I generated the following using a Keyword extraction API
(I searched for "Hitler" because no one is trying to sell you things when you search for him.)
x=[{"relevance"=>"0.592174", "text"=>"eight-year-old Hitler"}, {"relevance"=>"0.589796", "text"=>"Hitler states"}, {"relevance"=>"0.589118", "text"=>"Hitler lived."}, {"relevance"=>"0.585102", "text"=>"Hitler learnt"}, {"relevance"=>"0.580278", "text"=>"Hitler Youth"}, {"relevance"=>"0.414842", "text"=>"German Workers"}, {"relevance"=>"0.413532", "text"=>"German military leaders"}, {"relevance"=>"0.404701", "text"=>"nazi party"}, {"relevance"=>"0.391943", "text"=>"Mein Kampf"}, {"relevance"=>"0.388932", "text"=>"Reichstag"}, ]
So the database should have :
Eight-year-old hitler
Hitler states
...
I've tried x.each do |x| and
x.to_a.each do
x["text"]
x
None of which work.
Since you haven't given the following information, I will make some assumptions:
Database table name
Schema for table
Model name
ORM
Let's rename x to search_results. Let's also assume that we have a table in the database called search_results, a model called SearchResult, that the search_results table has a column called text, and that we are using ActiveRecord as the ORM:
search_results.each do |data|
SearchResult.create(text: data[:text])
end
Or since you have an array of hashes, simply:
SearchResult.create(search_results)
Related
I have a set of legacy database tables that i cannot normalize out to what should have been done in the first place. e.g one big table with 200 columns.
I'm building an API and would like to represent this data to the consumer in a better state, and perhaps address the database issues at a later stage, there are many backend systems that reply on the data and changes are not easy.
I wanted to represent the current database schema using Active Record, however perform a model transformation into a new model that will be used for presentation only to an API consumer as json data.
current database schema:
Products table (200 columns)
New Model:
Product
+ Pricing
+ Assets
+ Locations
+ Supplier
I could hard-code a json string in a template, but feel that would not be a very poor approach.
What approach or gem would you recommend to tackle this best?
I have looked at :
RABL
ActiveModel::Serializers
If you define an as_json method that returns a hash, ActiveRecord will take care of the serialization for you. E.g.
class Product < ActiveRecord::Base
def as_json options = {}
{
product: <product value>,
pricing: <pricing value>,
# ... etc.
}
end
end
Now you can do:
> Product.first.to_json
=> "{\"product\":<product_value> ... }"
You can even render these as json from the controllers via:
render json: #model
I am using the pg_array extension and sequel version 4.1.1.
I have added the extension like this:
Sequel::Database.extension :pg_array
I have created a column like this:
alter_table :emails do
add_column :references, "text[]", null: true
end
I can load and retrieve arrays into a postgress array column, just like working with normal arrays.
What is not clear from the above link is how do I execute a query based on the values in this array column.
For example, if one row in the emails table contained these values in the references column:
references
--------------------------------------------------------------------
{}
{5363f773bccf9_32123fe75c45e6f090953#Pauls-MacBook-Pro.local.mail}
How can I query the emails table to find a row that contains a references array value of the above value:
Email.where(references: ????)
Use the pg_array_ops extension:
Sequel.extension :pg_array_ops
Email.where(Sequel.pg_array_op(:references).contains('5363f773bccf9_32123fe75c45e6f090953#Pauls-MacBook-Pro.local.mail'))
Have you tried?
ref = '5363f773bccf9'
emails = Email.arel_table
Email.where( emails[ :references ].matches( "%#{ref}%" ))
I have two models with the appropriate foreign key created in the people table:
class Person < ActiveRecord::Base
belongs_to :family
class Family < ActiveRecord::Base
has_many :people
If I do the following I get an object - #family_members - as an instance variable and I have no problems:
#family_members = Family.find(1)
I can access the 'child' people table fields easily in my view:
#family_members.people.first_name
However, if I use the arel way with "where" etc. I get an "ActiveRecord::Relation", not a normal object, which leaves me stumped as to how to access the same "first_name" field form the people table like I accessed above:
#family_members = Family.where(:id => 1)
or even
#family_members = Family.joins(:people).where(:id => 1)
(is the "joins" even required??)
I understand that using ".first" will cause the query to run:
#family_members = Family.where(:id => 1).first
But it returns an array, not an object, so if I use in my view:
#family_members.people.first_name
I get a "method 'people' unknown" error.
How can I access the 'first_name' field of the people table like I did with the object created by "find" but using an ActiveRecord relation?
* added information 7/15 ********
To clarify what I am looking for -- here is what I would have written if I were writing SQL instead of Arel:
SELECT f.home_phone, f.address, p.first_name, p.last_name, p.birthday
FROM families f INNER JOIN people p ON p.family.id = f.id WHERE family_id = 1
With that query's results loaded into a result set I could access:
myResultSet("home_phone") -- the home_phone from the families table
myResultSet("address") -- the address from the families table
myResultSet("first_name") -- the first_name from the people table
myResultSet("birthdate") -- the birthdate from the people table
If the two tables in the query have a same-named field I would just use "AS" to request one of the fields by another name.
