General developer forum

Hi Iñigo,

I think its a great move to move towards PostgreSQL from Oracle as it tends to get much more use (and therefore better testing, less bugs).

The dbtransfer tool uses the xmldb schema definitions in Moodle and takes data from one database to another. Its location at http://yourmoodle/admin/tool/dbtransfer and it simply takes destination database credentials. It uses your moodles currently configured credentials (in config.php) to connect to the current moodle database and transfer the data to the destination. If I remember rightly it will do some pre-checks before attempting to transfer, checking data matches the xmldb defintions.

The caveats I can think of are:

• It depends on the XMLDB data definitions being defined and correct, anything outside of this definition will not be transfered. This is all good and correct for Moodle core, but you should pay special attention to third party plugins. We've required xmldb for 2.x plugins, but its possible you might have some data which is not covered by this.
• [The 'experimental aspect'] I believe there is a risk that the ids in mdl_log entries are not matched up correctly. i.e. a forum view log entry might point to the wrong forum post after migration. The log data will still be in tact, but that additional metadata which allows you to click onto a log entry may be invalid.

Having said that, i've succesfully migrated 5 or 10 production sites from MySQL to Postgres using this tool and no have been encountered.