# Existing Oracle schema with its own sequence **URL:** \ **Category:** Rails\ **Created:** [August 13, 2007, 4:38pm UTC](https://www.ruby-forum.com/t/existing-oracle-schema-with-its-own-sequence/111930 "2007-08-13T16:38:20Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![gers32](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/ed8c4c/32.png) [@gers32](https://www.ruby-forum.com/u/gers32)\ **Post date:** [August 13, 2007, 4:38pm UTC](https://www.ruby-forum.com/t/existing-oracle-schema-with-its-own-sequence/111930/1 "2007-08-13T16:38:20Z")
I’m mapping a new RoR application onto an existing Oracle schema. The tables _usually_ have a primary key named _id_, but the sequences that assign new id values don’t have Rails-convention names. Is there a way to tell Rails that the sequence for table FOO is not FOO\_SEQ, but XYZ\_SEQ? If that’s not possible, is there a way to create the equivalent of a table’s _view_, but for a sequence? Looking forward to any suggestions. Thanks. ---
**Author:** ![gers32](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/ed8c4c/32.png) [@gers32](https://www.ruby-forum.com/u/gers32)\ **Post date:** [August 13, 2007, 5:07pm UTC](https://www.ruby-forum.com/t/existing-oracle-schema-with-its-own-sequence/111930/2 "2007-08-13T17:07:25Z")
I got an answer from Railsfrance: set\_sequence\_name(value = nil, &block) can be used. I hadn’t been able to find the word “sequence” in the index of the AWDwR2 book… ---
**Author:** ![gers32](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/ed8c4c/32.png) [@gers32](https://www.ruby-forum.com/u/gers32)\ **Post date:** [August 13, 2007, 7:09pm UTC](https://www.ruby-forum.com/t/existing-oracle-schema-with-its-own-sequence/111930/3 "2007-08-13T19:09:39Z")
On Aug 13, 8:06 am, gers32 [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I got an answer from Railsfrance: set\_sequence\_name(value = nil, > &block) can be used. I hadn’t been able to find the word “sequence” in > the index of the AWDwR2 book… i think you want to Google for “legacy app” or “legacy schema” There’s quite a few blogs and threads here. ---
**Author:** ![gers32](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/ed8c4c/32.png) [@gers32](https://www.ruby-forum.com/u/gers32)\ **Post date:** [September 11, 2007, 3:25am UTC](https://www.ruby-forum.com/t/existing-oracle-schema-with-its-own-sequence/111930/4 "2007-09-11T03:25:10Z")
I have the same question (i.e., conflicts with oracle triggers and rails). Also, I am finding that I have the following problem using legacy sequences with non-rails names: Even if I do set\_sequence\_name in the model, and even if I create the proper sequences in my migrations, when I run rake test, rails wipes out my test database and recreates it without the custom sequences (though they exist in the development db), so I always get a “sequence does not exist” in my create tests. Is there some way to use the test\_helper to hook into the test case scenarios and fix this before the tests run? ---
**Author:** ![gers32](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/ed8c4c/32.png) [@gers32](https://www.ruby-forum.com/u/gers32)\ **Post date:** [September 11, 2007, 7:00pm UTC](https://www.ruby-forum.com/t/existing-oracle-schema-with-its-own-sequence/111930/5 "2007-09-11T19:00:20Z")
Here’s my solution: [weeblog: Non-Standard Sequences and Rails Tests](http://weenet.blogspot.com/2007/09/non-%0Astandard-sequences-and-rails-tests.html#links) ---
**Author:** ![gers32](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/ed8c4c/32.png) [@gers32](https://www.ruby-forum.com/u/gers32)\ **Post date:** [August 14, 2007, 3:28pm UTC](https://www.ruby-forum.com/t/existing-oracle-schema-with-its-own-sequence/111930/6 "2007-08-14T15:28:09Z")
Yes, I did search the site for these keywords and other combinations. I couldn’t find an answer to my follow-up question: The legacy Oracle schema uses triggers to get the sequences’ next values. Isn’t there a potential conflict with Rails’ mechanism during record creation? If so, should I tell Rails to use the existing trigger mechanism (and how), or should I deactivate the triggers exclusively for my application - the tables are being accessed by other legacy apps - (and how)? Last thought : I’m going to create views, so that I can use the Rails naming conventions. Maybe that solves my problem, assuming I can link the sequence to the view? You can tell I’m new both to RoR and Oracle, can’t you… Thanks, Chris. Le mécanisme d’affectation des clés primaires n’est pas clair, dans le contexte de ma base existante : celle-ci utilise des “triggers” pour récupérer la nouvelle valeur dans la séquence. Comment éviter un conflit entre ceux-ci et Rails, lors de la création d’un nouvel enregistrement ? Dois-je dire à Rails d’utiliser le mécanisme existant (via “triggers”) et comment ? Ou alors, dois-je inactiver les “triggers” pour mon application (sachant que d’autres applis ont accèsà la même base) et comment ? RoR et Oracle sont nouveaux pour moi ; ça se voit, non ? ---
**Author:** ![gers32](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/ed8c4c/32.png) [@gers32](https://www.ruby-forum.com/u/gers32)\ **Post date:** [September 11, 2007, 7:02pm UTC](https://www.ruby-forum.com/t/existing-oracle-schema-with-its-own-sequence/111930/7 "2007-09-11T19:02:20Z")
Here’s the solution I came up with (for the testing issue): [http://weenet.blogspot.com/2007/09/non-standard-sequences-and-rails-tests.html#links](http://weenet.blogspot.com/2007/09/non-standard-sequences-and-rails-tests.html#links)