Rails-PluckInWhere.md

Pattern: Use of pluck in where

Issue: -

Description

This rule identifies places where pluck is used in where query methods and can be replaced with select.

Since pluck is an eager method and hits the database immediately, using select helps to avoid additional database queries.

This rule has two different enforcement modes. When the EnforcedStyle is conservative (the default) then only calls to pluck on a constant (i.e. a model class) in the where is used as offenses.

When the EnforcedStyle is aggressive then all calls to pluck in the where is used as offenses. This may lead to false positives as the rule cannot replace to select between calls to pluck on an ActiveRecord::Relation instance vs a call to pluck on an Array instance.

Examples

# bad
Post.where(user_id: User.active.pluck(:id))

# good
Post.where(user_id: User.active.select(:id))
Post.where(user_id: active_users.select(:id))

EnforcedStyle: conservative (default)

# good
Post.where(user_id: active_users.pluck(:id))

EnforcedStyle: aggressive

# bad
Post.where(user_id: active_users.pluck(:id))

Further Reading

• RuboCop - Rails/PluckInWhere