add to log when overviews are being used in dataviews

lib/cartodb/backends/dataview.js

@@ -64,7 +64,13 @@ DataviewBackend.prototype.getDataview = function (mapConfigProvider, user, param
                 return callback(err);
             }
 
-            return callback(null, dataviewResult);
+            const stats = {};
+
+            if (dataviewResult && dataviewResult.usesOverviews) {
+                stats.usesOverviews = dataviewResult.usesOverviews;
+            }
+
+            return callback(null, dataviewResult, stats);
         });
     });
 };

lib/cartodb/models/dataview/base.js

@@ -21,7 +21,7 @@ function getPGTypeName (pgType) {
 
 module.exports = class BaseDataview {
     getResult (psql, override, callback) {
-        this.sql(psql, override, (err, query) => {
+        this.sql(psql, override, (err, query, flags = { usesOverviews : false }) => {
             if (err) {
                 return callback(err);
             }
@@ -33,7 +33,8 @@ module.exports = class BaseDataview {
 
                 result = this.format(result, override);
                 result.type = this.getType();
-
+                result.usesOverviews = flags.usesOverviews;
+                
                 return callback(null, result);
 
             }, true); // use read-only transaction

lib/cartodb/models/dataview/overviews/aggregation.js

@@ -209,7 +209,7 @@ Aggregation.prototype.sql = function(psql, override, callback) {
 
     debug(aggregationSql);
 
-    return callback(null, aggregationSql);
+    return callback(null, aggregationSql, { usesOverviews: true });
 };
 
 var aggregationFnQueryTpl = {

lib/cartodb/models/dataview/overviews/formula.js

@@ -74,5 +74,5 @@ Formula.prototype.sql = function (psql, override, callback) {
 
     debug(formulaSql);
 
-    return callback(null, formulaSql);
+    return callback(null, formulaSql, { usesOverviews: true });
 };

lib/cartodb/models/dataview/overviews/histogram.js

@@ -178,7 +178,7 @@ Histogram.prototype.sql = function(psql, override, callback) {
 
     var histogramSql = this._buildQuery(override);
 
-    return callback(null, histogramSql);
+    return callback(null, histogramSql, { usesOverviews: true });
 };
 
 Histogram.prototype._buildQuery = function (override) {