rename sql directory to lib-sql

Also introduces a separate constant for the sql directory, so that
it can be put separately from the rest of the data if required.

lib-sql/functions/postcode_triggers.sql

@@ -0,0 +1,40 @@
+-- Trigger functions for location_postcode table.
+
+
+-- Trigger for updates of location_postcode
+--
+-- Computes the parent object the postcode most likely refers to.
+-- This will be the place that determines the address displayed when
+-- searching for this postcode.
+CREATE OR REPLACE FUNCTION postcode_update()
+  RETURNS TRIGGER
+  AS $$
+DECLARE
+  partition SMALLINT;
+  location RECORD;
+BEGIN
+    IF NEW.indexed_status != 0 OR OLD.indexed_status = 0 THEN
+        RETURN NEW;
+    END IF;
+
+    NEW.indexed_date = now();
+
+    partition := get_partition(NEW.country_code);
+
+    SELECT * FROM get_postcode_rank(NEW.country_code, NEW.postcode)
+      INTO NEW.rank_search, NEW.rank_address;
+
+    NEW.parent_place_id = 0;
+    FOR location IN
+      SELECT place_id
+        FROM getNearFeatures(partition, NEW.geometry, NEW.rank_search)
+        WHERE NOT isguess ORDER BY rank_address DESC, distance asc LIMIT 1
+    LOOP
+        NEW.parent_place_id = location.place_id;
+    END LOOP;
+
+    RETURN NEW;
+END;
+$$
+LANGUAGE plpgsql;
+