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")

2 files changed, 6 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 800235a302..0fe16270ed 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -573,6 +573,7 @@ module ActiveRecord
         end
 
         # See https://dev.mysql.com/doc/refman/5.7/en/server-error-reference.html
+        ER_DB_CREATE_EXISTS     = 1007
         ER_DUP_ENTRY            = 1062
         ER_NOT_NULL_VIOLATION   = 1048
         ER_NO_REFERENCED_ROW    = 1216
@@ -592,6 +593,8 @@ module ActiveRecord
 
         def translate_exception(exception, message:, sql:, binds:)
           case error_number(exception)
+          when ER_DB_CREATE_EXISTS
+            DatabaseAlreadyExists.new(message, sql: sql, binds: binds)
           when ER_DUP_ENTRY
             RecordNotUnique.new(message, sql: sql, binds: binds)
           when ER_NO_REFERENCED_ROW, ER_ROW_IS_REFERENCED, ER_ROW_IS_REFERENCED_2, ER_NO_REFERENCED_ROW_2
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 0a7c6d8ac4..f33ba87435 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -467,6 +467,7 @@ module ActiveRecord
         UNIQUE_VIOLATION      = "23505"
         SERIALIZATION_FAILURE = "40001"
         DEADLOCK_DETECTED     = "40P01"
+        DUPLICATE_DATABASE    = "42P04"
         LOCK_NOT_AVAILABLE    = "55P03"
         QUERY_CANCELED        = "57014"
 
@@ -488,6 +489,8 @@ module ActiveRecord
             SerializationFailure.new(message, sql: sql, binds: binds)
           when DEADLOCK_DETECTED
             Deadlocked.new(message, sql: sql, binds: binds)
+          when DUPLICATE_DATABASE
+            DatabaseAlreadyExists.new(message, sql: sql, binds: binds)
           when LOCK_NOT_AVAILABLE
             LockWaitTimeout.new(message, sql: sql, binds: binds)
           when QUERY_CANCELED