MySQL和PostgreSQL之间的结果不同

Question

Locally I use MySQL and remotely I use PostgreSQL (on Heroku) and I'm getting different results.

controller

 @customer = current_customer
 @shows = @customer.shows
 @musicals = Musical.find(:all, :conditions =>['show_id in (?)', @shows])

 @musicals.each do |musical|
   @musical_activities = Activity.where('musical_id in (?)', musical.id).count(:group => "activity_type_id")
 end

view

<table>
  <tr>
<th>Activity</th>
<th>Number</th>     
  </tr>

<% @activities.each do |activity_id, count| %>
  <tr>
<td><%= activity_description(activity_id) %></td>
<td><%= count %></td>
  </tr>  
<% end %>
</table>

Previously, I had used = instead of in, but I changed it because I was getting a PGError saying that argument of WHERE must be type boolean, not type record. Whether I use = or IN, I get the correct results locally.

When I run it on Heroku, and replace = with IN, the error goes away, but the result is wrong. I simply get one row where the first column (activity_description) is blank and instead of showing me the counts by activity types, the count is either aggregated or only only one activity_type is showing. Ie, only one row appears even though I have many activity_types and the one row didn't return the activity_id.

Answer 1

When you migrate your database to Heroku, Heroku internally uses the taps gem to import your local DB to Heroku.
But, there are some constraints to it(foreign keys and Postgres Bigint).

Taps gem constraints when importing local DB to Postgres

If, this doesn't help you, here are some great links to help you with the conversion.

1. Converting Rails application data from MySQL to PostgreSQL
2. Rake task to transfer a Rails database, say from MySQL to Postgres and back again

Answer 2

或者，使用ClearDB mySQL插件（http://addons.heroku.com/cleardb）并保留在mySQL上。