I create Rails APP and I would like to fetch data batch starting from specific point. I use AR and my table structure looks following:
create_table(:types) do |t|
t.string :name, null: false
t.string :type, null: false
t.string :type_id, null: false
t.text :metadata
t.timestamps
end
To get data I use type_id which is in following format (GUID):
"b2d506fd-409d-4ec7-b02f-c6d2295c7edd"
I would like to fetch specific count of data, ascending or descending ,starting from specific type_id. To be more specific I want do do something like this:
Model.get_batch(type_id: type, count: 20).desc
Can I do it simply in ActiveRecord?
You can use ActiveRecord::Batches to find records in batches
example
Model.where('your condition').find_in_batches(start: 2000, batch_size: 2000) do |group|
# do something with batch
end
check also ActiveRecord::Batches.find_in_batch
You can do like following
Model.find_by_type_id(type).offset(batch_offset).limit(amount_in_batch)
Or as on answer above
Model.where(type_id: your_value).find_in_batches(start: 2000, batch_size: 2000) do |group|
# do something with batch
end
Related
I have the following example:
#ads = Ad.all
I need to sort by popularity so it is based on two integer columns: contacts_count and visualizations.
I want to know if there is any of these options:
1) List first the ads with the most number of contacts and to the records with contacts_count = 0 show the records sorted by visualizations number.
2) Somehow attribute weighs to the two fields like: 5 to contacts and 3 to visualizations or something like that and sort by relevance by this.
How can I do this with active record or any search gem?
schema.rb
create_table "ads", force: :cascade do |t|
t.string "photo"
t.text "description"
t.string "category"
t.integer "user_id"
t.integer "visualizations", default: 0
t.integer "contacts_count", default: 0
t.index ["user_id"], name: "index_ads_on_user_id", using: :btree
end
From what I understood from your description, what you need is not searching but sorting.
Short answer:
#ads = Ad.order(:contacts_count, :visualization)
Wait but why?:
list first the ads with the most number of contacts
order first by contacts
to the records with contacts_count = 0 show the records sorted by visualizations number.
This statement is a bit inaccurate, you will use visualizations as a tiebreaker (even in the case of contacts_count = 0 or just equal contacts_count.
I would like to seed my Rails app database with the permutation of an existing array of objects, and am unsure about the best way to go about this.
I currently have a Country model, with the following attributes:
create_table :countries do |t|
t.string :name
t.float :latitude_dec
t.float :longitude_dec
t.timestamps null: false
end
I have seeded this model from a .yaml file (as these attributes are static), and now would like to use these records to seed a CountryPair model (where the attributes are also static). This model will have the following attributes:
create_table :country_pairs do |t|
t.string :country_a
t.string :country_b
t.string :pair_name
t.float :country_a_latitude_dec
t.float :country_b_latitude_dec
t.float :country_a_longitude_dec
t.float :country_b_longitude_dec
t.float :distance
t.timestamps null: false
end
The aim is to permutate the array of Country objects, and create a CountryPair object from each permutation (and seed the database with the output). I understand the Ruby array#permutation method, but am unsure about how to pull out the appropriate values into the new array of CountryPair objects. The order of countries in the pair is important here, so I'd like to use permutations rather than combinations.
Ultimately, I'd also like to calculate the distance between the country pairs, but I'm hoping to start figuring that out once I have the CountryPair model filled!!
This is my first foray back into Rails after a five year absence, so apologies if I've got some of the terminology/methodology wrong - please do ask for clarification if any further information is required! Thanks in advance!
You can add this snippet to your seeds.rb after the Countries are seeded.
Country.all.permutation(2) do |p|
CountryPair.create(
country_a: p[0].name,
country_b: p[1].name,
pair_name: p[0]name + p[1].name,
country_a_latitude_dec: p[0].latitude.dec,
country_b_latitude_dec: p[1].latitude.dec,
country_a_longitude_dec: p[0].longitude.dec,
country_b_longitude_dec: p[1].longitude.dec,
distance: # An algorithm to calculate distance
)
end
Then run it with: rake db:setup
So, I'm using Rails 4, and I have an enum column on my "Sales_Opportunity" object called pipeline_status - this enables me to move it through a sales pipeline (e.g. New Lead, Qualified Lead, Closed deal etc). This all works fine. I'm able to find the number of sales_opportunities that a company has by status through using the following:
<%= #company.sales_opportunities.where(pipeline_status: 3).count %>
This all works fine. What I want to do is to find all sales_opportunities that have the pipeline_status of "closed_won" (enum value of 4 in my app) and sum the value of each won deal (so I can represent the total value of the customer based on the deals that are won in the system). A Sales_Opportunity in my model has a sale_value field, so I tried:
<%= #company.sales_opportunities.where(pipeline_status: 4).each.sale_value.sum %>
which returns the following error:
undefined method `sale_value' for #<Enumerator:0x007f9b87a9d128>
This is probably a trivial error but I can't for the life of me figure out what's going on. Is there where statement returning the enumerator or the sales_opportunity objects with that enumerator? Any help would be gratefully appreciated.
