I'm currently using
puts #object.inspect
to debug the results of queries in rails, but the output doesn't seem to include any joins I've defined for the query. How do I get the full array to show?
For example, if I do the following
#object = Object.joins("JOIN associations ON associations.id = object.association_id")
.where(:id => params[:object_id])
.select("objects.*, associations.*")
.first
puts #object.inspect
I get the all the Object fields in my debug array, but none of the association fields. Yet they are there when I try to use them in my view (#object.association_field etc)
PS - the above query looks ugly, I'm only trying to pull one record, but I was getting various errors if I tried to use .find() instead of .where().first. Suggestions welcome on how to make it more railsy
Why not the simplest possible way:
#object = Object.find(params[:object_id])
#association = #object.associations.first
puts "#{#object.inspect}, #{#association.inspect}"
(assuming that has_many :associations is defined in Object)
And the reason you are not getting fields for association is because the only thing that joins does is joining to another table in SQL. It does not fetch joined data. select only select subset of object's attributes, I think the rest is just ignored.
Related
I'm not sure if this is just a lacking of the Rails language, or if I am searching all the wrong things here on Stack Overflow, but I cannot find out how to add an attribute to each record in an array.
Here is an example of what I'm trying to do:
#news_stories.each do |individual_news_story|
#user_for_record = User.where(:id => individual_news_story[:user_id]).pluck('name', 'profile_image_url');
individual_news_story.attributes(:author_name) = #user_for_record[0][0]
individual_news_story.attributes(:author_avatar) = #user_for_record[0][1]
end
Any ideas?
If the NewsStory model (or whatever its name is) has a belongs_to relationship to User, then you don't have to do any of this. You can access the attributes of the associated User directly:
#news_stories.each do |news_story|
news_story.user.name # gives you the name of the associated user
news_story.user.profile_image_url # same for the avatar
end
To avoid an N+1 query, you can preload the associated user record for every news story at once by using includes in the NewsStory query:
NewsStory.includes(:user)... # rest of the query
If you do this, you won't need the #user_for_record query — Rails will do the heavy lifting for you, and you could even see a performance improvement, thanks to not issuing a separate pluck query for every single news story in the collection.
If you need to have those extra attributes there regardless:
You can select them as extra attributes in your NewsStory query:
NewsStory.
includes(:user).
joins(:user).
select([
NewsStory.arel_table[Arel.star],
User.arel_table[:name].as("author_name"),
User.arel_table[:profile_image_url].as("author_avatar"),
]).
where(...) # rest of the query
It looks like you're trying to cache the name and avatar of the user on the NewsStory model, in which case, what you want is this:
#news_stories.each do |individual_news_story|
user_for_record = User.find(individual_news_story.user_id)
individual_news_story.author_name = user_for_record.name
individual_news_story.author_avatar = user_for_record.profile_image_url
end
A couple of notes.
I've used find instead of where. find returns a single record identified by it's primary key (id); where returns an array of records. There are definitely more efficient ways to do this -- eager-loading, for one -- but since you're just starting out, I think it's more important to learn the basics before you dig into the advanced stuff to make things more performant.
I've gotten rid of the pluck call, because here again, you're just learning and pluck is a performance optimization useful when you're working with large amounts of data, and if that's what you're doing then activerecord has a batch api you should look into.
I've changed #user_for_record to user_for_record. The # denote instance variables in ruby. Instance variables are shared and accessible from any instance method in an instance of a class. In this case, all you need is a local variable.
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 need to do some bulk updates in some models and set value of a field as value of another field.
Right now I can do that with raw sql like this:
ActiveRecord::Base.connection.execute("UPDATE `deleted_contents` SET `deleted_contents`.`original_id` = `deleted_contents`.`id` WHERE `deleted_contents`.`original_id` is NULL")
This is working fine, however I need to do this using ActiveRecord query interface due to many reasons.
I tried:
DeletedContent.where(original_id: nil).update_all(original_id: value_of_id_column)
For value_of_id_column I tried :id, self.id, id, etc, nothing works. What should I set for value_of_id_column to get the original query generated by rails? Is this possible, or using the raw sql is the only solution?
