From d769596aec7daa2ff43f86c8fad4211fbc4f607d Mon Sep 17 00:00:00 2001 From: Yorick Peterse Date: Thu, 12 Nov 2015 16:16:49 +0100 Subject: Added Gitlab::SQL::Union class This class can be used to join multiple AcitveRecord::Relation objects together using a SQL UNION statement. ActiveRecord < 5.0 sadly doesn't support UNION and existing Gems out there don't handle prepared statements (e.g. they never incremented the variable bindings). --- lib/gitlab/sql/union.rb | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) create mode 100644 lib/gitlab/sql/union.rb (limited to 'lib/gitlab/sql') diff --git a/lib/gitlab/sql/union.rb b/lib/gitlab/sql/union.rb new file mode 100644 index 00000000000..1a62eff0b31 --- /dev/null +++ b/lib/gitlab/sql/union.rb @@ -0,0 +1,34 @@ +module Gitlab + module SQL + # Class for building SQL UNION statements. + # + # ORDER BYs are dropped from the relations as the final sort order is not + # guaranteed any way. + # + # Example usage: + # + # union = Gitlab::SQL::Union.new(user.personal_projects, user.projects) + # sql = union.to_sql + # + # Project.where("id IN (#{sql})") + class Union + def initialize(relations) + @relations = relations + end + + def to_sql + # Some relations may include placeholders for prepared statements, these + # aren't incremented properly when joining relations together this way. + # By using "unprepared_statements" we remove the usage of placeholders + # (thus fixing this problem), at a slight performance cost. + fragments = ActiveRecord::Base.connection.unprepared_statement do + @relations.map do |rel| + "(#{rel.reorder(nil).to_sql})" + end + end + + fragments.join(' UNION ') + end + end + end +end -- cgit v1.2.1