I'm using rails with the oracleenhanced adaptor to create a new interface for a legacy application.
Database migrations work successfully, but take an incredibly long amount of time before rake finishes. The database changes happen pretty quickly (1 or 2 seconds), but the db/schema.db dump takes over an hour to complete. (See example migration below.)
It's a relatively large schema (about 150 tables), but I'm sure it shouldn't be taking this long to dump out each table description.
Is there anyway to speed this up by just taking the last schema.db and applying the change specified in the migration to it? Or am I able to skip this schema dump altogether?
I understand this schema.db is used to create the test database from scratch each time, but this case, there's a large chunk of the database logic in table triggers which aren't included in the schema.rb anyway, so the rake tests are no good to us in any case. (That's a whole different issue that I need to sort out at some other point.)
dgs@dgs-laptop:~/rails/voyager$ time rake db:migrate (in /home/dgs/rails/voyager) == 20090227012452 AddModuleActionAndControllerNames: migrating ================ -- add_column(:modules, :action_name, :text) -> 0.9619s -> 0 rows -- add_column(:modules, :controller_name, :text) -> 0.1680s -> 0 rows == 20090227012452 AddModuleActionAndControllerNames: migrated (1.1304s) ======= real 87m12.961s user 0m12.949s sys 0m2.128s
After all migrations are applied to database then rake db:migrate calls db:schema:dump task to generate schema.rb file from current database schema.
db:schema:dump call adapter's "tables" method to get the list of all tables, then for each table calls "indexes" method and "columns" method. You can find SQL SELECT statements that are used in these methods in activerecord-oracle_enhanced-adapter gem's oracle_enhanced_adapter.rb file. Basically it does selects from ALL% or USER% data dictionary tables to find all the information.
Initially I had issues with original Oracle adapter when I used it with databases with lot of different schemas (as performance might be affected by the total number of table in the database - not just in your schema) and therefore I did some optimizations in Oracle enhanced adapter. It would be good to find out which methods are slow in your case (I suspect that it could be either "indexes" or "columns" method which is executed for each table).
One way hoe to debug this issue would be if you would put some debug messages in oracle_enhanced_adapter.rb file so that you could identify which method calls are taking so long time.