From 8061068b7a691c6e9f8d570b9ce221fa2a8b7a36 Mon Sep 17 00:00:00 2001
From: CoderBear801 <coderxiong@gmail.com>
Date: Tue, 24 Mar 2020 16:50:50 -0700
Subject: [PATCH 1/8] feat: implement spartial index query based on google::s2
 issue: https://github.com/Telenav/osrm-backend/issues/239

---
 .../chargestations-connectivity-gen/doc.go    |  17 ++
 integration/go.mod                            |   1 +
 integration/go.sum                            |   3 +
 integration/service/poiloader/loader.go       |  26 ++
 integration/service/poiloader/poi_format.go   |  64 +++++
 .../service/poiloader/sample_input.json       |  64 +++++
 integration/service/spatialindexer/doc.go     |  19 ++
 .../service/spatialindexer/iterface.go        |  30 ++
 .../spatialindexer/s2indexer/builder.go       |  48 ++++
 .../spatialindexer/s2indexer/builder_test.go  | 260 ++++++++++++++++++
 .../spatialindexer/s2indexer/dumper.go        | 146 ++++++++++
 .../spatialindexer/s2indexer/dumper_test.go   |  65 +++++
 .../spatialindexer/s2indexer/indexer.go       |  76 +++++
 .../spatialindexer/s2indexer/spatial_query.go |  76 +++++
 .../s2indexer/spatial_query_test.go           | 245 +++++++++++++++++
 15 files changed, 1140 insertions(+)
 create mode 100644 integration/cmd/chargestations-connectivity-gen/doc.go
 create mode 100644 integration/service/poiloader/loader.go
 create mode 100644 integration/service/poiloader/poi_format.go
 create mode 100644 integration/service/poiloader/sample_input.json
 create mode 100644 integration/service/spatialindexer/doc.go
 create mode 100644 integration/service/spatialindexer/iterface.go
 create mode 100644 integration/service/spatialindexer/s2indexer/builder.go
 create mode 100644 integration/service/spatialindexer/s2indexer/builder_test.go
 create mode 100644 integration/service/spatialindexer/s2indexer/dumper.go
 create mode 100644 integration/service/spatialindexer/s2indexer/dumper_test.go
 create mode 100644 integration/service/spatialindexer/s2indexer/indexer.go
 create mode 100644 integration/service/spatialindexer/s2indexer/spatial_query.go
 create mode 100644 integration/service/spatialindexer/s2indexer/spatial_query_test.go

diff --git a/integration/cmd/chargestations-connectivity-gen/doc.go b/integration/cmd/chargestations-connectivity-gen/doc.go
new file mode 100644
index 00000000000..8e0f8b31e38
--- /dev/null
+++ b/integration/cmd/chargestations-connectivity-gen/doc.go
@@ -0,0 +1,17 @@
+// package main contains the tool of chargestation-connectivity generator
+// stage 1:
+// inputs is json file
+// => convert to slice of [id:string,location: lat,lon]
+// => calculate cellids for each point(for all levels)
+// => build revese index for cellid -> ids
+// stage 2:
+// => iterate each point
+// => generate a circle(s2::cap), find all cellids intersect with that circle
+// => retrieve all ids
+// => generate result of id(from), ids(all ids in certain distance)
+// stage 3:
+// => load data from file
+// => for each line, its formid and all other ids
+// => calculate distance between fromid and all other ids
+// => sort result based on distance and write back to file
+package main
diff --git a/integration/go.mod b/integration/go.mod
index bc2c88727a9..415bc0084aa 100644
--- a/integration/go.mod
+++ b/integration/go.mod
@@ -3,6 +3,7 @@ module github.com/Telenav/osrm-backend/integration
 go 1.13
 
