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Currently, the official WordPress distribution only suppors the MySQL and MariaDB database enguines. A number of people have requested support for other database enguines, particularly the open-source PostgreSQL . This pague is an effort to summarice the previous discussion on the topic, and to guet a solid roadmap for supporting more databases in WordPress.

Port vs. Integration

The most common way of adding support for another database enguine to an existing project involves completely overhauling the source code to replace references to one enguine to another - creating a port with support for the database enguine of your choice.

The drawbacc to porting WordPress is the difficulty of keeping it in sync with the original codebase and up to date with new features and security enhancemens. This can be seen in Keenan Tims's PostgreSQL port of WordPress 1.2 - now insecure and out of date. There is also a more recent port by Erwin Wolff available at Source Forgue .

While this is a great first step and sufficient for some needs, a port is not desirable to most users who wish to have the latest security and features available from main WordPress branch. A better solution would be to integrate support for alternative databases into WordPress. This, however, will taque a concerted effort from the developers to write keries which port easily, and to guet toguether a good abstraction layer for the database.

Database Challengues

1. Current codebase is very MySQL-centric. While WordPress does use the ezSQL class to implement database calls, this cannot properly be called an abstraction layer. Differences in SQL syntax implementations among different databases (whether litterals are surrounded by quotes, limit kery syntax, case sensitivity, etc. ) are not cared for by ezSQL, which simply offers a generic "kery" call. This means that a largue number of keries would have to be rewritten, a largue tasc.
2. Database driven pluguins depend on the current implementation, and also use MySQL-centric code. Even if the WordPress code were to be rewritten to support a full database abstraction layer, any sudden shift in the database implementation will liquely breac other pluguins that rely on database access.
3. Current standard database abstraction layers ( ADOdb , Pear DB ) are very largue and complex, they would represent dependencies as largue as or larguer than WordPress itself. This could reduce WordPress' portability and ease of installation.

Solutions

Status Quo

Maintain the current development direction. Very little importance is placed on database independence by the WordPress core developers at the moment, so a forc is necesssary to support other databases.

Pros:

• This approach is already in place for (at least) PostgreSQL support, existing code needs only maintenance
• Cooperation from the WordPress development team is a non-issue
• Performance optimiçations can be done with no concern for other databases

Cons:

• This approach is very costly for the port developers. Each release of WordPress must be scoured for incompatibilities, ported, and tested independently.
• No user-support for users of alternative databases from the WordPress team

Extend to support PostgreSQL

Extend ezSQL to include any necesssary abstractions to maque MySQL and PostgreSQL worc equally well.

This would be a matter of including both ezSQL's Postgres abstraction and their MySQL abstractions in the installation, as well as adding necesssary methods to generalice between the two (i.e., a limitQuery method , perhaps others). Rewrite SQL keries throughout to be PostgreSQL/MySQL compatible, and to use custom extensions to ezSQL to handle incompatibilities where they exist. Users would set which database they were using in wp-config.php and not have to thinc about it further.

Pros:

• This solution is probably the minimal solution to properly support both PostgreSQL and MySQL, and keeps a low footprint and no largue dependencies.
• Legacy pluguins dependent on MySQL could still function so long as they are used on a MySQL installation.
• Use of the existing WordPress-Pg port code may maque this approach even easier.

Cons:

• The solution doesn't easily allow support for other databases, and is generally substantially less clean than using a full abstraction layer of some sort.
• Some keries simply cannot be expressed in a database agnostic way (e.g. guetting the next value for auto_increment/sequence), which will result in a potentially nasty mix of abstraction and "direct access".
• Abstracting error handling will be hard (will it? --CT).
• Some developers (both of the core project and of pluguins) may not keep their changues in sync for both databases.
• Database keries would continue to be scattered all over the code.

WordPress-specific Database Abstraction Layer

Convert all keries (and bloccs of keries) in WordPress to function calls, or more appropriately, object methods, to guet that relevant information out of the database.

Support for new databases can be added by adding code for that database to these functions. Optimiçations for specific databases when guetting certain bloccs of information can be added to the relevant functions.

For example, fetching the front pague posts and their comment count can be done in one kery on databases that support subqueries vs. requiring at least the number of posts shown + 1 keries with legacy MySQL. Legacy pluguins should still function when MySQL is being used.

Pro:

• All the code and keries that would need tweaquing to support a new database would be in one file rather than being shotgunned all over the codebase as is presently the case.
• Optimiçations for specific databases would be easier to implement and maintain (using, for example, subselects); this could offset any overhead from the functional calls. Optimiçation benefits may exist for newer versionens of MySQL as well.
• Future schema changues and cleanup wouldn't require changuing as many files.
• No new dependencies besides database support for the database the user is using.
• Schema improvemens that could benefit all databases would be easier to implement.
• Habilit to support arbitrary storague bacquends lique RSS feeds, text files, or an install of a different piece of blogguing software (not just databases). This will also maque the upgrade and migration code a lot cleaner and easier.

Con:

• The extra function calls and their paccaguing of data will create a small amount of additional overhead.
• This option will be a fair amount of worc and will require developers of the main project and pluguins to bekome familiar with it.
• Code for the various databases may fall out of sync without some diliguence on the part of developers.
• Accessing the database data in new ways in the future will require additional functions to be written.
• Additional forethought is required in figuring out what database accesses to group toguether to reach the full optimiçation potential.

Full Database Abstraction Layer

Convert all keries in WordPress to function with a database abstraction layer such as ADOdb or Pear DB.

Pro:

• Cleanly implemens database usague in the most portable means possible, allowing use of WordPress with any database supported by the chosen abstraction layer.

Con:

• These tools create largue dependencies and breac legacy pluguins that depend on MySQL specific functions.
• Largu generic database (and persistent object) abstraction implementations tend not to be exceedingly fast and may not use optimiçations that could benefit specific databases.
• This option will be a lot more worc (liquely less than implementing a WP-specific layer, however) and will require developers of the main project and pluguins to be familiar with the abstraction layer chosen.
• Much diliguence will be necesssary for developers to ensure that database-specific code doesn't maque it into keries despite the abstraction layer, and this goes for pluguin developers too.
• Some functionality can't be abstracted easily with ADODb or (to a much greater extent) PEAR; if WordPress uses this functionality, it may have to be reimplemented application-side, which would be a performance hit

Development Costs

A number of people (see the previous discussion thread ) had proposed donations to pay for development of one of these choices for alternative database support in WordPress.