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/update-postcodes.sql

@@ -0,0 +1,58 @@
+-- Create a temporary table with postcodes from placex.
+
+CREATE TEMP TABLE tmp_new_postcode_locations AS
+SELECT country_code,
+       upper(trim (both ' ' from address->'postcode')) as pc,
+       ST_Centroid(ST_Collect(ST_Centroid(geometry))) as centroid
+  FROM placex
+ WHERE address ? 'postcode'
+       AND address->'postcode' NOT SIMILAR TO '%(,|;|:)%'
+       AND geometry IS NOT null
+GROUP BY country_code, pc;
+
+CREATE INDEX idx_tmp_new_postcode_locations
+          ON tmp_new_postcode_locations (pc, country_code);
+
+-- add extra US postcodes
+INSERT INTO tmp_new_postcode_locations (country_code, pc, centroid)
+    SELECT 'us', postcode, ST_SetSRID(ST_Point(x,y),4326)
+      FROM us_postcode u
+      WHERE NOT EXISTS (SELECT 0 FROM tmp_new_postcode_locations new
+                         WHERE new.country_code = 'us' AND new.pc = u.postcode);
+-- add extra UK postcodes
+INSERT INTO tmp_new_postcode_locations (country_code, pc, centroid)
+    SELECT 'gb', postcode, geometry FROM gb_postcode g
+     WHERE NOT EXISTS (SELECT 0 FROM tmp_new_postcode_locations new
+                             WHERE new.country_code = 'gb' and new.pc = g.postcode);
+
+-- Remove all postcodes that are no longer valid
+DELETE FROM location_postcode old
+  WHERE NOT EXISTS(SELECT 0 FROM tmp_new_postcode_locations new
+                   WHERE old.postcode = new.pc
+                         AND old.country_code = new.country_code);
+
+-- Update geometries where necessary
+UPDATE location_postcode old SET geometry = new.centroid, indexed_status = 1
+  FROM tmp_new_postcode_locations new
+ WHERE old.postcode = new.pc AND old.country_code = new.country_code
+       AND ST_AsText(old.geometry) != ST_AsText(new.centroid);
+
+-- Remove all postcodes that already exist from the temporary table
+DELETE FROM tmp_new_postcode_locations new
+    WHERE EXISTS(SELECT 0 FROM location_postcode old
+                 WHERE old.postcode = new.pc AND old.country_code = new.country_code);
+
+-- Add newly added postcode
+INSERT INTO location_postcode
+  (place_id, indexed_status, country_code, postcode, geometry)
+  SELECT nextval('seq_place'), 1, country_code, pc, centroid
+    FROM tmp_new_postcode_locations new;
+
+-- Remove unused word entries
+DELETE FROM word
+    WHERE class = 'place' AND type = 'postcode'
+          AND NOT EXISTS (SELECT 0 FROM location_postcode p
+                          WHERE p.postcode = word.word);
+
+-- Finally index the newly inserted postcodes
+UPDATE location_postcode SET indexed_status = 0 WHERE indexed_status > 0;