Precompute Centroid for Location Polygons

The centroid is used for calculating the distances on the vacancy
searches.

The centroid for a polygon area doesn't change unless the area changes
too.

As we dinamically calculate it for every location polygon area
against every vacancy during the searches, if we pre-compute it we
save the DB to execute again the centroid calculation on every search.

app/services/ons_data_import/base.rb

@@ -18,18 +18,27 @@ def call
         geometry = feature["geometry"].to_json
 
         Rails.logger.info("Persisting new area data for '#{name}' (#{type})")
-        ActiveRecord::Base.connection.exec_update("
-          UPDATE location_polygons
-          SET area=ST_GeomFromGeoJSON(#{ActiveRecord::Base.connection.quote(geometry)}),
-              location_type=#{ActiveRecord::Base.connection.quote(type)}
-          WHERE id='#{location_polygon.id}'
-        ")
+        set_area_data(location_polygon, geometry, type)
       end
     end
   end
 
   private
 
+  def set_area_data(location_polygon, geometry, type)
+    ActiveRecord::Base.connection.exec_update("
+      WITH geom AS (
+        SELECT ST_GeomFromGeoJSON(#{ActiveRecord::Base.connection.quote(geometry)}) AS geo
+      )
+      UPDATE location_polygons
+      SET area=geom.geo,
+          location_type=#{ActiveRecord::Base.connection.quote(type)},
+          centroid=ST_Centroid(geom.geo)
+      FROM geom
+      WHERE id='#{location_polygon.id}'
+    ")
+  end
+
   def arcgis_features(offset)
     params = [
       "where=1%3D1",

app/services/ons_data_import/create_composites.rb

@@ -7,13 +7,16 @@ def call
       quoted_constituents = constituents.map { |c| ActiveRecord::Base.connection.quote(c.downcase) }
 
       ActiveRecord::Base.connection.exec_update("
+        WITH composite_area AS (
+          SELECT ST_Union(area::geometry)::geography AS geo
+          FROM location_polygons
+          WHERE name IN (#{quoted_constituents.join(', ')})
+        )
         UPDATE location_polygons
-        SET area=(
-              SELECT ST_Union(area::geometry)::geography
-              FROM location_polygons
-              WHERE name IN (#{quoted_constituents.join(', ')})
-            ),
-            location_type='composite'
+        SET area=composite_area.geo,
+            location_type='composite',
+            centroid=ST_Centroid(composite_area.geo)
+        FROM composite_area
         WHERE id='#{composite.id}'
       ")
     end

config/analytics.yml

@@ -208,6 +208,7 @@ shared:
     - name
     - location_type
     - area
+    - centroid
     - created_at
     - updated_at
   notifications:

config/brakeman.ignore

@@ -115,29 +115,6 @@
       ],
       "note": ""
     },
-    {
-      "warning_type": "SQL Injection",
-      "warning_code": 0,
-      "fingerprint": "549d2779be79702f98156c6ec1a388b35ff19d87b0978910d4fad9d59a424cb9",
-      "check_name": "SQL",
-      "message": "Possible SQL injection",
-      "file": "app/services/ons_data_import/create_composites.rb",
-      "line": 14,
-      "link": "https://brakemanscanner.org/docs/warning_types/sql_injection/",
-      "code": "ActiveRecord::Base.connection.exec_update(\"\\n        UPDATE location_polygons\\n        SET area=(\\n              SELECT ST_Union(area::geometry)::geography\\n              FROM location_polygons\\n              WHERE name IN (#{constituents.map do\n ActiveRecord::Base.connection.quote(c.downcase)\n end.join(\", \")})\\n            ),\\n            location_type='composite'\\n        WHERE id='#{LocationPolygon.find_or_create_by(:name => name).id}'\\n      \")",
-      "render_path": null,
-      "location": {
-        "type": "method",
-        "class": "OnsDataImport::CreateComposites",
-        "method": "call"
-      },
-      "user_input": "constituents.map do\n ActiveRecord::Base.connection.quote(c.downcase)\n end.join(\", \")",
-      "confidence": "Medium",
-      "cwe_id": [
-        89
-      ],
-      "note": "This is our own static data with no user input provided in the query"
-    },
     {
       "warning_type": "Unscoped Find",
       "warning_code": 82,
@@ -218,6 +195,29 @@
       ],
       "note": ""
     },
+    {
+      "warning_type": "SQL Injection",
+      "warning_code": 0,
+      "fingerprint": "b2035069089eae3a5d8ec3a3a615aee253ec3cf2cd68c5535af152b8de779f46",
+      "check_name": "SQL",
+      "message": "Possible SQL injection",
+      "file": "app/services/ons_data_import/create_composites.rb",
+      "line": 13,
+      "link": "https://brakemanscanner.org/docs/warning_types/sql_injection/",
+      "code": "ActiveRecord::Base.connection.exec_update(\"\\n        WITH composite_area AS (\\n          SELECT ST_Union(area::geometry)::geography AS geo\\n          FROM location_polygons\\n          WHERE name IN (#{constituents.map do\n ActiveRecord::Base.connection.quote(c.downcase)\n end.join(\", \")})\\n        )\\n        UPDATE location_polygons\\n        SET area=composite_area.geo,\\n            location_type='composite',\\n            centroid=ST_Centroid(composite_area.geo)\\n        FROM composite_area\\n        WHERE id='#{LocationPolygon.find_or_create_by(:name => name).id}'\\n      \")",
+      "render_path": null,
+      "location": {
+        "type": "method",
+        "class": "OnsDataImport::CreateComposites",
+        "method": "call"
+      },
+      "user_input": "constituents.map do\n ActiveRecord::Base.connection.quote(c.downcase)\n end.join(\", \")",
+      "confidence": "Medium",
+      "cwe_id": [
+        89
+      ],
+      "note": ""
+    },
     {
       "warning_type": "SQL Injection",
       "warning_code": 0,

db/migrate/20250114180542_add_centroid_to_location_polygons.rb

@@ -0,0 +1,8 @@
+class AddCentroidToLocationPolygons < ActiveRecord::Migration[7.2]
+  disable_ddl_transaction!
+
+  def change
+    add_column :location_polygons, :centroid, :st_point, geographic: true
+    add_index :location_polygons, :centroid, using: :gist, algorithm: :concurrently
+  end
+end

db/schema.rb

@@ -77,11 +77,11 @@
     t.uuid "job_application_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
-    t.integer "employment_type", default: 0
-    t.text "reason_for_break", default: ""
     t.text "organisation_ciphertext"
     t.text "job_title_ciphertext"
     t.text "main_duties_ciphertext"
+    t.integer "employment_type", default: 0
+    t.text "reason_for_break", default: ""
     t.uuid "jobseeker_profile_id"
     t.text "reason_for_leaving"
     t.index ["job_application_id"], name: "index_employments_on_job_application_id"
@@ -312,9 +312,9 @@
     t.date "account_closed_on"
     t.text "current_sign_in_ip_ciphertext"
     t.text "last_sign_in_ip_ciphertext"
+    t.string "govuk_one_login_id"
     t.string "account_merge_confirmation_code"
     t.datetime "account_merge_confirmation_code_generated_at"
-    t.string "govuk_one_login_id"
     t.index ["email"], name: "index_jobseekers_on_email", unique: true
     t.index ["govuk_one_login_id"], name: "index_jobseekers_on_govuk_one_login_id", unique: true
   end
@@ -333,7 +333,9 @@
     t.datetime "created_at", precision: nil, null: false
     t.datetime "updated_at", precision: nil, null: false
     t.geography "area", limit: {:srid=>4326, :type=>"geometry", :geographic=>true}
+    t.geography "centroid", limit: {:srid=>4326, :type=>"st_point", :geographic=>true}
     t.index ["area"], name: "index_location_polygons_on_area", using: :gist
+    t.index ["centroid"], name: "index_location_polygons_on_centroid", using: :gist
     t.index ["name"], name: "index_location_polygons_on_name"
   end
 
@@ -697,8 +699,8 @@
     t.boolean "include_additional_documents"
     t.boolean "visa_sponsorship_available"
     t.boolean "is_parental_leave_cover"
-    t.boolean "is_job_share"
     t.string "hourly_rate"
+    t.boolean "is_job_share"
     t.string "flexi_working"
     t.integer "extension_reason"
     t.string "other_extension_reason_details"