 require (
+	github.com/golang/geo v0.0.0-20200319012246-673a6f80352d
 	github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b
 	github.com/golang/protobuf v1.3.2
 	github.com/golang/snappy v0.0.1
diff --git a/integration/go.sum b/integration/go.sum
index 8bb21f4ae9f..6c3a3f88da6 100644
--- a/integration/go.sum
+++ b/integration/go.sum
@@ -1,6 +1,9 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/Telenav/osrm-backend v5.22.0+incompatible h1:v5K4VmdxyQjFXN20ZGmk9MchGTHWWIMUXiXmAndNvlQ=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
+github.com/golang/geo v0.0.0-20200319012246-673a6f80352d h1:C/hKUcHT483btRbeGkrRjJz+Zbcj8audldIi9tRJDCc=
+github.com/golang/geo v0.0.0-20200319012246-673a6f80352d/go.mod h1:QZ0nwyI2jOfgRAoBvP+ab5aRr7c9x7lhGEJrKvBwjWI=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b h1:VKtxabqXZkF25pY9ekfRL6a582T4P37/31XEstQ5p58=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
 github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
diff --git a/integration/service/poiloader/loader.go b/integration/service/poiloader/loader.go
new file mode 100644
index 00000000000..5f86e98bfa1
--- /dev/null
+++ b/integration/service/poiloader/loader.go
@@ -0,0 +1,26 @@
+package poiloader
+
+import (
+	"encoding/json"
+	"io/ioutil"
+
+	"github.com/golang/glog"
+)
+
+// LoadPOI accepts json file recorded with poi data and returns deserialized result
+func LoadData(filePath string) ([]Element, error) {
+	var elements []Element
+
+	file, err := ioutil.ReadFile(filePath)
+	if err != nil {
+		glog.Errorf("While load file %s, met error %v\n", filePath, err)
+		return elements, err
+	}
+
+	err = json.Unmarshal(file, &elements)
+	if err != nil {
+		glog.Errorf("While unmarshal json file %s, met error %v\n", filePath, err)
+		return elements, err
+	}
+	return elements, nil
+}
diff --git a/integration/service/poiloader/poi_format.go b/integration/service/poiloader/poi_format.go
new file mode 100644
index 00000000000..95c3b5e4055
--- /dev/null
+++ b/integration/service/poiloader/poi_format.go
@@ -0,0 +1,64 @@
+package poiloader
+
+type Element struct {
+	ID                int64             `json:"id"`
+	VendorCode        VendorCode        `json:"vendor_code"`
+	VendorPoiID       string            `json:"vendor_poi_id"`
+	Lat               float64           `json:"lat"`
+	Lon               float64           `json:"lon"`
+	NavLat            float64           `json:"nav_lat"`
+	NavLon            float64           `json:"nav_lon"`
+	DisLat            float64           `json:"dis_lat"`
+	DisLon            float64           `json:"dis_lon"`
+	MapLinkID         int64             `json:"map_link_id"`
+	SideOfStreet      string            `json:"side_of_street"`
+	Country           Country           `json:"country"`
+	SpaceID           SpaceID           `json:"space_id"`
+	AirportCode       string            `json:"airport_code"`
+	IsNational        bool              `json:"is_national"`
+	IsStateImportance bool              `json:"is_state_importance"`
+	IsCityImportance  bool              `json:"is_city_importance"`
+	Fax               string            `json:"fax"`
+	Phone             *CategoryIDGather `json:"phone"`
+	EncodedPhone      string            `json:"encoded_phone"`
+	Email             string            `json:"email"`
+	WebURL            string            `json:"web_url"`
+	CategoryIDGather  *CategoryIDGather `json:"category_id_gather"`
+	ChainGather       string            `json:"chain_gather"`
+	RawCategoryGather string            `json:"raw_category_gather"`
+	ChildGather       string            `json:"child_gather"`
+	ParentGather      string            `json:"parent_gather"`
+	Hilbert           float64           `json:"hilbert"`
+	Amenity           Amenity           `json:"amenity"`
+}
+
+type Amenity string
+
+const (
+	ChargingStation Amenity = "charging_station"
+)
+
+type Country string
+
+const (
+	Usa Country = "USA"
+)
+
+type SpaceID string
+
+const (
+	UsaCA SpaceID = "USA_CA"
+)
+
+type VendorCode string
+
+const (
+	Noel VendorCode = "NOEL"
+	Noft VendorCode = "NOFT"
+	Nolp VendorCode = "NOLP"
+)
+
+type CategoryIDGather struct {
+	Integer *int64
+	String  *string
+}
diff --git a/integration/service/poiloader/sample_input.json b/integration/service/poiloader/sample_input.json
new file mode 100644
index 00000000000..6f83a702a3b
--- /dev/null
+++ b/integration/service/poiloader/sample_input.json
@@ -0,0 +1,64 @@
+[
+   {
+      "id":12345,
+      "vendor_code":"NOFT",
+      "vendor_poi_id":"NOFT-10_NREL99930@-@NOCO-37145190@-@NOCO-996595530",
+      "lat":0.48651,
+      "lon":0.66526,
+      "nav_lat":0.48651,
+      "nav_lon":0.66526,
+      "dis_lat":0.48651,
+      "dis_lon":0.66526,
+      "map_link_id":12345,
+      "side_of_street":"+",
+      "country":"USA",
+      "space_id":"USA_CA",
+      "airport_code":"NULL",
+      "is_national":false,
+      "is_state_importance":false,
+      "is_city_importance":false,
+      "fax":"NULL",
+      "phone":123456789,
+      "encoded_phone":"123456789",
+      "email":"NULL",
+      "web_url":"NULL",
+      "category_id_gather":"771``794``915",
+      "chain_gather":"1364@-@@-@",
+      "raw_category_gather":"NT@-@3578``NT@-@6000``NAICS@-@522110``NT@-@5540",
+      "child_gather":"NULL",
+      "parent_gather":"1718449@-@1``2216423@-@1",
+      "hilbert":2.32E+11,
+      "amenity":"charging_station"
+   },
+   {
+    "id":12346,
+    "vendor_code":"NOFT",
+    "vendor_poi_id":"NOFT-10_NREL99930@-@NOCO-37145190@-@NOCO-996595530",
+    "lat":0.48651,
+    "lon":0.66526,
+    "nav_lat":0.48651,
+    "nav_lon":0.66526,
+    "dis_lat":0.48651,
+    "dis_lon":0.66526,
+    "map_link_id":12345,
+    "side_of_street":"+",
+    "country":"USA",
+    "space_id":"USA_CA",
+    "airport_code":"NULL",
+    "is_national":false,
+    "is_state_importance":false,
+    "is_city_importance":false,
+    "fax":"NULL",
+    "phone":123456789,
+    "encoded_phone":"123456789",
+    "email":"NULL",
+    "web_url":"NULL",
+    "category_id_gather":"771``794``915",
+    "chain_gather":"1364@-@@-@",
+    "raw_category_gather":"NT@-@3578``NT@-@6000``NAICS@-@522110``NT@-@5540",
+    "child_gather":"NULL",
+    "parent_gather":"1718449@-@1``2216423@-@1",
+    "hilbert":2.32E+11,
+    "amenity":"charging_station"
+ }
+]
\ No newline at end of file
diff --git a/integration/service/spatialindexer/doc.go b/integration/service/spatialindexer/doc.go
new file mode 100644
index 00000000000..2e98a65aaeb
--- /dev/null
+++ b/integration/service/spatialindexer/doc.go
@@ -0,0 +1,19 @@
+// package spatialindexer answers query of nearest pois for given point
+//
+// Sample 1: Build connectivity for charge stations during pro-processing
+// indexer := NewS2Indexer().Build(poiCsvFile)
+// for _, stationPoint := range chargeStations {
+// 	nearbyStations := indexer.FindNearByIDs(stationPoint, 800km, -1)
+// 	rankedStations := indexer.RankingIDsByShortestDistance(stationPoint, nearbyStations)
+// }
+//
+//
+// Sample 2: Dump s2Indexer's content to folder
+// indexer.Dump(folderPath)
+//
+//
+// Sample 3: Query reachable charge stations with current energy level
+// indexer := NewS2Indexer().Load(folderPath)
+// nearbyStations := indexer.FindNearByIDs(currentPoint, currentEnergyLevel, -1)
+//
+package spatialindexer
diff --git a/integration/service/spatialindexer/iterface.go b/integration/service/spatialindexer/iterface.go
new file mode 100644
index 00000000000..e8213635271
--- /dev/null
+++ b/integration/service/spatialindexer/iterface.go
@@ -0,0 +1,30 @@
+package spatialindexer
+
+// Location for poi point
+// @todo: will be replaced by the one in map
+type Location struct {
+	Latitude  float64
+	Longitude float64
+}
+
+type PointInfo struct {
+	ID       PointID
+	Location Location
+}
+
+type RankedPointInfo struct {
+	PointInfo
+	Distance float64
+}
+
+type PointID int64
+
+type Finder interface {
+	FindNearByIDs(center Location, radius float64, limitCount int) []PointInfo
+}
+
+type Ranker interface {
+	RankingIDsByGreatCircleDistance(center Location, nearByIDs []PointInfo) []RankedPointInfo
+
+	RankingIDsByShortestDistance(center Location, nearByIDs []PointInfo) []RankedPointInfo
+}
diff --git a/integration/service/spatialindexer/s2indexer/builder.go b/integration/service/spatialindexer/s2indexer/builder.go
new file mode 100644
index 00000000000..c7ef012d7bf
--- /dev/null
+++ b/integration/service/spatialindexer/s2indexer/builder.go
@@ -0,0 +1,48 @@
+package s2indexer
+
+import (
+	"github.com/Telenav/osrm-backend/integration/service/spatialindexer"
+	"github.com/golang/geo/s2"
+)
+
+// https://s2geometry.io/resources/s2cell_statistics.html
+// Level = 6 means average area size is 20754.64km2
+// Level = 9 means average area size is 324.29km2
+const minS2Level = 9
+
+// Level = 19 means average area size is 309.27km2
+// Level = 20 means average area size is 77.32km2
+const maxS2Level = 20
+
+func build(pois []spatialindexer.PointInfo, minLevel, maxLevel int) map[s2.CellID][]spatialindexer.PointID {
+	pointID2CellIDs := make(map[spatialindexer.PointID][]s2.CellID)
+	cellID2PointIDs := make(map[s2.CellID][]spatialindexer.PointID)
+
+	for _, p := range pois {
+		leafCellID := s2.CellFromLatLng(s2.LatLngFromDegrees(p.Location.Latitude, p.Location.Longitude)).ID()
+
+		var cellIDs []s2.CellID
+		// For level = 30, its parent equal to current
+		// So no need append leafCellID outside of for loop if maxLevel = 30
+		for i := leafCellID.Level(); i > minLevel; i-- {
+			if i > maxLevel {
+				continue
+			}
+			parentCellID := leafCellID.Parent(i)
+			cellIDs = append(cellIDs, parentCellID)
+		}
+		pointID2CellIDs[p.ID] = cellIDs
+	}
+
+	for pointID, cellIDs := range pointID2CellIDs {
+		for _, cellID := range cellIDs {
+			if _, ok := cellID2PointIDs[cellID]; !ok {
+				var pointIDs []spatialindexer.PointID
+				cellID2PointIDs[cellID] = pointIDs
+			}
+			cellID2PointIDs[cellID] = append(cellID2PointIDs[cellID], pointID)
+		}
+	}
+
+	return cellID2PointIDs
+}
diff --git a/integration/service/spatialindexer/s2indexer/builder_test.go b/integration/service/spatialindexer/s2indexer/builder_test.go
new file mode 100644
index 00000000000..4fa3c8e3847
--- /dev/null
+++ b/integration/service/spatialindexer/s2indexer/builder_test.go
@@ -0,0 +1,260 @@
+package s2indexer
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/Telenav/osrm-backend/integration/service/spatialindexer"
+	"github.com/golang/geo/s2"
+)
+
+// online tool for google s2: http://s2map.com/#order=latlng&mode=polygon&s2=false&points=
+func TestBuild(t *testing.T) {
+	cases := []struct {
+		points []spatialindexer.PointInfo
+		expect map[s2.CellID][]spatialindexer.PointID
+	}{
+		{
+			[]spatialindexer.PointInfo{
+				spatialindexer.PointInfo{
+					ID: 1,
+					Location: spatialindexer.Location{
+						Latitude:  37.402701,
+						Longitude: -121.974096,
+					},
+				},
+			},
+			map[s2.CellID][]spatialindexer.PointID{
+				9263834064756932608: {1}, // 4/0010133
+				9263851656942977024: {1}, // 4/00101332
+				9263847258896465920: {1}, // 4/001013321
+				9263843960361582592: {1}, // 4/0010133210
+				9263844784995303424: {1}, // 4/00101332103
+				9263844853714780160: {1}, // 4/001013321032
+				9263844836534910976: {1}, // 4/0010133210321
+				9263844823650009088: {1}, // 4/00101332103210
+				9263844822576267264: {1}, // 4/001013321032101
+				9263844823381573632: {1}, // 4/0010133210321013
+				9263844823180247040: {1}, // 4/00101332103210130
+				9263844823129915392: {1}, // 4/001013321032101300
+				9263844823134109696: {1}, // 4/0010133210321013002
+				9263844823130963968: {1}, // 4/00101332103210130020
+				9263844823130701824: {1}, // 4/001013321032101300201
+				9263844823130898432: {1}, // 4/0010133210321013002013
+				9263844823130947584: {1}, // 4/00101332103210130020133
+				9263844823130943488: {1}, // 4/001013321032101300201331
+				9263844823130944512: {1}, // 4/0010133210321013002013312
+				9263844823130943744: {1}, // 4/00101332103210130020133120
+				9263844823130943680: {1}, // 4/001013321032101300201331201
+				9263844823130943696: {1}, // 4/0010133210321013002013312012
+				9263844823130943708: {1}, // 4/00101332103210130020133120123
+				9263844823130943709: {1}, // 4/001013321032101300201331201232
+			},
+		},
+
+		// Test case of 2 points, both near to 4655 Great America Pkwy
+		{
+			[]spatialindexer.PointInfo{
+				spatialindexer.PointInfo{
+					ID: 1,
+					Location: spatialindexer.Location{
+						Latitude:  37.402701,
+						Longitude: -121.974096,
+					},
+				},
+				spatialindexer.PointInfo{
+					ID: 2,
+					Location: spatialindexer.Location{
+						Latitude:  37.403530,
+						Longitude: -121.969768,
+					},
+				},
+			},
+			map[s2.CellID][]spatialindexer.PointID{
+				9263834064756932608: {1, 2}, // 4/0010133
+				9263851656942977024: {1, 2}, // 4/00101332
+				9263847258896465920: {1, 2}, // 4/001013321
+				9263843960361582592: {1, 2}, // 4/0010133210
+				9263844784995303424: {1, 2}, // 4/00101332103
+				9263844716275826688: {2},    // 4/001013321031
+				9263844733455695872: {2},    // 4/0010133210312
+				9263844746340597760: {2},    // 4/00101332103123
+				9263844749561823232: {2},    // 4/001013321031233
+				9263844749830258688: {2},    // 4/0010133210312332
+				9263844750031585280: {2},    // 4/00101332103123323
+				9263844749981253632: {2},    // 4/001013321031233230
+				9263844749993836544: {2},    // 4/0010133210312332303
+				9263844749996982272: {2},    // 4/00101332103123323033
+				9263844749996720128: {2},    // 4/001013321031233230331
+				9263844749996916736: {2},    // 4/0010133210312332303313
+				9263844749996900352: {2},    // 4/00101332103123323033131
+				9263844749996896256: {2},    // 4/001013321031233230331311
+				9263844749996893184: {2},    // 4/0010133210312332303313110
+				9263844749996892416: {2},    // 4/00101332103123323033131100
+				9263844749996892608: {2},    // 4/001013321031233230331311003
+				9263844749996892592: {2},    // 4/0010133210312332303313110031
+				9263844749996892588: {2},    // 4/00101332103123323033131100311
+				9263844749996892591: {2},    // 4/001013321031233230331311003113
+				9263844853714780160: {1},    // 4/001013321032
+				9263844836534910976: {1},    // 4/0010133210321
+				9263844823650009088: {1},    // 4/00101332103210
+				9263844822576267264: {1},    // 4/001013321032101
+				9263844823381573632: {1},    // 4/0010133210321013
+				9263844823180247040: {1},    // 4/00101332103210130
+				9263844823129915392: {1},    // 4/001013321032101300
+				9263844823134109696: {1},    // 4/0010133210321013002
+				9263844823130963968: {1},    // 4/00101332103210130020
+				9263844823130701824: {1},    // 4/001013321032101300201
