#2786 Counter cache is updated on belongs_to reassignment when not needed - Ruby on Rails

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#2786 ✓committed

Counter cache is updated on belongs_to reassignment when not needed

Reported by Tarmo Tänav | June 10th, 2009 @ 02:30 PM | in 3.x

Comments and changes to this ticket

Tarmo Tänav June 10th, 2009 @ 02:32 PM
- no changes were found...
- 0001-Don-t-increment-and-then-decrement-the-same-counter-.patch 1.9 KB
Tarmo Tänav June 10th, 2009 @ 02:34 PM
Currently if you reassign a belongs_to association to the same record that it was before and that association has a counter cache the cache is decremented and then again incremented on the same record:
```
UPDATE "topics" SET "replies_count" = COALESCE("replies_count", 0) + 1 WHERE ("id" = 12) 
UPDATE "topics" SET "replies_count" = COALESCE("replies_count", 0) - 1 WHERE ("id" = 12)
```
That is certainly not useful so the counter cache should only be updated if the record being assigned differs from the one that was present before the assignment.

Patch against master, but also applies cleanly to 2-3-stable.
Tarmo Tänav June 10th, 2009 @ 03:11 PM
- Assigned user set to “Michael Koziarski”
Jeremy Kemper May 4th, 2010 @ 06:48 PM
- Milestone changed from “2.x” to “3.x”
[bulk edit]
Neeraj Singh July 7th, 2010 @ 05:37 PM
- State changed from “new” to “verified”
- Tag set to “activerecord, patch, rails3, verified”
- Importance changed from “” to “”
+1

works fine.

tests passes in all three adapters.
Repository July 30th, 2010 @ 02:39 AM
- State changed from “verified” to “committed”
(from [2ea922bcec333b6484a295b4fee1f4fa75c5704d]) Don't increment and then decrement the same counter when re-assigning a belongs_to association

[#2786 state:committed]

Signed-off-by: Santiago Pastorino santiago@wyeworks.com
http://github.com/rails/rails/commit/2ea922bcec333b6484a295b4fee1f4...