Question

我在node.js应用程序中使用Heroku Postgres数据库和knexjs作为SQL查询构建器。我尝试运行最新的knex migration，但收到错误relation already exists。当我尝试通过sql命令CREATE TABLE创建表时，它没有任何问题。

knexfile.js

// Update with your config settings.

require('dotenv').config({ path: require('find-config')('.env') });

module.exports = {
  development: {
    client: 'pg',
    useNullAsDefault: true,
    connection: process.env.DATABASE_URL,
    searchPath: ['knex', 'public'],
  },

  staging: {
    client: 'postgresql',
    connection: {
      database: 'my_db',
      user: 'username',
      password: 'password'
    },
    pool: {
      min: 2,
      max: 10
    },
    migrations: {
      tableName: 'knex_migrations'
    }
  },

  production: {
    client: 'postgresql',
    connection: {
      database: 'my_db',
      user: 'username',
      password: 'password'
    },
    pool: {
      min: 2,
      max: 10
    },
    migrations: {
      tableName: 'knex_migrations'
    }
  }
};

最新的迁移文件

迁移/ 20180120183247_users_test.js

/* eslint func-names: 0 */

exports.up = function (knex) {
  return knex.schema
    .createTable('users', (table) => {
      table.increments('id').primary();
      table.string('user_name', 100);
      table.text('password');
      table.string('email', 254);
    });
};

exports.down = function (knex) {
  return knex.schema
    .dropTableIfExists('users');
};

当我运行命令时：

knex migrate:latest --env development

我收到错误：

Using environment: development
Knex:warning - migration file "20180120184707_initial_schema.js" failed
Knex:warning - migration failed with error: create table "users" ("id" serial primary key, "user_name" varchar(100), "password" text, "email" varchar(254)) - relation "users" already exists
error: relation "users" already exists
    at Connection.parseE (.../node_modules/pg/lib/connection.js:546:11)
    at Connection.parseMessage (.../node_modules/pg/lib/connection.js:371:19)
    at TLSSocket.<anonymous> (.../node_modules/pg/lib/connection.js:114:22)
    at emitOne (events.js:115:13)
    at TLSSocket.emit (events.js:210:7)
    at addChunk (_stream_readable.js:252:12)
    at readableAddChunk (_stream_readable.js:239:11)
    at TLSSocket.Readable.push (_stream_readable.js:197:10)
    at TLSWrap.onread (net.js:589:20)

如果我连接到数据库并运行命令：

select * from users;

我明白了：

ERROR:  relation "users" does not exist
LINE 1: select * from users;

在Heroku Postgres设置中，我运行重置数据库以删除所有数据。我等了2-3分钟，然后又尝试再次运行最新的迁移，但是我得到了同样的错误信息。

Answer 1

我不知道knex migrate:latest命令运行所有迁移文件，因此在先前的迁移文件中创建了表users，这就是问题所在。

Answer 2

我遇到了这个问题，希望能找到一个简单的解决方案，以防万一其他人想知道如何解决此问题：

如果您的数据库确实与迁移文件匹配：

进入knex_migrations表（如果您将其重命名，则移至记录迁移的表），并在name列中添加一行相关迁移文件的名称

要检查其是否正常运行，请尝试knex migrate:list

knex迁移抛出错误关系已存在

2 个答案: