如何使用Rails在一个查询中执行多个语句？

Question

我正在使用带有ActiveRecord和PostgreSQL的Ruby on Rails.

如何执行多个SQL查询？

我需要它来运行自定义迁移脚本,例如:

Foo.connection.execute <<-SQL.split(';').map(&:strip).join
 delete from metadata where record_type = 'Foo';
 TRUNCATE table1 RESTART IDENTITY;
 TRUNCATE table2 RESTART IDENTITY;
 delete from schema_migrations where version > '20120806120823';
SQL

我不接受用户的数据,所以我不担心sql注入.

CLIENT_MULTI_STATEMENTS也许像MySQL 这样的东西？

来自MySQL/PHP文档:

CLIENT_MULTI_STATEMENTS:告诉服务器客户端可以在一个字符串中发送多个语句(以";"分隔).如果未设置此标志,则禁用多语句执行.有关此标志的更多信息,请参阅此表后面的注释.

Answer 1

它应该与PostgreSQL开箱即用,用pg gem和rails 3.2检查:

class Multitest < ActiveRecord::Migration
  def up
    execute <<-SQL
      create table x(id serial primary key);
      create table y(id serial primary key, i integer);
    SQL
  end

  def down
  end
end

另外,操纵schema_migrations直接看起来很奇怪.

Answer 2

对于 mysql

queries = File.read("/where/is/myqueries.sql")
# or
queries = <<-SQL
 TRUNCATE table1 RESTART IDENTITY;
 TRUNCATE table2 RESTART IDENTITY;
 delete from schema_migrations where version > '20120806120823';
SQL

queries.split(';').map(&:strip).each do |query| 
  execute(query)
end

您可能也想看到这个问题： Invoking a large set of SQL from a Rails 4 application

Answer 3

是的，您需要CLIENT_MULTI_STATEMENTS：

在database.yml：

development:
  adapter: mysql2
  database: project_development
  flags:
    - MULTI_STATEMENTS

然后在你的代码中：

connection.execute(multistatement_query)
# Hack for mysql2 adapter to be able query again after executing multistatement_query
connection.raw_connection.store_result while connection.raw_connection.next_result

有关详细信息，请参阅/sf/answers/787278621/