I have a model, Student, that with a habtm relationship with another model, Group. The following code:
Student.ransack(groups_id_eq: 22839).result
Produces the following SQL:
SELECT "students".* FROM "students"
LEFT OUTER JOIN "groups_students" ON "groups_students"."student_id" = "students"."id"
LEFT OUTER JOIN "groups" ON "groups"."id" = "groups_students"."group_id"
WHERE "groups"."id" = NULL
Notice that it's converting 22839 into NULL
This was working before upgrading to rails 5.
I have another model, User, with the same habtm relationship with groups. When I try Student.ransack(groups_id_eq: 22839).result it works and produces the desired SQL. The difference between two models is that Student has a uuid id, whereas User
Edit: This does appear to be a bug and I've submitted an issue with a more comprehensive gist.
I have resolved the issue by monkey patching ActiveRecord AliasTracker.
See my gh issue for the full explanation.
Related
I'm running the following query in Rails 5, with the goal of finding the user with the most Pitches:
User
.select("users.*, COUNT(user_id) as pitch_count")
.unscoped
.joins("LEFT JOIN pitches AS pitches ON pitches.user_id = users.id")
.group("pitch.user_id")
.order("pitch_count DESC")
.limit(5)
But I'm getting the error:
Caused by PG::UndefinedColumn: ERROR: column "pitch_count" does not exist
Why isn't the query orderable by pitch_count?
Problem is in the unscoped method. It removes all previously defined scopes including select statement. See the following example:
User.select(:full_name, :email).unscoped.to_sql
# => SELECT "users".* FROM "users"
User.unscoped.select(:full_name, :email).to_sql
# => SELECT "users"."full_name", "users"."email" FROM "users"
See the difference? unscoped called after select definition completely removed every thing defined in the select.
For you this means that you should modify your code to call unscoped right after the model name:
User
.unscoped
.select("users.*, COUNT(user_id) as pitch_count")
.joins("LEFT JOIN pitches AS pitches ON pitches.user_id = users.id")
.group("pitch.user_id")
.order("pitch_count DESC")
.limit(5)
Note: new lines added mostly for readability but it should work like this in your ruby files. If you want to execute it in the rails console. You will have to remove new lines
Btw. you still might get error that column "user.id" must appear in the GROUP BY clause or be used in an aggregate function. It should be fixed by modifying group statement to use users.id instead of pitch.user_id:
.group("users.id")
I suggest you use counter_cache to make it easy to maintain and good for performance as well. By adding counter cache, you can get the user record with most pitches by User.reorder(pitches_count: :desc).first.
When I do includes it left joins the table I want to filter on, but when I add pluck that join disappears. Is there any way to mix pluck and left join without manually typing the sql for 'left join'
Here's my case:
Select u.id
From users u
Left join profiles p on u.id=p.id
Left join admin_profiles a on u.id=a.uid
Where 2 in (p.prop, a.prop, u.prop)
Doing this is just loading all the values:
Users.includes(:AdminProfiles, :Profiles).where(...).map{ |a| a[:id] }
But when I do pluck instead of map, it doesn't left join the profile tables.
Your problem is that you're using includes which doesn't really do a join, instead it fires a second query after the first one to query for the associations, in your case you want them both to be actually joined, so for that replace includes(:something) with joins(:something) and every thing should work fine.
Replying to your comment, i'm gonna quote few parts from the rails guide about active record query interface
From the section Solution to N + 1 queries problem
clients = Client.includes(:address).limit(10)
clients.each do |client|
puts client.address.postcode
end
The above code will execute just 2 queries, as opposed to 11 queries in the previous case:
SELECT * FROM clients LIMIT 10
SELECT addresses.* FROM addresses WHERE (addresses.client_id IN (1,2,3,4,5,6,7,8,9,10))
as you can see, two queries, no joins at all.
From the section Specifying Conditions on Eager Loaded Associations link
Even though Active Record lets you specify conditions on the eager loaded associations just like joins, the recommended way is to use joins instead.
Then an example:
Article.includes(:comments).where(comments: { visible: true })
This would generate a query which contains a LEFT OUTER JOIN whereas the joins method would generate one using the INNER JOIN function instead.
SELECT "articles"."id" AS t0_r0, ... "comments"."updated_at" AS t1_r5 FROM "articles" LEFT OUTER JOIN "comments" ON "comments"."article_id" = "articles"."id" WHERE (comments.visible = 1)
If there was no where condition, this would generate the normal set of two queries.
I searched about how to pass empty array to ransack, for example:
#search = PromotionsRetailer.search(retailer_id_in: [])
This sql statement:
"SELECT `promotions_retailers`.* FROM `promotions_retailers` "
I found this link, to add -1 to empty array, so i used search(retailer_id_in: ([] + [-1])).
Any solution is better than this solution?
