responsibility of the database tasks to translate
the invalid statement from creating a duplicate database into an
ActiveRecord::Tasks::DatabaseAlreadyExists error.

It's actually easier for us to do this detection inside of the adapter,
where we already do a case statement on the return code to translate the
error.

This commit introduces ActiveRecord::DatabaseAlreadyExists, a subclass
of StatementInvalid, and updates both AbstractMysqlAdapter and
PostgresqlAdapter to return this more specific exception in that case.

Because this is a subclass of the old exception, StatementInvalid, it
should be backwards compatible with any code expecting that from
create_database.

This works for both create_database and exectute("CREATE DATABASE")

3 files changed, 0 insertions, 13 deletions

diff --git a/activerecord/lib/active_record/tasks/database_tasks.rb b/activerecord/lib/active_record/tasks/database_tasks.rb
index 5d1ce19829..300e67b0aa 100644
--- a/activerecord/lib/active_record/tasks/database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/database_tasks.rb
@@ -4,7 +4,6 @@ require "active_record/database_configurations"
 
 module ActiveRecord
   module Tasks # :nodoc:
-    class DatabaseAlreadyExists < StandardError; end # :nodoc:
     class DatabaseNotSupported < StandardError; end # :nodoc:
 
     # ActiveRecord::Tasks::DatabaseTasks is a utility class, which encapsulates
diff --git a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
index e3efeb75b5..b9a8ccb22c 100644
--- a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
@@ -15,12 +15,6 @@ module ActiveRecord
         establish_connection configuration_without_database
         connection.create_database configuration["database"], creation_options
         establish_connection configuration
-      rescue ActiveRecord::StatementInvalid => error
-        if connection.error_number(error.cause) == ER_DB_CREATE_EXISTS
-          raise DatabaseAlreadyExists
-        else
-          raise
-        end
       end
 
       def drop
diff --git a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
index 626ffdfdf9..fc37db216d 100644
--- a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
@@ -21,12 +21,6 @@ module ActiveRecord
         connection.create_database configuration["database"],
           configuration.merge("encoding" => encoding)
         establish_connection configuration
-      rescue ActiveRecord::StatementInvalid => error
-        if error.cause.is_a?(PG::DuplicateDatabase)
-          raise DatabaseAlreadyExists
-        else
-          raise
-        end
       end
 
       def drop