Thursday, 28 May 2009

Using Google Maps to Display Geographical Information in SharePoint

Google Maps provides a really simple way to display geographical information, such as a set of pinpoints or a route, in the context of the surrounding geography, and developers can use it for free on Internet-facing sites. If you have data stored in Microsoft SharePoint products or technologies that includes geographical information, you should consider if a map display might help your users. I'm going to show you how to use Google Maps with the SharePoint user interface and demonstrate some simple coding techniques.

Microsoft's flagship SharePoint product is Microsoft Office SharePoint Server 2007 but you could easily use maps in the free Windows SharePoint Services 3.0 or other products based on SharePoint, such as Search Server 2008.

Take a good look at all the mapping solutions before starting to code. You may prefer Virtual Earth's user interface or find that Yahoo! Maps have more detail in a location that is important to you. I've coded Google Maps for a customer, and it is the most popular solution, but if you chose Virtual Earth instead the only difference would be in the JavaScript code I describe.

I'll concentrate on the use of Google Maps to display search results but the methods described can be applied other sources of data such as a SharePoint list, an Excel spreadsheet, or a Business Data Catalog (BDC) connection.

General Architecture

SharePoint is built on the ASP.NET 2.0 server-side development technology and its user interface is built from ASP.NET Web Parts. Web Parts allow administrators and users to customize the user interface to match their needs. They can add or remove Web Parts or rearrange them on the page. In the Web Part Gallery, site administrators can control which Web Parts are available. When you develop user interface components for SharePoint you should create them as Web Parts to inherit this flexibility automatically. You should also consider whether to create more than one Web Part to encapsulate different aspects of functionality that users can easily differentiate.

As an example consider a search tool for geographical data. When the user clicks "Search" the tool presents a list of results that match their terms as you might see in an Internet search engine or the SharePoint Search Center. However this tool also presents a Google map with the results pinpointed. This tool might warrant three Web Parts; one for the search terms, one for the results in a list, and a final one for the results on a map. In this architecture users or administrators could show just the list, just the map, or both displays.

Unlike Web Parts, Google Maps are coded in client-side code. JavaScript is used in the browser to create and position the map, add pinpoints, add captions, and draw shapes. This is what makes life interesting. Your Google Maps SharePoint solution must address how to communicate between server-side Web Parts and client-side JavaScript. You could, for example, publish a Web Service on the server and have client-side code query it and present results. AJAX would provide a lot of help with this. In the method I used, a server-side Web Part generates XML and renders it as an island amongst the SharePoint HTML. In the browser, JavaScript can locate this island and use it to draw the map and add pinpoints.

Search Results Web Part

In most search tools, results are presented in a list with links to each, a short description, and sometimes other fields. To build a SharePoint Web Part that displays search results, you submit a query by using a Microsoft.SharePoint.Search.Query.FullTextSqlQuery object. This returns a ResultTable object through which you must loop to evaluate each individual result and display them to users.

XML Data Island

As your code loops through the ResultTable, you can build the XML to place as an island in the Web page that will be returned to the client. To do this, create a System.Xml.XmlWriter object and configure it with a corresponding XmlWriterSettings object:

//Create the XML Writer Settings for configuration

XmlWriterSettings settings = new XmlWriterSettings();

settings.Encoding = System.Text.Encoding.UTF8;

settings.Indent = true;

settings.OmitXmlDeclaration = true;

//This string builder will be used to render the XML

resultsForMap = new StringBuilder();

//Create the XML writer

XmlWriter writer = XmlWriter.Create(resultsForMap, settings);

Then you can write the start element for your XML:

writer.WriteStartElement("MapResults", "my.namespace");

Looping through the DataRow objects in the ResultTable.Rows collection, you can add XML elements with the properties you need. For example:

foreach (DataRow currentResult in myResults.Rows)
      writer.WriteElementString("Path", path);

You must remember to end the XML and flush the writer:


Your XML is now flushed to the StringBuilder object (named resultsForMap in the above example). To render this string on the SharePoint Web page you can use an ASP.NET Label like this:

returnedXmlLabel.Text = "<xml id="\">" +
      resultsForMap.ToString() + "</xml>";

The ID you use for this XML island allows JavaScript code to locate it when the map is rendered on the client.

