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Use a JOIN in IssuableFinder#by_project

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When using IssuableFinder/IssuesFinder to find issues for multiple
projects it's more efficient to use a JOIN + a "WHERE project_id IN"
condition opposed to running a sub-query.

This change means that when finding issues without labels we're now
using the following SQL:

    SELECT issues.*
    FROM issues
    JOIN projects ON projects.id = issues.project_id

    LEFT JOIN label_links ON label_links.target_type = 'Issue'
                          AND label_links.target_id  = issues.id

    WHERE (
        projects.id IN (...)
        OR projects.visibility_level IN (20, 10)
    )
    AND issues.state IN ('opened','reopened')
    AND label_links.id IS NULL
    ORDER BY issues.id DESC;

instead of:

    SELECT issues.*
    FROM issues
    LEFT JOIN label_links ON label_links.target_type = 'Issue'
                          AND label_links.target_id  = issues.id

    WHERE issues.project_id IN (
        SELECT id
        FROM projects
        WHERE id IN (...)
        OR visibility_level IN (20,10)
    )
    AND issues.state IN ('opened','reopened')
    AND label_links.id IS NULL
    ORDER BY issues.id DESC;

The big benefit here is that in the last case PostgreSQL can't properly
use all available indexes. In particular it ends up performing a
sequence scan on the "label_links" table (processing around 290 000
rows). The new query is roughly 2x as fast as the old query.
This commit is contained in:
Yorick Peterse 2015-11-11 12:50:36 +01:00
parent e9cd58f5d5
commit 8591cc02be
3 changed files with 13 additions and 3 deletions
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10
app/finders/issuable_finder.rb
View file

@ -190,8 +190,10 @@ class IssuableFinder
def by_project(items)
items =
if projects
items.of_projects(projects).references(:project)
if project?
items.of_projects(projects).references_project
elsif projects
items.merge(projects.reorder(nil)).join_project
else
items.none
end
@ -206,7 +208,9 @@ class IssuableFinder
end
def sort(items)
items.sort(params[:sort])
# Ensure we always have an explicit sort order (instead of inheriting
# multiple orders when combining ActiveRecord::Relation objects).
params[:sort] ? items.sort(params[:sort]) : items.reorder(id: :desc)
end
def by_assignee(items)

3
app/models/concerns/issuable.rb
View file

@ -35,6 +35,9 @@ module Issuable
scope :order_milestone_due_desc, -> { joins(:milestone).reorder('milestones.due_date DESC, milestones.id DESC') }
scope :order_milestone_due_asc, -> { joins(:milestone).reorder('milestones.due_date ASC, milestones.id ASC') }
scope :join_project, -> { joins(:project) }
scope :references_project, -> { references(:project) }
delegate :name,
:email,
to: :author,

3
app/models/merge_request.rb
View file

@ -134,6 +134,9 @@ class MergeRequest < ActiveRecord::Base
scope :closed, -> { with_state(:closed) }
scope :closed_and_merged, -> { with_states(:closed, :merged) }
scope :join_project, -> { joins(:target_project) }
scope :references_project, -> { references(:target_project) }
def self.reference_prefix
'!'
end