I have a user model with a friends column of type text. This migration was ran to use the array feature with postgres:
add_column :users, :friends, :text, array: true
The user model has this method:
def add_friend(target)
#target would be a value like "1234"
self.friends = [] if self.friends == nil
update_attributes friends: self.friends.push(target)
end
The following spec passes until I add user.reload after calling #add_friend:
it "adds a friend to the list of friends" do
user = create(:user, friends: ["123","456"])
stranger = create(:user, uid: "789")
user.add_friend(stranger.uid)
user.reload #turns the spec red
user.friends.should include("789")
user.friends.should include("123")
end
This happens in development as well. The model instance is updated and has the new uid in the array, but once reloaded or reloading the user in a different action, it reverts to what it was before the add_friend method was called.
Using Rails 4.0.0.rc2 and pg 0.15.1
What could this be?
I suspect that ActiveRecord isn't noticing that your friends array has changed because, well, the underlying array reference doesn't change when you:
self.friends.push(target)
That will alter the contents of the array but the array itself will still be the same array. I know that this problem crops up with the postgres_ext gem in Rails3 and given this issue:
String attribute isn't marked as dirty, when it changes with <<
I'd expect Rails4 to behave the same way.
The solution would be to create a new array rather than trying to modify the array in-place:
update_attributes friends: self.friends + [ target ]
There are lots of ways to create a new array while adding an element to an existing array, use whichever one you like.
It looks like the issue might be your use of push, which modifies the array in place.
I can't find a more primary source atm but this post says:
One important thing to note when interacting with array (or other mutable values) on a model. ActiveRecord does not currently track "destructive", or in place changes. These include array pushing and poping, advance-ing DateTime objects. If you want to use a "destructive" update, you must call <attribute>_will_change! to let ActiveRecord know you changed that value.
If you want to use Postgresql array type, you'll have to comply with its format. From Postgresql docs the input format is
'{10000, 10000, 10000, 10000}'
which is not what friends.to_s will return. In ruby:
[1,2,3].to_s => "[1,2,3]"
That is, brackets instead of braces. You'll have to do the conversion yourself.
However I'd much rather rely on ActiveRecord serialize (see serialize). The database does not need to know that the value is actually an array, that's your domain model leaking into your database. Let Rails do its thing and encapsulate that information; it already knows how to serialize/deserialize the value.
Note: This response is applicable to Rails 3, not 4. I'll leave here in case it helps someone in the future.
Related
I’m using Rails 4.2.7. How do I mass update a field of an array of my models without actually saving that information to the database? I tried
my_objcts_arr.update_all(my_object: my_object)
but this results in the error
NoMethodError: undefined method `update_all' for #<Array:0x007f80a81cae50>
I realize I could iteraet over the array and update each object individually, but I figure there's a slicker, one-line way in Ruby taht I'm not aware of.
update_all needs to be called on a class level active record model/relation, ie User or TaxReturn. Here is one somewhat related SO post showing some examples, and here is the api doc for update_all. It will send the UPDATE directly to the db (it is an active record method, after all), so it is not what you want.
You're best off iterating and updating the value yourself with collect or something similar, which is only one line.
foo = [{:a=>"a", :b=>"b"}, {:a=>"A", :b=>"B:}]
// => [{:a=>"a", :b=>"b"}, {:a=>"A", :b=>"B"}]
foo.collect{|x| x[:a]="C"}
// => ["C", "C"]
foo
// => [{:a=>"C", :b=>"b"}, {:a=>"C", :b=>"B"}]
I'm using Rails4's Store feature. I've added a new stored attributes namely "friends" with four accessors, first ... fourth.
The problem is how to utilize it in the "where" condition. When I use it as:
#persons = Person.where(friends.has_value?#user.id)
I receive this error:
NameError in UsersController#myfrineds
undefined local variable or method `friends'
I tried some other different ways but still I get error. Could you please help me to solve it? Or please let me know if you have any better idea to implement it (storing a dynamic hash of key/values)?
