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Add a note in guide for a counter cache caveat

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Counter cache can hold stale value if user changes primary key's value.
This caveat is not mentioned in guides, but according to #16159
comments it should be.
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Krzysztof Hasiński 2022-01-21 22:21:35 +01:00
parent 3f13828392
commit ea2226605a
1 changed files with 9 additions and 1 deletions
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10
guides/source/association_basics.md
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@ -1037,7 +1037,15 @@ end
NOTE: You only need to specify the `:counter_cache` option on the `belongs_to`
side of the association.
Counter cache columns are added to the containing model's list of read-only attributes through `attr_readonly`.
Counter cache columns are added to the owner model's list of read-only
attributes through `attr_readonly`.
If for some reason you change the value of an owner model's primary key, and do
not also update the foreign keys of the counted models, then the counter cache
may have stale data. In other words, any orphaned models will still count
towards the counter. To fix a stale counter cache, use [`reset_counters`][].
[`reset_counters`]: https://api.rubyonrails.org/classes/ActiveRecord/CounterCache/ClassMethods.html#method-i-reset_counters
##### `:dependent`