Added instructions to load database functions

See:
https://github.com/gravitystorm/openstreetmap-carto/blob/master/INSTALL.md#database-functions

Author: Andy Townsend

serving-tiles/manually-building-a-tile-server-debian-11.md

@@ -175,7 +175,15 @@ Since version v5.3.0, some extra indexes now need to be [applied manually](https
     cd ~/src/openstreetmap-carto/
     sudo -u _renderd psql -d gis -f indexes.sql
 
-It should respond with "CREATE INDEX" 14 times.
+It should respond with "CREATE INDEX" 16 times.
+
+## Database functions
+
+In version 5.9.0 of "OSM Carto" (released October 2024), some functions need to be loaded into the database manually. These can be added / re-loaded at any point using:
+
+    cd ~/src/openstreetmap-carto/
+    sudo -u _renderd psql -d gis -f functions.sql
+
 ## Shapefile download
 
 Although most of the data used to create the map is directly from the OpenStreetMap data file that you downloaded above, some shapefiles for things like low-zoom country boundaries are still needed. To download and index these, using the same account as we used previously:

serving-tiles/manually-building-a-tile-server-debian-12.md

@@ -178,7 +178,15 @@ Since version v5.3.0, some extra indexes now need to be [applied manually](https
     cd ~/src/openstreetmap-carto/
     sudo -u _renderd psql -d gis -f indexes.sql
 
-It should respond with "CREATE INDEX" 14 times.
+It should respond with "CREATE INDEX" 16 times.
+
+## Database functions
+
+In version 5.9.0 of "OSM Carto" (released October 2024), some functions need to be loaded into the database manually. These can be added / re-loaded at any point using:
+
+    cd ~/src/openstreetmap-carto/
+    sudo -u _renderd psql -d gis -f functions.sql
+
 ## Shapefile download
 
 Although most of the data used to create the map is directly from the OpenStreetMap data file that you downloaded above, some shapefiles for things like low-zoom country boundaries are still needed. To download and index these, using the same account as we used previously:

serving-tiles/manually-building-a-tile-server-ubuntu-22-04-lts.md

@@ -176,7 +176,14 @@ Since version v5.3.0, some extra indexes now need to be [applied manually](https
     cd ~/src/openstreetmap-carto/
     sudo -u _renderd psql -d gis -f indexes.sql
 
-It should respond with "CREATE INDEX" 14 times.
+It should respond with "CREATE INDEX" 16 times.
+
+## Database functions
+
+In version 5.9.0 of "OSM Carto" (released October 2024), some functions need to be loaded into the database manually. These can be added / re-loaded at any point using:
+
+    cd ~/src/openstreetmap-carto/
+    sudo -u _renderd psql -d gis -f functions.sql
 
 ## Shapefile download
 

serving-tiles/manually-building-a-tile-server-ubuntu-24-04-lts.md

@@ -178,6 +178,13 @@ Since version v5.3.0, some extra indexes now need to be [applied manually](https
 
 It should respond with "CREATE INDEX" 16 times.
 
+## Database functions
+
+In version 5.9.0 of "OSM Carto" (released October 2024), some functions need to be loaded into the database manually. These can be added / re-loaded at any point using:
+
+    cd ~/src/openstreetmap-carto/
+    sudo -u _renderd psql -d gis -f functions.sql
+
 ## Shapefile download
 
 Although most of the data used to create the map is directly from the OpenStreetMap data file that you downloaded above, some shapefiles for things like low-zoom country boundaries are still needed. To download and index these, using the same account as we used previously: