Merge pull request #861 from CartoDB/860-aggregation-min-res

Limit the minimum size of the the aggregation grid

lib/cartodb/models/aggregation/aggregation-query.js

@@ -131,7 +131,12 @@ const dimensionDefs = ctx => {
 // This is equivalent to `${256/ctx.res}*CDB_XYZ_Resolution(CDB_ZoomFromScale(!scale_denominator!))`
 // This is defined by the ctx.res parameter, which is the number of grid cells per tile linear dimension
 // (i.e. each tile is divided into ctx.res*ctx.res cells).
-const gridResolution = ctx => `(${256*0.00028/ctx.res}*!scale_denominator!)::double precision`;
+// We limit the the minimum resolution to avoid division by zero problems. The limit used is
+// the pixel size of zoom level 30 (i.e. 1/2*(30+8) of the full earth web-mercator extent), which is about 0.15 mm.
+const gridResolution = ctx => {
+    const minimumResolution = 2*Math.PI*6378137/Math.pow(2,38);
+    return `GREATEST(${256*0.00028/ctx.res}*!scale_denominator!, ${minimumResolution})::double precision`;
+};
 
 // Notes:
 // * We need to filter spatially using !bbox! to make the queries efficient because

test/acceptance/aggregation.js

@@ -1438,6 +1438,43 @@ describe('aggregation', function () {
                     done();
                 });
             });
+
+            it('aggregation should work with attributes', function (done) {
+                this.mapConfig = createVectorMapConfig([
+                    {
+                        type: 'cartodb',
+                        options: {
+                            sql: POINTS_SQL_1,
+                            cartocss: '#layer { marker-width: 7; }',
+                            cartocss_version: '2.3.0',
+                            aggregation: {
+                                threshold: 1
+                            },
+                            attributes: {
+                                id: 'cartodb_id',
+                                columns: [
+                                    'value'
+                                ]
+                            }
+                        }
+                    }
+                ]);
+                this.testClient = new TestClient(this.mapConfig);
+
+                this.testClient.getLayergroup((err, body) => {
+                    if (err) {
+                        return done(err);
+                    }
+
+                    assert.equal(typeof body.metadata, 'object');
+                    assert.ok(Array.isArray(body.metadata.layers));
+
+                    body.metadata.layers.forEach(layer => assert.ok(layer.meta.aggregation.mvt));
+                    body.metadata.layers.forEach(layer => assert.ok(layer.meta.aggregation.png));
+
+                    done();
+                });
+            });
         });
     });
 });