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Diffstat (limited to 'lib/gitlab/sql/union.rb')
-rw-r--r-- | lib/gitlab/sql/union.rb | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/lib/gitlab/sql/union.rb b/lib/gitlab/sql/union.rb new file mode 100644 index 00000000000..1cd89b3a9c4 --- /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("\nUNION\n") + end + end + end +end |