Optimization for non-cross geofence detection

This commit fixes a performance issue with the algorithm that
determines with geofences are potential candidates for
notifications following a SET operation.

Details

Prior to commit b471873 (10 commits ago) there was a bug where
the "cross" detection was not firing in all cases. This happened
because when looking for candidates for "cross" due to a SET
operation, only the geofences that overlapped the previous
position of the object and the geofences that overlapped the new
position where searched. But, in fac, all of the geofences that
overlapped the union rectangle of the old and new position should
have been searched.

That commit fixed the problem by searching a union rect of the
old and new positions. While this is an accurate solution, it
caused a slowdown on systems that have big/wild position changes
that might cross a huge number of geofences, even when those
geofences did not need actually need "cross" detection.

The fix

With this commit the geofences that have a "cross" detection
are stored in a seperated tree from those that do not. This
allows for a hybrid of the functionality prior and post b471873.

Fixes #583

internal/server/aof.go

@@ -15,7 +15,6 @@ import (
 	"time"
 
 	"github.com/tidwall/buntdb"
-	"github.com/tidwall/geojson/geometry"
 	"github.com/tidwall/gjson"
 	"github.com/tidwall/redcon"
 	"github.com/tidwall/resp"
@@ -227,55 +226,70 @@ func (s *Server) writeAOF(args []string, d *commandDetails) error {
 }
 
 func (s *Server) getQueueCandidates(d *commandDetails) []*Hook {
-	var candidates []*Hook
+	candidates := make(map[*Hook]bool)
 	// add the hooks with "outside" detection
-	if len(s.hooksOut) > 0 {
-		for _, hook := range s.hooksOut {
-			if hook.Key == d.key {
-				candidates = append(candidates, hook)
-			}
+	for _, hook := range s.hooksOut {
+		if hook.Key == d.key {
+			candidates[hook] = true
 		}
 	}
-	// search the hook spatial tree
-	// build a rectangle that fills the old and new which will be enough to
-	// handle "enter", "inside", "exit", and "cross" detections.
-	var rect geometry.Rect
-	if d.oldObj != nil {
-		rect = d.oldObj.Rect()
-		if d.obj != nil {
-			r2 := d.obj.Rect()
-			rect.Min.X = math.Min(rect.Min.X, r2.Min.X)
-			rect.Min.Y = math.Min(rect.Min.Y, r2.Min.Y)
-			rect.Max.X = math.Max(rect.Max.X, r2.Max.X)
-			rect.Max.Y = math.Max(rect.Max.Y, r2.Max.Y)
-		}
-	} else if d.obj != nil {
-		rect = d.obj.Rect()
-	} else {
-		return candidates
-	}
-	s.hookTree.Search(
-		[2]float64{rect.Min.X, rect.Min.Y},
-		[2]float64{rect.Max.X, rect.Max.Y},
-		func(_, _ [2]float64, value interface{}) bool {
-			hook := value.(*Hook)
-			if hook.Key != d.key {
-				return true
-			}
-			var found bool
-			for _, candidate := range candidates {
-				if candidate == hook {
-					found = true
-					break
+	// look for candidates that might "cross" geofences
+	if d.oldObj != nil && d.obj != nil && s.hookCross.Len() > 0 {
+		r1, r2 := d.oldObj.Rect(), d.obj.Rect()
+		s.hookCross.Search(
+			[2]float64{
+				math.Min(r1.Min.X, r2.Min.X),
+				math.Min(r1.Min.Y, r2.Min.Y),
+			},
+			[2]float64{
+				math.Max(r1.Max.X, r2.Max.X),
+				math.Max(r1.Max.Y, r2.Max.Y),
+			},
+			func(min, max [2]float64, value interface{}) bool {
+				hook := value.(*Hook)
+				if hook.Key == d.key {
+					candidates[hook] = true
 				}
-			}
-			if !found {
-				candidates = append(candidates, hook)
-			}
-			return true
-		},
-	)
-	return candidates
+				return true
+			})
+	}
+	// look for candidates that overlap the old object
+	if d.oldObj != nil {
+		r1 := d.oldObj.Rect()
+		s.hookTree.Search(
+			[2]float64{r1.Min.X, r1.Min.Y},
+			[2]float64{r1.Max.X, r1.Max.Y},
+			func(min, max [2]float64, value interface{}) bool {
+				hook := value.(*Hook)
+				if hook.Key == d.key {
+					candidates[hook] = true
+				}
+				return true
+			})
+	}
+	// look for candidates that overlap the new object
+	if d.obj != nil {
+		r1 := d.obj.Rect()
+		s.hookTree.Search(
+			[2]float64{r1.Min.X, r1.Min.Y},
+			[2]float64{r1.Max.X, r1.Max.Y},
+			func(min, max [2]float64, value interface{}) bool {
+				hook := value.(*Hook)
+				if hook.Key == d.key {
+					candidates[hook] = true
+				}
+				return true
+			})
+	}
+	if len(candidates) == 0 {
+		return nil
+	}
+	// return the candidates as a slice
+	ret := make([]*Hook, 0, len(candidates))
+	for hook := range candidates {
+		ret = append(ret, hook)
+	}
+	return ret
 }
 
