Add --stop-after option to tile-join

CHANGELOG.md

@@ -1,6 +1,7 @@
 # 2.38.0
 
 * `tippecanoe-overzoom` can now merge multiple tiles when overzooming them
+* Add `--stop-after` option to `tile-join` to limit the total number of tiles copied
 
 # 2.37.1
 

Makefile

@@ -431,7 +431,13 @@ join-test: tippecanoe tippecanoe-decode tile-join
 	./tile-join --overzoom -f -o tests/ne_110m_ocean/join/joined.mbtiles tests/ne_110m_ocean/join/ocean.mbtiles tests/ne_110m_ocean/join/countries.mbtiles
 	./tippecanoe-decode -x generator tests/ne_110m_ocean/join/joined.mbtiles > tests/ne_110m_ocean/join/joined.mbtiles.json.check
 	cmp tests/ne_110m_ocean/join/joined.mbtiles.json.check tests/ne_110m_ocean/join/joined.mbtiles.json
-	rm -f tests/ne_110m_ocean/join/ocean.mbtiles tests/ne_110m_ocean/join/countries.mbtiles tests/ne_110m_ocean/join/joined.mbtiles tests/ne_110m_ocean/join/joined.mbtiles.json.check
+	#
+	# Test overzooming with tile count limit
+	#
+	./tile-join --overzoom -f -o tests/ne_110m_ocean/join/joined.mbtiles --stop-after 50 tests/ne_110m_ocean/join/ocean.mbtiles tests/ne_110m_ocean/join/countries.mbtiles
+	./tippecanoe-decode -x generator tests/ne_110m_ocean/join/joined.mbtiles > tests/ne_110m_ocean/join/joined.mbtiles-50.json.check
+	cmp tests/ne_110m_ocean/join/joined.mbtiles-50.json.check tests/ne_110m_ocean/join/joined.mbtiles-50.json
+	rm -f tests/ne_110m_ocean/join/ocean.mbtiles tests/ne_110m_ocean/join/countries.mbtiles tests/ne_110m_ocean/join/joined.mbtiles tests/ne_110m_ocean/join/joined.mbtiles.json.check tests/ne_110m_ocean/join/joined.mbtiles-50.json.check
 
 join-filter-test: tippecanoe tippecanoe-decode tile-join
 	# Comes out different from the direct tippecanoe run because null attributes are lost

README.md

@@ -793,6 +793,7 @@ The options are:
 
  * `-z` _zoom_ or `--maximum-zoom=`_zoom_: Don't copy tiles from higher zoom levels than the specified zoom
  * `-Z` _zoom_ or `--minimum-zoom=`_zoom_: Don't copy tiles from lower zoom levels than the specified zoom
+ * `-a` _count_ or `--stop-after=`_count_: Stop copying tile from additional zoom levels after the specified _count_ of tiles has been written to the output.
 
 ### Merging attributes from a CSV file
 

man/tippecanoe.1

@@ -1005,6 +1005,8 @@ The options are:
 \fB\fC\-z\fR \fIzoom\fP or \fB\fC\-\-maximum\-zoom=\fR\fIzoom\fP: Don't copy tiles from higher zoom levels than the specified zoom
 .IP \(bu 2
 \fB\fC\-Z\fR \fIzoom\fP or \fB\fC\-\-minimum\-zoom=\fR\fIzoom\fP: Don't copy tiles from lower zoom levels than the specified zoom
+.IP \(bu 2
+\fB\fC\-a\fR \fIcount\fP or \fB\fC\-\-stop\-after=\fR\fIcount\fP: Stop copying tile from additional zoom levels after the specified \fIcount\fP of tiles has been written to the output.
 .RE
 .SS Merging attributes from a CSV file
 .RS

tile-join.cpp

@@ -54,6 +54,9 @@ int minzoom = 0;
 std::map<std::string, std::string> renames;
 bool exclude_all = false;
 
+size_t stop_after = 0;
+std::atomic<size_t> tiles_queued_for_write(0);
+
 bool want_overzoom = false;
 int buffer = 5;
 
@@ -1084,12 +1087,22 @@ void decode(struct tileset_reader *readers, std::map<std::string, layermap_entry
 		// Then this tile is done and we can safely run the output queue.
 
 		if (readers == NULL || readers->zoom != current.first.z || readers->x != current.first.x || readers->y != current.first.y) {
+			tiles_queued_for_write++;
 			if (tasks.size() > 100 * CPUS) {
 				dispatch_tasks(tasks, layermaps, outdb, outdir, header, mapping, exclude, include, ifmatched, keep_layers, remove_layers, filter, readers);
 				tasks.clear();
 			}
 		}
 
+		if (readers != NULL && readers->zoom != current.first.z && stop_after != 0 && tiles_queued_for_write >= stop_after) {
+			dispatch_tasks(tasks, layermaps, outdb, outdir, header, mapping, exclude, include, ifmatched, keep_layers, remove_layers, filter, readers);
+			tasks.clear();
+			if (!quiet) {
+				fprintf(stderr, "stopping after zoom %lld, after writing %zu tiles\n", current.first.z, (size_t) tiles_queued_for_write);
+				break;
+			}
+		}
+
 		// put the tileset_reader back onto the queue,
 		// in whatever sequence its next tile calls for
 
@@ -1315,6 +1328,7 @@ int main(int argc, char **argv) {
 		{"feature-filter", required_argument, 0, 'j'},
 		{"rename-layer", required_argument, 0, 'R'},
 		{"read-from", required_argument, 0, 'r'},
+		{"stop-after", required_argument, 0, 'a'},
 
 		{"no-tile-size-limit", no_argument, &pk, 1},
 		{"no-tile-compression", no_argument, &pC, 1},
@@ -1448,6 +1462,10 @@ int main(int argc, char **argv) {
 			remove_layers.insert(std::string(optarg));
 			break;
 
+		case 'a':
+			stop_after = atoll(optarg);
+			break;
+
 		case 'R': {
 			char *cp = strchr(optarg, ':');
 			if (cp == NULL || cp == optarg) {