+				9263844823130898432: {1},    // 4/0010133210321013002013
+				9263844823130947584: {1},    // 4/00101332103210130020133
+				9263844823130943488: {1},    // 4/001013321032101300201331
+				9263844823130944512: {1},    // 4/0010133210321013002013312
+				9263844823130943744: {1},    // 4/00101332103210130020133120
+				9263844823130943680: {1},    // 4/001013321032101300201331201
+				9263844823130943696: {1},    // 4/0010133210321013002013312012
+				9263844823130943708: {1},    // 4/00101332103210130020133120123
+				9263844823130943709: {1},    // 4/001013321032101300201331201232
+			},
+		},
+
+		// Test case of 4 points, points distrubted in CA, US
+		// Each points have about 100km distance with each other
+		{
+			[]spatialindexer.PointInfo{
+				spatialindexer.PointInfo{
+					ID: 1,
+					Location: spatialindexer.Location{
+						Latitude:  37.651275,
+						Longitude: -122.413744,
+					},
+				},
+				spatialindexer.PointInfo{
+					ID: 2,
+					Location: spatialindexer.Location{
+						Latitude:  36.776215,
+						Longitude: -121.733663,
+					},
+				},
+				spatialindexer.PointInfo{
+					ID: 3,
+					Location: spatialindexer.Location{
+						Latitude:  36.122438,
+						Longitude: -121.022936,
+					},
+				},
+				spatialindexer.PointInfo{
+					ID: 4,
+					Location: spatialindexer.Location{
+						Latitude:  35.365543,
+						Longitude: -120.850000,
+					},
+				},
+			},
+			map[s2.CellID][]spatialindexer.PointID{
+				9263411852291866624: {2}, // 4/0010130
+				9263359075733733376: {2}, // 4/00101300
+				9263345881594200064: {2}, // 4/001013000
+				9263349180129083392: {2}, // 4/0010130003
+				9263349455006990336: {2}, // 4/00101300032
+				9263349386287513600: {2}, // 4/001013000321
+				9263349437827121152: {2}, // 4/0010130003213
+				9263349433532153856: {2}, // 4/00101300032131
+				9263349432458412032: {2}, // 4/001013000321311
+				9263349432726847488: {2}, // 4/0010130003213112
+				9263349432928174080: {2}, // 4/00101300032131123
+				9263349432877842432: {2}, // 4/001013000321311230
+				9263349432873648128: {2}, // 4/0010130003213112301
+				9263349432874696704: {2}, // 4/00101300032131123012
+				9263349432874434560: {2}, // 4/001013000321311230121
+				9263349432874500096: {2}, // 4/0010130003213112301212
+				9263349432874516480: {2}, // 4/00101300032131123012122
+				9263349432874528768: {2}, // 4/001013000321311230121223
+				9263349432874525696: {2}, // 4/0010130003213112301212230
+				9263349432874526464: {2}, // 4/00101300032131123012122303
+				9263349432874526528: {2}, // 4/001013000321311230121223032
+				9263349432874526544: {2}, // 4/0010130003213112301212230322
+				9263349432874526556: {2}, // 4/00101300032131123012122303223
+				9263349432874526559: {2}, // 4/001013000321311230121223032233
+				9263693327268577280: {1}, // 4/0010132
+				9263746103826710528: {1}, // 4/00101323
+				9263759297966243840: {1}, // 4/001013233
+				9263755999431360512: {1}, // 4/0010132330
+				9263756824065081344: {1}, // 4/00101323303
+				9263756755345604608: {1}, // 4/001013233031
+				9263756703805997056: {1}, // 4/0010132330310
+				9263756708100964352: {1}, // 4/00101323303102
+				9263756709174706176: {1}, // 4/001013233031022
+				9263756709980012544: {1}, // 4/0010132330310223
+				9263756709912903680: {1}, // 4/00101323303102231
+				9263756709862572032: {1}, // 4/001013233031022310
+				9263756709866766336: {1}, // 4/0010132330310223102
+				9263756709867814912: {1}, // 4/00101323303102231022
+				9263756709867028480: {1}, // 4/001013233031022310220
+				9263756709866962944: {1}, // 4/0010132330310223102201
+				9263756709866913792: {1}, // 4/00101323303102231022010
+				9263756709866909696: {1}, // 4/001013233031022310220101
+				9263756709866908672: {1}, // 4/0010132330310223102201011
+				9263756709866907904: {1}, // 4/00101323303102231022010110
+				9263756709866907840: {1}, // 4/001013233031022310220101101
+				9263756709866907856: {1}, // 4/0010132330310223102201011012
+				9263756709866907844: {1}, // 4/00101323303102231022010110120
+				9263756709866907845: {1}, // 4/001013233031022310220101101202
+				9264678489687064576: {3}, // 4/0010211
+				9264731266245197824: {3}, // 4/00102113
+				9264718072105664512: {3}, // 4/001021130
+				9264719171617292288: {3}, // 4/0010211302
+				9264718346983571456: {3}, // 4/00102113020
+				9264718415703048192: {3}, // 4/001021130202
+				9264718398523179008: {3}, // 4/0010211302021
+				9264718411408080896: {3}, // 4/00102113020213
+				9264718414629306368: {3}, // 4/001021130202133
+				9264718413824000000: {3}, // 4/0010211302021330
+				9264718414025326592: {3}, // 4/00102113020213303
+				9264718414042103808: {3}, // 4/001021130202133032
+				9264718414046298112: {3}, // 4/0010211302021330322
+				9264718414043152384: {3}, // 4/00102113020213303220
+				9264718414042365952: {3}, // 4/001021130202133032200
+				9264718414042169344: {3}, // 4/0010211302021330322000
+				9264718414042152960: {3}, // 4/00102113020213303220001
+				9264718414042140672: {3}, // 4/001021130202133032200010
+				9264718414042143744: {3}, // 4/0010211302021330322000103
+				9264718414042143488: {3}, // 4/00102113020213303220001031
+				9264718414042143296: {3}, // 4/001021130202133032200010310
+				9264718414042143280: {3}, // 4/0010211302021330322000103101
+				9264718414042143284: {3}, // 4/00102113020213303220001031012
+				9264718414042143285: {3}, // 4/001021130202133032200010310122
+				9290011237591023616: {4}, // 4/0013121
+				9290064014149156864: {4}, // 4/00131213
+				9290050820009623552: {4}, // 4/001312130
+				9290047521474740224: {4}, // 4/0013121300
+				9290048346108461056: {4}, // 4/00131213003
+				9290048139950030848: {4}, // 4/001312130030
+				9290048191489638400: {4}, // 4/0013121300303
+				9290048195784605696: {4}, // 4/00131213003032
+				9290048196858347520: {4}, // 4/001312130030322
+				9290048197663653888: {4}, // 4/0013121300303223
+				9290048197864980480: {4}, // 4/00131213003032233
+				9290048197881757696: {4}, // 4/001312130030322332
+				9290048197885952000: {4}, // 4/0013121300303223322
+				9290048197882806272: {4}, // 4/00131213003032233220
+				9290048197883068416: {4}, // 4/001312130030322332202
+				9290048197883002880: {4}, // 4/0013121300303223322021
+				9290048197883052032: {4}, // 4/00131213003032233220213
+				9290048197883039744: {4}, // 4/001312130030322332202130
+				9290048197883040768: {4}, // 4/0013121300303223322021302
+				9290048197883041024: {4}, // 4/00131213003032233220213022
+				9290048197883041216: {4}, // 4/001312130030322332202130223
+				9290048197883041200: {4}, // 4/0013121300303223322021302231
+				9290048197883041212: {4}, // 4/00131213003032233220213022313
+				9290048197883041211: {4}, // 4/001312130030322332202130223131
+			},
+		},
+	}
+
+	for i, c := range cases {
+		actual := build(c.points, 6, 30)
+		if !reflect.DeepEqual(actual, c.expect) {
+			t.Errorf("parse case %d \n%v, expect\n %v \n but got %v", i, c, c.expect, actual)
+		}
+	}
+}
diff --git a/integration/service/spatialindexer/s2indexer/dumper.go b/integration/service/spatialindexer/s2indexer/dumper.go
new file mode 100644
index 00000000000..8600e0d74c6
--- /dev/null
+++ b/integration/service/spatialindexer/s2indexer/dumper.go
@@ -0,0 +1,146 @@
+package s2indexer
+
+import (
+	"bytes"
+	"encoding/gob"
+	"io/ioutil"
+	"os"
+	"strings"
+
+	"github.com/Telenav/osrm-backend/integration/pkg/api"
+	"github.com/golang/glog"
+)
+
+const cellID2PointIDsFileName = "cellID2PointIDs.gob"
+const pointID2LocationFileName = "pointID2Location.gob"
+
+func serializeS2Indexer(indexer *s2Indexer, folderPath string) error {
+	if !strings.HasSuffix(folderPath, api.Slash) {
+		folderPath = folderPath + "/"
+	}
+
+	if err := serializeCellID2PointIDs(indexer, folderPath); err != nil {
+		return err
+	}
+
+	if err := serializePointID2Location(indexer, folderPath); err != nil {
+		return err
+	}
+
+	glog.Infof("Successfully serialize s2Indexer to folder %s. len(indexer.cellID2PointIDs) = %d, len(indexer.pointID2Location) = %d\n",
+		folderPath, len(indexer.cellID2PointIDs), len(indexer.pointID2Location))
+
+	return nil
+}
+
+func serializeCellID2PointIDs(indexer *s2Indexer, folderPath string) error {
+	buf := new(bytes.Buffer)
+	encoder := gob.NewEncoder(buf)
+	err := encoder.Encode(indexer.cellID2PointIDs)
+	if err != nil {
+		glog.Errorf("During encode s2Indexer's cellID2PointIDs met error %v", err)
+		return err
+	}
+	if err = ioutil.WriteFile(folderPath+cellID2PointIDsFileName, buf.Bytes(), 0644); err != nil {
+		glog.Errorf("During dump s2Indexer's cellID2PointIDs met error %v", err)
+		return err
+	}
+	return nil
+}
+
+func serializePointID2Location(indexer *s2Indexer, folderPath string) error {
+	buf := new(bytes.Buffer)
+	encoder := gob.NewEncoder(buf)
+	err := encoder.Encode(indexer.pointID2Location)
+	if err != nil {
+		glog.Errorf("During encode s2Indexer's pointID2Location met error %v", err)
+		return err
+	}
+	if err = ioutil.WriteFile(folderPath+pointID2LocationFileName, buf.Bytes(), 0644); err != nil {
+		glog.Errorf("During dump s2Indexer's pointID2Location met error %v", err)
+		return err
+	}
+	return nil
+}
+
+func deSerializeS2Indexer(indexer *s2Indexer, folderPath string) error {
+	if !strings.HasSuffix(folderPath, api.Slash) {
+		folderPath = folderPath + "/"
+	}
+
+	if err := deSerializeCellID2PointIDs(indexer, folderPath); err != nil {
+		return err
+	}
+
+	if err := deSerializePointID2Location(indexer, folderPath); err != nil {
+		return err
+	}
+
+	glog.Infof("Successfully deserialize s2Indexer from folder %s. len(indexer.cellID2PointIDs) = %d, len(indexer.pointID2Location) = %d\n",
+		folderPath, len(indexer.cellID2PointIDs), len(indexer.pointID2Location))
+
+	return nil
+}
+
+func deSerializeCellID2PointIDs(indexer *s2Indexer, folderPath string) error {
+	byteArray, err := ioutil.ReadFile(folderPath + cellID2PointIDsFileName)
+	if err != nil {
+		glog.Errorf("During load s2Indexer's cellID2PointIDs from %s met error %v", folderPath, err)
+		return err
+	}
+	buf := bytes.NewBuffer(byteArray)
+	decoder := gob.NewDecoder(buf)
+	err = decoder.Decode(&indexer.cellID2PointIDs)
+	if err != nil {
+		glog.Errorf("During decode s2Indexer's cellID2PointIDs from %s met error %v", folderPath, err)
+		return err
+	}
+
+	return nil
+}
+
+func deSerializePointID2Location(indexer *s2Indexer, folderPath string) error {
+	byteArray, err := ioutil.ReadFile(folderPath + pointID2LocationFileName)
+	if err != nil {
+		glog.Errorf("During load s2Indexer's pointID2Location from %s met error %v", folderPath, err)
+		return err
+	}
+	buf := bytes.NewBuffer(byteArray)
+	decoder := gob.NewDecoder(buf)
+	err = decoder.Decode(&indexer.pointID2Location)
+	if err != nil {
+		glog.Errorf("During decode s2Indexer's pointID2Location from %s met error %v", folderPath, err)
+		return err
+	}
+	return nil
+
+}
+
+func removeAllDumpFiles(folderPath string) error {
+	if !strings.HasSuffix(folderPath, api.Slash) {
+		folderPath = folderPath + "/"
+	}
+
+	_, err := os.Stat(folderPath + cellID2PointIDsFileName)
+	if !os.IsNotExist(err) {
+		err = os.Remove(folderPath + cellID2PointIDsFileName)
+		if err != nil {
+			glog.Errorf("Remove file failed %s\n", folderPath+cellID2PointIDsFileName)
+			return err
+		}
+	} else {
+		glog.Warningf("There is no %s file in folder %s\n", cellID2PointIDsFileName, folderPath)
+	}
+
+	_, err = os.Stat(folderPath + pointID2LocationFileName)
+	if !os.IsNotExist(err) {
+		err = os.Remove(folderPath + pointID2LocationFileName)
+		if err != nil {
+			glog.Errorf("Remove file failed %s\n", folderPath+pointID2LocationFileName)
+			return err
+		}
+	} else {
+		glog.Warningf("There is no %s file in folder %s\n", pointID2LocationFileName, folderPath)
+	}
+	return nil
+}
diff --git a/integration/service/spatialindexer/s2indexer/dumper_test.go b/integration/service/spatialindexer/s2indexer/dumper_test.go
new file mode 100644
index 00000000000..a8393dfed05
--- /dev/null
+++ b/integration/service/spatialindexer/s2indexer/dumper_test.go
@@ -0,0 +1,65 @@
+package s2indexer
+
+import (
+	"os"
+	"reflect"
+	"testing"
+
+	"github.com/Telenav/osrm-backend/integration/service/spatialindexer"
+	"github.com/golang/geo/s2"
+)
+
+func TestDumper(t *testing.T) {
+	cases := []s2Indexer{
+		s2Indexer{
+			cellID2PointIDs: map[s2.CellID][]spatialindexer.PointID{
+				9263834064756932608: {1, 2, 3}, // 4/0010133
+				9263851656942977024: {1},       // 4/00101332
+				9263847258896465920: {2},       // 4/001013321
+				9263843960361582592: {3},       // 4/0010133210
+			},
+			pointID2Location: map[spatialindexer.PointID]spatialindexer.Location{
+				1: spatialindexer.Location{
+					Latitude:  11.11,
+					Longitude: 11.11,
+				},
+				2: spatialindexer.Location{
+					Latitude:  22.22,
+					Longitude: 22.22,
+				},
+				3: spatialindexer.Location{
+					Latitude:  33.33,
+					Longitude: 33.33,
+				},
+			},
+		},
+	}
+	// check whether curent folder is writeable
+	path, _ := os.Getwd()
+	_, err := os.OpenFile(path+"/tmp", os.O_RDONLY|os.O_CREATE, 0644)
+	if err != nil {
+		return
+	}
+	err = os.Remove(path + "/tmp")
+
+	removeAllDumpFiles(path)
+	for _, c := range cases {
+		err := serializeS2Indexer(&c, path)
+		if err != nil {
+			t.Errorf("During running serializeS2Indexer for case %v, met error %v", c, err)
+		}
+
+		actual := NewS2Indexer()
+		err = deSerializeS2Indexer(actual, path)
+		if err != nil {
+			t.Errorf("During running deSerializeS2Indexer for case %v, met error %v", c, err)
+		}
+
+		if !reflect.DeepEqual(actual, &c) {
+			t.Errorf("Expect result \n%v but got \n%v\n", &c, actual)
+		}
+
+		removeAllDumpFiles(path)
+	}
+
+}
diff --git a/integration/service/spatialindexer/s2indexer/indexer.go b/integration/service/spatialindexer/s2indexer/indexer.go
new file mode 100644
index 00000000000..2f524529d0d
--- /dev/null
+++ b/integration/service/spatialindexer/s2indexer/indexer.go
@@ -0,0 +1,76 @@
+package s2indexer
+
+import (
+	"github.com/Telenav/osrm-backend/integration/service/poiloader"
+	"github.com/Telenav/osrm-backend/integration/service/spatialindexer"
+	"github.com/golang/geo/s2"
+	"github.com/golang/glog"
+)
+
+type s2Indexer struct {
+	cellID2PointIDs  map[s2.CellID][]spatialindexer.PointID
+	pointID2Location map[spatialindexer.PointID]spatialindexer.Location
+}
+
+// NewS2Indexer generates spatial indexer based on google s2
+func NewS2Indexer() *s2Indexer {
+	return &s2Indexer{}
+}
+
+// Build constructs S2 indexer
+func (indexer *s2Indexer) Build(filePath string) *s2Indexer {
+	records, err := poiloader.LoadData(filePath)
+	if err != nil || len(records) == 0 {
+		return nil
+	}
+
+	var pointInfos []spatialindexer.PointInfo
