Define default overviews dataview behaviour in base class

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

@@ -1,14 +1,29 @@
 var _ = require('underscore');
 var BaseWidget = require('../base');
 
-function BaseOverviewsDataview() {}
+function BaseOverviewsDataview(query, queryOptions, BaseDataview, queryRewriter, queryRewriteData, options) {
+  this.BaseDataview = BaseDataview;
+  this.query = query;
+  this.queryOptions = queryOptions;
+  this.queryRewriter = queryRewriter;
+  this.queryRewriteData = queryRewriteData;
+  this.options = options;
+  this.baseDataview = new this.BaseDataview(this.query, this.queryOptions);
+}
 
 module.exports = BaseOverviewsDataview;
 
 BaseOverviewsDataview.prototype = new BaseWidget();
 BaseOverviewsDataview.prototype.constructor = BaseOverviewsDataview;
 
-var zoomLevelFactor = 100.0;
+// TODO: parameterized these settings
+var SETTINGS = {
+    // use overviews as a default fallback strategy
+    defaultOverviews: false,
+
+    // minimum ratio of bounding box size to grid size
+    zoomLevelFactor: 100.0
+};
 
 // Compute zoom level so that the the resolution grid size of the
 // selected overview is smaller (zoomLevelFactor times smaller at least)
@@ -27,8 +42,46 @@ BaseOverviewsDataview.prototype.zoomLevelForBbox = function(bbox) {
       // Find minimum suitable z
       // note that the QueryRewirter will use the minimum level overview
       // of level >= z if it exists, and otherwise the base table
-      var z = Math.ceil(-Math.log(maxDim*pxPerTile/earthWidth/zoomLevelFactor)/Math.log(2.0));
+      var z = Math.ceil(-Math.log(maxDim*pxPerTile/earthWidth/SETTINGS.zoomLevelFactor)/Math.log(2.0));
       return Math.max(z, 0);
     }
     return 0;
 };
+
+BaseOverviewsDataview.prototype.rewrittenQuery = function(query) {
+    var zoom_level = this.zoomLevelForBbox(this.options.bbox);
+    return this.queryRewriter.query(query, this.queryRewriteData, { zoom_level: zoom_level });
+};
+
+// Default behaviour
+BaseOverviewsDataview.prototype.defaultSql = function(psql, filters, override, callback) {
+    var query = this.query;
+    var dataview = this.baseDataview;
+    if ( SETTINGS.defaultOverviews ) {
+        query = this.rewrittenQuery(query);
+        dataview = new this.BaseDataview(query, this.queryOptions);
+    }
+    return dataview.sql(psql, filters, override, callback);
+};
+
+// default implementation that can be override in derived classes:
+
+BaseOverviewsDataview.prototype.sql = function(psql, filters, override, callback) {
+    return this.defaultSql(psql, filters, override, callback);
+};
+
+BaseOverviewsDataview.prototype.search = function(psql, userQuery, callback) {
+    return this.baseDataview.search(psql, userQuery, callback);
+};
+
+BaseOverviewsDataview.prototype.format = function(result) {
+    return this.baseDataview.format(result);
+};
+
+BaseOverviewsDataview.prototype.getType = function() {
+    return this.baseDataview.getType();
+};
+
+BaseOverviewsDataview.prototype.toString = function() {
+    return this.baseDataview.toString();
+};

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

@@ -28,16 +28,12 @@ var formulaQueryTpls = {
 };
 
 function Formula(query, options, queryRewriter, queryRewriteData, params) {
-    this.base_dataview = new BaseDataview(query, options);
-    this.query = query;
+    BaseOverviewsWidget.call(this, query, options, BaseDataview, queryRewriter, queryRewriteData, params);
     this.column = options.column || '1';
     this.operation = options.operation;
-    this.queryRewriter = queryRewriter;
-    this.queryRewriteData = queryRewriteData;
-    this.options = params;
 }
 
-Formula.prototype = new BaseOverviewsWidget();
+Formula.prototype = Object.create(BaseOverviewsWidget.prototype);
 Formula.prototype.constructor = Formula;
 
 module.exports = Formula;
@@ -61,18 +57,6 @@ Formula.prototype.sql = function(psql, filters, override, callback) {
         return callback(null, formulaSql);
     }
 
-    // For non supported operations (min, max) we're not using overviews.
-    return this.base_dataview.sql(psql, filters, override, callback);
-};
-
-Formula.prototype.format = function(result) {
-    return this.base_dataview.format(result);
-};
-
-Formula.prototype.getType = function() {
-    return this.base_dataview.getType();
-};
-
-Formula.prototype.toString = function() {
-    return this.base_dataview.toString();
+    // default behaviour
+    return this.defaultSql(psql, filters, override, callback);
 };