Rails Modeling Columns of a Counter_cache Column

Question

I use rspec for testing and hornsby scripts for graphing objects used in tests.

Is it good practice to initialize the columns of the cache columns to 0 instead of leaving them uninitialized (nil)? Or should I define a default value in the migrations that create these cache counter columns?

Answer 1

Yes, you must set the default value. Otherwise, special mathematical operations must be performed to process NULL.

Let's say you had an array of mail objects and you wanted to get the sum of the number of comments.

@posts.sum(&:comment_count), , , nil.

:

add_column :posts, :comments_count, :integer, :default => 0, :null => false

Answer 2

SQL

UPDATE posts SET comment_count = comment_count + 1, WHERE id IN (10, 15)

, , undefined +1 == 1, Rails . , . , ( ), . , , .