Map Results Web Part

Since the work of populating the map with points and captions is done in client-side code, there is little to be done in ASP.NET code for the Map Results Web Part. However it is necessary to render a <div> tag for the map, and a <script> tag for the Google Maps code library. This <script> tag is where you must render the Google Key associated with your Google Maps account.

protected override void Render(System.Web.UI.HtmlTextWriter writer)
      //Render the script tags that link to Google Maps API
      writer.WriteLine(String.Format("<script " +
            src="\" +
            file="api&v=2&key={0}\ " +
            type=\"text/javascript\"> </script>",
            "Your key here" ()));
      //Render the div that will display the map
      writer.Write("<br /><div id=\"map\" " +
            "style=\"width: 800px; height: 600px\" ></div>");

Registering and Embedding the Scripts

In the Map Results Web Part, you must also ensure that the JavaScript, which generates the map and populates it with pinpoints, executes when the page reaches the client. ASP.NET 2.0 provides an elegant way to do this: you can embed script files as resources in the same assembly as the Map Results Web Part. This makes deployment simple, because the script is part of the assembly.

You must complete several steps to embed a script file in your Web Part assembly:

  1. Add a JavaScript file to the Visual Studio project and write the JavaScript Code.

    This file is where you place all the Google Maps code. For examples of such code, see "JavaScript Files" below.

  2. Add Web resource entries to the AssemblyInfo.cs file.

    This file contains information about the assembly such as version numbers. You can add a reference to a script file like this:

    [assembly: WebResource("MyNameSpace.MapScripts.js",
          "text/javascript", PerformSubstitution = true)]

  3. In your Map Results Web Part, register the script resource.

    You should do this in the OnPreRender method:

    protected override void OnPreRender(EventArgs e)
          //Register the JavaScript file
               this.GetType(), "MyNameSpace.MapScripts.js");

  4. Make sure the script runs whenever the page loads.

    You do this by registering the script as a startup script. Add the following line to the Map Result Web Part in the Render method:

          this.GetType(), "MapScriptsStart", "loadMap();", true);


JavaScript Files

We now have an XML island rendered in the SharePoint Web Part that contains all the results that must appear on the map. We have also embedded a JavaScript file in the Web Part assembly to execute when the page loads on the client. The final task is to write JavaScript in the embedded file that loads the Google Map and add pinpoints and other objects.

Loading the Map

First, create a global variable to reference the map itself. You will need this throughout the script file:

var map;

Next create a function to load the map. This should match the function you specified in the RegisterStartupScript method in the previous section:

function loadMap(){
      //Create the map
      map = new GMap2(document.getElementById("map"));
      //Centre it on default latitude and longitude.
      map.setCenter(new GLatLng(54.59088, -4.24072), 16);
      //Set a default zoom level
      //Add the controls
      var mapControl = new GLargeMapControl();
      map.addControl(new GMapTypeControl());
      //Parse the XML in the HTML data

Parsing the XML Island

The last line of the above code calls a separate parseXmlIsland function. This function locates the XML island and loads it into a variable. This must be done slightly differently depending on the user's browser:

var xmlIsland;
try //Internet Explorer
      xmlIsland = new ActiveXObject("Microsoft.XMLDOM");
catch (e)
      try //Firefox, Mozilla, Opera etc.
            xmlIsland =
            document.implementation.createDocument("", "", null);
xmlIsland.async = "false";
xmlIsland.validateOnParse = "false";

Setup some variables and get all the results nodes you placed in the XML:

var Title, Path, Latitude, Longitude;
var resultNodes = xmlIsland.getElementsByTagName("Result");

Now, loop through the node, storing relevant information:

var resultNode;
var resultNodeChild;
for (i = 0; i < resultNodes.length; i++) {
      resultnode = resultNodes[i];
      for ( j = 0; j < resultNode.childNodes.length; j++) {
            resultNodeChild = resultNode.childNodes[j];
            switch (resultNodeChild.nodeName) {
            case "Title":
                  Title = resultNodeChild.text;
            case "Path":
                  Path = resultNodeChild.text;
            case "Latitude":
                  Latitude = parseFloat(resultNodeChild.text);
            case "Longitude":
                  Longitude = parseFloat(resultNodeChild.text);
      //Add a point for this result
      addPinPoint(Title, Path, Latitude, Longitude);

