[Deprecated] DMZ 1.5.3 (DataMapper OverZealous Edition)

[eluser]OverZealous[/eluser]
[quote author="jpi" date="1249484621"]I think you can only use a distinct clause with a group by clause. (not sure but try to add $c->group_by('city', 'asc');
[/quote]

This is not true. Distinct works with any query (at least in most databases).

The error OES is or was having relates to how the original DataMapper handled query results (by storing them in the all array according to their id). I eventually plan on removing this and using a non associative array, since I think it hides a lot of bad queries. However, it is a significant change, that will most likely break sites, so I cannot commit to it until probably DMZ 2.0.

I have tried for hours to alter a table to add a new column and to save a new property of my object in the new column (both operation in the same script).

I need to make this clear, because it comes up occasionally:

DataMapper does not support dynamically modified databases. At all. And it most likely never will. Getting something like that to work is considered a hack, and may break in the future. No warranties.

DataMapper doesn't "cache" the fields, per se, but instead stores them in a statically shared array, one for each model. This prevents them from being loaded for each and every object, which in a large query would be just foolish. The clear method only clears properties that are unique to each object.

In general, I can't understand why you would ever want to dynamically change a database table. It's very inefficient, and doesn't even make sense in your code sample. (Why not change it manually?) If you need to change a table, it will need to be changed on one HTTP request, and then the changes will show up on the next HTTP request. Of course, this is only true if you are not using the Production Cache. It also is not guaranteed to not break at some point in the future.