db: added index on scan_result

In particular, I've added the index on vulnerability_id and tag_id. As
reported on #2053, this index makes the scanning of vulnerability issues
way faster on large amounts of tags.

Fixes #2053

Signed-off-by: Miquel Sabaté Solà <[email protected]>

Author: mssola

app/models/scan_result.rb

@@ -10,6 +10,10 @@
 #  created_at       :datetime         not null
 #  updated_at       :datetime         not null
 #
+# Indexes
+#
+#  index_scan_results_on_vulnerability_id_and_tag_id  (vulnerability_id,tag_id)
+#
 
 # Relationship linking tags and vulnerabilities: a scan result involves
 # vulnerabilities for tags.

db/migrate/20181213101302_add_index_scan_results_vulnerability_tag.rb

@@ -0,0 +1,5 @@
+class AddIndexScanResultsVulnerabilityTag < ActiveRecord::Migration
+  def change
+    add_index(:scan_results, [:vulnerability_id, :tag_id])
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20180612145708) do
+ActiveRecord::Schema.define(version: 20181213101302) do
 
   create_table "activities", force: :cascade do |t|
     t.integer  "trackable_id",   limit: 4
@@ -105,6 +105,8 @@
     t.datetime "updated_at",                 null: false
   end
 
+  add_index "scan_results", ["vulnerability_id", "tag_id"], name: "index_scan_results_on_vulnerability_id_and_tag_id", using: :btree
+
   create_table "stars", force: :cascade do |t|
     t.integer  "user_id",       limit: 4
     t.integer  "repository_id", limit: 4