As stated by Uzbekjon, store is not made for this kind of things. Some workarounds to your problem:
Use a custom query (would be quite slow depending on table size so be careful):
#persons = Person.where('friends LIKE ? OR friends LIKE ? OR friends LIKE ? OR friends LIKE ?', "%first: #{#person.id}\n%", "%second: #{#person.id}\n%", "%third: #{#person.id}\n%", "%fourth: #{#person.id}\n%")
This assumes you used yaml for the serialization of friends attribute (it's the default). If you used json you'll have to change the query accordingly.
If you're using PostgreSQL you can use array attribute instead of store. Queries would have better timings since PostgreSQL supports this datatype.
Migration:
def change
add_column :people, :friends, :text, array: true, default: []
# if you want to add index:
add_index :people, :friends, using: 'gin'
end
Creation of records:
Person.create(..., friends: [friend_id_1, friend_id_2, friend_id_3, friend_id_4])
Query:
#persons = Person.where('? = ANY(friends)', #person.id)
You may also need to add to your Gemfile:
gem 'postgres_ext'
Hope it helps!
Short answer - You can't! Because, ActiveRecord stores your "hash" as a string in a single column. The only way I can think of is to use .where("friends LIKE :friend", friend: 'BFF') syntax. Don't forget to index your column though.
It is mentioned in the docs as well:
It's like a simple key/value store baked into your record when you don't care about being able to query that store outside the context of a single record.
I have a user model with a friends column of type text. This migration was ran to use the array feature with postgres:
add_column :users, :friends, :text, array: true
The user model has this method:
def add_friend(target)
#target would be a value like "1234"
self.friends = [] if self.friends == nil
update_attributes friends: self.friends.push(target)
end
The following spec passes until I add user.reload after calling #add_friend:
it "adds a friend to the list of friends" do
user = create(:user, friends: ["123","456"])
stranger = create(:user, uid: "789")
user.add_friend(stranger.uid)
user.reload #turns the spec red
user.friends.should include("789")
user.friends.should include("123")
end
This happens in development as well. The model instance is updated and has the new uid in the array, but once reloaded or reloading the user in a different action, it reverts to what it was before the add_friend method was called.
Using Rails 4.0.0.rc2 and pg 0.15.1
What could this be?
I suspect that ActiveRecord isn't noticing that your friends array has changed because, well, the underlying array reference doesn't change when you:
self.friends.push(target)
That will alter the contents of the array but the array itself will still be the same array. I know that this problem crops up with the postgres_ext gem in Rails3 and given this issue:
String attribute isn't marked as dirty, when it changes with <<
I'd expect Rails4 to behave the same way.
The solution would be to create a new array rather than trying to modify the array in-place:
update_attributes friends: self.friends + [ target ]
There are lots of ways to create a new array while adding an element to an existing array, use whichever one you like.
It looks like the issue might be your use of push, which modifies the array in place.
I can't find a more primary source atm but this post says:
One important thing to note when interacting with array (or other mutable values) on a model. ActiveRecord does not currently track "destructive", or in place changes. These include array pushing and poping, advance-ing DateTime objects. If you want to use a "destructive" update, you must call <attribute>_will_change! to let ActiveRecord know you changed that value.
If you want to use Postgresql array type, you'll have to comply with its format. From Postgresql docs the input format is
'{10000, 10000, 10000, 10000}'
which is not what friends.to_s will return. In ruby:
[1,2,3].to_s => "[1,2,3]"
That is, brackets instead of braces. You'll have to do the conversion yourself.
However I'd much rather rely on ActiveRecord serialize (see serialize). The database does not need to know that the value is actually an array, that's your domain model leaking into your database. Let Rails do its thing and encapsulate that information; it already knows how to serialize/deserialize the value.
Note: This response is applicable to Rails 3, not 4. I'll leave here in case it helps someone in the future.
I'm working with Rails 4.1.0, Ruby 2.1.0, and Postgres 9.3.0.0.
