Here is example from fb:editor documentation:

First we need to include fb:editor tag to the page to force loading of CSS files:

Now we should define basic structure of the form:

BTW, we have several enhancements in the original layout: we have specified for attribute for the label tag (now if you would click to the label, corresponding input would be selected), and added ability to mark required fields with required text (it’s impossible with fb:editor).

Or even:

Almost 50% of this could be easily removed, and you will get beautiful and clear code, just right after you will understand what the hell is operator ??. Here is information from MSDN:

The ?? operator returns the left-hand operand if it is not null, or else it returns the right operand.

Easy and clean explanation. Let’s try to rewrite all these examples using this operator:

In case of value-types this approach will not work: you will get NullReferenceException. But do not worry — in this case we can use Nullable-types. Before:

After:

When you are using ?? operator, expression will be evaluated in the left to right order, so you can use something like this:

Of course, it looks more readably than the:

And a fortiori than:

Add it to your armoury!

Experienced developer, even if he is not a paranoiac, will find possible problem immediately — NullReferenceException. That’s because of caching implementation in ASP.NET. In ideal case an object, that has been cached, will stay there up to application restart, but in real world it could be deleted between two calls: by the garbage collector when memory is over (because cache uses weak references WeakReference); by another thread to refresh cached data.

So the code I have mentioned before works in 99% of all cases, but sometimes you will get errors in your log, which can not be reproduced easily. Here is right cache usage approach:

Do not relax your vigilance, it’s exactly what they are waiting for! (about bugs)

And how do you search through the hash for a key with specified value?

Table of contents

• Multi-query support
• Extended engine V2
• 64-bit document and word IDs support
• Multiple-valued attributes
• Geodistance feature
• Download

Multi-query support

What does it mean? Multi-query support means sending multiple search queries to Sphinx at once. It’s saving network connection overheads and other round-trip costs. But what’s much more important, it unlocks possibilities to optimize “related” queries internally. Here is quote from the Sphinx home page:

One typical Sphinx usage pattern is to return several different “views” on the search results. For instance, one might need to display per-category match counts along with product search results, or maybe a graph of matches over time. Yes, that could be easily done earlier using the grouping features. However, one had to run the same query multiple times, but with different settings.

From now on, if you submit such queries through newly added multi-query interface (as a side note, ye good olde Query() interface is not going anywhere, and compatibility with older clients should also be in place), Sphinx notices that the full-text search query is the same and it is just sorting/grouping settings which are different. In this case it only performs expensive full-text search once, but builds several different (differently sorted and/or grouped) result sets from retrieved matches. I’ve seen speedups of 1.5-2 times on my simple synthetic queries; depending on different factors, the speedup could be even greater in practice.

To perform multi-query you should add several queries using AddQuery method (parameters are exactly the same as in Query call), and then call RunQueries. Please note, that all parameters, filters, query settings are stored between AddQuery calls. It means that if you have specified sort mode using SetSortMode before first AddQuery call, then sort mode will be the same for the second AddQuery call. Currently you can reset only filters (using ResetFilters) and group by (ResetGroupBy) settings. BTW, you can use Query as usually to perform single query, but don’t try to make this call after you have added query into the batch using AddQuery.

Stop speaking, let’s look the example:

As the result we will get array of 2 hashes:

Each hash contains the same data as result of Query method call. Also they have additional fields error and warning which contains error and warning message respectively when not empty.

Note: I have added ResetFilters call before creating second query. Without this call our query will have two filters with conflicting conditions, so there will be no results at all.

Extended engine V2

New querying engine (codenamed “extended engine V2″) is going to gradually replace all the currently existing matching modes. At the moment, it is fully identical to extended mode in functionality, but is much less CPU intensive for some queries. Here are notes from Sphinx author:

I have already seen improvements of up to 3-5 times in extreme cases. The only currently known case when it’s slower is processing complex extended queries with tens to thousands keywords; but forthcoming optimizations will fix that.

V2 engine is currently in alpha state and does not affect any other matching mode yet. Temporary SPH_MATCH_EXTENDED2 mode was added to provide a way to test it easily. We are in the middle of extensive internal testing process (under simulated production load, and then actual production load) right now. Your independent testing results would be appreciated, too!

So, to use new matching mode we should use SPH_MATCH_EXTENDED2 mode. Let’s do it!

Easy enough, right? You should try it by yourself to feel power of new engine. Please note, that this mode is temporary and it will be removed after release.

64-bit document and word IDs support

Before version 0.9.8 the Sphinx was limited to index up to 4 billion documents because of using 32-bit keys. From here on it has ability to use 64-bit IDs, and new feature does not impact on 32-bit keys performance. Let’s look at the example. First we will make query to DB with 32-bit keys:

As you can see, class of the id field is Fixnum. Let’s try to make call to index with 64-bit keys. You will get Bignum as the result, and it means that you can have more than 4 billion documents!

Multiple-valued attributes

Plain attributes only allow to attach 1 value per each document. However, there are cases (such as tags or categories) when it is necessary to attach multiple values of the same attribute and be able to apply filtering to value lists. In these cases we can use multiple-valued attributes now.

In case of using miltiple-valued attribute tag you will get result like:

As you can see, multiple-valued attributes returned as array of integers.

Geodistance feature

Sphinx now is able to compute geographical distance between two points specified by latitude and longitude pairs (in radians). So you now can specify per-query “anchor point” (and attribute names to fetch per-entry latitude and longitude from), and then use “@geodist” virtual attribute both in the filters and in the sorting clause. In this case distance (in meters) from anchor point to each match will be computed, used for filtering and/or sorting, and returned as a virtual attribute too.

