From: Sarah Hoffmann <lonvia@denofr.de>
Date: Thu, 20 Aug 2020 14:37:33 +0000 (+0200)
Subject: increase splitting for large geometries
X-Git-Tag: v3.6.0~88^2~1
X-Git-Url: https://git.openstreetmap.org./nominatim.git/commitdiff_plain/559fe513fa8ffa3a5bc3a7d07c252a872614c073

increase splitting for large geometries

When computing the address parts for a geometry, we need to do
a ST_Relates lookup in the location_area_large_* tables. This is
potentially very expensive for geometries with many vertices.
There is already a funtion for splitting large areas to reduce the
impact. This commit reduces the minimum area of a split, effectively
increasing the number of splits.

The effect on database size is minimal (around 3% increase), while
the indexing speed for streets increases by a good 60%.
---

diff --git a/sql/functions/utils.sql b/sql/functions/utils.sql
index a8c4638c..6697ff97 100644
--- a/sql/functions/utils.sql
+++ b/sql/functions/utils.sql
@@ -429,7 +429,7 @@ DECLARE
   geo RECORD;
 BEGIN
   -- 10000000000 is ~~ 1x1 degree
-  FOR geo IN select quad_split_geometry(geometry, 0.25, 20) as geom LOOP
+  FOR geo IN select quad_split_geometry(geometry, 0.01, 20) as geom LOOP
     RETURN NEXT geo.geom;
   END LOOP;
   RETURN;