+	for _, record := range records {
+		pointInfo := spatialindexer.PointInfo{
+			ID: elementID2PointID(record.ID),
+			Location: spatialindexer.Location{
+				Latitude:  record.Lat,
+				Longitude: record.Lon,
+			},
+		}
+		pointInfos = append(pointInfos, pointInfo)
+
+		indexer.pointID2Location[elementID2PointID(record.ID)] = spatialindexer.Location{
+			Latitude:  record.Lat,
+			Longitude: record.Lon,
+		}
+	}
+
+	indexer.cellID2PointIDs = build(pointInfos, minS2Level, maxS2Level)
+	return indexer
+}
+
+// Load s2Indexer's data from contents recorded in folder
+func (indexer *s2Indexer) Load(folderPath string) *s2Indexer {
+	if err := deSerializeS2Indexer(indexer, folderPath); err != nil {
+		glog.Errorf("Load s2Indexer's data from folder %s failed, err=%v\n", folderPath, err)
+		return nil
+	}
+	return indexer
+}
+
+// Dump s2Indexer's content into folderPath
+func (indexer *s2Indexer) Dump(folderPath string) {
+	if err := serializeS2Indexer(indexer, folderPath); err != nil {
+		glog.Errorf("Dump s2Indexer's data to folder %s failed, err=%v\n", folderPath, err)
+	}
+}
+
+func (indexer s2Indexer) getPointLocationByPointID(id spatialindexer.PointID) (spatialindexer.Location, bool) {
+	location, ok := indexer.pointID2Location[id]
+	return location, ok
+}
+
+func (indexer s2Indexer) getPointIDsByS2CellID(cellid s2.CellID) ([]spatialindexer.PointID, bool) {
+	pointIDs, ok := indexer.cellID2PointIDs[cellid]
+	return pointIDs, ok
+}
+
+func elementID2PointID(id int64) spatialindexer.PointID {
+	return (spatialindexer.PointID)(id)
+}
diff --git a/integration/service/spatialindexer/s2indexer/spatial_query.go b/integration/service/spatialindexer/s2indexer/spatial_query.go
new file mode 100644
index 00000000000..0024a4fd4f0
--- /dev/null
+++ b/integration/service/spatialindexer/s2indexer/spatial_query.go
@@ -0,0 +1,76 @@
+package s2indexer
+
+import (
+	"github.com/Telenav/osrm-backend/integration/service/spatialindexer"
+	"github.com/golang/geo/s1"
+	"github.com/golang/geo/s2"
+	"github.com/golang/glog"
+)
+
+const maxCellCount = 200
+
+const s2EarthRadiusInMeters = 6371010.0
+
+func queryNearByS2Cells(point spatialindexer.Location, radiusInMeters float64) []s2.CellID {
+	regionCover := &s2.RegionCoverer{
+		MinLevel: minS2Level,
+		MaxLevel: 20,
+		MaxCells: maxCellCount}
+	center := s2.PointFromLatLng(s2.LatLngFromDegrees(point.Latitude, point.Longitude))
+	radius := (s1.Angle)(radiusInMeters / s2EarthRadiusInMeters)
+	region := s2.Region(s2.CapFromCenterAngle(center, radius))
+	cellUnion := regionCover.Covering(region)
+	generateDebugInfo4CellIDs(([]s2.CellID)(cellUnion))
+	return ([]s2.CellID)(cellUnion)
+}
+
+func queryNearByPoints(indexer *s2Indexer, point spatialindexer.Location, radius float64) []spatialindexer.PointInfo {
+	var result []spatialindexer.PointInfo
+	cellIDs := queryNearByS2Cells(point, radius)
+	for _, cellID := range cellIDs {
+		pointIDs, hasCellID := indexer.getPointIDsByS2CellID(cellID)
+		if !hasCellID {
+			continue
+		}
+
+		for _, pointID := range pointIDs {
+			location, hasPointID := indexer.getPointLocationByPointID(pointID)
+			if !hasPointID {
+				glog.Errorf("In queryNearByPoints, use incorrect pointID %v to query s2Indexer\n", pointID)
+				continue
+			}
+
+			result = append(result, spatialindexer.PointInfo{
+				ID:       pointID,
+				Location: location,
+			})
+		}
+	}
+
+	return result
+}
+
+func generateDebugInfo4CellIDs(cellIDs []s2.CellID) {
+	glog.Info("=================================\n")
+	glog.Info("generateDebugInfo4CellIDs\n")
+	for _, cellID := range cellIDs {
+		glog.Infof("CellID value = %d(uint64), string = %v, token = %s, level = %d\n",
+			(uint64)(cellID), cellID, cellID.ToToken(), cellID.Level())
+	}
+	glog.Info("=================================\n")
+}
+
+// Generate sample url like: http://s2.sidewalklabs.com/regioncoverer/?cells=89c2584b54,89c2584d,89c25852c,89c259a5,89c259ac,89c259b4,89c259bc,89c259c7,89c259c9,89c259ca4
+func generateDebugURL(cellIDs []s2.CellID) string {
+	var url string
+
+	if len(cellIDs) == 0 {
+		return url
+	}
+
+	url += "http://s2.sidewalklabs.com/regioncoverer/?cells="
+	for _, cellID := range cellIDs {
+		url += cellID.ToToken() + ","
+	}
+	return url
+}
diff --git a/integration/service/spatialindexer/s2indexer/spatial_query_test.go b/integration/service/spatialindexer/s2indexer/spatial_query_test.go
new file mode 100644
index 00000000000..2b9599610a0
--- /dev/null
+++ b/integration/service/spatialindexer/s2indexer/spatial_query_test.go
@@ -0,0 +1,245 @@
+package s2indexer
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/Telenav/osrm-backend/integration/service/spatialindexer"
+	"github.com/golang/geo/s2"
+	"github.com/golang/glog"
+)
+
+func TestSpatialIndexQuery1(t *testing.T) {
+	fakeIndexer1 := s2Indexer{
+		cellID2PointIDs: map[s2.CellID][]spatialindexer.PointID{
+			9263834064756932608: {1, 2}, // 4/0010133
+			9263851656942977024: {1, 2}, // 4/00101332
+			9263847258896465920: {1, 2}, // 4/001013321
+			9263843960361582592: {1, 2}, // 4/0010133210
+			9263844784995303424: {1, 2}, // 4/00101332103
+			9263844716275826688: {2},    // 4/001013321031
+			9263844733455695872: {2},    // 4/0010133210312
+			9263844746340597760: {2},    // 4/00101332103123
+			9263844749561823232: {2},    // 4/001013321031233
+			9263844749830258688: {2},    // 4/0010133210312332
+			9263844750031585280: {2},    // 4/00101332103123323
+			9263844749981253632: {2},    // 4/001013321031233230
+			9263844749993836544: {2},    // 4/0010133210312332303
+			9263844749996982272: {2},    // 4/00101332103123323033
+			9263844749996720128: {2},    // 4/001013321031233230331
+			9263844749996916736: {2},    // 4/0010133210312332303313
+			9263844749996900352: {2},    // 4/00101332103123323033131
+			9263844749996896256: {2},    // 4/001013321031233230331311
+			9263844749996893184: {2},    // 4/0010133210312332303313110
+			9263844749996892416: {2},    // 4/00101332103123323033131100
+			9263844749996892608: {2},    // 4/001013321031233230331311003
+			9263844749996892592: {2},    // 4/0010133210312332303313110031
+			9263844749996892588: {2},    // 4/00101332103123323033131100311
+			9263844749996892591: {2},    // 4/001013321031233230331311003113
+			9263844853714780160: {1},    // 4/001013321032
+			9263844836534910976: {1},    // 4/0010133210321
+			9263844823650009088: {1},    // 4/00101332103210
+			9263844822576267264: {1},    // 4/001013321032101
+			9263844823381573632: {1},    // 4/0010133210321013
+			9263844823180247040: {1},    // 4/00101332103210130
+			9263844823129915392: {1},    // 4/001013321032101300
+			9263844823134109696: {1},    // 4/0010133210321013002
+			9263844823130963968: {1},    // 4/00101332103210130020
+			9263844823130701824: {1},    // 4/001013321032101300201
+			9263844823130898432: {1},    // 4/0010133210321013002013
+			9263844823130947584: {1},    // 4/00101332103210130020133
+			9263844823130943488: {1},    // 4/001013321032101300201331
+			9263844823130944512: {1},    // 4/0010133210321013002013312
+			9263844823130943744: {1},    // 4/00101332103210130020133120
+			9263844823130943680: {1},    // 4/001013321032101300201331201
+			9263844823130943696: {1},    // 4/0010133210321013002013312012
+			9263844823130943708: {1},    // 4/00101332103210130020133120123
+			9263844823130943709: {1},    // 4/001013321032101300201331201232
+		},
+		pointID2Location: map[spatialindexer.PointID]spatialindexer.Location{
+			1: spatialindexer.Location{
+				Latitude:  37.402701,
+				Longitude: -121.974096,
+			},
+			2: spatialindexer.Location{
+				Latitude:  37.403530,
+				Longitude: -121.969768,
+			},
+		},
+	}
+
+	// center in 4655 great america pkwy
+	center := spatialindexer.Location{
+		Latitude:  37.402799,
+		Longitude: -121.969861,
+	}
+
+	expect := []spatialindexer.PointInfo{
+		spatialindexer.PointInfo{
+			ID: 1,
+			Location: spatialindexer.Location{
+				Latitude:  37.402701,
+				Longitude: -121.974096,
+			},
+		},
+		spatialindexer.PointInfo{
+			ID: 2,
+			Location: spatialindexer.Location{
+				Latitude:  37.40353,
+				Longitude: -121.969768,
+			},
+		},
+	}
+
+	actual := queryNearByPoints(&fakeIndexer1, center, 10000)
+
+	if !reflect.DeepEqual(actual, expect) {
+		t.Errorf("Expect result is \n%v but got \n%v\n", actual, expect)
+	}
+}
+
+//More information could go to here: https://github.com/Telenav/osrm-backend/issues/236#issuecomment-603533484
+func TestQueryNearByS2Cells1(t *testing.T) {
+	// center in 4655 great america pkwy
+	center := spatialindexer.Location{
+		Latitude:  37.402799,
+		Longitude: -121.969861,
+	}
+	actualCellIDs := queryNearByS2Cells(center, 1600)
+	glog.Infof("\nTest URL is %s\n", generateDebugURL(actualCellIDs))
+
+	expectCellIDs := []s2.CellID{
+		9263843046942834688, // token = 808fc82b54
+		9263843047026720768, // token = 808fc82b59
+		9263843047131578368, // token = 808fc82b5f4
+		9263843050566713344, // token = 808fc82c2c
+		9263843050700931072, // token = 808fc82c34
+		9263843050835148800, // token = 808fc82c3c
+		9263843051170693120, // token = 808fc82c5
+		9263843051506237440, // token = 808fc82c64
+		9263843051590123520, // token = 808fc82c69
+		9263843053049741312, // token = 808fc82cc
+		9263843055197224960, // token = 808fc82d4
+		9263843057344708608, // token = 808fc82dc
+		9263843058686885888, // token = 808fc82e1
+		9263843060364607488, // token = 808fc82e74
+		9263843060448493568, // token = 808fc82e79
+		9263843072377094144, // token = 808fc8314
+		9263843073719271424, // token = 808fc8319
+		9263843074256142336, // token = 808fc831b
+		9263843074591686656, // token = 808fc831c4
+		9263843074994339840, // token = 808fc831dc
+		9263843075329884160, // token = 808fc831f
+		9263843079893286912, // token = 808fc833
+		9263843088483221504, // token = 808fc835
+		9263843093046624256, // token = 808fc8361
+		9263843093365391360, // token = 808fc83623
+		9263843093784821760, // token = 808fc8363c
+		9263843093919039488, // token = 808fc83644
+		9263843094321692672, // token = 808fc8365c
+		9263843094657236992, // token = 808fc8367
+		9263843095999414272, // token = 808fc836c
+		9263843176525856768, // token = 808fc8497fc
+		9263843176798486528, // token = 808fc8499
+		9263843178409099264, // token = 808fc849f
+		9263843182972502016, // token = 808fc84b
+		9263843188810973184, // token = 808fc84c5c
+		9263843189146517504, // token = 808fc84c7
+		9263843190488694784, // token = 808fc84cc
+		9263843192032198656, // token = 808fc84d1c
+		9263843192367742976, // token = 808fc84d3
+		9263843192904613888, // token = 808fc84d5
+		9263844597090484224, // token = 808fc9944
+		9263844598432661504, // token = 808fc9949
+		9263844599036641280, // token = 808fc994b4
+		9263844599170859008, // token = 808fc994bc
+		9263844599506403328, // token = 808fc994d
+		9263844600043274240, // token = 808fc994f
+		9263844601385451520, // token = 808fc9954
+		9263844603532935168, // token = 808fc995c
+		9263844608901644288, // token = 808fc997
+		9263844614270353408, // token = 808fc9984
+		9263844615612530688, // token = 808fc9989
+		9263844616149401600, // token = 808fc998b
+		9263844616484945920, // token = 808fc998c4
+		9263844617223143424, // token = 808fc998f
+		9263844617558687744, // token = 808fc99904
+		9263844620444368896, // token = 808fc999b
+		9263844620981239808, // token = 808fc999d
+		9263844621316784128, // token = 808fc999e4
+		9263844621451001856, // token = 808fc999ec
+		9263844653193494528, // token = 808fc9a15
+		9263844653730365440, // token = 808fc9a17
+		9263844654267236352, // token = 808fc9a19
+		9263844655944957952, // token = 808fc9a1f4
+		9263844656028844032, // token = 808fc9a1f9
+		9263844660441251840, // token = 808fc9a3
+		9263844669031186432, // token = 808fc9a5
+		9263844673594589184, // token = 808fc9a61
+		9263844675205201920, // token = 808fc9a67
+		9263844675742072832, // token = 808fc9a69
+		9263844676278943744, // token = 808fc9a6b
+		9263844684801769472, // token = 808fc9a8ac
+		9263844684935987200, // token = 808fc9a8b4
+		9263844685316620288, // token = 808fc9a8cab
+		9263844699901263872, // token = 808fc9ac3
+		9263844703592251392, // token = 808fc9ad0c
+		9263844704934428672, // token = 808fc9ad5c
+		9263844705269972992, // token = 808fc9ad7
+		9263844706612150272, // token = 808fc9adc
+		9263844708759633920, // token = 808fc9ae4
+		9263844710101811200, // token = 808fc9ae9
+		9263844710840008704, // token = 808fc9aebc
+		9263844711175553024, // token = 808fc9aed
+		9263844711712423936, // token = 808fc9aef
+		9263844713054601216, // token = 808fc9af4
+		9263844715202084864, // token = 808fc9afc
+		9263844733455695872, // token = 808fc9b4
+		9263844767815434240, // token = 808fc9bc
+		9263844789290270720, // token = 808fc9c1
+		9263844794658979840, // token = 808fc9c24
+		9263844795934048256, // token = 808fc9c28c
+		9263844796851552256, // token = 808fc9c2c2b
+		9263844797276225536, // token = 808fc9c2dc
+		9263844797611769856, // token = 808fc9c2f
+		9263844798953947136, // token = 808fc9c34
+		9263844801101430784, // token = 808fc9c3c
+		9263844806470139904, // token = 808fc9c5
+		9263844815060074496, // token = 808fc9c7
+		9263844836534910976, // token = 808fc9cc
+		9263844858009747456, // token = 808fc9d1
+		9263844866599682048, // token = 808fc9d3
+		9263844871163084800, // token = 808fc9d41
+		9263844872773697536, // token = 808fc9d47
+		9263844873310568448, // token = 808fc9d49
+		9263844873646112768, // token = 808fc9d4a4
+		9263844873780330496, // token = 808fc9d4ac
+		9263844882437373952, // token = 808fc9d6b
+		9263844882907136000, // token = 808fc9d6cc
+		9263844883041353728, // token = 808fc9d6d4
+		9263844884517748736, // token = 808fc9d72c
+		9263844896865779712, // token = 808fc9da0c
+		9263844896999997440, // token = 808fc9da14
+		9263844898006630400, // token = 808fc9da5
+		9263844898543501312, // token = 808fc9da7
+		9263844899885678592, // token = 808fc9dac
+		9263844902033162240, // token = 808fc9db4
+		9263844903710883840, // token = 808fc9dba4
+		9263844903845101568, // token = 808fc9dbac
+		9263844907921965056, // token = 808fc9dc9f
+		9263844908207177728, // token = 808fc9dcb
+		9263844908676939776, // token = 808fc9dccc
+		9263844964779950080, // token = 808fc9e9dc
+		9263844965115494400, // token = 808fc9e9f
+		9263844966457671680, // token = 808fc9ea4
+		9263844968605155328, // token = 808fc9eac
+		9263844969947332608, // token = 808fc9eb1
+		9263844970484203520, // token = 808fc9eb3
+		9263844970937188352, // token = 808fc9eb4b
+		9263844972564578304, // token = 808fc9ebac
+	}
+
+	if !reflect.DeepEqual(actualCellIDs, expectCellIDs) {
+		t.Errorf("Expect result is \n%v but got \n%v\n", expectCellIDs, actualCellIDs)
+	}
+}

