6074: Clear any existing ActiveRecord select() before adding our own,

[arvados.git] / services / api / app / controllers / application_controller.rb

diff --git a/services/api/app/controllers/application_controller.rb b/services/api/app/controllers/application_controller.rb
index a65bf3e328697da220d111c8be36460de82220bd..3a3f6d334589058b3e3af1c0dc13c97cfbf4bff3 100644 (file)
--- a/services/api/app/controllers/application_controller.rb
+++ b/services/api/app/controllers/application_controller.rb
@@ -191,9 +191,18 @@ class ApplicationController < ActionController::Base
            }.merge opts)
   end
 
+  def self.limit_index_columns_read
+    # This method returns a list of column names.
+    # If an index request reads that column from the database,
+    # find_objects_for_index will only fetch objects until it reads
+    # max_index_database_read bytes of data from those columns.
+    []
+  end
+
   def find_objects_for_index
     @objects ||= model_class.readable_by(*@read_users)
     apply_where_limit_order_params
+    limit_database_read if (action_name == "index")
   end
 
   def apply_filters model_class=nil
@@ -205,8 +214,9 @@ class ApplicationController < ActionController::Base
     end
   end
 
-  def apply_where_limit_order_params *args
-    apply_filters *args
+  def apply_where_limit_order_params model_class=nil
+    model_class ||= self.model_class
+    apply_filters model_class
 
     ar_table_name = @objects.table_name
     if @where.is_a? Hash and @where.any?
@@ -267,11 +277,8 @@ class ApplicationController < ActionController::Base
         # Map attribute names in @select to real column names, resolve
         # those to fully-qualified SQL column names, and pass the
         # resulting string to the select method.
-        api_column_map = model_class.attributes_required_columns
-        columns_list = @select.
-          flat_map { |attr| api_column_map[attr] }.
-          uniq.
-          map { |s| "#{table_name}.#{ActiveRecord::Base.connection.quote_column_name s}" }
+        columns_list = model_class.columns_for_attributes(@select).
+          map { |s| "#{ar_table_name}.#{ActiveRecord::Base.connection.quote_column_name s}" }
         @objects = @objects.select(columns_list.join(", "))
       end
 
@@ -288,6 +295,30 @@ class ApplicationController < ActionController::Base
     @objects = @objects.uniq(@distinct) if not @distinct.nil?
   end
 
+  def limit_database_read
+    limit_columns = self.class.limit_index_columns_read
+    limit_columns &= model_class.columns_for_attributes(@select) if @select
+    return if limit_columns.empty?
+    model_class.transaction do
+      limit_query = @objects.
+        except(:select).
+        select("(%s) as read_length" %
+               limit_columns.map { |s| "octet_length(#{s})" }.join(" + "))
+      new_limit = 0
+      read_total = 0
+      limit_query.find_each do |record|
+        new_limit += 1
+        read_total += record.read_length.to_i
+        break if ((read_total >= Rails.configuration.max_index_database_read) or
+                  (new_limit >= @limit))
+      end
+      @limit = new_limit
+      @objects = @objects.limit(@limit)
+      # Force @objects to run its query inside this transaction.
+      @objects.each { |_| break }
+    end
+  end
+
   def resource_attrs
     return @attrs if @attrs
     @attrs = params[resource_name]
@@ -436,8 +467,8 @@ class ApplicationController < ActionController::Base
   end
   accept_param_as_json :reader_tokens, Array
 
-  def render_list
-    @object_list = {
+  def object_list
+    list = {
       :kind  => "arvados##{(@response_resource_name || resource_name).camelize(:lower)}List",
       :etag => "",
       :self_link => "",
@@ -446,11 +477,15 @@ class ApplicationController < ActionController::Base
       :items => @objects.as_api_response(nil, {select: @select})
     }
     if @objects.respond_to? :except
-      @object_list[:items_available] = @objects.
+      list[:items_available] = @objects.
         except(:limit).except(:offset).
         count(:id, distinct: true)
     end
-    send_json @object_list
+    list
+  end
+
+  def render_list
+    send_json object_list
   end
 
   def remote_ip