ActiveRecord excels at providing methods that balance convenience and performance. Among the most powerful are delete_all and update_all, which execute bulk operations directly in SQL. However, until recently, they behaved inconsistently when used with certain query methods like limit or distinct.
With the introduction of PR #54231, Rails has unified how these methods validate queries before execution, putting an end to this long-standing inconsistency.
The Problem: Different Rules for Similar Operations
Even though both methods operate on Relations, Rails used to impose different restrictions on each.
For instance, if you tried to use update_all on a query containing a limit or an offset, Rails would often throw an error (especially on databases that don’t natively support those clauses in an UPDATE statement). Meanwhile, delete_all might allow the operation or fail in a different way depending on how the query was constructed.
This discrepancy led to confusing bugs when refactoring logic—such as switching from a hard delete to a soft delete—expecting the API to handle the scopes identically.
The Solution: Standardized Validation
The new PR ensures that if an operation is invalid for the database (such as an UPDATE or DELETE combined with DISTINCT, LIMIT, or GROUP BY in certain contexts), both methods will now respond consistently.
Example:
Previously, you might encounter divergent behavior. Now, the validation is standardized:
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# Attempting to update or delete within a complex scope
scoped_query = User.where(active: true).limit(10)
# Both now follow the same validation rules
scoped_query.update_all(status: 'archived')
# => Raises ActiveRecordError if the query is incompatible
scoped_query.delete_all
# => Follows the exact same error logic as update_all
Why This Matters
This change is fundamental for three main reasons:
- Predictability: You no longer need to memorize which SQL clauses are permitted for
delete_allversusupdate_all. If the Relation is invalid for bulk modification, it is invalid for both. - Data Safety: It prevents deletion operations from being executed partially or unexpectedly due to joins or limits being misinterpreted by the database.
- Refactor-Friendly: It makes it much safer to toggle between “clearing data” and “flagging data as deleted” without worrying about breaking the underlying query logic.
The Rails Way
The focus here isn’t just about fixing a bug; it’s about reinforcing the ActiveRecord interface. By unifying these behaviors, the framework reduces the developer’s cognitive load, allowing you to trust that sibling methods will behave like siblings.