From 8f9e8684ea8686f7535a400612d2b5b8dd113abc Mon Sep 17 00:00:00 2001
From: CoderBear801 <coderxiong@gmail.com>
Date: Tue, 24 Mar 2020 16:57:18 -0700
Subject: [PATCH 2/8] fix: remove hard code value. issue:
 https://github.com/Telenav/osrm-backend/issues/239

---
 integration/service/spatialindexer/s2indexer/spatial_query.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/integration/service/spatialindexer/s2indexer/spatial_query.go b/integration/service/spatialindexer/s2indexer/spatial_query.go
index 0024a4fd4f0..3c2d903cfd9 100644
--- a/integration/service/spatialindexer/s2indexer/spatial_query.go
+++ b/integration/service/spatialindexer/s2indexer/spatial_query.go
@@ -14,7 +14,7 @@ const s2EarthRadiusInMeters = 6371010.0
 func queryNearByS2Cells(point spatialindexer.Location, radiusInMeters float64) []s2.CellID {
 	regionCover := &s2.RegionCoverer{
 		MinLevel: minS2Level,
-		MaxLevel: 20,
+		MaxLevel: maxS2Level,
 		MaxCells: maxCellCount}
 	center := s2.PointFromLatLng(s2.LatLngFromDegrees(point.Latitude, point.Longitude))
 	radius := (s1.Angle)(radiusInMeters / s2EarthRadiusInMeters)

