Suggest to use hash index, instead of btree index in migration.

.github/workflows/main.yml

@@ -19,6 +19,7 @@ jobs:
     name: Tests
     runs-on: ubuntu-latest
     strategy:
+      fail-fast: false
       matrix:
         ruby-version: [3.2.2]
         database: [sqlite, postgres, mysql]

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 +1,11 @@
+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 +1,11 @@
+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/solid_cache/store/api.rb

@@ -16,6 +16,7 @@ def delete_matched(matcher, options = {})
         instrument :delete_matched, matcher do
           raise ArgumentError, "Only strings are supported: #{matcher.inspect}" unless String === matcher
           raise ArgumentError, "Strings cannot start with wildcards" if SQL_WILDCARD_CHARS.include?(matcher[0])
+          raise NotImplementedError, "Primary Key uses a Hash Index, delete_matched method is not supported in this case" if primary_key_using_hash_index?
 
           options ||= {}
           batch_size = options.fetch(:batch_size, 1000)
@@ -49,6 +50,10 @@ def clear(options = nil)
       end
 
       private
+        def primary_key_using_hash_index?
+          ActiveRecord::Base.connection.indexes(:activesupport_cache_entries).first { |i| i.columns.first == "key" }.using == :hash
+        end
+
         def read_entry(key, **options)
           deserialize_entry(read_serialized_entry(key, **options), **options)
         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