PostGIS Compute vector Tiles (i)-Unique value rendering

???? No mistake, the vector slices are calculated using PostGIS. Before that, prepare a data: A GIS data table (point data of 1 million in this case, coordinates: 4326), and add X, y fields to the table to facilitate subsequent data filtering. The SQL uses the
ST_ASMVT and St_asmvtgeom.

???? Creating a vector slice in this article is simple, using one of the following SQL to run the results like. Then write a vector slice of the HTTP service (refer to Go-vtile-example, this example, the vector tile compression rate is higher), and use the Mapbox for the front-end display (Tips: SQL ' Points ' string is consistent with the Source-layer in Mapbox in the rendering). See the bottom of the code.

SELECT ST_AsMVT(tile,‘points‘) tile  FROM(SELECT ST_AsMVTGeom(geom,ST_MakeEnvelope(100,10,125,22, 4326),4096, 0, true)     AS geom FROM grid20180322 ) AS  tile where  tile.geom is not null

Package Mainimport (_ "GITHUB.COM/LIB/PQ" "Database/sql" "Time" "Log" "Math" "Errors" "FMT" "N Et/http "" RegExp "" StrConv "" strings ") Func tilepathtoxyz (Path string) (TileID, error) {xyzreg: = RegExp. Mustcompile ("(? p<z>[0-9]+)/(? p<x>[0-9]+)/(? p<y>[0-9]+) Matches: = Xyzreg.findstringsubmatch (path) If Len (matches) = = 0 {return tileid{}, errors . New ("Unable to parse path as tile")} x, err: = StrConv. Parseuint (Matches[2], ten, +) if err! = Nil {return tileid{}, err} y, err: = StrConv. Parseuint (Matches[3], ten, +) if err! = Nil {return tileid{}, err} Z, err: = StrConv. Parseuint (Matches[1], ten, +) if err! = Nil {return tileid{}, err} return Tileid{x:uint32 (x), Y:uint32    (y), Z:uint32 (z)}, Nil}type Lnglat struct {LNG float64 lat float64}type TileID struct {x uint32 y UInt32 Z uint32}func tile2lon (x int, z int) (a float64) {return float64 (x)/math. Pow (2, float64 (z)) * 360.0-180; } func Tile2lat (y int, z int) (a float64) {n: = Math. Pi-(2.0 * Math. Pi * float64 (y))/math.   Pow (2, float64 (z)); return Math. Atan (Math. Sinh (n)) *180/math. Pi; } func floattostring (Input_num float64) string {//To convert a float number to a string return StrConv. Formatfloat (Input_num, ' F ', 6, +)} func LoadData (xyz TileID) (a []byte) {ymax: =floattostring (Tile2lat (int (XYZ.Y), int (    (XYZ.Z)));    Ymin: = floattostring (Tile2lat (int (xyz.y+1), int (xyz.z)));    Xmin: = floattostring (Tile2lon (int (xyz.x), int (xyz.z)));    Xmax: = floattostring (Tile2lon (int (xyz.x+1), int (xyz.z))); Fmt. Println ("Ymax:", Ymax) fmt. Println ("ymin:", ymin) fmt. Println ("Xmin:", xmin) fmt. Println ("Xmax:", xmax) ConnStr: = "dbname=xx user=xx password=xx host=localhost port=5433 sslmode=disable" db, er r: = SQL. Open ("Postgres", connstr) if err! = Nil {panic (ERR)} defer db. Close () Err = db. Ping () if err! = Nil {PANic (Err)} FMT.    Println ("Successfully connected!") var tile []byte s: = []string{xmin,ymin,xmax,ymax} maxmin:=strings. Join (S, ",") s2: = []string{"where (x between", Xmin, "and", Xmax, ") and (Y between", ymin, "and", Ymax, ")"} Wmaxmin: =strings. Join (S2, "") sql:= "select ST_ASMVT (Tile, ' points ') tile from (select St_asmvtgeom (W.geom,st_makeenvelope (" +maxmin+ ", 4    326), 4096, 0, true) as Geom from (select Geom from grid20180322 "+wmaxmin+") W) as tile where tile.geom are NOT NULL " rows1:= db. Queryrow (sql) ERR1: = rows1. Scan (&tile) if err1! = Nil {log. Fatal (ERR1)} fmt. PRINTLN (SQL)//defer rows1. Close () return tile}func main () {//t1: = time. Now () Mux: = http. Newservemux () Tilebase: = "/tiles/" MUX. Handlefunc (Tilebase, func (w http. Responsewriter, R *http. Request) {t2: = time. Now () log. Printf ("URL:%s", R.url. Path) Tilepart: = R.url. Path[len (tilebase):] FMT.     Println ("Tilepart:", Tilepart)   XYZ, Err: = TILEPATHTOXYZ (Tilepart) fmt. Println ("xyz:", xyz) if err! = Nil {http. Error (W, "Invalid tile url", "page") return} tile:=loaddata (XYZ)//all this APi to        Be requests from the other domains. W.header (). Set ("Content-type", "Application/x-protobuf") W.header (). Set ("Access-control-allow-origin", "*") W.header (). Set ("Access-control-allow-methods", "GET, POST, OPTIONS") w.write (tile) Elapsed2: = time. Since (T2) fmt. Println ("Time-consuming:", ELAPSED2)}) log. Fatal (http. Listenandserve (": 8081", MUX))}

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PostGIS compute vector Tiles (one)-Unique value rendering