gitlab-org--gitlab-foss/lib/gitlab/sql/union.rb
Yorick Peterse 9eefae6917 Fix UNION syntax for MySQL
Apparently MySQL doesn't support this syntax:

    (...) UNION (...)

instead it only supports:

    ...
    UNION
    ...
2015-11-18 13:31:18 +01:00

34 lines
1 KiB
Ruby

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