A travel expense must have information on which cost center paid for the ticket, and which cost center paid for the traveling costs.
I've ran the following migration, attempting to create two foreign keys to map to cost_centers, which worked fine for SQLite:
def change
add_reference :expense_travels, :air_ticket_cost_center, index: true
add_reference :expense_travels, :travel_cost_center, index: true
add_foreign_key :expense_travels, :cost_centers, column: :air_ticket_cost_center_id
add_foreign_key :expense_travels, :cost_centers, column: :travel_cost_center_id
end
this, however, doesn't work for PostgreSQL:
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:
PG::UndefinedTable: ERROR: relation "air_ticket_cost_centers" does not exist
: CREATE TABLE "expense_travels" ("id" serial primary key, "expense_id" integer, "person_id" integer, "manager" character varying, "travel_type_id" integer, "air_ticket_amount" decimal(15,2), "air_ticket_cost_center_id" integer, "travel_amount" decimal(15,2), "travel_cost_center_id" integer, "total_amount" decimal(15,2), "start_date" date, "end_date" date, "itinerary" text, "created_at" timestamp NOT NULL, "updated_at" timestamp NOT NULL, CONSTRAINT "fk_rails_51368cd47f"
FOREIGN KEY ("expense_id")
REFERENCES "expenses" ("id")
, CONSTRAINT "fk_rails_4c8cafa3f7"
FOREIGN KEY ("person_id")
REFERENCES "people" ("id")
, CONSTRAINT "fk_rails_41906a97fa"
FOREIGN KEY ("travel_type_id")
REFERENCES "travel_types" ("id")
, CONSTRAINT "fk_rails_c4144cce64"
FOREIGN KEY ("air_ticket_cost_center_id")
REFERENCES "air_ticket_cost_centers" ("id")
, CONSTRAINT "fk_rails_8d209073b1"
FOREIGN KEY ("travel_cost_center_id")
REFERENCES "travel_cost_centers" ("id")
)
It attempts to set FOREIGN KEY ("air_ticket_cost_center_id") as REFERENCE of "air_ticket_cost_centers" ("id"), which should have been a reference to cost_centers instead.
TLDR: On PostgreSQL, in order to reference the same existing table twice on another table without conflicts, how can I set my migration?
Thanks in advance!
UPDATE - Including Full Stack Trace
== 20170109120056 AddCostCentersToExpenseTravels: migrating ===================
-- add_column(:expense_travels, :air_ticket_cost_center_id, :integer)
-> 0.0014s
-- add_column(:expense_travels, :travel_cost_center_id, :integer)
-> 0.0007s
-- add_foreign_key(:expense_travels, :cost_centers, {:column=>:air_ticket_cost_center_id})
-> 0.0000s
-- add_foreign_key(:expense_travels, :cost_centers, {:column=>:travel_cost_center_id})
-> 0.0000s
-- add_index(:expense_travels, :air_ticket_cost_center_id)
-> 0.0030s
-- add_index(:expense_travels, :travel_cost_center_id)
-> 0.0033s
== 20170109120056 AddCostCentersToExpenseTravels: migrated (0.0091s) ==========
db:schema:dump --> 0.250000 0.010000 0.260000 ( 0.267062)
db:_dump --> 0.250000 0.010000 0.260000 ( 0.267429)
db:migrate --> 0.710000 0.070000 0.780000 ( 1.101759)
db:abort_if_pending_migrations --> 0.040000 0.010000 0.050000 ( 0.040145)
db:seed --> 0.170000 0.020000 0.190000 ( 0.215987)
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:
PG::UndefinedTable: ERROR: relation "air_ticket_cost_centers" does not exist
: CREATE TABLE "expense_travels" ("id" serial primary key, "expense_id" integer, "person_id" integer, "manager" character varying, "travel_type_id" integer, "air_ticket_amount" decimal(15,2), "air_ticket_cost_center_id" integer, "travel_amount" decimal(15,2), "travel_cost_center_id" integer, "total_amount" decimal(15,2), "start_date" date, "end_date" date, "itinerary" text, "created_at" timestamp NOT NULL, "updated_at" timestamp NOT NULL, CONSTRAINT "fk_rails_51368cd47f"
FOREIGN KEY ("expense_id")
REFERENCES "expenses" ("id")
, CONSTRAINT "fk_rails_4c8cafa3f7"
FOREIGN KEY ("person_id")
REFERENCES "people" ("id")
, CONSTRAINT "fk_rails_41906a97fa"
FOREIGN KEY ("travel_type_id")
REFERENCES "travel_types" ("id")
, CONSTRAINT "fk_rails_c4144cce64"
FOREIGN KEY ("air_ticket_cost_center_id")
REFERENCES "air_ticket_cost_centers" ("id")
, CONSTRAINT "fk_rails_8d209073b1"
FOREIGN KEY ("travel_cost_center_id")
REFERENCES "travel_cost_centers" ("id")
)
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:98:in `async_exec'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:98:in `block in execute'
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/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:845:in `block in method_missing'
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/home/yadayada/workspace/yadayada/sources/db/migrate/20161201174226_create_expense_travels.rb:3:in `change'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:788:in `exec_migration'
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/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:771:in `block in migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:398:in `with_connection'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:770:in `migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:950:in `migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:1211:in `block in execute_migration_in_transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:1279:in `block in ddl_transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `block in transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/connection_adapters/abstract/transaction.rb:189:in `within_new_transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/transactions.rb:211:in `transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:1279:in `ddl_transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:1210:in `execute_migration_in_transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:1183:in `block in migrate_without_lock'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:1182:in `each'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:1182:in `migrate_without_lock'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:1131:in `block in migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:1298:in `with_advisory_lock'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:1131:in `migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-5.0.0.1/lib/active_record/migration.rb:1005:in `up'
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答案 0 :(得分：1)
句子add_reference :expense_travels, :air_ticket_cost_center将尝试查找名为 expense_travels 的表格，另一个名为 air_ticket_cost_center 的表格，然后在它们之间创建引用。这就是为什么你得到关系＆＃34; air_ticket_cost_centers＆＃34;不存在
让我们试试这个：
add_reference :expense_travels, :air_ticket_cost_center, table: :cost_centers, index: true
add_reference :expense_travels, :travel_cost_center, table: :cost_centers, index: true
add_foreign_key :expense_travels, :cost_centers, column: :air_ticket_cost_center_id
add_foreign_key :expense_travels, :cost_centers, column: :travel_cost_center_id
如果仍然不起作用，则可以通过分割步骤来解决问题：
add_column :expense_travels, :air_ticket_cost_center_id, :integer
add_column :expense_travels, :travel_cost_center_id, :integer
add_foreign_key :expense_travels, :cost_centers, column: :air_ticket_cost_center_id
add_foreign_key :expense_travels, :cost_centers, column: :travel_cost_center_id
add_index :expense_travels, :air_ticket_cost_center_id
add_index :expense_travels, :travel_cost_center_id