New Query Cache Feature (part deux) (#763)

* Adds in the ability to store query results in cache. Fixes #63

* Move the query cache setup to Fiber so it's cleared per HTTP request. This also circumvents the singlton setup from Habitat that would cause your query cache to be stored in redis or something

* Caching queries for longer periods will be done at a lower level cache. Remove these

* cache any? and select_count queryable methods. Making cache_key public

* lock lucky_cache in to specific version

shard.yml

@@ -34,6 +34,9 @@ dependencies:
   pulsar:
     github: luckyframework/pulsar
     version: ~> 0.2.2
+  lucky_cache:
+    github: luckyframework/lucky_cache
+    version: ~> 0.1.0
 
 development_dependencies:
   ameba:

spec/queryable_spec.cr

@@ -32,7 +32,20 @@ end
 class PostQuery < Post::BaseQuery
 end
 
+class UserQuery
+  class_property query_counter : Int32 = 0
+
+  private def exec_query
+    @@query_counter += 1
+    super
+  end
+end
+
 describe Avram::Queryable do
+  Spec.before_each do
+    UserQuery.query_counter = 0
+  end
+
   it "can chain scope methods" do
     ChainedQuery.new.young.named("Paul")
   end
@@ -1358,7 +1371,7 @@ describe Avram::Queryable do
 
       users = UserQuery.new.group(&.age).group(&.id)
       users.query.statement.should eq "SELECT #{User::COLUMN_SQL} FROM users GROUP BY users.age, users.id"
-      users.map(&.name).should eq ["Dwight", "Michael", "Jim"]
+      users.map(&.name).sort!.should eq ["Dwight", "Jim", "Michael"]
     end
 
     it "raises an error when grouped incorrectly" do
@@ -1471,4 +1484,22 @@ describe Avram::Queryable do
       query.to_sql.should eq original_query_sql
     end
   end
+
+  describe "with query cache" do
+    it "only runs the query once" do
+      # We're testing the actual caching
+      Fiber.current.query_cache = LuckyCache::MemoryStore.new
+      Avram.temp_config(query_cache_enabled: true) do
+        UserFactory.create &.name("Amy")
+        UserQuery.query_counter.should eq(0)
+
+        UserQuery.new.name("Amy").first
+        UserQuery.new.name("Amy").first
+        user = UserQuery.new.name("Amy").first
+
+        UserQuery.query_counter.should eq(1)
+        user.name.should eq("Amy")
+      end
+    end
+  end
 end

spec/spec_helper.cr

@@ -21,6 +21,10 @@ Db::VerifyConnection.new(quiet: true).run_task
 
 Spec.before_each do
   TestDatabase.truncate
+  # All specs seem to run on the same Fiber,
+  # so we set back to NullStore before each spec
+  # to ensure queries aren't randomly cached
+  Fiber.current.query_cache = LuckyCache::NullStore.new
 end
 
 class SampleBackupDatabase < Avram::Database

src/avram.cr

@@ -2,6 +2,7 @@ require "dexter"
 require "wordsmith"
 require "habitat"
 require "pulsar"
+require "lucky_cache"
 require "db"
 require "pg"
 require "uuid"
@@ -22,6 +23,7 @@ module Avram
     setting database_to_migrate : Avram::Database.class, example: "AppDatabase"
     setting time_formats : Array(String) = [] of String
     setting i18n_backend : Avram::I18nBackend = Avram::I18n.new, example: "Avram::I18n.new"
+    setting query_cache_enabled : Bool = false
   end
 
   Log            = ::Log.for(Avram)

src/avram/charms/fiber.cr

@@ -0,0 +1,12 @@
+# https://crystal-lang.org/api/latest/Fiber.html
+class Fiber
+  # This is stored on Fiber so it's released after each
+  # HTTP Request.
+  property query_cache : LuckyCache::BaseStore do
+    if Avram.settings.query_cache_enabled
+      LuckyCache::MemoryStore.new
+    else
+      LuckyCache::NullStore.new
+    end
+  end
+end

src/avram/model.cr

@@ -18,6 +18,7 @@ abstract class Avram::Model
   macro inherited
     COLUMNS = [] of Nil # types are not checked in macros
     ASSOCIATIONS = [] of Nil # types are not checked in macros
+    include LuckyCache::Cachable
   end
 
   def self.primary_key_name : Symbol?

src/avram/queryable.cr

@@ -214,23 +214,29 @@ module Avram::Queryable(T)
   end
 
   def any? : Bool
-    queryable = clone
-    new_query = queryable.query.limit(1).select("1 AS one")
-    results = database.query_one?(new_query.statement, args: new_query.args, queryable: schema_class.name, as: Int32)
-    !results.nil?
+    cache_store.fetch(cache_key, as: Bool) do
+      queryable = clone
+      new_query = queryable.query.limit(1).select("1 AS one")
+      results = database.query_one?(new_query.statement, args: new_query.args, queryable: schema_class.name, as: Int32)
+      !results.nil?
+    end
   end
 
   def none? : Bool
     !any?
   end
 
   def select_count : Int64
-    table = "(#{query.statement}) AS temp"
-    new_query = Avram::QueryBuilder.new(table).select_count
-    result = database.scalar new_query.statement, args: query.args, queryable: schema_class.name
-    result.as(Int64)
-  rescue e : DB::NoResultsError
-    0_i64
+    cache_store.fetch(cache_key, as: Int64) do
+      begin
+        table = "(#{query.statement}) AS temp"
+        new_query = Avram::QueryBuilder.new(table).select_count
+        result = database.scalar new_query.statement, args: query.args, queryable: schema_class.name
+        result.as(Int64)
+      rescue e : DB::NoResultsError
+        0_i64
+      end
+    end
   end
 
   def each
@@ -245,9 +251,19 @@ module Avram::Queryable(T)
     @preloads << block
   end
 
+  def cache_store
+    Fiber.current.query_cache
+  end
+
+  def cache_key : String
+    [query.statement, query.args].join(':')
+  end
+
   def results : Array(T)
-    exec_query.tap do |records|
-      preloads.each(&.call(records))
+    cache_store.fetch(cache_key, as: Array(T)) do
+      exec_query.tap do |records|
+        preloads.each(&.call(records))
+      end
     end
   end