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There are a number of gotchas when using rails with legacy db’s. Here are the ones I’ve ran headfirst into and how I got round them

Table name doesn’t follow rails naming conventions:
set_table_name ‘legacy_name’

Primary key doesn’t follow rails naming conventions:
set_primary_key ‘legacy_primary_key_name’

Using a sequence (need to do this in oracle):
set_sequence_name ‘legacy_sequence_name’

So far so straightforward, you might however also run into problems with some field names.

Table.type:
set_inheritance_column ‘not_type’
ActiveRecord inheritance works automagically comes into play if you have a column named type, by setting it to not type it won’t try to use pixiedust on your model.

Table.class:
class << self
def instance_method_already_implemented?(method_name)
return true if method_name == ‘class’
super
end
end

def pclass=(text)
self[:class] = text
end
def pclass
self[:class]
end

You might find some of your field names clashing with some basic ruby / rails keywords the first section will prevent your field being hidden and the pclass attr allows you to rename the field name in your model.

If I come across any other I’ll update this list but it’s handy stuff to know.