Rails 3 数据库移植

Question

Had to quickly slap something together to move a table (approx 30k records) from one db to another with different names.

My hack solution using RoR was this:

for old_line in SaleItemsOld.where(:sale_id => old_sale.id)
    line = LineItems.new
        line.sale_id = new_sale.id
        ...
    line.save
end

I had the thought that this should be sped up by constructing all these new lines as SQL queries in a single string and then executing that in one go.

Is there a better Rails solution for this?

Answer 1

Usually you can do this sort of thing with a migration and some carefully constructed SQL. Generally the idea is do to something along the lines of:

INSERT INTO line_items (sale_id) SELECT id FROM sale_items_old

You can add other values as required both to the insert list and the select specification.

In a migration you can run arbitrary SQL by placing it in your up method:

def self.up
  execute("...")
end