Merge pull request #462 from CartoDB/turbo-carto-category

Adds turbo-carto category quantification with exact strategy

lib/cartodb/utils/style/postgres-datasource.js

@@ -23,8 +23,35 @@ var methodTemplates = Object.keys(methods).reduce(function(methodTemplates, meth
     return methodTemplates;
 }, {});
 
+methodTemplates.category = dot.template([
+    'WITH',
+    'categories AS (',
+    '  SELECT {{=it._column}} AS category, count(1) AS value, row_number() OVER (ORDER BY count(1) desc) as rank',
+    '  FROM ({{=it._sql}}) _cdb_aggregation_all',
+    '  GROUP BY {{=it._column}}',
+    '  ORDER BY 2 DESC',
+    '),',
+    'agg_categories AS (',
+    '  SELECT \'__other\' category',
+    '  FROM categories',
+    '  WHERE rank >= {{=it._buckets}}',
+    '  GROUP BY 1',
+    '  UNION ALL',
+    '  SELECT CAST(category AS text)',
+    '  FROM categories',
+    '  WHERE rank < {{=it._buckets}}',
+    ')',
+    'SELECT array_agg(category) AS category FROM agg_categories'
+].join('\n'));
+
+var STRATEGY = {
+    SPLIT: 'split',
+    EXACT: 'exact'
+};
+
 var method2strategy = {
-    headtails: 'split'
+    headtails: STRATEGY.SPLIT,
+    category: STRATEGY.EXACT
 };
 
 function PostgresDatasource (pgQueryRunner, username, query) {
@@ -53,11 +80,15 @@ PostgresDatasource.prototype.getRamp = function (column, buckets, method, callba
             return callback(err);
         }
 
-        var ramp = result[0][methodName].sort(function(a, b) {
+        var strategy = method2strategy[methodName];
-            return a - b;
+        var ramp = result[0][methodName];
-        });
+        if (strategy !== STRATEGY.EXACT) {
+            ramp = ramp.sort(function(a, b) {
+                return a - b;
+            });
+        }
 
-        return callback(null, { ramp: ramp, strategy: method2strategy[methodName] });
+        return callback(null, { ramp: ramp, strategy: strategy });
     });
 };