问题

I'm in the process of upgrading an application to Rails 3. I've decided to go with the mysql2 gem. There's some legacy code in the app that makes calls like:

results = ActiveRecord::Base.connection.execute(sql)

In the 2.3.x version, it used

results.each_hash do |row|
...

But with gem mysql2, results is type Mysql2::Result, which has only an each method. Checked the docs and they specify results should be a hash keyed on field name. Great!

But in fact, it is an Array, not a Hash.

When I use the rails console and instantiate my own Mysql2::Client and run the query there, the results are a Hash, which is what I want.

In the rails application, I think it's better to use ActiveRecord::Base.connection, since it's been instantiated with options from database.yml.

Note, unfortunately the result does not map to a model, so I can't use that.

What I've done for now is, for example:

result = ActiveRecord::Base.connection.execute(sql)
field_index = result.fields.index("field")
result.each do |row|
  row[field_index]
end

Which is ugly as sin.

Does anyone how I can get it to return a Hash instead of Array?

回答1:

If you just want to reuse the database.yml configuration, you can do this:

config = ActiveRecord::Base.configurations[RAILS_ENV].symbolize_keys
conn = Mysql2::Client.new(config)
conn.query("select * from users").each do |user|
  # user should be a hash
end

回答2:

I faced a similar issue a while back and found this to work:

result = ActiveRecord::Base.connection.execute(sql) 
result.each(:as => :hash) do |row| 
   row["field"] 
end

edit: you could also use the select_all method of the connection object that returns a hash

回答3:

instead of

result = ActiveRecord::Base.connection.execute(sql)

results = ActiveRecord::Base.connection.exec_query(sql)

And that'll do exactly what you want. In particular,

results.first

will be a hash, and so on.

Thanks to @_fx for figuring this out!

For more, see http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/Mysql2Adapter.html#method-i-exec_query

回答4:

results = ActiveRecord::Base.connection.select(sql)

table header

results.first.keys.each do |key|
 key
end

table data

results.each do |result| %>
  result.values.each do |value| %>
    value
  end
end

回答5:

Improving dan's answer, Rails 3.2.8 won't accept RAILS_ENV.


    config = ActiveRecord::Base.configurations[Rails.env].symbolize_keys
    conn = Mysql2::Client.new(config)
    conn.query("select * from users").each do |user|
        # user should be a hash
    end

来源：https://stackoverflow.com/questions/5760100/why-does-rails-3-with-mysql2-gem-activerecordbase-connection-executesql-retu

标签

ruby-on-rails-3

gem

mysql2

Why does Rails 3 with Mysql2 Gem ActiveRecord::Base.connection.execute(sql) return Array not Hash?

问题