1 files changed, 50 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/explain.rb b/activerecord/lib/active_record/explain.rb
new file mode 100644
index 0000000000..919e96cd7a
--- /dev/null
+++ b/activerecord/lib/active_record/explain.rb
@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+require "active_record/explain_registry"
+
+module ActiveRecord
+  module Explain
+    # Executes the block with the collect flag enabled. Queries are collected
+    # asynchronously by the subscriber and returned.
+    def collecting_queries_for_explain # :nodoc:
+      ExplainRegistry.collect = true
+      yield
+      ExplainRegistry.queries
+    ensure
+      ExplainRegistry.reset
+    end
+
+    # Makes the adapter execute EXPLAIN for the tuples of queries and bindings.
+    # Returns a formatted string ready to be logged.
+    def exec_explain(queries) # :nodoc:
+      str = queries.map do |sql, binds|
+        msg = +"EXPLAIN for: #{sql}"
+        unless binds.empty?
+          msg << " "
+          msg << binds.map { |attr| render_bind(attr) }.inspect
+        end
+        msg << "\n"
+        msg << connection.explain(sql, binds)
+      end.join("\n")
+
+      # Overriding inspect to be more human readable, especially in the console.
+      def str.inspect
+        self
+      end
+
+      str
+    end
+
+    private
+
+      def render_bind(attr)
+        value = if attr.type.binary? && attr.value
+          "<#{attr.value_for_database.to_s.bytesize} bytes of binary data>"
+        else
+          connection.type_cast(attr.value_for_database)
+        end
+
+        [attr.name, value]
+      end
+  end
+end