How to select where ID in Array Rails ActiveRecord without exception

Question

When I have array of ids, like

ids = [2,3,5]

and I perform

Comment.find(ids)

everything works fine. But when there is id that doesn't exist, I get an exception. This occurs generaly when I get list of IDs that match some filter and than I do something like

current_user.comments.find(ids)

This time I may have a valid comment ID, which however does not belong to given User, so it is not found and I get an exception.

I've tried find(:all, ids), but it returns all of the records.

The only way I can do it now is

current_user.comments.select { |c| ids.include?(c.id) }

But that seems to me like super inefficient solution.

Is there better way to select ID in Array without getting exception on non-existing record?

Snowman · Accepted Answer · 2016-07-01 21:10:25Z

255

If it is just avoiding the exception you are worried about, the "find_all_by.." family of functions works without throwing exceptions.

Comment.find_all_by_id([2, 3, 5])

will work even if some of the ids don't exist. This works in the

user.comments.find_all_by_id(potentially_nonexistent_ids)

case as well.

Update: Rails 4

Comment.where(id: [2, 3, 5])

edited Jul 1, 2016 at 21:10

Snowman

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answered Sep 17, 2009 at 23:22

prismofeverything

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7 Comments

Sam Saffron Over a year ago

this is my preferred solution, it seems cleaner than the exception handling route

Omar Qureshi Over a year ago

As another extension to this, should you need to chain complex conditions, you could even do Comment.all(:conditions => ["approved and id in (?)", [1,2,3]])

Jonathan Lin Over a year ago

this will be deprecated in Rails 4: edgeguides.rubyonrails.org/…

Gavin Miller Over a year ago

@JonathanLin is correct, mjnissim's answer should be preferred: stackoverflow.com/a/11457025/33226

Joshua Pinter Over a year ago

This returns an Array instead of an ActiveRecord::Relation, which limits what you can do with it afterwards. Comment.where(id: [2, 3, 5]) does return an ActiveRecord::Relation.

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Jon Schneider · Accepted Answer · 2024-10-01 15:54:10Z

153

Update: This answer is more relevant for Rails 4.x

Do this:

current_user.comments.where(id: [123, "456", "Michael Jackson"])

The stronger side of this approach is that it returns a Relation object, to which you can join more .where clauses, .limit clauses, etc., which is very helpful. It also allows non-existent IDs without throwing exceptions.

edited Oct 1, 2024 at 15:54

Jon Schneider

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answered Jul 12, 2012 at 17:10

mjnissim

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2 Comments

Mark Berry Over a year ago

Thanks for confirming the where syntax when comparing to an array. I thought I might have to code the SQL with an IN statement, but this looks cleaner and is an easy replacement for the deprecated scoped_by_id.

atw Over a year ago

What is this called and how does it work? Is it Rails magic?! As a colleague commented, its like 'comparing an integer with an object list".

Joshua Pinter · Accepted Answer · 2015-04-12 17:35:55Z

29

If you need more control (perhaps you need to state the table name) you can also do the following:

Model.joins(:another_model_table_name)
  .where('another_model_table_name.id IN (?)', your_id_array)

edited Apr 12, 2015 at 17:35

Joshua Pinter

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answered Sep 25, 2014 at 11:42

Jonathan Lin

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3 Comments

Joshua Pinter Over a year ago

Is there any way to keep the order of the your_id_array when you get the objects back?

Jonathan Lin Over a year ago

@JoshPinter I don't think this is a reliable way to expect the database to return things in the same order. Perhaps add a ORDER BY query at the end to ensure the right order of things.

Joshua Pinter Over a year ago

@JonathanLin Thanks for the response Jonathan. You're certainly right. Using an ORDER BY won't work in my situation because the order is not based on an attribute. However, there is a way to do it via SQL (so it's fast) and someone has even created a gem for it. Check out this Q&A: stackoverflow.com/questions/801824/…

Sumit Munot · Accepted Answer · 2014-06-11 23:11:31Z

16

Now .find and .find_by_id methods are deprecated in rails 4. So instead we can use below:

Comment.where(id: [2, 3, 5])

It will work even if some of the ids don't exist. This works in the

user.comments.where(id: avoided_ids_array)

Also for excluding ID's

Comment.where.not(id: [2, 3, 5])

answered Jun 11, 2014 at 23:11

Sumit Munot

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1 Comment

Canna Over a year ago

github.com/rails/activerecord-deprecated_finders .find and .find_by_id methods are NOT deprecated in rails 4.

rogeriopvl · Accepted Answer · 2009-09-17 23:20:15Z

0

To avoid exceptions killing your app you should catch those exceptions and treat them the way you wish, defining the behavior for you app on those situations where the id is not found.

begin
  current_user.comments.find(ids)
rescue
  #do something in case of exception found
end

Here's more info on exceptions in ruby.

answered Sep 17, 2009 at 23:20

rogeriopvl

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2 Comments

Jakub Arnold Over a year ago

yep this solves the problem, but it's not really a clean solution

Haegin Over a year ago

If you're going to catch an exception you should declare the exception you expect to catch, otherwise you risk it catching something you weren't expecting and hiding an actual problem.

mtfk · Accepted Answer · 2010-09-08 15:53:08Z

0

You can also use it in named_scope if You want to put there others conditions

for example include some other model:

named_scope 'get_by_ids', lambda { |ids| { :include => [:comments], :conditions => ["comments.id IN (?)", ids] } }

answered Sep 8, 2010 at 15:53

mtfk

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