Good day everyone, I am trying to validate the uniqueness of my indexes (2 indexes) in a table before an insert. Can I use validate_uniqueness_of to do this? It seems it can only validate uniqueness for a column, but not for a combination of 2 or more. Example: a table has a PK of column#1 and column#2. Thanks in advance, Will T. -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Make a unique index in the database, and write this: begin ModelName.create rescue Exception => e # interrogate e to determine what sort of failure it was # and take the appropriate action. end This is the right way to do this. Testing before insert doesn''t work because it''s possible that after you test, but before you insert, another process may have inserted a duplicate! -- -- Tom Mornini, CTO -- Engine Yard, Ruby on Rails Hosting -- Reliability, Ease of Use, Scalability -- (866) 518-YARD (9273) On Nov 17, 2006, at 12:33 PM, Will T. wrote:> Good day everyone, > > I am trying to validate the uniqueness of my indexes (2 indexes) in a > table before an insert. Can I use validate_uniqueness_of to do > this? It > seems it can only validate uniqueness for a column, but not for a > combination of 2 or more. > > Example: a table has a PK of column#1 and column#2. > > Thanks in advance, > > Will T. > > -- > Posted via http://www.ruby-forum.com/. > >--~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On 11/17/06, Will T. <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:> > Good day everyone, > > I am trying to validate the uniqueness of my indexes (2 indexes) in a > table before an insert. Can I use validate_uniqueness_of to do this? It > seems it can only validate uniqueness for a column, but not for a > combination of 2 or more. > > Example: a table has a PK of column#1 and column#2. > > Thanks in advance, > > Will T. > > -- > Posted via http://www.ruby-forum.com/. > > > >Will, I''ve only used multiple column in indexes when scoping relationships like the following: create_table :accounts, :force => true do |t| t.column :name, :string, :null => false, :limit => 50 ... end create_table :users, :force => true do |t| t.column :account_id, :integer, :null => false t.column :email_address, :string ... end add_index :users, [ :account_id, :email_address ], :unique => true Then you can use: validates_uniqueness_of :email_address, :scope => :account_id, :message => ''There is already another user with this email address.'' It sounds like if your PK is made of two columns you might want to just override before_validation(). Rails has never had great composite key functionality although I think there are some plugins out there that might ease the pain... Hope this helps. -- Zack Chandler http://depixelate.com --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Tom Mornini wrote:> Make a unique index in the database, and write this: > > begin > ModelName.create > rescue Exception => e > # interrogate e to determine what sort of failure it was > # and take the appropriate action. > end > > This is the right way to do this. Testing before insert doesn''t > work because it''s possible that after you test, but before you > insert, another process may have inserted a duplicate! > > -- > -- Tom Mornini, CTO > -- Engine Yard, Ruby on Rails Hosting > -- Reliability, Ease of Use, Scalability > -- (866) 518-YARD (9273)I agree with Tom that defining a unique key in your DB and letting the DB enforce it is the best way to go. I question the usefulness of validates_uniqueness_of in general because: 1) validates_uniqueness_of can''t guarantee that the field you are about to save to the DB is indeed unique (as Tom explained) 2) validates_uniqueness_of needs to query the DB in order to validate your model, which defeats the whole purpose of an application-side validation (IMO) I started a discussion about this on my blog, and no one has successfully made a case for using validates_uniqueness_of yet. If anybody out there does have a scenario where it makes sense to use this validation, please let me know so I can stop criticizing it :) http://allyourdatabase.blogspot.com/2006/11/generating-activerecord-data.html Cheers. -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
I tried using drysql for my application (http://drysql.rubyforge.org/ for my guide) and kept getting this NameError message. I have a table called "room_types" and a class called "RoomType" My controller looks like: def new require_gem ''drysql'' @room_type = RoomType.new end My model looks like: class RoomType < ActiveRecord::Base set_table_name "room_types" end Any insight to this matter is much appreciated, Will T. Bryan Evans wrote:> Tom Mornini wrote: >> Make a unique index in the database, and write this: >> >> begin >> ModelName.create >> rescue Exception => e >> # interrogate e to determine what sort of failure it was >> # and take the appropriate action. >> end >> >> This is the right way to do this. Testing before insert doesn''t >> work because it''s possible that after you test, but before you >> insert, another process may have inserted a duplicate! >> >> -- >> -- Tom Mornini, CTO >> -- Engine Yard, Ruby on Rails Hosting >> -- Reliability, Ease of Use, Scalability >> -- (866) 518-YARD (9273) > > I agree with Tom that defining a unique key in your DB and letting the > DB enforce it is the best way to go. > > I question the usefulness of validates_uniqueness_of in general because: > > 1) validates_uniqueness_of can''t guarantee that the field you are about > to save to the DB is indeed unique (as Tom explained) > > 2) validates_uniqueness_of needs to query the DB in order to validate > your model, which defeats the whole purpose of an application-side > validation (IMO) > > I started a discussion about this on my blog, and no one has > successfully made a case for using validates_uniqueness_of yet. If > anybody out there does have a scenario where it makes sense to use this > validation, please let me know so I can stop criticizing it :) > http://allyourdatabase.blogspot.com/2006/11/generating-activerecord-data.html > > Cheers.-- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On 11/17/06, Bryan Evans <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:> > Tom Mornini wrote: > > Make a unique index in the database, and write this: > > > > begin > > ModelName.create > > rescue Exception => e > > # interrogate e to determine what sort of failure it was > > # and take the appropriate action. > > end > > > > This is the right way to do this. Testing before insert doesn''t > > work because it''s possible that after you test, but before you > > insert, another process may have inserted a duplicate! > > > > -- > > -- Tom Mornini, CTO > > -- Engine Yard, Ruby on Rails Hosting > > -- Reliability, Ease of Use, Scalability > > -- (866) 518-YARD (9273) > > I agree with Tom that defining a unique key in your DB and letting the > DB enforce it is the best way to go. > > I question the usefulness of validates_uniqueness_of in general because: > > 1) validates_uniqueness_of can''t guarantee that the field you are about > to save to the DB is indeed unique (as Tom explained) > > 2) validates_uniqueness_of needs to query the DB in order to validate > your model, which defeats the whole purpose of an application-side > validation (IMO) > > I started a discussion about this on my blog, and no one has > successfully made a case for using validates_uniqueness_of yet. If > anybody out there does have a scenario where it makes sense to use this > validation, please let me know so I can stop criticizing it :) > http://allyourdatabase.blogspot.com/2006/11/generating-activerecord-data.html > > Cheers. > > -- > Posted via http://www.ruby-forum.com/. > > > >Bryan, I think validates_uniqueness_of does have a "valid" place. It lets you keep your code DRY and works in 99.999% of the cases. It only fails in the very rare case where another insert occurs after one thread (or mongrel process) has checked for uniqueness. In that very rare case the db''s unique index would catch it and the database would stay valid. The only side effect is that the app would render an error page to the user. I''m willing to bet that this would likely never happen until a site got really big, and in even then it would have to be the perfect storm. -- Zack Chandler http://depixelate.com --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Zack Chandler wrote:> On 11/17/06, Bryan Evans <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote: >> > >> I agree with Tom that defining a unique key in your DB and letting the >> >> >> > >> > > Bryan, > > I think validates_uniqueness_of does have a "valid" place. It lets > you keep your code DRY and works in 99.999% of the cases. It only > fails in the very rare case where another insert occurs after one > thread (or mongrel process) has checked for uniqueness. In that very > rare case the db''s unique index would catch it and the database would > stay valid. The only side effect is that the app would render an > error page to the user. I''m willing to bet that this would likely > never happen until a site got really big, and in even then it would > have to be the perfect storm. > > -- > Zack Chandler > http://depixelate.comHi Zack I agree with you that it would be a rare occurrance for a duplicate value to be inserted into the DB after ActiveRecord does the uniqueness check and before it actually saves your record. However, it is possible. As well, your DB already does a duplicate key check on insert/update (assuming that you defined a unique key on the DB), so the uniqueness check done by the validation is redundant database I/O and can''t be guaranteed to be accurate. In terms of functionality and performance, using the validation actually seems to me to be detrimental to an application, rather than beneficial. Evaluating the validation on a more subjective criterion, I don''t believe that using validates_uniqueness_of provides any DRYness to my application code that can''t be achieved by extending ActiveRecord::Base to handle a duplicate key error returned from the DB. Given that validates_uniqueness_of needs to be defined multiple times in your application code (once for each unique key), I think that defining a generic duplicate key error handler in ActiveRecord::Base is actually a more DRY approach, but I suppose that it is a matter of personal taste. From my perspective, the application-side validations'' prime purpose is to provide "fast" model validation by avoiding DB I/O. If an application-side validation needs to perform redundant DB I/O in order to validate an object, I can''t see the advantage of using it, especially if it can''t even guarantee model validity. This is just my opinion, and I respect yours as well. Cheers. -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On 11/17/06, Bryan Evans <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:> > Evaluating the validation on a more subjective criterion, I don''t > believe that using validates_uniqueness_of provides any DRYness to my > application code that can''t be achieved by extending ActiveRecord::Base > to handle a duplicate key error returned from the DB. Given that > validates_uniqueness_of needs to be defined multiple times in your > application code (once for each unique key), I think that defining a > generic duplicate key error handler in ActiveRecord::Base is actually a > more DRY approach, but I suppose that it is a matter of personal taste.I agree. If only the databases and their drivers provided these info in a more standard, accessible way. I tried parsing postgres contraint violation errors and it''s a real pain to deduce which table and columns were affected, especially since these messages are locale dependent and change between versions. That said, a common way to introspect database *errors* in addition to tables + columns would be wonderful. jeremy --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Jeremy Kemper wrote:> On 11/17/06, Bryan Evans <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote: >> >> Evaluating the validation on a more subjective criterion, I don''t >> believe that using validates_uniqueness_of provides any DRYness to my >> application code that can''t be achieved by extending ActiveRecord::Base >> to handle a duplicate key error returned from the DB. Given that >> validates_uniqueness_of needs to be defined multiple times in your >> application code (once for each unique key), I think that defining a >> generic duplicate key error handler in ActiveRecord::Base is actually a >> more DRY approach, but I suppose that it is a matter of personal taste. > > > I agree. If only the databases and their drivers provided these info in > a > more standard, accessible way. I tried parsing postgres contraint > violation > errors and it''s a real pain to deduce which table and columns were > affected, > especially since these messages are locale dependent and change between > versions. > > That said, a common way to introspect database *errors* in addition to > tables + columns would be wonderful. > > jeremyGood point, Jeremy. I think you''ve identified a hole in my argument ...and you''ve also given me an excellent idea for a future enhancement to DrySQL: http://drysql.rubyforge.org/ -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---