Also I do not want to iterate over each record and update. This is not a valid solution for me:
DeletedContent.where(original_id: nil).each do |deleted_content|
update_each_record
end
I'm pretty sure you cannot obtain that query by passing a hash to update_all.
The closest to what you want to obtain would be:
DeletedContent.where(original_id: nil).update_all("original_id = id")
I'm trying to make an sql query using activerecord and I'm having a hard time specifying a specific column from multiple joined tables.
for instance in sql
select go.id, sequence.name, sequence.id from sequence join (goterms,...) on ...
this is not beautiful sql but my point is that I'm able to specify which .id I want returned
in activerecord I'm doing this:
results = Sequence.joins(:Foreigndb,:Goterm,:Taxa)
.select(:header,:taxaclass, :genus, :interpro_desc,:description,:dbname,:read_depth, :name)
.distinct
I want to be able to get id from :Goterm but :Taxa and :Foreigndb also use id as a column in the database so i'm getting uninformative errors that I assume stem from this issue when I do the following.
results = Sequence.joins(:Foreigndb,:Goterm,:Taxa)
.select(:header,:taxaclass, :genus, :interpro_desc,:description,:dbname,:read_depth, :name,:id)
.distinct
What is the correct way to just specify that I want Goterm.id?
edit - Here is the error:
ActiveRecord::StatementInvalid: Mysql2::Error: Unknown column 'Goterm.id' in 'field list'
when I run:
results = Sequence.joins(:Foreigndb,:Goterm,:Taxa).select(:header,:taxaclass,:genus, :interpro_desc,:description,:dbname, :read_depth, :name,'Goterm.id').limit(5).offset(0).dresults = Sequence.joins(:Foreigndb,:Goterm,:Taxa).select(:header,:taxaclass, :genus, :interpro_desc,:description,:dbname, :read_depth, :name,'Goterm.id').limit(5).offset(0).distinct
results = Sequence.joins(:Foreigndb,:Goterm,:Taxa).select(:header,:taxaclass, :genus, :interpro_desc,:description,:dbname,:read_depth, :name, 'sequences.id')
.distinct
It turns out that ilan's answer is correct, however be sure that everything is lower case. I was using 'Goterm.id' to make the selection when it needs to be 'goterm.id'
If anyone else runs into this, I also ran into difficulties grabbing the goterm.id data out of the returned query objects. Each time I called object.id on that return set it would give me something different from what I was expecting. I think the attribute I was expecting was being obscured by something else. To get the data I needed I did the following:
results = Sequence.joins(:Foreigndb,:Goterm,:Taxa).select(:header,:taxaclass, :genus,:interpro_desc,:description,:dbname,:read_depth, :name).distinct
firstRes = results[0]
firstRes.attributes['id']
I write follow code to get one record from the table webeehs:
webeehs_result = Webeeh.find(:all, :conditions=>["webeeh_project_id=#{project_id}"])
Then I want to get one column value from this record, how could I do?
For example, the column name is webeeh_date.
first of all, never EVER write code like that. Building your own conditions as pure strings can leave you vulnerable to SQL injection exploits. If you must do conditions, then do it like this:
:conditions => ["webeeh_project_id = ?", project_id]
if you have a Project model, you should rename the webeeh_project_id column from your Webeeh model into project_id and have an association in your Project model like has_many :webeehs
Then, you won't need to call that find anymore, just do a p = Project.find(id) and then p.webeehs will return the webeehs you need.
the result will be an array which you can iterate through. And to get your webeeh.webeeh_date member, just call it like this:
result.each do |webeeh|
date = webeeh.webeeh_date
end
webeehs_result = Webeeh.findwebeeh_dates
is enough to get all columnn values.
For a different method and performance issues check the following: http://www.stopdropandrew.com/2010/01/28/finding-ids-fast-with-active-record.html
webeeh_result will usually be an array of results for the database.
You can iterate throughit using
webeehs_result.each do |webeeh|
# use "webeeh.webeeh_date" to access the column_name or do whatever you want with it.
end