Fixed rounding errors by recalculating using closer origin

community/kernel/src/test/java/org/neo4j/kernel/impl/index/schema/GenericAccessorPointsTest.java

@@ -189,8 +189,13 @@ public void mustHandlePointArraysWithinSameTile() throws IndexEntryConflictExcep
         exactMatchOnAllValues( pointArrays );
     }
 
+    /**
+     * The test mustHandlePointArraysWithinSameTile was flaky on random numbers that placed points just
+     * within the tile upper bound, and allocated points to adjacent tiles due to rounding errors.
+     * This test uses a specific point that triggers that exact failure in a non-flaky way.
+     */
     @Test
-    public void exactTest()
+    public void shouldNotGetRoundingErrorsWithPointsJustWithinTheTileUpperBound()
     {
         PointValue origin = Values.pointValue( WGS84, 0.0, 0.0 );
         long derivedValueForCenterPoint = curve.derivedValueFor( origin.coordinate() );

community/spatial-index/src/main/java/org/neo4j/gis/spatial/index/curves/SpaceFillingCurve.java

@@ -396,7 +396,13 @@ long[] getNormalizedCoord( double[] coord )
             }
             else
             {
-                normalizedCoord[dim] = (long) ((value - range.getMin( dim )) * scalingFactor[dim]);
+                normalizedCoord[dim] = (long) ((value - range.getMin(dim)) * scalingFactor[dim]);
+                // Since we calculated this with an origin at the min extreme, we can get numerical rouding errors, which can be corrected by recalculating using a closer origin
+                double tileCenter = ((double) normalizedCoord[dim]) / scalingFactor[dim] + range.getMin(dim) + getTileWidth(dim, maxLevel) / 2.0;
+                // The 1E-16 is to create the behavior of the [min,max) bounds without an expensive if...else if...else check
+                long normalizedOffset = (long) ((value - tileCenter) * scalingFactor[dim] - 0.5 + 1E-16);
+                // normalizedOffset is almost always 0, but can be +1 or -1 if there were rounding errors we need to correct for
+                normalizedCoord[dim] += normalizedOffset;
             }
         }
         return normalizedCoord;