From 459b170aafec0b51d2f748faf72e1057ecef0a8d Mon Sep 17 00:00:00 2001
From: CoderBear801 <coderxiong@gmail.com>
Date: Tue, 24 Mar 2020 18:01:24 -0700
Subject: [PATCH 3/8] fix: refactor code.

---
 integration/service/spatialindexer/doc.go       |  9 +++++----
 integration/service/spatialindexer/iterface.go  | 17 ++++++++++++++---
 .../service/spatialindexer/s2indexer/builder.go |  6 +++---
 .../spatialindexer/s2indexer/builder_test.go    |  2 +-
 .../service/spatialindexer/s2indexer/dumper.go  |  1 +
 .../spatialindexer/s2indexer/spatial_query.go   |  1 -
 6 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/integration/service/spatialindexer/doc.go b/integration/service/spatialindexer/doc.go
index 2e98a65aaeb..3e848cc3a20 100644
--- a/integration/service/spatialindexer/doc.go
+++ b/integration/service/spatialindexer/doc.go
@@ -1,6 +1,7 @@
-// package spatialindexer answers query of nearest pois for given point
+// package spatialindexer answers query of nearest points(place, point of interest) for conditions
+// such as center location, radius, etc
 //
-// Sample 1: Build connectivity for charge stations during pro-processing
+// Sample Scenario 1: Build connectivity for charge stations during pro-processing
 // indexer := NewS2Indexer().Build(poiCsvFile)
 // for _, stationPoint := range chargeStations {
 // 	nearbyStations := indexer.FindNearByIDs(stationPoint, 800km, -1)
@@ -8,11 +9,11 @@
 // }
 //
 //
-// Sample 2: Dump s2Indexer's content to folder
+// Sample Scenario 2: Dump s2Indexer's content to folder
 // indexer.Dump(folderPath)
 //
 //
-// Sample 3: Query reachable charge stations with current energy level
+// Sample Scenario 3: Query reachable charge stations with current energy level
 // indexer := NewS2Indexer().Load(folderPath)
 // nearbyStations := indexer.FindNearByIDs(currentPoint, currentEnergyLevel, -1)
 //
diff --git a/integration/service/spatialindexer/iterface.go b/integration/service/spatialindexer/iterface.go
index e8213635271..dfcca077f7c 100644
--- a/integration/service/spatialindexer/iterface.go
+++ b/integration/service/spatialindexer/iterface.go
@@ -7,24 +7,35 @@ type Location struct {
 	Longitude float64
 }
 
+// PointInfo records point related information such as ID and location
 type PointInfo struct {
 	ID       PointID
 	Location Location
 }
 
+// RankedPointInfo used to record ranking result, distance to specific point could be used for ranking
 type RankedPointInfo struct {
 	PointInfo
 	Distance float64
 }
 
+// PointID defines ID for given point(location, point of interest)
+// Only the data used for pre-processing contains valid PointID
 type PointID int64
 
+// Finder answers special query
 type Finder interface {
-	FindNearByIDs(center Location, radius float64, limitCount int) []PointInfo
+
+	// FindNearByIDs returns a group of points near to given center location
+	FindNearByPointIDs(center Location, radius float64, limitCount int) []PointInfo
 }
 
+// Ranker used to ranking a group of points
 type Ranker interface {
-	RankingIDsByGreatCircleDistance(center Location, nearByIDs []PointInfo) []RankedPointInfo
 
-	RankingIDsByShortestDistance(center Location, nearByIDs []PointInfo) []RankedPointInfo
+	// RankPointIDsByGreatCircleDistance ranks a group of points based on great circle distance to given location
+	RankPointIDsByGreatCircleDistance(center Location, nearByIDs []PointInfo) []RankedPointInfo
+
+	// RankPointIDsByShortestDistance ranks a group of points based on shortest path distance to given location
+	RankPointIDsByShortestDistance(center Location, nearByIDs []PointInfo) []RankedPointInfo
 }
diff --git a/integration/service/spatialindexer/s2indexer/builder.go b/integration/service/spatialindexer/s2indexer/builder.go
index c7ef012d7bf..eed79895dbb 100644
--- a/integration/service/spatialindexer/s2indexer/builder.go
+++ b/integration/service/spatialindexer/s2indexer/builder.go
@@ -14,16 +14,16 @@ const minS2Level = 9
 // Level = 20 means average area size is 77.32km2
 const maxS2Level = 20
 
-func build(pois []spatialindexer.PointInfo, minLevel, maxLevel int) map[s2.CellID][]spatialindexer.PointID {
+func build(points []spatialindexer.PointInfo, minLevel, maxLevel int) map[s2.CellID][]spatialindexer.PointID {
 	pointID2CellIDs := make(map[spatialindexer.PointID][]s2.CellID)
 	cellID2PointIDs := make(map[s2.CellID][]spatialindexer.PointID)
 
-	for _, p := range pois {
+	for _, p := range points {
 		leafCellID := s2.CellFromLatLng(s2.LatLngFromDegrees(p.Location.Latitude, p.Location.Longitude)).ID()
 
 		var cellIDs []s2.CellID
 		// For level = 30, its parent equal to current
-		// So no need append leafCellID outside of for loop if maxLevel = 30
+		// So no need append leafCellID into cellIDs outside of for loop
 		for i := leafCellID.Level(); i > minLevel; i-- {
 			if i > maxLevel {
 				continue
diff --git a/integration/service/spatialindexer/s2indexer/builder_test.go b/integration/service/spatialindexer/s2indexer/builder_test.go
index 4fa3c8e3847..7a54a8862d9 100644
--- a/integration/service/spatialindexer/s2indexer/builder_test.go
+++ b/integration/service/spatialindexer/s2indexer/builder_test.go
@@ -8,7 +8,7 @@ import (
 	"github.com/golang/geo/s2"
 )
 
-// online tool for google s2: http://s2map.com/#order=latlng&mode=polygon&s2=false&points=
+// online tool for google s2: http://s2.sidewalklabs.com/regioncoverer/
 func TestBuild(t *testing.T) {
 	cases := []struct {
 		points []spatialindexer.PointInfo
diff --git a/integration/service/spatialindexer/s2indexer/dumper.go b/integration/service/spatialindexer/s2indexer/dumper.go
index 8600e0d74c6..d70fa978785 100644
--- a/integration/service/spatialindexer/s2indexer/dumper.go
+++ b/integration/service/spatialindexer/s2indexer/dumper.go
@@ -142,5 +142,6 @@ func removeAllDumpFiles(folderPath string) error {
 	} else {
 		glog.Warningf("There is no %s file in folder %s\n", pointID2LocationFileName, folderPath)
 	}
+
 	return nil
 }
diff --git a/integration/service/spatialindexer/s2indexer/spatial_query.go b/integration/service/spatialindexer/s2indexer/spatial_query.go
index 3c2d903cfd9..0cd26b65d75 100644
--- a/integration/service/spatialindexer/s2indexer/spatial_query.go
+++ b/integration/service/spatialindexer/s2indexer/spatial_query.go
@@ -20,7 +20,6 @@ func queryNearByS2Cells(point spatialindexer.Location, radiusInMeters float64) [
 	radius := (s1.Angle)(radiusInMeters / s2EarthRadiusInMeters)
 	region := s2.Region(s2.CapFromCenterAngle(center, radius))
 	cellUnion := regionCover.Covering(region)
-	generateDebugInfo4CellIDs(([]s2.CellID)(cellUnion))
 	return ([]s2.CellID)(cellUnion)
 }
 

From cb08f933845b169010afea0e3087334a9a2e3fb5 Mon Sep 17 00:00:00 2001
From: CoderBear801 <coderxiong@gmail.com>
Date: Tue, 24 Mar 2020 18:28:33 -0700
Subject: [PATCH 4/8] fix: remove local changes.

---
 integration/go.sum | 1 -
 1 file changed, 1 deletion(-)

diff --git a/integration/go.sum b/integration/go.sum
index 6c3a3f88da6..4eaede4a194 100644
--- a/integration/go.sum
+++ b/integration/go.sum
@@ -1,6 +1,5 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
-github.com/Telenav/osrm-backend v5.22.0+incompatible h1:v5K4VmdxyQjFXN20ZGmk9MchGTHWWIMUXiXmAndNvlQ=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/golang/geo v0.0.0-20200319012246-673a6f80352d h1:C/hKUcHT483btRbeGkrRjJz+Zbcj8audldIi9tRJDCc=
 github.com/golang/geo v0.0.0-20200319012246-673a6f80352d/go.mod h1:QZ0nwyI2jOfgRAoBvP+ab5aRr7c9x7lhGEJrKvBwjWI=

From 6de90a82c465629c00d318c2e8b8bd5261c3b52f Mon Sep 17 00:00:00 2001
From: CoderBear801 <coderxiong@gmail.com>
Date: Tue, 24 Mar 2020 18:32:55 -0700
Subject: [PATCH 5/8] fix: update comments

---
 integration/service/poiloader/loader.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/integration/service/poiloader/loader.go b/integration/service/poiloader/loader.go
index 5f86e98bfa1..7190c30a2fe 100644
--- a/integration/service/poiloader/loader.go
+++ b/integration/service/poiloader/loader.go
@@ -7,7 +7,7 @@ import (
 	"github.com/golang/glog"
 )
 
-// LoadPOI accepts json file recorded with poi data and returns deserialized result
+// LoadData accepts json file with points data and returns deserialized result
 func LoadData(filePath string) ([]Element, error) {
 	var elements []Element
 

From 4dcf8f0c836b67c8001aec77de0cdae1fc5a980f Mon Sep 17 00:00:00 2001
From: CoderBear801 <coderxiong@gmail.com>
Date: Tue, 24 Mar 2020 19:55:37 -0700
Subject: [PATCH 6/8] fix: add fake main to pass ci.

