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prepared statements and stored procedures

I’m still working on cleaning up the import scripts for GPNL, and I’m going to have to start using PHP’s PDO database layer to connect to an SQLite3 database at one point.

I haven’t used it yet, but I had heard it was coming in PHP 5 for a while. Personally, I’ve always used PEAR::DB and was quite happy with that.

I’m still not sold on using the new layer anyway, but I figured I’d do some reading while I am getting ready to use it in this very small instance that I’m implementing.

On the docs page, I found a great summary of why prepared statements and stored procedures are handy and helpful. In short: they save you time for queries you have to repeat a lot, by pre-compiling the preparation that is common to all the queries, so that the database is really only processing the new data, and thus using less resources.

Prepared statements I haven’t played with much before until a few weeks ago, but I’ve slowly started using them in my import scripts. Performance-wise, I’ve only seen about a 15 to 20 percent speed increase. The thing I like the most about them, though, is that I don’t have to escape my strings anymore. That’s a nice little advantage I can live with.

Anyway, php.net’s PDO documentation page has a nice writeup as well, and instead of trying to summarize it myself any more, I’ll just quote it verbatim:

Many of the more mature databases support the concept of prepared statements. What are they? You can think of them as a kind of compiled template for the SQL that you want to run, that can be customized using variable parameters. Prepared statements offer two major benefits:

  • The query only needs to be parsed (or prepared) once, but can be executed multiple times with the same or different parameters. When the query is prepared, the database will analyze, compile and optimize it’s plan for executing the query. For complex queries this process can take up enough time that it will noticeably slow down your application if you need to repeat the same query many times with different parameters. By using a prepared statement you avoid repeating the analyze/compile/optimize cycle. In short, prepared statements use fewer resources and thus run faster.
  • The parameters to prepared statements don’t need to be quoted; the driver handles it for you. If your application exclusively uses prepared statements, you can be sure that no SQL injection will occur. (However, if you’re still building up other parts of the query based on untrusted input, you’re still at risk).