Decrement a numeric field by one, via a direct SQL update.
This works the same as increment_counter but reduces the column value by 1 instead of increasing it.
counter_name - The name of the field that should be decremented.
id - The id of the object that should be decremented or an Array of ids.
# Decrement the post_count column for the record with an id of 5 DiscussionBoard.decrement_counter(:post_count, 5)
# File activerecord/lib/active_record/counter_cache.rb, line 117 def decrement_counter(counter_name, id) update_counters(id, counter_name => -1) end