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To: Larry Garfield <larry@garfieldtech.com>
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Subject: Re: [PHP-DEV] PDO Restriction ( was 5.2.4RC1 Released )
From: mls@pooteeweet.org (Lukas Kahwe Smith)

Larry Garfield wrote:
> On Tuesday 07 August 2007, Lester Caine wrote:
>> Lester Caine wrote:
>>> Christopher Jones wrote:
>>>> Lester Caine wrote:
>>>>> I keep being told that the PDO drivers can be extended to include all
>>>>> of the things already available in the native driver, but the second
>>>>> you do that they become incompatible, so in addition to the PDO
>>>>> driver you need to also run the native driver simply to provide the
>>>>> areas NOT covered by PDO. We need a generic framework that addresses
>>>>> the real problems not one that creates an artificial lowest common
>>>>> denominator strangle hold :( PDO could evolve into that, but not with
>>>>> it's current restrictions.
>>>> Can you list the current restrictions as you see them?
>>> Actually the very first one has been addressed and has nothing to do
>>> with PDO. Up until recently is was essential to provide backwards
>>> compatibility with PHP4 and all of the projects I currently work with
>>> WOULD still install on PHP4. Although *I* never used it in production,
>>> the continued support meant that there was a large base that insisted on
>>> retaining it. So ADOdb's continued underlying support for PHP4 is useful
>>> and until there are a higher percentage of PHP5 users than PHP4 - PDO
>>> takes second place as it is not available on a large number of hosts?
> 
> As you noted, this one is no longer an issue[1][2].
> 
> [1] http://gophp5.org/
> [2] http://www.php.net/index.php#2007-07-13-1
> 
>>> The next problem builds on the above one. From the PDO manual "PDO does
>>> not provide a database  abstraction; it doesn't rewrite SQL or emulate
>>> missing features. You should use a full-blown abstraction layer if you
>>> need that facility." ADOdb will run PDO drivers quite happily, but on
>>> current information the performance of the PDO drivers is slower than
>>> using the same native driver. So given a choice the native one is
>>> preferable and currently essential for PHP4 support.
> 
> I've seen some of the numbers posted, at least as far as MySQL.  As Ilia has 
> noted before, MySQL's native prepared statement support sucks all on its own.  
> It's faster to use PDO's internal implementation.
> 
> That said, you need to make a direct comparison.  PDO, especially with 
> prepared statements, does a lot more processing than a direct implementation.  
> That takes a lot more cycles than just passing mysql_query() a string.  
> However, just passing mysql_query() a string is not secure.  You need to 
> implement your own escaping mechanism on top of it (because trusting yourself 
> to always call mysql_real_escape_string() in every instance is a recipe for 
> disaster).  That takes even more cycles, because it's happening in PHP rather 
> than in C.
> 
> As a case in point, I recently tried to implement a PDO layer for Drupal as an 
> alternative to the mysql_* implementation.  Drupal currently implements its 
> own prepared statements in user-space, using a printf()-like syntax and 
> preg_replace_callback().  When I replaced that with PDO's own prepared 
> statements, I found performance was about a wash[3].  On the other hand we do 
> get type-safe prepared statements and simpler code, so we're planning to move 
> to PDO in Drupal 7 at this point.
> 
> [3] http://drupal.org/node/134580
> 
>>> NEITHER of the above are restricted to Firebird and apply equally to all
>>> databases, but they are the main reason to date that no one has had the
>>> inclination to fix the pdo_firebird driver as it's deployment potential
>>> is currently limited.
> 
> My knowledge and experience with Firebird is nil, so I cannot say anything 
> useful for that.
> 
>>> The internals of PDO restrict things to using SQL access to the
>>> database. While it will probably be said that the database should ONLY
>>> provide SQL access to everything, Firebird has a services interface
>>> which is used for such things as backup, user management, and the event
>>> handler. How should all those be handled if they are moved to the PDO
>>> driver?
> 
> Are you talking about Firebird-specific features, or all non-SQL-standard 
> queries?  As far as I know PDO allows arbitrary strings as queries so 
> SQL-esque database-specific stuff should still work.  Wez, is that not the 
> case?

> I make no claim of being a PDO expert either, and my database experience is 
> 98% MySQL, but the above is my experience and reading so far with it.  PDO's 
> main selling points are 1) A fully OO API and 2) A common API for all 
> databases.  By nature, it does result in "lowest common denominator" issues 
> as well, including potentially performance.  If you're aiming for 
> cross-database compatibility, I'd recommend it over rolling your own.  If you 
> can guarantee that you'll only need <insert some database here>, then the 
> specific driver may be a better option in some cases.  YMMV and so forth.

No, the idea is that there is a common set of methods and a common 
infrastructure to support those. However every driver is free to 
implement driver specific things and prefix those methods with the 
driver name. So in theory all the RDBMS specific goodies in all of the 
native drivers can also go into PDO.

regards
Lukas