If it helps here are the fields in my sales_opportunities table:
create_table "sales_opportunities", force: true do |t|
t.datetime "close_date"
t.integer "user_id"
t.datetime "created_at"
t.datetime "updated_at"
t.integer "pipeline_status", default: 0
t.string "opportunity_name"
t.integer "company_id"
t.decimal "sale_value", precision: 15, scale: 2, default: 0.0
end
A Sales_opportunity belongs_to a Company Object and a User Object, if that makes any difference.
use aggregate function sum
<%= #company.sales_opportunities.where(pipeline_status: 4).sum(:sale_value) %>
Other possibility is to use
<%= #company.sales_opportunities.where(pipeline_status: 4).pluck(:sale_value).reduce(0, :+) %>
Let's say we have the following model.
create_table :meetings do |t|
t.datetime :started_at
t.datetime: ended_at
end
class Meeting < ActiveRecord::base
end
How would I order a meetings_result, so that the longest meeting is the first meeting in the collection and the shortest meeting the last.
Something like
Meeting.order(longest(started_at..ended_at))
Obviously that doesn't work.
How would I achieve this, preferably without using raw SQL?
I don't think you can do it without using raw SQL.
Using Raw SQL:
Meeting.order('(ended_at - start_at) DESC')
(works with PostGreSQL)
No SQL? Two options come to mind. Create an array of hashes and sort it there, or add another column in the db and sort on that.
# How many records in the meetings table? This array of hashes could get huge.
meetings_array = []
Meeting.all.each do |meeting|
meetings_array << {id: meeting.id, started_at: meeting.started_at, ended_at: meeting.ended_at , duration: meeting.ended_at - meeting.started_at }
end
meetings_array.sort_by { |hsh| hsh[:duration] }
Or, create another column:
# Is it worth adding another column?
create_table :meetings do |t|
t.datetime :started_at
t.datetime :ended_at
t.datetime :duration
end
Update this column whenever you have both started_at and ended_at. Then you can:
Meeting.order("duration")
This might seem like a duplicate question, but I can't find any information on this. I want to show the results from a remotely acquired json array excluding certain results by comparing them to a local table. I have a gallery model with:
t.integer :smugmug_id
t.string :smugmug_key
t.integer :category_id
t.string :category_name
t.string :description
t.integer :highlight_id
t.string :highlight_key
t.string :highlight_type
t.string :keywords
t.string :nicename
t.integer :subcategory_id
t.string :subcategory_name
t.string :title
t.string :url
The data for this model gets populated by a rake task that connects to the smugmug api (json) and stores the data locally. I'm trying to create a view that shows all the smugmug galleries that are not stored locally.
Here's what I've tried so far, but it's not excluding the locally stored galleries like I thought it would.
def self.not_stored
smugmug_list = Smug::Client.new.albums(heavy = true)
gallery_list = Gallery.select(:smugmug_id)
smugmug_list.each do |smugmug|
smugmug unless gallery_list.include? smugmug.id
end
end
Hopefully this makes sense. I'm getting a json array of galleries, and I want to display that array excluding results where the album id matches the smugmug_id of any of my locally stored records.
Quick edit: I'm using an adaptation of this gem to connect to the smugmug api.
Just use the difference operator.
General Example:
ruby-1.9.2-p136 :001 > [3,2,1] - [2,1]
=> [3]
So you would have:
smugmug_list.collect{|e| e.id} - gallery_list
Enumerable#collect will turn the smugmug_list into a list of id's. From there, you can do the difference operator, which will return all the id's of all the smugmug galleries that are not stored locally.
Another option to maintain the list of galleries:
smugmug_list.select{|e|!gallery_list.include?(e.id)}