Improve error handling for geocoderDataIterator

lib/mbtiles.js

@@ -633,18 +633,24 @@ MBTiles.prototype.geocoderDataIterator = function(type) {
         while (nextQueue.length && dataQueue.length) {
             var nextCb = nextQueue.shift(), data, cbValue;
             if (dataQueue[0] == doneSentinel) {
-                cbValue = {value: undefined, done: true};
+                cbValue = {
+                    err: null,
+                    row: {value: undefined, done: true}
+                }
             } else {
                 data = dataQueue.shift();
                 maybeRefillBuffer();
 
-                cbValue = {value: {shard: data.shard, data: zlib.inflateSync(data.data)}, done: false};
+                cbValue = {
+                    err: data.err,
+                    row: {value: {shard: data.row.shard, data: zlib.inflateSync(data.row.data)}, done: false}
+                };
             }
             // bind the callback and data now so that they don't change before the setImmediate
             // callback is executed
             (function(nextCb, cbValue) {
                 setImmediate(function() {
-                    nextCb(cbValue);
+                    nextCb(cbValue.err, cbValue.row);
                 });
             })(nextCb, cbValue);
         }
@@ -657,7 +663,7 @@ MBTiles.prototype.geocoderDataIterator = function(type) {
         refilling = true;
         var segmentCount = 0;
         _this._db.each('SELECT shard, data FROM geocoder_data WHERE type = ? ORDER BY shard limit ?,?', type, position, chunkSize, function(err, row) {
-            dataQueue.push(row);
+            dataQueue.push({row: row, err: err});
             segmentCount += 1;
             sendIfAvailable();
         }, function() {

test/geocoder.test.js

@@ -80,7 +80,8 @@ tape('putGeocoderData', function(assert) {
 tape('geocoderDataIterator', function(assert) {
     var it = to.geocoderDataIterator("term");
     var data = [];
-    var n = function(item) {
+    var n = function(err, item) {
+        assert.ifError(err);
         if (item.done) {
             assert.equal(data.length, 2, "iterator produces two shards");