I have used this kind of query/result set for many years in web apps and I am trying to deduce how to do the same in Rails and ActiveRecord.
#family_members.people.first_name shouldn't ever work so I'm surprised you find it working ... #family_members contains a Family object, #family_members.people is an array of Person objects.
The fact that you're calling it #family_members seems to make me think you're expecting it to be an array of Persons... in which case the correct code would be...
#family_members = Family.find(1).people # finds people in first Family object
If you expect #family_members to contain just the first family member, then...
#family_members = Family.find(1).people.first
If you want an array of first names of all family members, then...
#family_members = Family.find(1).people # finds people in 1st Family object
#family_members.map {|member| member.first_name} # array of first_name
#family_members = Family.find(1) and #family_members = Family.where(:id => 1) are functionally identical.. both retrieve the first Family object in the database in each case may contain zero, one, or multiple people.
Just to be clear, the "1" in all examples above refer to which Family object is retrieved, not which Person in the Family.
I have a table named subs which has many articles. The articles table has a timestamp column called published.
Sub.select( "subs.*,MAX(articles.published) published").joins("LEFT OUTER JOIN articles ON subs.id=articles.sub_id").group("subs.id").first.published.class
=> String
Article.select("max(published) published").group("id").first.published.class
=> ActiveSupport::TimeWithZone
I want to get an ActiveSupport::TimeWithZone object back from the first query.
Rails 3
Rails determines how to type cast attributes based on their database column definitions. For example, say you have a created_at method on your Sub model. When a record is loaded read_attribute is used (ActiveRecord::AttributeMethods::Read). This uses type_cast_attribute which determines how to cast the value based on the column info. For example, if you are using PostgreSQL it may use:
Sub.columns.detect { |c| c.name == "created_at" }.type_cast_code("v")
=> "ActiveRecord::ConnectionAdapters::PostgreSQLColumn.string_to_time(v)"
But Rails doesn't know what to do with columns that aren't on the Sub model. So it just gives back a String. If you need to work with a ActiveSupport::TimeWithZone object, you can cast the value with:
published = Sub.select( "subs.*,MAX(articles.published) published").joins("LEFT OUTER JOIN articles ON subs.id=articles.sub_id").group("subs.id").first.published
published.present? ? Time.zone.parse(published) : nil
Rails 4
In Rails 4, Rails is smarter about this kind of type-casting. When the SQL is executed, ActiveRecord::Result is created and the column_types are passed to the initializer. In your example Sub.select query, the published column would be cast as a Time object.
Is there a Ruby, or Activerecord method that can write and read a hash to and from a database field?
I need to write a web utility to accept POST data and save it to a database, then later on pull it from the database in its original hash form. But ideally without 'knowing' what the structure is. In other words, my data store needs to be independent of any particular set of hash keys.
For example, one time the external app might POST to my app:
"user" => "Bill",
"city" => "New York"
But another time the external app might POST to my app:
"company" => "Foo Inc",
"telephone" => "555-5555"
So my utility needs to save an arbitrary hash to a text field in the database, then, later, recreate the hash from what was saved.
Rails 4 adds support for the Postgres hstore data type which will let you add hashes directly into your (postgres) database.
If you are using Rails 4 and Postgres, you can use hstore in your migration:
def up
execute "create extension hstore"
add_column :table, :column, :hstore
end
def down
remove_column :table, :column
end
That execute command will enable hstore in Postgres, so you only have to do that once.
This will enable you to store a hash in :column just like you would any other data type.
There are two ways to do this:
Serialize your hash and store it in a text field.
Split the hash and store each key in a separate row.
The problem with the first approach is that finding and manipulating is difficult and expensive. For example, prefix a "0" before the telephone number of all employees working in Foo Inc. will be a nightmare, compared to storing the data in regular tabular format.
Your schema would be:
employees (id, created_at, updated_at)
employee_details (id, employee_id, key, value)
So, to store
"company" => "Foo Inc",
"telephone" => "555-5555"
you would do:
employees: 1, 2012-01-01, 2012-01-01
employee_details (1, 1, "company", "Foo Inc"), (2, 1, "telephone", "555-5555")
Drawbacks of this approach: Rails does not natively support such kind of a schema.
You can use serialization with 3 options: Marshal in binary format, YAML and JSON human-readable formats of data store.
Once you are trying each of methods, do not forget to measure time to serialize and deserialize as well. If you need to pull data back in origin format, JSON is the good choice to use, because you don't need to deserialize it, but use it as a string itself.
You're looking for serialization. It will help you to do exactly what you want.
Rails 4 has a new feature called Store, so you can easily use it to solve your problem. You can define an accessor for it and it is recommended you declare the database column used for the serialized store as a text, so there's plenty of room. The original example:
class User < ActiveRecord::Base
store :settings, accessors: [ :color, :homepage ], coder: JSON
end
u = User.new(color: 'black', homepage: '37signals.com')
u.color # Accessor stored attribute
u.settings[:country] = 'Denmark' # Any attribute, even if not specified with an accessor
# There is no difference between strings and symbols for accessing custom attributes
u.settings[:country] # => 'Denmark'
u.settings['country'] # => 'Denmark'