PG DuplicateTable: 错误，关系表“Products”已经存在 - Heroku db:migrate 尝试

Question

一名Rails新手试图将数据库迁移到Heroku。请原谅这个错误信息的冗长，但我认为包含所有信息可能很重要。我不知道为什么会出现这种情况或者它的含义。在我的schema中只有一个products表和一个create products migration。

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)

- Alb

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相关问题及类似答案：https://dev59.com/214c5IYBdhLWcg3wv8lm - GDP2

Answer 1

前往Heroku rails控制台，并运行以下命令删除产品（假设它们不包含任何数据）表：

ActiveRecord::Migration.drop_table(:products)

并重新运行迁移。

或者只需从db/migration中删除创建产品表的迁移文件。

这也可以起作用。

- neo

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我会在这里丢失一些我想要的东西吗？ - Alb

如果这是一个新的部署，那么没问题，但如果您有现有的产品，则它将擦除它们，您将不得不重新创建它们，还要检查编辑内容。 - neo

我相信我已经拥有它们，这就是为什么我会收到错误信息，但我不明白我做了什么导致它创建了另一个重复的表。 - Alb

这不是它， 在Heroku上的Rails控制台中运行Product.all.count，如果它等于0，则表示您的产品表中没有任何数据。 - neo

我从迁移中删除了create_products并重新运行了heroku run rake db:migrate，但仍然得到相同的错误。 - Alb

Answer 2

我认为你的数据库中的schema_migration表存在问题，其中包含每个迁移的时间戳值。如果你没有针对产品表的重复迁移文件，那么你可以清空数据库并再次运行rake db:migrate。希望这能解决问题。

- user3252359

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我在哪里可以查看这个schema_migration表？ - Alb

在您的数据库中，记录了每个迁移及其时间戳。 - user3252359

我需要从终端查看吗？命令是什么？谢谢 @Avishek - Alb

虽然晚了三年，但是一旦进入您的数据库，这就是命令：select * from schema_migrations; - davideghz