 func (s *Server) queueHooks(d *commandDetails) error {

internal/server/crud.go

@@ -514,6 +514,7 @@ func (server *Server) cmdFlushDB(msg *Message) (res resp.Value, d commandDetails
 	server.hooks = make(map[string]*Hook)
 	server.hooksOut = make(map[string]*Hook)
 	server.hookTree = rbang.RTree{}
+	server.hookCross = rbang.RTree{}
 	d.command = "flushdb"
 	d.updated = true
 	d.timestamp = time.Now()

internal/server/hooks.go

@@ -197,6 +197,12 @@ func (s *Server) cmdSetHook(msg *Message, chanCmd bool) (
 			[2]float64{rect.Min.X, rect.Min.Y},
 			[2]float64{rect.Max.X, rect.Max.Y},
 			prevHook)
+		if prevHook.Fence.detect["cross"] {
+			s.hookCross.Delete(
+				[2]float64{rect.Min.X, rect.Min.Y},
+				[2]float64{rect.Max.X, rect.Max.Y},
+				prevHook)
+		}
 	}
 	// add hook to spatial index
 	if hook != nil && hook.Fence != nil && hook.Fence.obj != nil {
@@ -205,6 +211,12 @@ func (s *Server) cmdSetHook(msg *Message, chanCmd bool) (
 			[2]float64{rect.Min.X, rect.Min.Y},
 			[2]float64{rect.Max.X, rect.Max.Y},
 			hook)
+		if hook.Fence.detect["cross"] {
+			s.hookCross.Insert(
+				[2]float64{rect.Min.X, rect.Min.Y},
+				[2]float64{rect.Max.X, rect.Max.Y},
+				hook)
+		}
 	}
 
 	hook.Open() // Opens a goroutine to notify the hook
@@ -246,6 +258,12 @@ func (s *Server) cmdDelHook(msg *Message, chanCmd bool) (
 				[2]float64{rect.Min.X, rect.Min.Y},
 				[2]float64{rect.Max.X, rect.Max.Y},
 				hook)
+			if hook.Fence.detect["cross"] {
+				s.hookCross.Delete(
+					[2]float64{rect.Min.X, rect.Min.Y},
+					[2]float64{rect.Max.X, rect.Max.Y},
+					hook)
+			}
 		}
 		d.updated = true
 	}
@@ -298,6 +316,12 @@ func (s *Server) cmdPDelHook(msg *Message, channel bool) (
 				[2]float64{rect.Min.X, rect.Min.Y},
 				[2]float64{rect.Max.X, rect.Max.Y},
 				hook)
+			if hook.Fence.detect["cross"] {
+				s.hookCross.Delete(
+					[2]float64{rect.Min.X, rect.Min.Y},
+					[2]float64{rect.Max.X, rect.Max.Y},
+					hook)
+			}
 		}
 		d.updated = true
 		count++

internal/server/server.go

@@ -115,7 +115,8 @@ type Server struct {
 	shrinking  bool             // aof shrinking flag
 	shrinklog  [][]string       // aof shrinking log
 	hooks      map[string]*Hook // hook name
-	hookTree   rbang.RTree      // hook spatial tree containing all
+	hookCross  rbang.RTree      // hook spatial tree for "cross" geofences
+	hookTree   rbang.RTree      // hook spatial tree for all
 	hooksOut   map[string]*Hook // hooks with "outside" detection
 	aofconnM   map[net.Conn]bool
 	luascripts *lScriptMap