Using Yii with Oracle through PDO

When you are developing an webapp with Yii that will be using Oracle RDBMS you should take a look at these issues in which you may run into it.

Forcing charset ¶

Oracle database does not support setting charset in configuration file with charset parameter, i.e. like this:

//Database component
'db'=>array
(
    'class'=>'CDbConnection',
    'connectionString'=>'oci:dbname=10.10.4.106:1521/orcl',
    'charset'=>'UTF8'
),

You have to use DSN (connectionString) for this purpose, for example like that:

'connectionString'=>'oci:dbname=10.10.4.106:1521/orcl;charset=UTF8'

There was a bug in Yii 1.1.4 which caused that an attempt to pass charset as in first example would cause an error, because Yii tried to set charset with SET NAMES statement, which is not supported by PL/SQL on board Oracle. This bug has been corrected, but even so, if you use second approach, you'll be able to force Oracle to return result in any charset encoding you want (if it is supported by Oracle, of course).

Setting login information ¶

Some (all?) versions of Oracle don't support passing login and password as a part of DSN string. You'll have to pass it like this:

'db'=>array
(
    'class'=>'CDbConnection',
    'connectionString'=>'oci:dbname=10.10.4.106:1521/orcl;charset=UTF8'
    'username'=>'###',
    'password'=>'###',
),

In case of these version, if you pass login and password via DSN but leave login and password parameters empty, you'll receive error that login attempt failed.

Errors in DSN ¶

Oracle has a very bad feature which causes that, if you have an error in your DSN, it will first try to connect with provided login and password on localhost and only if this attempt fail, it will issue an error.

I had three computers (A, B and C), two with installed Oracle and with the same copy of database (A and B) and third without Oracle at all. I was developing my app on machine A but trying to connect to machine B. I made a mistake in DSN. Forgot about dbname= part, which is mandatory in Oracle and not obligatory in other RDBMSes.

Instead of return an error, saying that my destination (B) machines is not reachable and connection can't be established, I was kept connected to my localhost copy of database (machine A) and the app run smudgily. I then move app from machine A to machine C and my app again attempted to connect machine B, which failed and was also unable to connect to localhost and only then issued an error message.

I spend hours trying to find why exactly the same code is not working on machine C, while it works with no problems on machine A? Only to find out that app on neither of these machines is connecting to machine B (due to errors in DSN), but tries to connect to localhost.

Names case-sensitivity ¶

Column names in Oracle are case-sensitive. This means that if you use all uppercase characters when creating a table (common behaviour among Oracle developers) and then try to access it with model and ActiveRecord for example like this:

$users = Users::model()->findAll();
 
foreach($users as $user)
{
        echo 'logn = '.$user->LOGIN.'<br />';
        echo 'pass = '.$user->pass.'<br /><br />';
}

You will get data only for first iteration and for first field in it. When evaluating second field, you app will throw exception saying that Property Users.pass is undefined.

Tip: The cause is seems to be only partially Oracle-related. Oracle does not rely on case-sensitivity of column names as long as they are not specified within quotation marks. If so, it takes exact column name spelling as provided. Therefore, it seems that somewhere in Yii code underlying below ActiveRecord there have to be a part which escapes table name with quotation mark, making above mentioned problems.

Active Record and Oracle ¶

There is a large performance degradation when using AR in connections to Oracle, especially on a slow server. Original code written for AR works fine for MySQL and other RDBMS but fails on Oracle as it is using one of the slowest queries. One of possible solutions for this has been presented in article "Incresing AR performance in connections with Oracle".