Adding Pinpoints

The above code calls the addPinPoint function for every result in the XML island. This function adds a pinpoint to the Google map in the standard way:

function addPinPoint(Title, Path, Latitude, Longitude){
      //Set up the icon
      var myIcon = new GIcon(G_DEFAULT_ICON);
      //Select the right icon
      myIcon.image = "mapimages/myPinPointIcon.png";
      myIcon.iconSize = new GSize(12, 30);
      myIcon.shadow = "mapimages/myPinPointShadow.png";
      myIcon.shadowSize = new GSize(23, 30);
      myIcon.iconAnchor = new GPoint(6, 30);
      markerOptions = { icon:myIcon };

      //Formulate the HTML that goes into the caption window
      var infoHtml = "&lta href="">" + Title + "</a>";

      //Add the marker
      var point = new GLatLng(Latitude, Longitude, false);
      var marker = new GMarker(point, markerOptions);

      //Add an info window
      GEvent.addListener(marker, "click", function () {

      //Add the overlay

Licensing Considerations

The techniques I've outlined illustrate that Google Maps can be easily integrated into a SharePoint site and become a valuable addition to SharePoint functionality. However, before you develop such a solution, you must investigate licensing restrictions fully. This section describes the main issues and alternative map providers.

Licensing Google Maps

Google Maps is free for use on Internet-facing, non-subscription sites. If you use SharePoint to host your organisation's main Web site, or more targeted sites for departments, subsidiaries, or products, you can use Google Maps for no charge on pages with no access restrictions.

Google Maps does not allow free use on any password-protected page or on intranet sites. In such cases you can still use the technology, but you must take out a Google Maps for Enterprise license. Google Maps for Enterprise is licensed on a per-concurrent-user basis.

Microsoft Virtual Earth and Other Providers

Microsoft's Virtual Earth service competes directly with Google Maps and works in a similar way. There is an approximately equivalent set of features and maps are drawn and populated by using client-side code just like Google Maps. To use Virtual Earth with SharePoint your general approach can be identical to that described above although you must rewrite the JavaScript code to use the Virtual Earth classes and methods. On the intranet, Virtual Earth is licensed on the basis of total users.

Yahoo! also have a mapping service. This can be used free on both Internet and intranet sites so you should consider it carefully for SharePoint enterprise content management or knowledge management solutions restricted to your internal users. Yahoo! Maps cannot be used in applications for which you charge users. There are also other alternatives, such as PushPin.


Google Maps represents the easiest way to display geographical data on Web sites, including those hosted in Microsoft SharePoint products and technologies. If you carefully plan how to integrate the server-side SharePoint technology with the client-side Google Maps code, you can easily integrate the two and generate a rich user experience for geographical data.


Windows SharePoint Services Developer Center

SharePoint Server Developer Center

Google Maps API Documentation

Thursday, 14 May 2009

SQL Server 2008 Resource Governor

As the number of queries hitting a database grows, contention for memory and CPU resources increases, giving rise to problems such as runaway queries that monopolize resources and deny them to other applications, and unpredictable workload execution, which occurs because jobs run more quickly at times when competition for resources is minimal and more slowly at other times, when competition is greater.

Predictable workload execution
Resource Governor, a new SQL Server 2008 Enterprise Edition feature, addresses these problems by enabling administrators to explicitly control the allocation of resources to competing workloads by applying administrator-defined CPU and memory limits to specified workloads, such as regular maintenance jobs or periodic resource intensive queries. This helps to make query execution more predictable and can prevent the occurrence of runaway queries.

You define the available resources by creating resource pools, and you use classifier functions and workload groups to identify workloads and apply limits.

Resource pools
Resource pools limit the available resources in terms of maximum and minimum CPU and memory percentages, which you define. You can create multiple pools, each with different resource settings to reflect the different workloads on the system. Resource Governor will use the percentage values that you supply to calculate a shared percentage value and an effective maximum value for CPU and memory for each of the pools. When calculating these figures, Resource Governor takes account of the competing requirements of each pool so that resource usage is balanced. In addition to user defined resource pools, there are two default resource pools, called ‘Internal’ and ‘Default’, which are used by the Internal and Default workload groups respectively.

Workload groups
A workload group is effectively a container into which incoming sessions are placed. Administrators can define multiple workload groups to represent the different types of workload that the system experiences, and SQL Server also has the two built-in workload groups, ‘Internal’ and ‘Default’, that we mentioned above. Connecting sessions are allocated to the Default group when they are not explicitly allocated to any other group, and the internal group is for use by SQL Server itself, for processes such as Lazy Writer.

