[postgis-tickets] r15661 - #3873, st_geohash drops a char for some non-point features,

[Paul Ramsey]

Author: pramsey
Date: 2017-09-08 06:04:38 -0700 (Fri, 08 Sep 2017)
New Revision: 15661

Modified:
   trunk/liblwgeom/cunit/cu_algorithm.c
   trunk/liblwgeom/lwalgorithm.c
Log:
#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


Modified: trunk/liblwgeom/cunit/cu_algorithm.c
===================================================================
--- trunk/liblwgeom/cunit/cu_algorithm.c	2017-09-08 03:48:45 UTC (rev 15660)
+++ trunk/liblwgeom/cunit/cu_algorithm.c	2017-09-08 13:04:38 UTC (rev 15661)
@@ -788,7 +788,7 @@
 	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);
 

Modified: trunk/liblwgeom/lwalgorithm.c
===================================================================
--- trunk/liblwgeom/lwalgorithm.c	2017-09-08 03:48:45 UTC (rev 15660)
+++ trunk/liblwgeom/lwalgorithm.c	2017-09-08 13:04:38 UTC (rev 15661)
@@ -795,6 +795,19 @@
 		{
 			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 @@
 			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
 		{