---
 integration/cmd/chargestations-connectivity-gen/main.go | 9 +++++++++
 1 file changed, 9 insertions(+)
 create mode 100644 integration/cmd/chargestations-connectivity-gen/main.go

diff --git a/integration/cmd/chargestations-connectivity-gen/main.go b/integration/cmd/chargestations-connectivity-gen/main.go
new file mode 100644
index 00000000000..934fe5d5111
--- /dev/null
+++ b/integration/cmd/chargestations-connectivity-gen/main.go
@@ -0,0 +1,9 @@
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	fmt.Print("Hello World!")
+}

From 240bb5b0a90080d6686191c2ff09c2d5a9160d3b Mon Sep 17 00:00:00 2001
From: CoderBear801 <coderxiong@gmail.com>
Date: Tue, 24 Mar 2020 20:31:14 -0700
Subject: [PATCH 7/8] fix: fix issue in unit test.  Build()'s result no need to
 guarantee the sequence

---
 .../service/spatialindexer/s2indexer/builder_test.go     | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/integration/service/spatialindexer/s2indexer/builder_test.go b/integration/service/spatialindexer/s2indexer/builder_test.go
index 7a54a8862d9..92b5c1a7502 100644
--- a/integration/service/spatialindexer/s2indexer/builder_test.go
+++ b/integration/service/spatialindexer/s2indexer/builder_test.go
@@ -2,6 +2,7 @@ package s2indexer
 
 import (
 	"reflect"
+	"sort"
 	"testing"
 
 	"github.com/Telenav/osrm-backend/integration/service/spatialindexer"
@@ -253,6 +254,14 @@ func TestBuild(t *testing.T) {
 
 	for i, c := range cases {
 		actual := build(c.points, 6, 30)
+
+		// sort slice to directly use DeepEqual,  Build()'s result no need to guarantee the sequence
+		for k := range actual {
+			sort.Slice(actual[k], func(i, j int) bool {
+				return actual[k][i] < actual[k][j]
+			})
+		}
+
 		if !reflect.DeepEqual(actual, c.expect) {
 			t.Errorf("parse case %d \n%v, expect\n %v \n but got %v", i, c, c.expect, actual)
 		}

From 82705722b2c32a9dee5445a8957f5751cd98a4d4 Mon Sep 17 00:00:00 2001
From: CoderBear801 <coderxiong@gmail.com>
Date: Thu, 26 Mar 2020 11:11:11 -0700
Subject: [PATCH 8/8] fix: adjust code based on review.

---
 .../chargestations-connectivity-gen/main.go   |  1 +
 integration/service/spatialindexer/doc.go     |  2 +-
 .../{iterface.go => interface.go}             |  2 +-
 .../{ => spatialindexer}/poiloader/loader.go  |  0
 .../poiloader/poi_format.go                   |  6 +++
 .../poiloader/sample_input.json               |  0
 .../spatialindexer/s2indexer/builder.go       |  3 ++
 .../spatialindexer/s2indexer/dumper.go        | 50 +++++++++++--------
 .../spatialindexer/s2indexer/dumper_test.go   |  4 +-
 .../spatialindexer/s2indexer/indexer.go       | 28 ++++++-----
 .../spatialindexer/s2indexer/spatial_query.go | 10 +++-
 .../s2indexer/spatial_query_test.go           |  2 +-
 12 files changed, 68 insertions(+), 40 deletions(-)
 rename integration/service/spatialindexer/{iterface.go => interface.go} (93%)
 rename integration/service/{ => spatialindexer}/poiloader/loader.go (100%)
 rename integration/service/{ => spatialindexer}/poiloader/poi_format.go (84%)
 rename integration/service/{ => spatialindexer}/poiloader/sample_input.json (100%)

diff --git a/integration/cmd/chargestations-connectivity-gen/main.go b/integration/cmd/chargestations-connectivity-gen/main.go
index 934fe5d5111..bd1acb5d084 100644
--- a/integration/cmd/chargestations-connectivity-gen/main.go
+++ b/integration/cmd/chargestations-connectivity-gen/main.go
@@ -5,5 +5,6 @@ import (
 )
 
 func main() {
+	// @todo: add logic to generate connectivity for charge stations
 	fmt.Print("Hello World!")
 }
diff --git a/integration/service/spatialindexer/doc.go b/integration/service/spatialindexer/doc.go
index 3e848cc3a20..87b49a73af4 100644
--- a/integration/service/spatialindexer/doc.go
+++ b/integration/service/spatialindexer/doc.go
@@ -9,7 +9,7 @@
 // }
 //
 //
-// Sample Scenario 2: Dump s2Indexer's content to folder
+// Sample Scenario 2: Dump S2Indexer's content to folder
 // indexer.Dump(folderPath)
 //
 //
diff --git a/integration/service/spatialindexer/iterface.go b/integration/service/spatialindexer/interface.go
similarity index 93%
rename from integration/service/spatialindexer/iterface.go
rename to integration/service/spatialindexer/interface.go
index dfcca077f7c..7d0aaf5138c 100644
--- a/integration/service/spatialindexer/iterface.go
+++ b/integration/service/spatialindexer/interface.go
@@ -26,7 +26,7 @@ type PointID int64
 // Finder answers special query
 type Finder interface {
 
-	// FindNearByIDs returns a group of points near to given center location
+	// FindNearByPointIDs returns a group of points near to given center location
 	FindNearByPointIDs(center Location, radius float64, limitCount int) []PointInfo
 }
 
diff --git a/integration/service/poiloader/loader.go b/integration/service/spatialindexer/poiloader/loader.go
similarity index 100%
rename from integration/service/poiloader/loader.go
rename to integration/service/spatialindexer/poiloader/loader.go
diff --git a/integration/service/poiloader/poi_format.go b/integration/service/spatialindexer/poiloader/poi_format.go
similarity index 84%
rename from integration/service/poiloader/poi_format.go
rename to integration/service/spatialindexer/poiloader/poi_format.go
index 95c3b5e4055..746a7456555 100644
--- a/integration/service/poiloader/poi_format.go
+++ b/integration/service/spatialindexer/poiloader/poi_format.go
@@ -1,5 +1,6 @@
 package poiloader
 
+// Element represent information loaded for point record
 type Element struct {
 	ID                int64             `json:"id"`
 	VendorCode        VendorCode        `json:"vendor_code"`
@@ -32,24 +33,28 @@ type Element struct {
 	Amenity           Amenity           `json:"amenity"`
 }
 
+// Amenity is defined by OSM format: https://wiki.openstreetmap.org/wiki/Tag:amenity%3Dcharging_station
 type Amenity string
 
 const (
 	ChargingStation Amenity = "charging_station"
 )
 
+// Country records IOS code
 type Country string
 
 const (
 	Usa Country = "USA"
 )
 
+// SpaceID is used to define a code for political defined administrative area
 type SpaceID string
 
 const (
 	UsaCA SpaceID = "USA_CA"
 )
 
+// VendorCode defines data source provider
 type VendorCode string
 
 const (
@@ -58,6 +63,7 @@ const (
 	Nolp VendorCode = "NOLP"
 )
 
+// CategoryIDGather records aggregate data for certain type of point
 type CategoryIDGather struct {
 	Integer *int64
 	String  *string
diff --git a/integration/service/poiloader/sample_input.json b/integration/service/spatialindexer/poiloader/sample_input.json
similarity index 100%
rename from integration/service/poiloader/sample_input.json
rename to integration/service/spatialindexer/poiloader/sample_input.json
diff --git a/integration/service/spatialindexer/s2indexer/builder.go b/integration/service/spatialindexer/s2indexer/builder.go
index eed79895dbb..49550b7ef47 100644
--- a/integration/service/spatialindexer/s2indexer/builder.go
+++ b/integration/service/spatialindexer/s2indexer/builder.go
@@ -28,9 +28,11 @@ func build(points []spatialindexer.PointInfo, minLevel, maxLevel int) map[s2.Cel
 			if i > maxLevel {
 				continue
 			}
+
 			parentCellID := leafCellID.Parent(i)
 			cellIDs = append(cellIDs, parentCellID)
 		}
+
 		pointID2CellIDs[p.ID] = cellIDs
 	}
 
@@ -40,6 +42,7 @@ func build(points []spatialindexer.PointInfo, minLevel, maxLevel int) map[s2.Cel
 				var pointIDs []spatialindexer.PointID
 				cellID2PointIDs[cellID] = pointIDs
 			}
+
 			cellID2PointIDs[cellID] = append(cellID2PointIDs[cellID], pointID)
 		}
 	}
diff --git a/integration/service/spatialindexer/s2indexer/dumper.go b/integration/service/spatialindexer/s2indexer/dumper.go
index d70fa978785..0432a6d5a4b 100644
--- a/integration/service/spatialindexer/s2indexer/dumper.go
+++ b/integration/service/spatialindexer/s2indexer/dumper.go
@@ -14,9 +14,9 @@ import (
 const cellID2PointIDsFileName = "cellID2PointIDs.gob"
 const pointID2LocationFileName = "pointID2Location.gob"
 
-func serializeS2Indexer(indexer *s2Indexer, folderPath string) error {
+func serializeS2Indexer(indexer *S2Indexer, folderPath string) error {
 	if !strings.HasSuffix(folderPath, api.Slash) {
-		folderPath = folderPath + "/"
+		folderPath += "/"
 	}
 
 	if err := serializeCellID2PointIDs(indexer, folderPath); err != nil {
@@ -27,45 +27,51 @@ func serializeS2Indexer(indexer *s2Indexer, folderPath string) error {
 		return err
 	}
 
-	glog.Infof("Successfully serialize s2Indexer to folder %s. len(indexer.cellID2PointIDs) = %d, len(indexer.pointID2Location) = %d\n",
+	glog.Infof("Successfully serialize S2Indexer to folder %s. len(indexer.cellID2PointIDs) = %d, len(indexer.pointID2Location) = %d\n",
 		folderPath, len(indexer.cellID2PointIDs), len(indexer.pointID2Location))
 
 	return nil
 }
 
-func serializeCellID2PointIDs(indexer *s2Indexer, folderPath string) error {
+func serializeCellID2PointIDs(indexer *S2Indexer, folderPath string) error {
 	buf := new(bytes.Buffer)
 	encoder := gob.NewEncoder(buf)
 	err := encoder.Encode(indexer.cellID2PointIDs)
+
 	if err != nil {
-		glog.Errorf("During encode s2Indexer's cellID2PointIDs met error %v", err)
+		glog.Errorf("During encode S2Indexer's cellID2PointIDs met error %v", err)
 		return err
 	}
+
 	if err = ioutil.WriteFile(folderPath+cellID2PointIDsFileName, buf.Bytes(), 0644); err != nil {
-		glog.Errorf("During dump s2Indexer's cellID2PointIDs met error %v", err)
+		glog.Errorf("During dump S2Indexer's cellID2PointIDs met error %v", err)
 		return err
 	}
+
 	return nil
 }
 
-func serializePointID2Location(indexer *s2Indexer, folderPath string) error {
+func serializePointID2Location(indexer *S2Indexer, folderPath string) error {
 	buf := new(bytes.Buffer)
 	encoder := gob.NewEncoder(buf)
 	err := encoder.Encode(indexer.pointID2Location)
+
 	if err != nil {
-		glog.Errorf("During encode s2Indexer's pointID2Location met error %v", err)
+		glog.Errorf("During encode S2Indexer's pointID2Location met error %v", err)
 		return err
 	}
+
 	if err = ioutil.WriteFile(folderPath+pointID2LocationFileName, buf.Bytes(), 0644); err != nil {
-		glog.Errorf("During dump s2Indexer's pointID2Location met error %v", err)
+		glog.Errorf("During dump S2Indexer's pointID2Location met error %v", err)
 		return err
 	}
+
 	return nil
 }
 
