Added naive BigMin interleaved implementation for interleaved spatial query.

common/coords.go

@@ -21,6 +21,10 @@ type (
 		X, Y, Z int16
 	}
 
+	Cuboid struct {
+		P1, P2 Coord
+	}
+
 	KeyTransformer func(int64) int64
 	KeyEncoder     func(int64) ([]byte, error)
 	KeyDecoder     func([]byte) (int64, error)
@@ -29,6 +33,12 @@ type (
 	KeyJoiner      func(Coord) int64
 )
 
+func (cub Cuboid) Contains(c Coord) bool {
+	return c.X >= cub.P1.X && c.X <= cub.P2.X &&
+		c.Y >= cub.P1.Y && c.Y <= cub.P2.Y &&
+		c.Z >= cub.P1.Z && c.Z <= cub.P2.Z
+}
+
 func (c Coord) String() string {
 	return fmt.Sprintf("(%d, %d, %d)", c.X, c.Y, c.Z)
 }
@@ -204,3 +214,23 @@ func TranscodeInterleavedToPlain(key []byte) ([]byte, error) {
 		return EncodeStringToBytes(TransformInterleavedToPlain(pos))
 	}
 }
+
+// For correctness checks only.
+func NaiveBigMin(minz, maxz, zcode int64) int64 {
+	c1, c2 := InterleavedToCoord(minz), InterleavedToCoord(maxz)
+
+	cand := minz
+
+	for x := c1.X; x <= c2.X; x++ {
+		for y := c1.Y; y <= c2.Y; y++ {
+			for z := c1.Z; z <= c2.Z; z++ {
+				z := CoordToInterleaved(Coord{X: x, Y: y, Z: z})
+				if z > zcode && z < cand {
+					cand = z
+				}
+			}
+		}
+	}
+
+	return cand
+}