Merge pull request #10152 from Noemj/statement_cache

Statement cache

Conflicts:
	activerecord/CHANGELOG.md

1 files changed, 26 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/statement_cache.rb b/activerecord/lib/active_record/statement_cache.rb
new file mode 100644
index 0000000000..4a8c54414d
--- /dev/null
+++ b/activerecord/lib/active_record/statement_cache.rb
@@ -0,0 +1,26 @@
+module ActiveRecord
+
+  # Statement cache is used to cache a single statement in order to avoid creating the AST again.
+  # Initializing the cache is done by passing the statement in the initialization block:
+  #
+  # cache = ActiveRecord::StatementCache.new do
+  #   Book.where(:name => "my book").limit(100)
+  # end
+  #
+  # The cached statement is executed by using the +execute+ method:
+  #
+  # cache.execute
+  #
+  # The relation returned by yield is cached, and for each +execute+ call the cached relation gets duped.
+  # Database is queried when +to_a+ is called on the relation.
+  class StatementCache
+    def initialize
+      @relation = yield
+      raise ArgumentError.new("Statement cannot be nil") if @relation.nil?
+    end
+
+    def execute
+      @relation.dup.to_a
+    end
+  end
+end