Sketch of vector overviews support

lib/cartodb/api/overviews_api.js

@@ -0,0 +1,65 @@
+var queue = require('queue-async');
+var QueryTablesApi = require('./query_tables_api');
+
+function OverviewsApi(pgQueryRunner) {
+   if (pgQueryRunner.pgQueryRunner != null) {
+       this.queryTablesApi = pgQueryRunner;
+       this.pgQueryRunner = this.queryTablesApi.pgQueryRunner;
+   } else {
+       this.pgQueryRunner = pgQueryRunner;
+       this.queryTablesApi = new QueryTablesApi(pgQueryRunner);
+  }
+}
+
+module.exports = OverviewsApi;
+
+OverviewsApi.prototype.getOverviewsMetadata = function (username, sql, callback) {
+    this.queryTablesApi.getAffectedTablesInQuery(username, sql, function(err, tableNames){
+        if (err) {
+            callback(err);
+        } else {
+            metadata = {};
+
+            var parallelism = 2;
+            var q = queue(parallelism);
+
+            for ( var i=0; i < tableNames.length; ++i ) {
+                (function(tableName) {
+                    q.defer(function(done){
+                        var sql = "SELECT * FROM CDB_Overviews('" + tableName + "');";
+                        this.pgQueryRunner.run(username, query, handleOverviewsRows, function(err, table_metadata){
+                            if (err) {
+                                done(err);
+                            } else {
+                                metadata[tableName] = table_metadata;
+                                done(null);
+                            }
+                        });
+                    });
+                }(tableNames[i]));
+            }
+
+            q.awaitAll(function(err, results){
+              if (err) {
+                  return callback(err);
+              } else {
+                  return callback(null, metadata);
+              }
+            });
+        };
+    });
+};
+
+function handleOverviewsRows(err, rows, callback) {
+    if (err){
+        var msg = err.message ? err.message : err;
+        callback(new Error('could not get overviews metadata: ' + msg));
+        return;
+    }
+    var metadata = {};
+    for ( var i=0; i<rows.length; ++i ) {
+      var row = rows[i];
+      metadata[row.z] = { table: row.overview_table };
+    };
+    callback(null, metadata);
+}

lib/cartodb/controllers/map.js

@@ -18,6 +18,8 @@ var TablesCacheEntry = require('../cache/model/database_tables_entry');
 var MapConfigNamedLayersAdapter = require('../models/mapconfig_named_layers_adapter');
 var NamedMapMapConfigProvider = require('../models/mapconfig/named_map_provider');
 var CreateLayergroupMapConfigProvider = require('../models/mapconfig/create_layergroup_provider');
+var OverviewsApi = require('../api/overviews_api');
+var MapConfigOverviewsAdapter = require('../models/mapconfig_overviews_adapter');
 
 /**
  * @param {AuthApi} authApi
@@ -41,11 +43,13 @@ function MapController(authApi, pgConnection, templateMaps, mapBackend, metadata
     this.mapBackend = mapBackend;
     this.metadataBackend = metadataBackend;
     this.queryTablesApi = queryTablesApi;
+    this.overviewsApi = new OverviewsApi(this.queryTablesApi);
     this.surrogateKeysCache = surrogateKeysCache;
     this.userLimitsApi = userLimitsApi;
     this.layergroupAffectedTables = layergroupAffectedTables;
 
     this.namedLayersAdapter = new MapConfigNamedLayersAdapter(templateMaps);
+    this.overviewsAdapter = new MapConfigOverviewsAdapter(overviewsApi);
 }
 
 util.inherits(MapController, BaseController);
@@ -148,6 +152,16 @@ MapController.prototype.create = function(req, res, prepareConfigFn) {
                 }
             );
         },
+        function addOverviewsInformation(err, requestMapConfig, datasource) {
+          assert.ifError(err);
+          var next = this;
+          self.overviewsAdapter.getMapConfig(req.context.user, requestMapConfig, function(err, mapconfig) {
+                if (err) {
+                    return next(err);
+                }
+                return next(null, mapconfig, datasource);
+          });
+        },
         function createLayergroup(err, requestMapConfig, datasource) {
             assert.ifError(err);
             mapConfig = new MapConfig(requestMapConfig, datasource || Datasource.EmptyDatasource());

lib/cartodb/models/mapconfig_overviews_adapter.js

@@ -0,0 +1,40 @@
+var queue = require('queue-async');
+
+function MapConfigNamedLayersAdapter(overviewsApi) {
+    this.overviewsApi = overviewsApi;
+}
+
+module.exports = MapConfigNamedLayersAdapter;
+
+MapConfigNamedLayersAdapter.prototype.getMapConfig = function(username, mapconfig, callback) {
+
+    // TODO: we're modifying mapconfig in place and then returning it... not very nice
+
+    var layers = mapconfig.getlayers();
+
+    var parallelism = 2;
+    var q = queue(parallelism);
+
+    for ( var i=0; i < layers.length; ++i ) {
+        (function(layer) {
+            q.defer(function(done){
+                this.overviewsApi.getOverviewsMetadata(username, layer.options.sql, function(err, metadata){
+                     // TODO: is it legit to modify layer like this?
+                     layer.options.overviews = metadata;
+                });
+            });
+        })(layers[i]);
+    };
+
+    q.awaitAll(function(err){
+      if (err) {
+          return callback(err);
+      } else {
+          return callback(null, mapconfig);
+      }
+    });
+};
+
+// TODO: document in https://github.com/CartoDB/Windshaft/blob/master/doc/MapConfig-1.5.0.md
+// (as OPTIONAL)
+//  overviews: { table_name: { zoom_level: { table: overview_table_name } }}