I'm trying to save changes to a column which is an array of hstores (an array of hashes in ruby parlance).
Here's the (simplified) code in the product model, used for saving the changes:
def add_to_cart_with_credits(cart)
cart.added_product_hashes << {"id" => self.id.to_s, "method" => "credits"}
# For some reason, this isn't saving (without the exclamation, as well)
cart.save!
end
A few things of note:
The cart is initialised with an empty array in the added_product_hashes column
I'm storing added products as hashes because there are a couple of ways to add products to the cart, and they each require their own logic to remove and customise.
Each user has their own cart, and needs to reference it later, which is why carts are saved to the DB like this (instead of using a session variable, I guess).
Any ideas what I'm doing wrong? I'm not seeing an error: the server logs note that the cart.added_product_hashes column updates correctly, but the changes don't persist.
SOLUTION
As James pointed out, << doesn't flag the record as being dirty, as it edits the array in-place. While I wasn't changing the hstores themselves within the array column, it appears that changes to the enclosing array aren't picked up unless the attribute is explicitly reconstructed. The below code fixes the problem:
def add_to_cart_with_credits(cart)
cart.added_product_hashes = cart.added_product_hashes + [{"id" => self.id.to_s, "method" => "credits"}]
# Now we're all good to go!
cart.save!
end
James also suggests a particular method that would be more terse.
See "New data not persisting to Rails array column on Postgres"
ActiveRecord isn't recognizing the change to the array as attributes are being updated in place.
You can also do something like this:
cart.added_product_hashes_will_change!
I have a user model with a friends column of type text. This migration was ran to use the array feature with postgres:
add_column :users, :friends, :text, array: true
The user model has this method:
def add_friend(target)
#target would be a value like "1234"
self.friends = [] if self.friends == nil
update_attributes friends: self.friends.push(target)
end
The following spec passes until I add user.reload after calling #add_friend:
it "adds a friend to the list of friends" do
user = create(:user, friends: ["123","456"])
stranger = create(:user, uid: "789")
user.add_friend(stranger.uid)
user.reload #turns the spec red
user.friends.should include("789")
user.friends.should include("123")
end
This happens in development as well. The model instance is updated and has the new uid in the array, but once reloaded or reloading the user in a different action, it reverts to what it was before the add_friend method was called.
Using Rails 4.0.0.rc2 and pg 0.15.1
What could this be?
I suspect that ActiveRecord isn't noticing that your friends array has changed because, well, the underlying array reference doesn't change when you:
self.friends.push(target)
That will alter the contents of the array but the array itself will still be the same array. I know that this problem crops up with the postgres_ext gem in Rails3 and given this issue:
String attribute isn't marked as dirty, when it changes with <<
I'd expect Rails4 to behave the same way.
The solution would be to create a new array rather than trying to modify the array in-place:
update_attributes friends: self.friends + [ target ]
There are lots of ways to create a new array while adding an element to an existing array, use whichever one you like.
It looks like the issue might be your use of push, which modifies the array in place.
I can't find a more primary source atm but this post says:
One important thing to note when interacting with array (or other mutable values) on a model. ActiveRecord does not currently track "destructive", or in place changes. These include array pushing and poping, advance-ing DateTime objects. If you want to use a "destructive" update, you must call <attribute>_will_change! to let ActiveRecord know you changed that value.
If you want to use Postgresql array type, you'll have to comply with its format. From Postgresql docs the input format is
'{10000, 10000, 10000, 10000}'
which is not what friends.to_s will return. In ruby:
[1,2,3].to_s => "[1,2,3]"
That is, brackets instead of braces. You'll have to do the conversion yourself.
However I'd much rather rely on ActiveRecord serialize (see serialize). The database does not need to know that the value is actually an array, that's your domain model leaking into your database. Let Rails do its thing and encapsulate that information; it already knows how to serialize/deserialize the value.
Note: This response is applicable to Rails 3, not 4. I'll leave here in case it helps someone in the future.