New find_or_create_by behaviour raises RecordNotFound in edge rails #48035
Comments
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Yes, transactions are the reasons. Here is what happened.
We need to somehow read the up to date data for this row without restarting a transaction. This is achieved by So, I come up with the following: diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 2e21c22849..f53a94efed 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -215,7 +215,7 @@ def find_or_create_by!(attributes, &block)
def create_or_find_by(attributes, &block)
transaction(requires_new: true) { create(attributes, &block) }
rescue ActiveRecord::RecordNotUnique
- find_by!(attributes)
+ where(attributes).lock.find_by!(attributes)
end
# Like #create_or_find_by, but calls
@@ -224,7 +224,7 @@ def create_or_find_by(attributes, &block)
def create_or_find_by!(attributes, &block)
transaction(requires_new: true) { create!(attributes, &block) }
rescue ActiveRecord::RecordNotUnique
- find_by!(attributes)
+ where(attributes).lock.find_by!(attributes)
end
# Like #find_or_create_by, but calls {new}[rdoc-ref:Core#new]If that looks ok and I am not missing something, I can open a PR. |
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Ahh, thanks - I couldn't figure out the REPEATABLE READ step. The patch looks promising... though my actual code ends up doing a second lookup of the tag during a subsequent validation, which ends up raising RecordNotFound again, again due to REPEATABLE READ 😬. I'll see if I can avoid the extra lookup somehow |
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Yep, works well once I've removed the unnecessary lookup |
Hum, should we only do that if we're inside a transaction? Feel free to open a PR we can discuss it there. |
Steps to reproduce
Expected behavior
In Rails 7.0, one of the
find_or_create_bycalls raises RecordNotUnique (which we rescue and handle at the application-level).Actual behavior
In 7.1 alpha, it raises RecordNotFound:
Backtrace
though, apparently, only when there's a transaction wrapping the find_or_create call. Without the transaction, the new find_or_create_by improvements successfully return a tag in both threads.
(I'd happily remove our rescue block and leave Rails to handle the unique keys internally, if find_or_create can be fixed to do so)
cc @casperisfine
System configuration
Rails version: 7.1.0 alpha @ 719558c
Ruby version: 3.1.3
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