Rails新手试图将DB迁移到heroku。请原谅这个错误信息的多汁性，但我认为它可能是重要的，包括所有。我不知道为什么会这样，也不知道这意味着什么。我的模式中只有一个产品表和一个创建产品迁移。
Migrating to CreateProducts (20140804010848)
== 20140804010848 CreateProducts: migrating ===================================
-- create_table(:products)
PG::DuplicateTable: ERROR: relation "products" already exists
: CREATE TABLE "products" ("id" serial primary key, "name" character varying(255), "price" float, "description" text, "image" character varying(255), "color" character varying(255), "created_at" timestamp, "updated_at" timestamp)
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:
PG::DuplicateTable: ERROR: relation "products" already exists
: CREATE TABLE "products" ("id" serial primary key, "name" character varying(255), "price" float, "description" text, "image" character varying(255), "color" character varying(255), "created_at" timestamp, "updated_at" timestamp) /app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/connection_adapters/postgresql/database_statements.rb:128:in `async_exec'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/connection_adapters/postgresql/database_statements.rb:128:in `block in execute'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract_adapter.rb:373:in `block in log'
/app/vendor/bundle/ruby/2.0.0/gems/activesupport-4.1.4/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract_adapter.rb:367:in `log'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/connection_adapters/postgresql/database_statements.rb:127:in `execute'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/schema_statements.rb:205:in `create_table'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:649:in `block in method_missing'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:621:in `block in say_with_time'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:621:in `say_with_time'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:641:in `method_missing'
/app/db/migrate/20140804010848_create_products.rb:3:in `change'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:595:in `exec_migration'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:579:in `block (2 levels) in migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:578:in `block in migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:294:in `with_connection'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:577:in `migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:752:in `migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:992:in `block in execute_migration_in_transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:1038:in `block in ddl_transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/database_statements.rb:201:in `block in transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/database_statements.rb:209:in `within_new_transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/database_statements.rb:201:in `transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/transactions.rb:208:in `transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:1038:in `ddl_transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:991:in `execute_migration_in_transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:953:in `block in migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:949:in `each'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:949:in `migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:807:in `up'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/migration.rb:785:in `migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.1.4/lib/active_record/railties/databases.rake:34:in `block (2 levels) in <top (required)>'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)
转到Heroku rails控制台，通过运行:
删除产品表(假设它们不包含任何数据):ActiveRecord::Migration.drop_table(:products)
并重新运行迁移。
或者直接从db/migration
中删除创建products表的迁移文件这也可以。
我认为您在数据库中包含每次迁移的时间戳值的schema_migration表有问题。如果没有产品表的重复迁移文件，那么可以截断数据库并再次运行rake db:migrate。