Be able to aggregate by a field

lib/cartodb/api/map/clustered-features-layergroup-controller.js

@@ -43,7 +43,7 @@ module.exports = class AggregatedFeaturesLayergroupController {
             authorize(this.authBackend),
             dbConnSetup(this.pgConnection),
             rateLimit(this.userLimitsBackend, RATE_LIMIT_ENDPOINTS_GROUPS.ATTRIBUTES),
-            cleanUpQueryParams(),
+            cleanUpQueryParams([ 'aggregation' ]),
             createMapStoreMapConfigProvider(
                 this.mapStore,
                 this.userLimitsBackend,
@@ -67,11 +67,13 @@ function getClusteredFeatures (clusterBackend) {
         const { user, token } = res.locals;
         const { dbuser, dbname, dbpassword, dbhost, dbport } = res.locals;
         const { layer, z: zoom, clusterId } = req.params;
+        const { aggregation } = req.query;
 
         const params = {
             user, token,
             dbuser, dbname, dbpassword, dbhost, dbport,
-            layer, zoom, clusterId
+            layer, zoom, clusterId,
+            aggregation
         };
 
         clusterBackend.getClusterFeatures(mapConfigProvider, params, (err, features, stats = {}) => {

lib/cartodb/backends/cluster.js

@@ -38,6 +38,7 @@ module.exports = class ClusterBackend {
                 return callback(error);
             }
 
+            const { aggregation } = params;
             const query = layer.options.sql_raw;
             const resolution = layer.options.aggregation.resolution || 1;
 
@@ -48,7 +49,7 @@ module.exports = class ClusterBackend {
 
                 const { zoom, clusterId } = params;
 
-                getClusterFeatures(pg, zoom, clusterId, columns, query, resolution, (err, features) => {
+                getClusterFeatures(pg, zoom, clusterId, columns, query, resolution, aggregation, (err, features) => {
                     if (err) {
                         return callback(err);
                     }
@@ -85,8 +86,8 @@ function getColumnsName (pg, query, callback) {
     }, true);
 }
 
-function getClusterFeatures (pg, zoom, clusterId, columns, query, resolution, callback) {
-    const sql = clusterFeaturesQuery({
+function getClusterFeatures (pg, zoom, clusterId, columns, query, resolution, aggregation, callback) {
+    let sql = clusterFeaturesQuery({
         zoom: zoom,
         id: clusterId,
         query: query,
@@ -94,6 +95,17 @@ function getClusterFeatures (pg, zoom, clusterId, columns, query, resolution, ca
         columns: columns
     });
 
+    if (aggregation !== undefined) {
+        aggregation = JSON.parse(aggregation);
+        const { columns = [], expresions = [] } = aggregation;
+
+        sql = aggregationQuery({
+            columns,
+            query: sql,
+            expresions
+        });
+    }
+
     debug('> getClusterFeatures:', sql);
 
     pg.query(sql, (err, data) => {
@@ -133,15 +145,17 @@ const clusterFeaturesQuery = ctx => `
     ) __cdb_non_geoms_query
 `;
 
-// SQL expression to compute the aggregation resolution (grid cell size).
-// 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).
-// 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.
-// Computing this using !scale_denominator!, !pixel_width! or !pixel_height! produces
-// inaccurate results due to rounding present in those values.
 const gridResolution = ctx => {
     const minimumResolution = 2*Math.PI*6378137/Math.pow(2,38);
     const pixelSize = `CDB_XYZ_Resolution(${ctx.zoom})`;
     return `GREATEST(${256/ctx.res}*${pixelSize}, ${minimumResolution})::double precision`;
 };
+
+const aggregationQuery = ctx => `
+    SELECT
+        count(1) as _cdb_feature_count
+        ${ctx.columns.length ? `,${ctx.columns.join(', ')}` : ''}
+        ${ctx.expresions.length ? `,${ctx.expresions.join(', ')}` : ''}
+    FROM (${ctx.query}) __cdb_aggregation
+    ${ctx.columns.length ? `GROUP BY ${ctx.columns.join(', ')}` : ''}
+`;