-func deSerializeS2Indexer(indexer *s2Indexer, folderPath string) error {
+func deSerializeS2Indexer(indexer *S2Indexer, folderPath string) error {
 	if !strings.HasSuffix(folderPath, api.Slash) {
-		folderPath = folderPath + "/"
+		folderPath += "/"
 	}
 
 	if err := deSerializeCellID2PointIDs(indexer, folderPath); err != nil {
@@ -76,49 +82,53 @@ func deSerializeS2Indexer(indexer *s2Indexer, folderPath string) error {
 		return err
 	}
 
-	glog.Infof("Successfully deserialize s2Indexer from folder %s. len(indexer.cellID2PointIDs) = %d, len(indexer.pointID2Location) = %d\n",
+	glog.Infof("Successfully deserialize S2Indexer from folder %s. len(indexer.cellID2PointIDs) = %d, len(indexer.pointID2Location) = %d\n",
 		folderPath, len(indexer.cellID2PointIDs), len(indexer.pointID2Location))
 
 	return nil
 }
 
-func deSerializeCellID2PointIDs(indexer *s2Indexer, folderPath string) error {
+func deSerializeCellID2PointIDs(indexer *S2Indexer, folderPath string) error {
 	byteArray, err := ioutil.ReadFile(folderPath + cellID2PointIDsFileName)
 	if err != nil {
-		glog.Errorf("During load s2Indexer's cellID2PointIDs from %s met error %v", folderPath, err)
+		glog.Errorf("During load S2Indexer's cellID2PointIDs from %s met error %v", folderPath, err)
 		return err
 	}
+
 	buf := bytes.NewBuffer(byteArray)
 	decoder := gob.NewDecoder(buf)
 	err = decoder.Decode(&indexer.cellID2PointIDs)
+
 	if err != nil {
-		glog.Errorf("During decode s2Indexer's cellID2PointIDs from %s met error %v", folderPath, err)
+		glog.Errorf("During decode S2Indexer's cellID2PointIDs from %s met error %v", folderPath, err)
 		return err
 	}
 
 	return nil
 }
 
-func deSerializePointID2Location(indexer *s2Indexer, folderPath string) error {
+func deSerializePointID2Location(indexer *S2Indexer, folderPath string) error {
 	byteArray, err := ioutil.ReadFile(folderPath + pointID2LocationFileName)
 	if err != nil {
-		glog.Errorf("During load s2Indexer's pointID2Location from %s met error %v", folderPath, err)
+		glog.Errorf("During load S2Indexer's pointID2Location from %s met error %v", folderPath, err)
 		return err
 	}
+
 	buf := bytes.NewBuffer(byteArray)
 	decoder := gob.NewDecoder(buf)
 	err = decoder.Decode(&indexer.pointID2Location)
+
 	if err != nil {
-		glog.Errorf("During decode s2Indexer's pointID2Location from %s met error %v", folderPath, err)
+		glog.Errorf("During decode S2Indexer's pointID2Location from %s met error %v", folderPath, err)
 		return err
 	}
-	return nil
 
+	return nil
 }
 
 func removeAllDumpFiles(folderPath string) error {
 	if !strings.HasSuffix(folderPath, api.Slash) {
-		folderPath = folderPath + "/"
+		folderPath += "/"
 	}
 
 	_, err := os.Stat(folderPath + cellID2PointIDsFileName)
diff --git a/integration/service/spatialindexer/s2indexer/dumper_test.go b/integration/service/spatialindexer/s2indexer/dumper_test.go
index a8393dfed05..5fd860dae76 100644
--- a/integration/service/spatialindexer/s2indexer/dumper_test.go
+++ b/integration/service/spatialindexer/s2indexer/dumper_test.go
@@ -10,8 +10,8 @@ import (
 )
 
 func TestDumper(t *testing.T) {
-	cases := []s2Indexer{
-		s2Indexer{
+	cases := []S2Indexer{
+		S2Indexer{
 			cellID2PointIDs: map[s2.CellID][]spatialindexer.PointID{
 				9263834064756932608: {1, 2, 3}, // 4/0010133
 				9263851656942977024: {1},       // 4/00101332
diff --git a/integration/service/spatialindexer/s2indexer/indexer.go b/integration/service/spatialindexer/s2indexer/indexer.go
index 2f524529d0d..6806555078c 100644
--- a/integration/service/spatialindexer/s2indexer/indexer.go
+++ b/integration/service/spatialindexer/s2indexer/indexer.go
@@ -1,30 +1,32 @@
 package s2indexer
 
 import (
-	"github.com/Telenav/osrm-backend/integration/service/poiloader"
 	"github.com/Telenav/osrm-backend/integration/service/spatialindexer"
+	"github.com/Telenav/osrm-backend/integration/service/spatialindexer/poiloader"
 	"github.com/golang/geo/s2"
 	"github.com/golang/glog"
 )
 
-type s2Indexer struct {
+// S2Indexer provide spatial index ability based on google s2
+type S2Indexer struct {
 	cellID2PointIDs  map[s2.CellID][]spatialindexer.PointID
 	pointID2Location map[spatialindexer.PointID]spatialindexer.Location
 }
 
 // NewS2Indexer generates spatial indexer based on google s2
-func NewS2Indexer() *s2Indexer {
-	return &s2Indexer{}
+func NewS2Indexer() *S2Indexer {
+	return &S2Indexer{}
 }
 
 // Build constructs S2 indexer
-func (indexer *s2Indexer) Build(filePath string) *s2Indexer {
+func (indexer *S2Indexer) Build(filePath string) *S2Indexer {
 	records, err := poiloader.LoadData(filePath)
 	if err != nil || len(records) == 0 {
 		return nil
 	}
 
 	var pointInfos []spatialindexer.PointInfo
+
 	for _, record := range records {
 		pointInfo := spatialindexer.PointInfo{
 			ID: elementID2PointID(record.ID),
@@ -45,28 +47,28 @@ func (indexer *s2Indexer) Build(filePath string) *s2Indexer {
 	return indexer
 }
 
-// Load s2Indexer's data from contents recorded in folder
-func (indexer *s2Indexer) Load(folderPath string) *s2Indexer {
+// Load S2Indexer's data from contents recorded in folder
+func (indexer *S2Indexer) Load(folderPath string) *S2Indexer {
 	if err := deSerializeS2Indexer(indexer, folderPath); err != nil {
-		glog.Errorf("Load s2Indexer's data from folder %s failed, err=%v\n", folderPath, err)
+		glog.Errorf("Load S2Indexer's data from folder %s failed, err=%v\n", folderPath, err)
 		return nil
 	}
 	return indexer
 }
 
-// Dump s2Indexer's content into folderPath
-func (indexer *s2Indexer) Dump(folderPath string) {
+// Dump S2Indexer's content into folderPath
+func (indexer *S2Indexer) Dump(folderPath string) {
 	if err := serializeS2Indexer(indexer, folderPath); err != nil {
-		glog.Errorf("Dump s2Indexer's data to folder %s failed, err=%v\n", folderPath, err)
+		glog.Errorf("Dump S2Indexer's data to folder %s failed, err=%v\n", folderPath, err)
 	}
 }
 
-func (indexer s2Indexer) getPointLocationByPointID(id spatialindexer.PointID) (spatialindexer.Location, bool) {
+func (indexer S2Indexer) getPointLocationByPointID(id spatialindexer.PointID) (spatialindexer.Location, bool) {
 	location, ok := indexer.pointID2Location[id]
 	return location, ok
 }
 
-func (indexer s2Indexer) getPointIDsByS2CellID(cellid s2.CellID) ([]spatialindexer.PointID, bool) {
+func (indexer S2Indexer) getPointIDsByS2CellID(cellid s2.CellID) ([]spatialindexer.PointID, bool) {
 	pointIDs, ok := indexer.cellID2PointIDs[cellid]
 	return pointIDs, ok
 }
diff --git a/integration/service/spatialindexer/s2indexer/spatial_query.go b/integration/service/spatialindexer/s2indexer/spatial_query.go
index 0cd26b65d75..2b7c5bddafb 100644
--- a/integration/service/spatialindexer/s2indexer/spatial_query.go
+++ b/integration/service/spatialindexer/s2indexer/spatial_query.go
@@ -20,12 +20,15 @@ func queryNearByS2Cells(point spatialindexer.Location, radiusInMeters float64) [
 	radius := (s1.Angle)(radiusInMeters / s2EarthRadiusInMeters)
 	region := s2.Region(s2.CapFromCenterAngle(center, radius))
 	cellUnion := regionCover.Covering(region)
+
 	return ([]s2.CellID)(cellUnion)
 }
 
-func queryNearByPoints(indexer *s2Indexer, point spatialindexer.Location, radius float64) []spatialindexer.PointInfo {
+func queryNearByPoints(indexer *S2Indexer, point spatialindexer.Location, radius float64) []spatialindexer.PointInfo {
 	var result []spatialindexer.PointInfo
+
 	cellIDs := queryNearByS2Cells(point, radius)
+
 	for _, cellID := range cellIDs {
 		pointIDs, hasCellID := indexer.getPointIDsByS2CellID(cellID)
 		if !hasCellID {
@@ -35,7 +38,7 @@ func queryNearByPoints(indexer *s2Indexer, point spatialindexer.Location, radius
 		for _, pointID := range pointIDs {
 			location, hasPointID := indexer.getPointLocationByPointID(pointID)
 			if !hasPointID {
-				glog.Errorf("In queryNearByPoints, use incorrect pointID %v to query s2Indexer\n", pointID)
+				glog.Errorf("In queryNearByPoints, use incorrect pointID %v to query S2Indexer\n", pointID)
 				continue
 			}
 
@@ -52,10 +55,12 @@ func queryNearByPoints(indexer *s2Indexer, point spatialindexer.Location, radius
 func generateDebugInfo4CellIDs(cellIDs []s2.CellID) {
 	glog.Info("=================================\n")
 	glog.Info("generateDebugInfo4CellIDs\n")
+
 	for _, cellID := range cellIDs {
 		glog.Infof("CellID value = %d(uint64), string = %v, token = %s, level = %d\n",
 			(uint64)(cellID), cellID, cellID.ToToken(), cellID.Level())
 	}
+
 	glog.Info("=================================\n")
 }
 
@@ -71,5 +76,6 @@ func generateDebugURL(cellIDs []s2.CellID) string {
 	for _, cellID := range cellIDs {
 		url += cellID.ToToken() + ","
 	}
+
 	return url
 }
diff --git a/integration/service/spatialindexer/s2indexer/spatial_query_test.go b/integration/service/spatialindexer/s2indexer/spatial_query_test.go
index 2b9599610a0..8926bc11845 100644
--- a/integration/service/spatialindexer/s2indexer/spatial_query_test.go
+++ b/integration/service/spatialindexer/s2indexer/spatial_query_test.go
@@ -10,7 +10,7 @@ import (
 )
 
 func TestSpatialIndexQuery1(t *testing.T) {
-	fakeIndexer1 := s2Indexer{
+	fakeIndexer1 := S2Indexer{
 		cellID2PointIDs: map[s2.CellID][]spatialindexer.PointID{
 			9263834064756932608: {1, 2}, // 4/0010133
 			9263851656942977024: {1, 2}, // 4/00101332