This gem for change Mongoid id field as Integer like MySQL.

Idea from MongoDB document: How to Make an Auto Incrementing Field

NOTE! This Gem has helped Ruby China in pass 4 years，and produce over million rows, it's work very will. In now, Ruby China (Homeland) has changed to ActiveRecord to use PostgreSQL as Database, so may be I don't have time keep this gem compatible with new versions of Mongoid. But even that, I am be sure that this gem still working for Mongoid 5.0 and lower version.

Status

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Installation

# Mongoid 3.0.x
gem 'mongoid_auto_increment_id', "0.6.1"
# Mongoid 3.1.x
gem 'mongoid_auto_increment_id', "0.6.2"
# Mongoid 4.x
gem 'mongoid_auto_increment_id', "0.7.0"
# Mongoid 5.x
gem 'mongoid_auto_increment_id', "0.8.1"

Configure

If you want use sequence cache to reduce MongoDB write, you can enable cache:

config/initializes/mongoid_auto_increment_id.rb

# Mongoid::AutoIncrementId.cache_store = ActiveSupport::Cache::MemoryStore.new
# First call will generate 200 ids and caching in cache_store
# Then the next 199 ids will return from cache_store
# Until 200 ids used, it will generate next 200 ids again.
Mongoid::AutoIncrementId.seq_cache_size = 200

NOTE: mongoid_auto_increment_id is very fast in default config, you may don't need enable that, if you project not need insert huge rows in a moment.

USAGE

ruby > post = Post.new(:title => "Hello world")
 => #<Post _id: , _type: nil, title: "Hello world", body: nil>
ruby > post.save
 => true
ruby > post.inspect
 => "#<Post _id: 6, _type: nil, title: \"Hello world\", body: nil>"
ruby > Post.find("6")
 => "#<Post _id: 6, _type: nil, title: \"Hello world\", body: nil>"
ruby > Post.find(6)
 => "#<Post _id: 6, _type: nil, title: \"Hello world\", body: nil>"
ruby > Post.desc(:_id).all.to_a.collect { |row| row.id }
 => [20,19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1]

Performance

This is a branchmark results run in MacBook Pro Retina.

with mongoid_auto_increment_id:

       user     system      total        real
Generate 1  0.000000   0.000000   0.000000 (  0.004301)
Post current: 1

Generate 100  0.070000   0.000000   0.070000 (  0.091638)
Post current: 101

Generate 10,000  7.300000   0.570000   7.870000 (  9.962469)
Post current: 10101

without:

       user     system      total        real
Generate 1  0.000000   0.000000   0.000000 (  0.002569)
Post current: 1

Generate 100  0.050000   0.000000   0.050000 (  0.052045)
Post current: 101

Generate 10,000  5.220000   0.170000   5.390000 (  5.389207)
Post current: 10101