diff options
| -rw-r--r-- | lib/gitlab/sql/union.rb | 34 | ||||
| -rw-r--r-- | spec/lib/gitlab/sql/union_spec.rb | 16 |
2 files changed, 50 insertions, 0 deletions
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 diff --git a/spec/lib/gitlab/sql/union_spec.rb b/spec/lib/gitlab/sql/union_spec.rb new file mode 100644 index 00000000000..976360af9b5 --- /dev/null +++ b/spec/lib/gitlab/sql/union_spec.rb @@ -0,0 +1,16 @@ +require 'spec_helper' + +describe Gitlab::SQL::Union do + describe '#to_sql' do + it 'returns a String joining relations together using a UNION' do + rel1 = User.where(email: 'alice@example.com') + rel2 = User.where(email: 'bob@example.com') + union = described_class.new([rel1, rel2]) + + sql1 = rel1.reorder(nil).to_sql + sql2 = rel2.reorder(nil).to_sql + + expect(union.to_sql).to eq("(#{sql1}) UNION (#{sql2})") + end + end +end |