将数据从sqlite导出到Rails中的csv文件

Question

I have app that uses sqlite db and there are entries in that table. Now i have to change sqlite to postgres . And the table design is also changed.

If it is the same table design then i would have gone to use taps or dump the data using yaml-db and then push the data to postgres, but in my scenario the table design also changes but i want to move the data from the sqlite to postgres according to the new table.

So i thought of exporting the data from sqlite to a csv file and then move the data from csv to postgres. Is this is the way i have to do or is there is any other way for doing it? If this is the way then how can i export to csv and import to postgres ?

Another thing is, after exporting the data from sqlite, is there is a way to push the data through migration ? please help me.

Answer 1

To export in a CSV format just add to a controller action a respond_to for csv and then in the matching view folder create a .csv.erb file to create the csv. This can then be called by just adding .csv to the URL.

So your controller would be something like this:

def index
  @people = Person.all

  respond_to do |format|
    format.html # index.html.erb
    format.json { render json: @people }
    format.csv
  end
end

And you view which would be saved in a file (something like /app/views/people/index.csv.erb) would contain:

First Name,Last Name
<% @people.each do |p| %>
  <%= raw "\"#{p.first_name}\"" %>,<%= raw "\"#{p.last_name}\"" %>
<% end %>

This way creating you CSV is not dependent on the database in use.