Create base class for overviews dataviews

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

@@ -0,0 +1,34 @@
+var _ = require('underscore');
+var BaseWidget = require('../base');
+
+function BaseOverviewsDataview() {}
+
+module.exports = BaseOverviewsDataview;
+
+BaseOverviewsDataview.prototype = new BaseWidget();
+BaseOverviewsDataview.prototype.constructor = BaseOverviewsDataview;
+
+var zoomLevelFactor = 100.0;
+
+// Compute zoom level so that the the resolution grid size of the
+// selected overview is smaller (zoomLevelFactor times smaller at least)
+// than the bounding box size.
+BaseOverviewsDataview.prototype.zoomLevelForBbox = function(bbox) {
+    var pxPerTile = 256.0;
+    var earthWidth = 360.0;
+    // TODO: now we assume overviews are computed for 1-pixel tolerance;
+    // should use extended overviews metadata to compute this properly.
+    if ( bbox ) {
+      var bboxValues = _.map(bbox.split(','), function(v) { return +v; });
+      var w = Math.abs(bboxValues[2]-bboxValues[0]);
+      var h = Math.abs(bboxValues[3]-bboxValues[1]);
+      var maxDim = Math.min(w, h);
+
+      // 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));
+      return Math.max(z, 0);
+    }
+    return 0;
+};

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

@@ -1,5 +1,4 @@
-var _ = require('underscore');
-var BaseWidget = require('../base');
+var BaseOverviewsWidget = require('./base');
 var BaseDataview = require('../formula');
 
 var debug = require('debug')('windshaft:widget:formula:overviews');
@@ -38,43 +37,18 @@ function Formula(query, options, queryRewriter, queryRewriteData, params) {
     this.options = params;
 }
 
-Formula.prototype = new BaseWidget();
+Formula.prototype = new BaseOverviewsWidget();
 Formula.prototype.constructor = Formula;
 
 module.exports = Formula;
 
-var zoom_level_factor = 100.0;
-
-// Compute zoom level so that the the resolution grid size of the
-// selected overview is smaller (zoom_level_factor times smaller at least)
-// than the bounding box size.
-function zoom_level_for_bbox(bbox) {
-    var px_per_tile = 256.0;
-    var earth_width = 360.0;
-    // TODO: now we assume overviews are computed for 1-pixel tolerance;
-    // should use extended overviews metadata to compute this properly.
-    if ( bbox ) {
-      var bbox_values = _.map(bbox.split(','), function(v) { return +v; });
-      var w = Math.abs(bbox_values[2]-bbox_values[0]);
-      var h = Math.abs(bbox_values[3]-bbox_values[1]);
-      var max_dim = Math.min(w, h);
-
-      // 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(max_dim*px_per_tile/earth_width/zoom_level_factor)/Math.log(2.0));
-      return Math.max(z, 0);
-    }
-    return 0;
-}
-
 Formula.prototype.sql = function(psql, filters, override, callback) {
     var _query = this.query;
     var formulaQueryTpl = formulaQueryTpls[this.operation];
 
     if ( formulaQueryTpl ) {
         // supported formula for use with overviews
-        var zoom_level = zoom_level_for_bbox(this.options.bbox);
+        var zoom_level = this.zoomLevelForBbox(this.options.bbox);
         _query = this.queryRewriter.query(_query, this.queryRewriteData, { zoom_level: zoom_level });
         var formulaSql = formulaQueryTpl({
             _query: _query,