From: Paul Ramsey <pramsey@cleverelephant.ca>
Date: Fri, 8 Sep 2017 13:04:38 +0000 (+0000)
Subject: #3873, st_geohash drops a char for some non-point features,
X-Git-Tag: 2.4.0rc1~40
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d35ada3169b548f49b44630e3e38920e2ea4b47c;p=postgis

#3873, st_geohash drops a char for some non-point features,
due to a difference between the calculation of the correct
amount of precision to return and the calculation of the
effective geohash bounds of a feature


git-svn-id: http://svn.osgeo.org/postgis/trunk@15661 b70326c6-7e19-0410-871a-916f4a2858ee
---

diff --git a/liblwgeom/cunit/cu_algorithm.c b/liblwgeom/cunit/cu_algorithm.c
index c24f38028..1acd1dcd0 100644
--- a/liblwgeom/cunit/cu_algorithm.c
+++ b/liblwgeom/cunit/cu_algorithm.c
@@ -788,7 +788,7 @@ static void test_geohash(void)
 	lwline = (LWLINE*)lwgeom_from_wkt("LINESTRING(23.0 23.0,23.001 23.001)", LW_PARSER_CHECK_NONE);
 	geohash = lwgeom_geohash((LWGEOM*)lwline,0);
 	//printf("geohash %s\n",geohash);
-	CU_ASSERT_STRING_EQUAL(geohash, "ss06g7");
+	CU_ASSERT_STRING_EQUAL(geohash, "ss06g7h");
 	lwline_free(lwline);
 	lwfree(geohash);
 
diff --git a/liblwgeom/lwalgorithm.c b/liblwgeom/lwalgorithm.c
index 3f8404c65..f01b4a513 100644
--- a/liblwgeom/lwalgorithm.c
+++ b/liblwgeom/lwalgorithm.c
@@ -795,6 +795,19 @@ int lwgeom_geohash_precision(GBOX bbox, GBOX *bounds)
 		{
 			lonmaxadjust = -1 * lonwidth / 2.0;
 		}
+		if ( lonminadjust || lonmaxadjust )
+		{
+			lonmin += lonminadjust;
+			lonmax += lonmaxadjust;
+			/* Each adjustment cycle corresponds to 2 bits of storage in the
+			** geohash.	*/
+			precision++;
+		}
+		else
+		{
+			break;
+		}
+		
 		if ( miny > latmin + latwidth / 2.0 )
 		{
 			latminadjust = latwidth / 2.0;
@@ -804,15 +817,13 @@ int lwgeom_geohash_precision(GBOX bbox, GBOX *bounds)
 			latmaxadjust = -1 * latwidth / 2.0;
 		}
 		/* Only adjust if adjustments are legal (we haven't crossed any edges). */
-		if ( (lonminadjust || lonmaxadjust) && (latminadjust || latmaxadjust ) )
+		if ( latminadjust || latmaxadjust )
 		{
 			latmin += latminadjust;
-			lonmin += lonminadjust;
 			latmax += latmaxadjust;
-			lonmax += lonmaxadjust;
 			/* Each adjustment cycle corresponds to 2 bits of storage in the
 			** geohash.	*/
-			precision += 2;
+			precision++;
 		}
 		else
 		{