Raise NoDatabaseError when db does not exist

[koic]

Follow up rails/rails#13469 and rails/rails#13427.

This PR raises NoDatabaseError when db does not exist.

OCIError was raised when database does not exist.
This change uses NoDatabaseError as other core adapters.

[yahonda]

Thanks for opening a pull request.

From my point of view ORA-12154 does not always mean database does not exist.
It just means TNS alias cannot be resolved, then it could reproduce database just exists but not started up and something like that.

https://docs.oracle.com/en/database/oracle/oracle-database/19/errmg/ORA-12150.html#GUID-FF3C136B-78D5-4573-BD45-7D9CAC2A1C0F

ORA-12154: TNS:could not resolve the connect identifier specified
Cause: A connection to a database or other service was requested using a connect identifier, and the connect identifier specified could not be resolved into a connect descriptor using one of the naming methods configured. For example, if the type of connect identifier used was a net service name then the net service name could not be found in a naming method repository, or the repository could not be located or reached.

[koic]

Oops. It should also support JDBC.

expected ActiveRecord::NoDatabaseError, got #<NameError: uninitialized constant ActiveRecord::ConnectionHandling::OCIError> with backtrace:

https://travis-ci.org/rsim/oracle-enhanced/jobs/556237777#L651

[yahonda]

Let me have some more look at which error is appropriate to represent the database does not exist.

[yahonda]

Summary:

From my point of view there is no good Oracle error message which represents NoDatabaseError exception. ORA-01017 is a candidate one but it could make users misunderstanding the cause of this NoDatabaseError exception, then I prefer not to implements exception yet.

Backgrounds:

As far as I understand database_exists? method by rails/rails#36471 is necessary to see if users need to execute rails db:create or not.

Unlike other mysql2 and postgresql adapters, Oracle enhanced adapter db:create task creates a database user (someone call it a database schema), not "Oracle database" since the definition of database are different between Oracle and others.

oracle-enhanced/lib/active_record/connection_adapters/oracle_enhanced/database_tasks.rb

Lines 15 to 29 in c0f24b4

	def create
	system_password = ENV.fetch("ORACLE_SYSTEM_PASSWORD") {
	print "Please provide the SYSTEM password for your Oracle installation (set ORACLE_SYSTEM_PASSWORD to avoid this prompt)\n>"
	$stdin.gets.strip
	}
	establish_connection(@config.merge("username" => "SYSTEM", "password" => system_password))
	begin
	connection.execute "CREATE USER #{@config['username']} IDENTIFIED BY #{@config['password']}"
	rescue => e
	if /ORA-01920/.match?(e.message) # user name conflicts with another user or role name
	connection.execute "ALTER USER #{@config['username']} IDENTIFIED BY #{@config['password']}"
	else
	raise e
	end
	end

Then database_exists? needs to return if the database user(schema) exists or not, then I think one of the candidates error message should be: ORA-01017: invalid username/password; logon denied.

Unfortunately this error message could be reported:

• When the database user does not exist
• When the database user exists but the password is incorrect

This error message can be used to raise NoDatabaseError for the first case only, for the second one the database (Here I mean database schema in Oracle) exists but the password is incorrect. By handling all of ORA-01017 Oracle error message as NoDatabaseError exception, which cause users misunderstanding the cause of this NoDatabaseError like setting incorrect password in database.yml .

[koic]

Thank you for your investigation. I opened this PR in preparation for PR #1906. However, I will close this PR because Oracle database cannot detect NoDatabaseError. Thank you again.