ability to change index to hash

README.md

@@ -43,7 +43,15 @@ $ gem install solid_cache
 Add the migration to your app:
 
 ```bash
-$ bin/rails solid_cache:install:migrations
+$ rake solid_cache:install
+```
+
+By default, this migration uses a btree index which descent through index to find a right entry. Hash index offers a faster record lookup, it’s O(1) operation that should improve lookup performance by 40-60%. But main drawback is that #delete_matched method will not be operational with hash index.
+
+In case, you want to go with hash index run the following instead:
+
+```bash
+$ rake solid_cache:install[hash]
 ```
 
 Then run it:

lib/generators/solid_cache/install/install_generator.rb

@@ -1,6 +1,11 @@
+require 'rails/generators/active_record'
+
 class SolidCache::InstallGenerator < Rails::Generators::Base
-  class_option :skip_migrations,    type: :boolean, default: nil,
-                                    desc: "Skip migrations"
+  include ActiveRecord::Generators::Migration
+
+  source_root File.expand_path("templates", __dir__)
+  class_option :skip_migrations,    type: :boolean, default: nil, desc: "Skip migrations"
+  class_option :index,             type: :string, default: 'btree', desc: "Index type for key column"
 
   def add_rails_cache
     %w[development test production].each do |env_name|
@@ -11,8 +16,13 @@ def add_rails_cache
   end
 
   def create_migrations
-    unless options[:skip_migrations]
-      rails_command "railties:install:migrations FROM=solid_cache", inline: true
+    return if options[:skip_migrations]
+
+    case options[:index]
+    when 'btree'
+      migration_template 'create_solid_cache_entries_btree.rb', 'db/migrate/create_solid_cache_entries.rb'
+    when 'hash'
+      migration_template 'create_solid_cache_entries_hash.rb', 'db/migrate/create_solid_cache_entries.rb'
     end
   end
 end

lib/generators/solid_cache/install/templates/create_solid_cache_entries_btree.rb

@@ -0,0 +1,12 @@
+class CreateSolidCacheEntries < ActiveRecord::Migration[7.0]
+    def change
+      create_table :solid_cache_entries do |t|
+        t.binary   :key,        null: false,   limit: 1024
+        t.binary   :value,      null: false,   limit: 512.megabytes
+        t.datetime :created_at, null: false
+
+        t.index    :key,        unique: true
+      end
+    end
+  end
+

lib/generators/solid_cache/install/templates/create_solid_cache_entries_hash.rb

@@ -0,0 +1,12 @@
+class CreateSolidCacheEntries < ActiveRecord::Migration[7.0]
+    def change
+      create_table :solid_cache_entries do |t|
+        t.binary   :key,        null: false,   limit: 1024
+        t.binary   :value,      null: false,   limit: 512.megabytes
+        t.datetime :created_at, null: false
+
+        t.index    :key,        unique: true,  using: :hash
+      end
+    end
+  end
+

lib/tasks/solid_cache_tasks.rake

@@ -1,6 +1,12 @@
 desc "Copy over the migration, and set cache"
 namespace :solid_cache do
-  task :install do
-    Rails::Command.invoke :generate, [ "solid_cache:install" ]
+  task :install, [:index] do |_t, args|
+    args.with_defaults(index: 'btree')
+
+    if args[:index] == 'btree' || args[:index] == 'hash'
+       Rails::Command.invoke :generate, [ "solid_cache:install", "--index=#{args[:index]}" ]
+    else
+       abort "Invalid index type - only 'btree' and 'hash' are supported."
+    end
   end
 end

test/unit/delete_matched_test.rb

@@ -51,13 +51,6 @@ class DeleteMatchedTest < ActiveSupport::TestCase
     assert @cache.exist?(other_key)
   end
 
-  test "will raise error if hash index is used" do
-    # TODO: change migration to have hash index.
-    assert_raise NotImplementedError do
-      @cache.delete_matched("foo")
-    end
-  end
-
   test "fails when starts with %" do
     assert_raise ArgumentError do
       @cache.delete_matched("%foo")