Sequelize.sync：表不存在时创建索引

Question

根据文档， sequelize.sync()没有{force: true}或{alter:true}应该忽略已经存在的表并仅创建/同步新表。但是，至少有两种用例未完全忽略现有表并且会引入错误。

我的设置：

1. sequelize.sync()用作预迁移步骤来创建架构中不存在的表
2. sequelize.migrate()用于更改任何现有表。

注意：Sequelize 模型被视为反映数据库模式的单一事实来源。它们始终会更新以反映数据库中存在的所有索引/字段。

重现步骤

第 1 步：创建具有两个字段和 的User模型。有一个唯一的索引nameemailEmail

const users = sequelizeClient.define('users', {
    name: {
      type: DataTypes.STRING,
      allowNull: false,
    },
    email: {
      type: DataTypes.STRING,
      allowNull: false,
    },
  }, {
    indexes: [
      {
        unique: true,
        fields: ['email'],
      },
    ],
  });

没有迁移，因此预计将使用sequelize.sync(). 一切都按预期进行。以下是生成的 SQL 脚本。

Executing (default): CREATE TABLE IF NOT EXISTS "users" ("id"  SERIAL , "name" VARCHAR(255) NOT NULL, "email" VARCHAR(255) NOT NULL, PRIMARY KEY ("id"));
Executing (default): SELECT i.relname AS name, ix.indisprimary AS primary, ix.indisunique AS unique, ix.indkey AS indkey, array_agg(a.attnum) as column_indexes, array_agg(a.attname) AS column_names, pg_get_indexdef(ix.indexrelid) AS definition FROM pg_class t, pg_class i, pg_index ix, pg_attribute a WHERE t.oid = ix.indrelid AND i.oid = ix.indexrelid AND a.attrelid = t.oid AND t.relkind = 'r' and t.relname = 'users' GROUP BY i.relname, ix.indexrelid, ix.indisprimary, ix.indisunique, ix.indkey ORDER BY i.relname;
Executing (default): CREATE UNIQUE INDEX "users_email" ON "users" ("email")

步骤2在Users表中添加新字段phonenumber并添加唯一索引。添加将更改表结构并创建索引的迁移。预计sequelize.sync()会忽略此表，但迁移永远不会执行，因为sequelize.sync()会引发以下错误。

Executing (default): CREATE TABLE IF NOT EXISTS "users" ("id"  SERIAL , "name" VARCHAR(255) NOT NULL, "email" VARCHAR(255) NOT NULL, PRIMARY KEY ("id"));
Executing (default): SELECT i.relname AS name, ix.indisprimary AS primary, ix.indisunique AS unique, ix.indkey AS indkey, array_agg(a.attnum) as column_indexes, array_agg(a.attname) AS column_names, pg_get_indexdef(ix.indexrelid) AS definition FROM pg_class t, pg_class i, pg_index ix, pg_attribute a WHERE t.oid = ix.indrelid AND i.oid = ix.indexrelid AND a.attrelid = t.oid AND t.relkind = 'r' and t.relname = 'users' GROUP BY i.relname, ix.indexrelid, ix.indisprimary, ix.indisunique, ix.indkey ORDER BY i.relname;
Executing (default): CREATE UNIQUE INDEX "users_phonenumber" ON "users" ("phonenumber")
{"_bitField":18087936,"_fulfillmentHandler0":{"name":"SequelizeDatabaseError","parent":{"name":"error","length":101,"severity":"ERROR","code":"42703","file":"indexcmds.c","line":"1083","routine":"ComputeIndexAttrs","sql":"CREATE UNIQUE INDEX \"users_phonenumber\" ON \"users\" (\"phonenumber\")"},"original":{"name":"error","length":101,"severity":"ERROR","code":"42703","file":"indexcmds.c","line":"1083","routine":"ComputeIndexAttrs","sql":"CREATE UNIQUE INDEX \"users_phonenumber\" ON \"users\" (\"phonenumber\")"},"sql":"CREATE UNIQUE INDEX \"users_phonenumber\" ON \"users\" (\"phonenumber\")"},"_trace":{"_promisesCreated":0,"_length":1},"level":"error","message":"Unhandled Rejection at: Promise "}

这是最终的模型

const users = sequelizeClient.define('users', {
    name: {
      type: DataTypes.STRING,
      allowNull: false,
    },
    email: {
      type: DataTypes.STRING,
      allowNull: false,
    },
    phoneNumber: { // new field
      type: DataTypes.STRING,
      allowNull: false,
    },

  }, {
    indexes: [
      {
        unique: true,
        fields: ['email'],
      },
      { // new index
        unique: true,
        fields: ['phoneNumber'],
      },
    ],
  });

有人可以在这里建议一种解决方法，以便仅在表不存在时才创建索引

---

另一个用例是当您添加带有注释的新字段时

    fieldWithComment: {
      type: DataTypes.STRING,
      comment: 'my comment goes here',
    },

生成的 SQL 显然会抛出错误，因为新列尚不存在。

CREATE TABLE IF NOT EXISTS "users" (
    "id"   SERIAL, 
    "name" VARCHAR(255) NOT NULL, 
    "email" VARCHAR(255) NOT NULL, 
    "phonenumber" VARCHAR(255) NOT NULL, 
    "fieldWithComment" VARCHAR(255) , PRIMARY KEY ("id")); 
        COMMENT ON COLUMN "users"."fieldWithComment" IS 'my comment goes here';

Answer 1

在生产中同步数据库的正确且非破坏性的方法是通过迁移。这样可以确保操作的顺序（新字段创建、索引创建等）。

所以，一般情况下，sync应该只在开发和测试环境中使用。

引用官方文档：

sync({force:true}) 和sync({alter:true}) 可能是破坏性操作。因此，不建议将它们用于生产级软件。相反，应该在 Sequelize CLI 的帮助下，使用迁移的高级概念来完成同步。

更多信息请参见此处（部分：“生产中的同步”）。