Commit 4f3fa519 authored by Yorick Peterse's avatar Yorick Peterse Committed by Robert Speicher
Browse files

Use a UNION in MergeRequest.in_projects

The OR condition for source_project_id/target_project_id leads to a
query plan that performs rather poorly on PostgreSQL due to the use of
sub-queries. Because Rails offers no easy alternative for this
particular problem we're forced to using a UNION for both conditions.
The resulting query performs much faster than just using an OR.
parent 1b62c4f9c794
......@@ -135,7 +135,6 @@ class MergeRequest < ActiveRecord::Base
scope :by_branch, ->(branch_name) { where("(source_branch LIKE :branch) OR (target_branch LIKE :branch)", branch: branch_name) }
scope :cared, ->(user) { where('assignee_id = :user OR author_id = :user', user: user.id) }
scope :by_milestone, ->(milestone) { where(milestone_id: milestone) }
scope :in_projects, ->(project_ids) { where("source_project_id in (:project_ids) OR target_project_id in (:project_ids)", project_ids: project_ids) }
scope :of_projects, ->(ids) { where(target_project_id: ids) }
scope :merged, -> { with_state(:merged) }
scope :closed_and_merged, -> { with_states(:closed, :merged) }
......@@ -161,6 +160,24 @@ def self.link_reference_pattern
super("merge_requests", /(?<merge_request>\d+)/)
end
# Returns all the merge requests from an ActiveRecord:Relation.
#
# This method uses a UNION as it usually operates on the result of
# ProjectsFinder#execute. PostgreSQL in particular doesn't always like queries
# using multiple sub-queries especially when combined with an OR statement.
# UNIONs on the other hand perform much better in these cases.
#
# relation - An ActiveRecord::Relation that returns a list of Projects.
#
# Returns an ActiveRecord::Relation.
def self.in_projects(relation)
source = where(source_project_id: relation).select(:id)
target = where(target_project_id: relation).select(:id)
union = Gitlab::SQL::Union.new([source, target])
where("merge_requests.id IN (#{union.to_sql})")
end
def to_reference(from_project = nil)
reference = "#{self.class.reference_prefix}#{iid}"
......
......@@ -80,6 +80,12 @@
it { is_expected.to respond_to(:merge_when_build_succeeds) }
end
describe '.in_projects' do
it 'returns the merge requests for a set of projects' do
expect(described_class.in_projects(Project.all)).to eq([subject])
end
end
describe '#to_reference' do
it 'returns a String reference to the object' do
expect(subject.to_reference).to eq "!#{subject.iid}"
......
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