Each workload group is associated with a resource pool, which dictates the memory and CPU resources that are available to the workload group, as described earlier. Workload groups have additional settings that can be used to fine tune resource usage, including the maximum number of CPUs that the group can use, and LOW, MEDIUM, and HIGH importance settings to prioritize workload groups relative to other workload groups. By allocating sessions to a specific workload group, you limit the resources that an application has access to, which prevents problems such as runaway queries from ever arising.

Classifier functions
Classifier functions examine incoming sessions as they connect to the server and allocate them to user defined or system workload groups. When you define a classifier function, you can use functions such as HOSTNAME(), SUSER_SNAME(), and APP_NAME() to identify sessions and stream them into the appropriate workload group. For example, you can create a function that uses APP_NAME() to check the names of applications that initiate sessions, and to place them into workload groups that were created to apply limits specifically for those applications. For maximum efficiency, classifier functions should ideally group together sessions that perform similar tasks so that each workload group is as uniform as possible.

Resource Governor is a powerful tool that is likely to become an essential part of the way we manage SQL Server databases. However, it is not a panacea for poorly performing queries, and you still need to consider all of the ‘traditional’ ways of improving query performance, such as good index and query design. There are also a couple of limitations to consider before you race off to implement it on your servers: Firstly, with the current release, Resource Governor can only be used to manage workloads within an instance of SQL Server; so if you’re running a multi-instance set-up, workloads from one instance can still impact upon with the execution of workloads from other instances, just as they always did. Secondly, Resource Governor can only be used to manage the database engine itself, and not to manage Integration Services, Reporting Services, or Analysis Services.

Friday, 1 May 2009

SQL Server 2008 Star Join Query Optimization

As Business Intelligence (BI) has become ever more important in helping business to maintain their competitive edge, the databases that handle BI queries have had to cope with a corresponding increase in their workload. Nowadays, it is not uncommon for queries that are run against large databases such as data warehouses and data marts to return millions of rows, and when you consider that these types of queries frequently involve joining multiple tables, it’s easy to see why users often experience extended query response times. SQL Server 2008 Enterprise Edition addresses this issue with a new feature called ‘Star Join Query Optimization’, which is a mechanism that uses bitmap filtering to improve the performance of certain types of queries by making the retrieval of rows from fact tables more efficient.

Improved Query Response Times
Data warehouses generally use dimensionally modelled star or snowflake schemas, which feature one or more fact tables that contain transactional data, and various dimension tables which contain the information (such as product data, customer information, and times and dates) that gives meaning to the fact table data. Foreign keys are usually used to maintain the relationships between the rows in fact tables and those in the dimension tables. SQL Server 2008 Enterprise can recognize databases that have star schemas and use the new Star Join Query logic to process queries against them more quickly, with the result that typical data warehouse queries run 15 to 20 percent faster on average.

Automatically Implemented
Star Join Query Optimization is implemented automatically by SQL Server, and requires no special database or application configuration. The query processor will usually elect to optimize queries that are of medium selectivity (that is, those that retrieve between approximately 10% and 75% of the rows from a fact table). Such queries are generally handled by using hash joins to join the dimension and fact tables, using the foreign keys to identify matching rows. Hash joins work by building a hash table for each dimension table referenced in the query, and the optimization process uses these hash tables to derive bitmap filters. Bitmap filters identify the key values from each dimension table that qualify for inclusion in the query. The bitmap filters are applied to the fact table as it is scanned and they act to eliminate the fact table rows that do not qualify for inclusion in the result set. The most selective bitmap filter is applied first because it eliminates the greatest number of rows. Because the eliminated rows require no further processing, subsequent filters do not have to be applied to them, and the efficiency of the process is improved.

Query Selectivity
Bitmap filtering improves performance in medium selectivity queries because it filters out rows early on, before any joins are implemented and as a result, the number of rows that are processed by each join is reduced. Bitmap filtering is not generally used when queries are very highly selective (returning fewer than 10% of the rows in a fact table) because a nested loop join will usually be more efficient. Likewise, on queries that are not very selective at all (returning more than 75% of the rows in a fact table), bitmap filtering will not be used because there are very few rows to be filtered out, so there is no performance benefit to be gained.

Integer Data Types
Star join optimization is most efficient when the columns used in joins are of the integer data type because this enables the filter to be applied as part of the initial table or index scan rather than at a later stage in the query plan. Because it is common practice to implement foreign key relationships by using integer based alternate key columns, the majority of queries should be able to benefit from star join optimization.