Rename column with long name and index result in postgres error

[bobbus]

In Rails 4, an error is raise when we rename a column with an index to a too long name.

Error stack :

Input string is longer than NAMEDATALEN-1 (63)/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql/quoting.rb:152:in `quote_ident'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql/quoting.rb:152:in `quote_column_name'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql/quoting.rb:139:in `quote_table_name'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql/schema_statements.rb:424:in `rename_index'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract/schema_statements.rb:854:in `block in rename_column_indexes'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract/schema_statements.rb:848:in `each'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract/schema_statements.rb:848:in `rename_column_indexes'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql/schema_statements.rb:411:in `rename_column'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/migration.rb:625:in `block in method_missing'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/migration.rb:597:in `block in say_with_time'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/1.9.1/benchmark.rb:280:in `measure'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/migration.rb:597:in `say_with_time'
/home/bob/.rbenv/versions/1.9.3-p429/lib/ruby/gems/1.9.1/gems/activerecord-4.0.0/lib/active_record/migration.rb:617:in `method_missing'
/home/bob/doc/dev/test-apps/testing4/db/migrate/20131018132332_rename_table.rb:3:in `change'

An app with the failure could be found here, relevant commit is : bobbus/testing-rails4@4296e5d

[laurocaetano]

The problem is that rails is trying to create an index for this new column, and it's named index_table_with_long_names_on_field_with_too_too_too_too_too_long_name.

This will raise Input string is longer than NAMEDATALEN-1 (63). You can find more about it here: http://rubydoc.info/github/ged/ruby-pg/PGconn.quote_ident

It's not a Rails issue. Thanks.

[bobbus]

Thanks for these informations @laurocaetano . Actually, a workaround could be to rescue the line which rename the column but this is not really elegant and I would think it could be good to add a way to prevent this in Rails ?

[senny]

@bobbus I'm not sure we can prevent this problem completely. If you have to work with very long table / field names It would be best to specify the index names. This way Rails won't rename them when you rename a field. Also you can pick shorter index names as Rails would.

EDIT: This is not really a problem of rename_column. You'll run into the same issue when you try to call add_index for a long table and field name.

[robinbortlik]

I got same problem, so I monkey patched index_name method like this

module ActiveRecord
  module ConnectionAdapters
    module SchemaStatements

      def index_name_with_length(table_name, options)
        name = index_name_without_length(table_name, options)
        name = name[0..63] if name.length > 64
        name
      end
      alias_method_chain :index_name, :length

    end
  end
end

[laurocaetano]

Closing this one, as commented in #13209 (comment)

Thanks guys.

[bobbus]

@laurocaetano , I can understand that we do not want the fix in #13209 in Rails but I believe a better error message or a warning would be useful.

The actual error message is a bit brittle, don't you think ?

Also, I'm wondering which fix you would recommend in the case of rename_column ? It could be renaming the index before renaming the column but it seems odd ? Actually, I use a rescue clause on the rename_column line for this error, it is not really elegant..

[laurocaetano]

@bobbus I agree that the error message is a bit brittle.

We could work on improving the error message instead of preventing the error, what do you think? cc @rafaelfranca

[senny]

@bobbus what is the full error you get? If possible I'd like to forward the error from the database to the user. It signals that it's not a Rails limitation but something related to the DB backend. Of course that only works if the error links to the cause.