How to search using retailer_id in promotion table, if i have many-to-many relation between promotions/retailers without using breaking table PromotionsRetailer by ransack gem?
First part of question is vital. This should be a separate question.
Unfortunately, there in no more elegant way to cope with it, than:
search(retailer_id_in: ([] + [-1]))
The problem lays somewhere in the gem. And if you pass empty array, or array filled with nil values as a parameter, there will be join in SQL, but all the conditions will be ignored, e.g.:
Ruby:
Article.ransack({authors_id_in: [nil, nil, nil]}).result
SQL:
SELECT "articles".* FROM "articles" LEFT OUTER JOIN "articles_authors" ON "articles_authors"."article_id" = "articles"."id" LEFT OUTER JOIN "authors" ON "authors"."id" = "articles_authors"."author_id"
Your second part of question is about searching through HABTM relations using ransack, which is explained in Rails 3.1 Ransack HABTM pretty good.
Therefore:
Promotion.ransack({retailer_id_in: [1,2,3]}).result
You should not use PromotionsRetailer class itself.
I'm trying to find the best way to count the number of Users who have one (or many) instances of a has_many relation.
For example, User has_many :bank_accounts and :credit_accounts (and a few other relations). I want to find the number of unique Users who have at least one bank_account and at least one credit_account, and ideally implement this inside of a scope so I can run where queries on it.
At the moment I'm implementing it (poorly) using the following code:
(BankAccount.select(:user_id).uniq + CreditAccount.select(:user_id) + ...).uniq.count
I've played around a lot with some joins, however I'm not getting any results. For example, I've toyed around a lot with different forms of User.joins(:bank_accounts, :credit_accounts).uniq('users.id').count however I don't appear to be getting any results.
Any help would be greatly appreciated, thanks!
If you are fine with using normal sql. You can use the below query
select distinct(user_id) from
(select user_id from bank_accounts union select user_id from credit_accounts) a;
I am not sure if a rails way exists for this.
In this case all we need is an INNER JOIN of users with credit_accounts and bank_accounts.
User.joins(:credit_accounts, :bank_accounts).uniq.count
The above query works for me. The sql generated by this query is below
"SELECT DISTINCT COUNT(DISTINCT `users`.`id`) FROM `users`.* FROM `users` INNER JOIN `credit_accounts` ON `credit_accounts`.`user_id` = `users`.`id` INNER JOIN `bank_accounts` ON `bank_accounts`.`user_id` = `users`.`id`"
That title is a bit obtuse, so here's an example. Suppose we have a Rails 3 app with models Ship, Pirate, and Parrot. A ship has_many pirates, and a pirate has_many parrots.
Ship.includes(pirates: :parrots).where('parrots.name LIKE ?', '%polly%')
This returns ships having at least one pirate with at least one parrot whose name is like "polly". I would also like it to eager-load all of the pirates and parrots for those ships... but in reality only the pirates with matching parrots are eager-loaded, and among those, only the matching parrots are eager-loaded. The generated SQL is something like this:
SELECT ships.id AS t0_r0, ships.name AS t0_r1, pirates.id AS t1_r0, pirates.name AS t1_r1, parrots.id AS t2_r0, parrots.name AS t2_r1 FROM ships LEFT OUTER JOIN pirates ON pirates.ship_id = ships.id LEFT OUTER JOIN parrots ON parrots.pirate_id = pirates.id WHERE (parrots.name LIKE '%polly%')
When doing Ship.includes(pirates: :parrots) without the condition, ActiveRecord generates a bundle of queries that is somewhat closer to what I want:
SELECT ships.* FROM ships
SELECT pirates.* FROM pirates WHERE pirates.ship_id IN (ship IDs from previous query)
SELECT parrots.* FROM parrots WHERE parrots.pirate_id IN (pirate IDs from previous query)
If I could somehow change that first query to use the SQL from the first example, it would do exactly what I want:
SELECT ships.* FROM ships LEFT OUTER JOIN pirates ON pirates.ship_id = ships.id LEFT OUTER JOIN parrots ON parrots.pirate_id = pirates.id WHERE (parrots.name LIKE '%polly%')
SELECT pirates.* FROM pirates WHERE pirates.ship_id IN (ship IDs from previous query)
SELECT parrots.* FROM parrots WHERE parrots.pirate_id IN (pirate IDs from previous query)
But I'm not aware of any way to get ActiveRecord to do this, or any way to do it myself and "manually" wire up the eager-loading (which is necessary in my situation to avoid an N+1 query explosion). Any ideas or advice would be appreciated.
Ship.joins(pirates: :parrots).where('parrots.name LIKE ?', '%polly%').preload(pirates: :parrots)
requires rails 3+
If INNER JOIN is what you're looking for, I think
Ship.includes(pirates: :parrots).where('parrots.name LIKE ?', '%polly%').joins(pirates: :parrots)
gets it done.