Collection Mapping

Naming conventions

All the tables and columns in the database are all lowercase. (Which is quite handy with an Mysql database because the names are case-sensitive if the underlying file system is also case-sensitive. So Mysql Names are case sensitive on Linux but not on Windows.)

Tablenames are plural.

Prototype names start with upper case and are camel case. Prototype names are singular.

Property- Object- and Collection-Mapping start with lower case and are also camel case.

Foreign keys are prefixed with the name of the table they are referring to.

1:n relation

DB schema

Mapping

Gallery/type.properties

   images         = Collection(Image)
   images.local   = gallery_id
   images.foreign = galleries_gallery_id

m:n relation

DB schema

Mapping

Image/type.properties

   tags                          = Collection(Tag)
   tags.filter                   = ${image_id} = tags2images.images_image_id AND \
                                   tags2images.tags_tag_id = tags.tag_id
   tags.filter.additionalTables  = tags2images

The Backslash "\" is only necessary when you have a filter that continues in the next line.

Comments

#1 by maks at 2008/05/09 05:09

While the above works well as a "view" for m:n mappings, it cannot currently be used as a normal collection, as Helma is Not able to add new objects to collections that have filters defined.

#2 by Philipp at 2009/12/16 23:30

The better* solution is a subscription-model: http://helma.org/wiki/Many-to-many+Relationships/

*) that's my opinion ;-)