Rails set all record values to zero

How can I set all records to 0 in a table? -- UPDATE -- What I want to do is the following. I have a table called Pages with an attributed called position. When I delete page from the table i want som function to reorder the positions, so that there wont be any not used po开发者_StackOverflow社区sitions.

EX. Position 1, 2, 4, 8, 9, 12 becomes 1, 2, 3, 4, 5, 6

Pages.find(:all).sort_by(&:position).each_with_index do |page, index|
  page.position = index + 1
  page.save
end

To answer your first question,

Pages.update_all(:position => 0)

One way to update the position array when a position is deleted is in a before_destroy callback. This is reliable only if Rails' destroy method is the only way records are deleted!

def decrement_positions
  Pages.update_all('position = position - 1', ['position > ?', position])
end

before_destroy :decrement_positions

One race-condition free way to set all positions to adjacent values at once would be to drop into SQL:

Pages.update_all('position = 1 + (select count(1) from pages p where p.position < pages.position)')

Model.all.map { |m| m.field = 0 }.save!

However this will create as many requests as records you have, so in case you have lots or records I'd suggest to use something like this.

If you're using the acts_as_list plugin, it should deal with the renumbering of positions automatically.

I would think using the plugin acts_as_list, like Andrew suggested, is a good idea if you need all the features, otherwise, I would just setup an after_destroy filter.

after_destroy :fix_order
def fix_order
  Page.order('position asc').all.each_with_index do |page, index|
    page.update_attribute(:position, index + 1) unless page.position == index + 1
  end
end