github/rails
1
1
Fork 0
mirror of https://github.com/github/rails.git synced 2026-04-26 03:00:59 -04:00
Code Issues Packages Projects Releases Wiki Activity

User.each is a lie

Browse Source
This commit is contained in:
Pratik Naik
2010-08-30 23:05:14 +01:00
parent 19d99971f7
commit c30f6c270d
1 changed files with 2 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
railties/guides/source/active_record_querying.textile
View File

@@ -159,14 +159,14 @@ The following may seem very straight forward at first:
<ruby>
# Very inefficient when users table has thousands of rows.
User.each do |user|
User.all.each do |user|
NewsLetter.weekly_deliver(user)
end
</ruby>
But if the total number of rows in the table is very large, the above approach may vary from being under performant to just plain impossible.
This is because +User.each+ makes Active Record fetch _the entire table_, build a model object per row, and keep the entire array in the memory. Sometimes that is just too many objects and demands too much memory.
This is because +User.all.each+ makes Active Record fetch _the entire table_, build a model object per row, and keep the entire array in the memory. Sometimes that is just too many objects and demands too much memory.
h5. +find_each+