implement pmtiles extract [#31, #52]

* Experimental cli support for extracting a region from a larger archive, given a maxzoom and GeoJSON multipolygon region.
* Limited to credentialed buckets or local files now, public HTTP to come later
* Limited to a single download thread
* Change directory optimization to be faster and match Java implementation, affects root/leaf sizes

main.go

@@ -45,12 +45,13 @@ var cli struct {
 	} `cmd:"" help:"Fetch one tile from a local or remote archive and output on stdout."`
 
 	Extract struct {
-		Input   string `arg:"" help:"Input local or remote archive."`
-		Output  string `arg:"" help:"Output archive." type:"path"`
-		Bucket  string `help:"Remote bucket of input archive."`
-		Region  string `help:"local GeoJSON Polygon or MultiPolygon file for area of interest." type:"existingfile"`
-		Maxzoom int    `help:"Maximum zoom level, inclusive."`
-		DryRun  bool   `help:"Calculate tiles to extract based on header and directories, but don't download them."`
+		Input     string  `arg:"" help:"Input local or remote archive."`
+		Output    string  `arg:"" help:"Output archive." type:"path"`
+		Bucket    string  `help:"Remote bucket of input archive."`
+		Region    string  `help:"local GeoJSON Polygon or MultiPolygon file for area of interest." type:"existingfile"`
+		Maxzoom   uint8   `help:"Maximum zoom level, inclusive."`
+		DryRun    bool    `help:"Calculate tiles to extract based on header and directories, but don't download them."`
+		Overfetch float32 `default:0.1 help:"What ratio of extra data to download to minimize # requests; 0.2 is 20%"`
 	} `cmd:"" help:"Create an archive from a larger archive for a subset of zoom levels or geographic region."`
 
 	Verify struct {
@@ -119,7 +120,10 @@ func main() {
 		logger.Printf("Serving %s %s on port %d with Access-Control-Allow-Origin: %s\n", cli.Serve.Bucket, cli.Serve.Path, cli.Serve.Port, cli.Serve.Cors)
 		logger.Fatal(http.ListenAndServe(":"+strconv.Itoa(cli.Serve.Port), nil))
 	case "extract <input> <output>":
-		logger.Fatalf("This command is not yet implemented.")
+		err := pmtiles.Extract(logger, cli.Extract.Bucket, cli.Extract.Input, cli.Extract.Maxzoom, cli.Extract.Region, cli.Extract.Output, cli.Extract.Overfetch)
+		if err != nil {
+			logger.Fatalf("Failed to extract, %v", err)
+		}
 	case "convert <input> <output>":
 		path := cli.Convert.Input
 		output := cli.Convert.Output
@@ -160,6 +164,8 @@ func main() {
 			logger.Fatalf("Failed to upload file, %v", err)
 		}
 	case "verify <input>":
+		// check clustered
+		// check counts (addressed tiles, tile entries, # tile contents)
 		logger.Fatalf("This command is not yet implemented.")
 	case "version":
 		fmt.Printf("pmtiles %s, commit %s, built at %s\n", version, commit, date)

pmtiles/convert.go

@@ -114,14 +114,14 @@ func Convert(logger *log.Logger, input string, output string, deduplicate bool,
 func add_directoryv2_entries(dir DirectoryV2, entries *[]EntryV3, f *os.File) {
 	for zxy, rng := range dir.Entries {
 		tile_id := ZxyToId(zxy.Z, zxy.X, zxy.Y)
-		*entries = append(*entries, EntryV3{tile_id, rng.Offset, rng.Length, 1})
+		*entries = append(*entries, EntryV3{tile_id, rng.Offset, uint32(rng.Length), 1})
 	}
 
 	var unique = map[uint64]uint32{}
 
 	// uniqify the offset/length pairs
 	for _, rng := range dir.Leaves {
-		unique[rng.Offset] = rng.Length
+		unique[rng.Offset] = uint32(rng.Length)
 	}
 
 	for offset, length := range unique {

pmtiles/directory.go

@@ -313,24 +313,31 @@ func build_roots_leaves(entries []EntryV3, leaf_size int) ([]byte, []byte, int)
 }
 
 func optimize_directories(entries []EntryV3, target_root_len int) ([]byte, []byte, int) {
-	test_root_bytes := serialize_entries(entries)
-
-	// Case1: the entire directory fits into the target len
-	if len(test_root_bytes) <= target_root_len {
-		return test_root_bytes, make([]byte, 0), 0
-	} else {
-
-		// TODO: case 2: mixed tile entries/directory entries in root
-
-		// case 3: root directory is leaf pointers only
-		// use an iterative method, increasing the size of the leaf directory until the root fits
-		leaf_size := 4096
-		for {
-			root_bytes, leaves_bytes, num_leaves := build_roots_leaves(entries, leaf_size)
-			if len(root_bytes) <= target_root_len {
-				return root_bytes, leaves_bytes, num_leaves
-			}
-			leaf_size *= 2
+	if len(entries) < 16384 {
+		test_root_bytes := serialize_entries(entries)
+		// Case1: the entire directory fits into the target len
+		if len(test_root_bytes) <= target_root_len {
+			return test_root_bytes, make([]byte, 0), 0
 		}
 	}
+
+	// TODO: case 2: mixed tile entries/directory entries in root
+
+	// case 3: root directory is leaf pointers only
+	// use an iterative method, increasing the size of the leaf directory until the root fits
+
+	var leaf_size float32
+	leaf_size = float32(len(entries)) / 3500
+
+	if leaf_size < 4096 {
+		leaf_size = 4096
+	}
+
+	for {
+		root_bytes, leaves_bytes, num_leaves := build_roots_leaves(entries, int(leaf_size))
+		if len(root_bytes) <= target_root_len {
+			return root_bytes, leaves_bytes, num_leaves
+		}
+		leaf_size *= 1.2
+	}
 }

pmtiles/downloader.go

@@ -72,7 +72,7 @@ func DownloadParts(getter func (Range) []byte, ranges []Range, numThreads int) c
 
 // an number for overhead: 0.2 is 20% overhead, 1.0 is 100% overhead
 // a number of maximum chunk size: n chunks * threads is the max memory usage
-// store the smallest gaps in a heap
+// store the smallest gaps in a heap; merge ranges until overhead budget is reached
 func DownloadBatchedParts(getter func (Range) []byte, ranges []Range, overhead float32, maxSizeBytes int, numThreads int) chan []byte {
 	orderedOutput := make(chan []byte, 8)
 	return orderedOutput