gitlab-org--gitlab-foss/app/finders/union_finder.rb
Yorick Peterse 8a72f5c427
Added FromUnion to easily select from a UNION
This commit adds the module `FromUnion`, which provides the class method
`from_union`. This simplifies the process of selecting data from the
result of a UNION, and reduces the likelihood of making mistakes. As a
result, instead of this:

    union = Gitlab::SQL::Union.new([foo, bar])

    Foo.from("(#{union.to_sql}) #{Foo.table_name}")

We can now write this instead:

    Foo.from_union([foo, bar])

This commit also includes some changes to make this new setup work
properly. For example, a bug in Rails 4
(https://github.com/rails/rails/issues/24193) would break the use of
`from("sub-query-here").includes(:relation)` in certain cases. There was
also a CI query which appeared to repeat a lot of conditions from an
outer query on an inner query, which isn't necessary.

Finally, we include a RuboCop cop to ensure developers use this new
module, instead of using Gitlab::SQL::Union directly.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/51307
2018-09-17 12:39:43 +02:00

15 lines
305 B
Ruby

# frozen_string_literal: true
class UnionFinder
def find_union(segments, klass)
unless klass < FromUnion
raise TypeError, "#{klass.inspect} must include the FromUnion module"
end
if segments.length > 1
klass.from_union(segments)
else
segments.first
end
end
end