rake db:test:clone_structure might fail with multiple schemas in postgres.

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It is easy to reproduce the problem. These are the steps:

Create a Rails application that uses postgresql:

$ rails new postgres_clone -d postgresql
$ cd postgres_clone

Then create a migration:

#db/migrate/20110421194621_my_migration.rb
class MyMigration < ActiveRecord::Migration
  def self.up
    connection.execute 'CREATE SCHEMA z_schema;'
    connection.execute 'CREATE TABLE z_schema.table1 (id integer, name varchar[255]);'
    connection.execute 'CREATE UNIQUE INDEX unique_table1_name ON z_schema.table1 USING btree (name);'
  end
end

And the run:

$ rake db:create
$ rake db:migrate
$ rake db:test:clone_structure

(in /home/juan/projects/postgres_clone)
psql:/home/juan/projects/postgres_clone/db/development_structure.sql:75: ERROR:  relation "schema_migrations" does not exist
LÍNEA 1: INSERT INTO schema_migrations (version) VALUES ('20110421194...
                     ^

The first patch I attached does not apply anymore because 'databases.rake' changed.

This is the same patch but created recently from 'master'.