From 2fbd9893bd4b8fc97b1383317adc750b69a791d9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Garc=C3=ADa=20Aubert?=
 <danielgarciaaubert@gmail.com>
Date: Mon, 2 Sep 2019 14:09:13 +0200
Subject: [PATCH] Going green: do not fail when source is empty

---
 lib/cartodb/backends/layer-stats/mapnik-layer-stats.js | 5 +++++
 test/acceptance/stats/mapnik_stats_layergroup.js       | 9 ++-------
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/lib/cartodb/backends/layer-stats/mapnik-layer-stats.js b/lib/cartodb/backends/layer-stats/mapnik-layer-stats.js
index 7212eccb..3d229799 100644
--- a/lib/cartodb/backends/layer-stats/mapnik-layer-stats.js
+++ b/lib/cartodb/backends/layer-stats/mapnik-layer-stats.js
@@ -139,6 +139,11 @@ function _sample(ctx) {
     return queryUtils.queryPromise(ctx.dbConnection, sqlMaxMin)
         .then(maxMinRes => {
             const { min_id: min, id_span: span } = maxMinRes.rows[0];
+
+            if (!min || !span) {
+                return { rows: {} };
+            }
+
             const values = _getSampleValuesFromRange(min, span, limit);
             const sqlSample = _getSQL(ctx, sql => queryUtils.getSampleFromIdsQuery(sql, values, columns));
 
diff --git a/test/acceptance/stats/mapnik_stats_layergroup.js b/test/acceptance/stats/mapnik_stats_layergroup.js
index 76d8770b..1f8ca067 100644
--- a/test/acceptance/stats/mapnik_stats_layergroup.js
+++ b/test/acceptance/stats/mapnik_stats_layergroup.js
@@ -596,8 +596,7 @@ describe(`[${desc}] Create mapnik layergroup`, function() {
                         "metadata": {
                             "sample": {
                                 "num_rows": 30
-                            },
-                            "sql": "select * from test_table_100 limit 0"
+                            }
                         }
                     }
                 }
@@ -606,11 +605,7 @@ describe(`[${desc}] Create mapnik layergroup`, function() {
 
         testClient.getLayergroup(function(err, layergroup) {
             assert.ifError(err);
-            assert.equal(layergroup.metadata.layers[0].id, mapnikBasicLayerId(0));
-            assert.equal(layergroup.metadata.layers[0].meta.stats.estimatedFeatureCount, 100);
-            assert(layergroup.metadata.layers[0].meta.stats.sample.length > 0);
-            const expectedCols = [ 'cartodb_id', 'value', 'the_geom', 'the_geom_webmercator' ].sort();
-            assert.deepEqual(Object.keys(layergroup.metadata.layers[0].meta.stats.sample[0]).sort(), expectedCols);
+            assert.deepStrictEqual(layergroup.metadata.layers[0].meta.stats.sample, {});
             testClient.drain(done);
         });
     });