[Firestore] Extract the collection with where condition in Ruby and delete the record

Overview

When using the Firestore API in Ruby, I summarized what to do if you want to delete only the specified collection that meets the where condition.

Assumptions, etc.

• Since Firestore API is used in Ruby, the document here for environment settings and how to throw queries. And I want to play with Firestore from Rails.
• This time we will use the batch mechanism. It seems that the limit of updates in batch is 500, so let's consider that as well. Although it is implemented in JavaScript, Delete Collection in Firestore is helpful.
• For the batch specifications in Ruby, refer to the document here.

Implementation sample

sample.rb

def delete_sample
  #Get firestore object
  firestore = Google::Cloud::Firestore.new
  #For storing the doc array to be deleted
  doc_array = []
  #Get collection
  col_ref = firestore.col 'sample_collection'
  #Collection criteria
  query = col_ref.where 'category', '==', 'test'
  query.get do |r|
    #Store the target doc in an array
    doc_array.push r.ref
  end
  #Consider that you can only delete up to 500
  document_index = 0
  batch_index = 0
  #Delete in batch
  while document_index < doc_array.size
    firestore.batch do |b|
      #Suspended at 501st index
      break if batch_index == 500

      b.delete doc_array[document_index]
      document_index += 1
      batch_index += 1
    end
    batch_index = 0
  end
end