Alien Pastures

My thoughts on Slackware, life and everything

Tag: pdo

New SQLite driver for the blog

January 2, 2014 / / 2 Comments

Ever since this blog’s inception I have used a plugin called “PDO for WordPress” which allowed me to have a SQLite (file-based) database instead of the default MySQL database used by WordPress.

There are a couple of bugs in PDO for WordPress that I was getting tired of, and perhaps some of the people writing comments have been annoyed too, when their post failed to show up on the blog. Most notorious bug was that any text containing the two characters ) and ‘ immediately after eachother would silently be discarded by the driver… the only way to get your precious text back was to hit your browser’s “Back” button and try to find out what was wrong with the text.

The PDO for WordPress plugin has not been maintained for a while, mostly because the development pace of the WordPress code was faster than the PDO for WordPress author could manage. Some of the bugs were addressed with patches, but these were never incorporated into a new release.

I was finally so irritated with this that I was going to attempt to apply these patches to my own blog. Luckily, I did my research properly and I ran into a new plugin that can replace the old PDO for WordPress plugin: it is called “SQLite Integration“. This plugin uses PDO just like the old one.

Remember, PDO stands for PHP Data Objects. Quoting the PHP manual: “PDO provides a data-access abstraction layer, which means that, regardless of which database you’re using, you use the same functions to issue queries and fetch data. PDO does not provide a database abstraction; it doesn’t rewrite SQL or emulate missing features“. This is what allows the use of a different database than MySQL and at the same time is the cause of the bugs in my blog – there are incompatibilities in the way WordPress creates SQL queries (targeted at MySQL syntax which does not always work for SQLite).

Interesting enough, the discussion among the WordPress developers about the possible use of PDO has been revived now that the  mysql_* functions are officially deprecated in PHP 5.4.

This new SQLite Integration plugin will work with versions of WordPress starting with 3.3. My blog is at the latest 3.8 release so that is OK.  Thus I proceeded to do the installation of the plugin and re-configuration of the blog, following the instructions (I always RTFM before applying irreversible changes – and make a full backup too 😉

As you can see, the blog is still here. I have not checked whether the text entry bugs have gone now, but at least I am running on a well-maintained database driver again.

Eric

Using SQLite for this blog

July 1, 2012 / / 0 Comments

Just to let you know, I created a permanent page (as opposed to a blog article) called “PDO Powered“. You’ll find it in the left sidebar of the blog – right below the link to my  “About” page.

A few posts back when I wrote about a blog upgrade where I finally fixed my database tables and my performance issues, someone asked me if it were possible  that I create a pre-configured empty blog using SQLite. The reason being that it is no longer possible to configure a SQLite backend if you start off with the most recent version of WordPress.

The instruction set on my new page is meant to show you how to do that yourself. I also added a link to a tarball containing such a pre-configured blog so that you can use that too as a bootstrap for your own portable blog.

If you used my instructions or the tarball, it would be nice if you add a link to your blog in the comments section of the “PDO Powered” page (I will check for SPAM attempts!). Perhaps if enough independent blogs show up using SQLite, the WordPress developers will reconsider their point of view (they do not care for other database backends except MySQL).

Eric

Blog updated to 3.4, sqlite database fixed

June 16, 2012 / / 10 Comments

I just upgraded my blog to WordPress 3.4.

My blog’s database backend is not MySQL but instead (for portability reasons) I am using PDO for WordPress, a plugin which uses PDO (a PHP data access abstraction layer) to allow the use a sqlite database; i.e. a simple file.

Unfortunately this sqlite backend is not 100% compatible with WordPress installations starting with version 3.3. You can not even create a new blog using the PDO plugin with WordPress 3.3 and higher. The blog has to be created using wordpress-2.2.x, and then upgraded to 3.3 or later.

It looks like the maintainer of the PDO plugin will not be able to give adequate support for the sqlite backend. Not because he does not want to, but because it is difficult to create the proper glue between WordPress SQL code and generic SQL backends (WordPress developers have stated that they are not interested in supporting anything else than MySQL).

The problems with the PDO plugin show when creating a new post… the blog will be “dead” for at least five minutes and the apache log full of SQL errors. I am considering to  move “back” to a supported backend and wanted to check if I could export the full blog so that I could import it to a fresh installation with a MySQL backend.

I quickly discovered that this was not possible. Somewhere along the line, WordPress has added a new table to the database (wp_commentmeta) and the PDO plugin apparently has not been able to add that to my sqlite database. An attempt to export the blog to an XML file (one of the standard tools in WordPress) would lead to a lot of errors in the apache log about “Problem preparing the PDO SQL Statement.  Error was no such table: wp_commentmeta“.

I compared my blog’s sqlite database to a fresh MySQL-backed blog database and thus found the new table’s properties. I upgraded the database on the fly using the sqlite3 command-line program as follows:

$ sqlite MyBlog.sqlite > CREATE TABLE wp_commentmeta (
 meta_id integer NOT NULL PRIMARY KEY AUTO_INCREMENT,
 comment_id integer NOT NULL DEFAULT '0',
 meta_key text DEFAULT NULL,
 meta_value text); > .quit

After that modification, exporting the blog to XML took only seconds to create a 4.3 MB file instead of the previous 400 KB partial dump which took painstakingly long. I still have not tried to import that XML dump into an empty blog. Also, this new post will be a test to see how the blog recovers… will it still take many minutes before it is available again after I press “Publish”?

Eric

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