Download

As always, you can download Sphinx Client API from project home page. Take into account that version 0.3.1 of the client API intended to use with Sphinx 0.9.7, and Sphinx Client API 0.4.0 r909 requires Sphinx 0.9.8 r909 development snapshot. You could download Sphinx from the Download section of the Sphinx home page.

Just take a look into the MSDN’s topic about Encoding.Default: Gets an encoding for the system’s current ANSI code page. And below we can find Caution:

Different systems might use different encodings as the default; therefore, data streamed from one system to another might be translated incorrectly. To ensure that the encoded bytes are decoded properly, use a Unicode encoding (that is, UTF8Encoding, UnicodeEncoding, or UTF32Encoding) with a preamble. Another option is to use a higher level protocol to ensure that the same format is used for encoding and decoding.

Holly shit! Guys, did you read MSDN before writing libraries for others to use? I think you didn’t.

Anyways, I have fixed my local copy:

Of course, it started working perfectly. I have posted a bug to the tracker and decided to look at the Facebook.NET, a better and much cleaner implementation according to AjaxNinja.

And what do you think? Just open CreateSignature method in Framework/Service/Core/FacebookRequestParameterList.cs file:

Aaaaaaaaaa. They ate my brain! I don’t know what to do. I don’t know, how to explain to all developers about non-ASCII code pages. We are living in world that is not ideal. We have tons of languages, encodings, code pages. And we have UTF8, which should simplify our life. Hey, guys, WTF?

Updated 23 Sep 2007: Facebook.NET developers has closed this bug. Hope I will never see something like this again. Facebook Development Toolkit still does not working for me. I see 27 open bugs in its tracker, so I decided to use Facebook.NET.

via Artjom Kurapov’s blog.

For the beginning, I’ll post a few key points about user profiles. If you want to add some content to the profile of specific user, you should call profile.setFBML routine. For users that you have not called profile.setFBML for, the actions are read from the content in “Default FBML” section of your application settings. For the most part, this will apply to any user who has not added your application. What is “Default FBML” itself? If you have added application, you will see “Default FBML” on all profiles of users that you have not called profile.setFBML for, and it does not matter, if they have added your application or not (good place to put “Invite” link). The same behavior you would see, if you would call profile.setFBML for all users (and if you are crazy enough.)

Please note, “Default FBML” is cached indefinitely, so wait some time to get your content on profiles. Another thing — you can add only action links to user profiles, that have not added your application, and only your application user will see them. This is most important part of the documentation, and you should completely understand it. More detailed description could be found in the documentation for fb:profile-action tag and profile.setFBML routine.

FBML-content for user profiles

There are 4 profile-specific FBML tags exist:

• fb:profile-action is used to add action links under the user picture.
• fb:subtitle will be shown right under the title of the your application box.
• fb:wide specifies content to be shown when your application box placed in wide column.
• fb:narrow specifies content to be shown when your application box placed in narrow column.

Easy, right? So let’s examine these tags more precisely.

As I said early, fb:profile-action is used to place action links on the user’s profile. Usually you will add one link:

What about following scenario: I want to see the link “View my products” when I’m looking my own profile, “View Taisia’s products”, if I’m looking profile of my wife Taisia (and she has added application too), and “Invite Roman to MyApp” when I’m looking profile of my friend Roman, and he has not added application. Here is the code:

Please note: this example is similar to example on the fb:profile-action documentation page, but has one big difference — it’s working: fb:if-is-app-user uid="profileowner" (in documentation example uid takes default value “loggedinuser”, but we need uid of the profile owner.)

This code will work completely only if you will put it into the “Default FBML” section of your application settings, or if you will call profile.setFBML for user, that has not added your application (but this is madness, what I have talked about early): I have specified action “Invite someone to MyApp” in section, which will be shown only on profile of user that has not added application.

BTW, do not forget to remove all line breaks before updating “Default FBML”, because Facebook replaces them with <br/>.

Another interesting thing you could see from working example: Facebook adds parameter id for all links in profile-action, and it equals to owner’s of the profile ID. In my previous example, if I will navigate to Roman’s profile, I will see hyperlink with URL http://apps.facebook.com/myapp/Invite.aspx?id=603839739. Great!

This example is simple, so let’s move ahead. We have two columns on the profile: left (narrow) and right (wide). You can specify in application settings which one will be default. To put content in wide column, use fb:wide, in narrow column — fb:narrow. Quite clear, right?

One more interesting issue. You can specify as many fb:wide and fb:narrow tags as you wish. All content, specified in fb:wide tags will be shown if you application box placed in wide column, all content from fb:narrow tags — when application box placed in narrow column. You can add content outside one of these tags, and it will be shown in both cases — when application in wide or narrow column. If no content specified for one of column, Facebook will show “No content to display.” text.

When to generate profile FBML?

Your application box on the user’s profile should reflect latest changes related to him. Facebook does not know when to update profile information, so you need to do it by yourself (anyway, only you as application developer know when something changes). So, usually you would call profile.setFBML after some changes in your application (for example, user or his friends added some data), depending on which information you are rendering on the profile. Sometimes it’s a good idea to set default data after user has added your application.

Creating profile FBML content with ASP.NET

For profile content generating I propose to use UserControls:

How to get string to put it into the profile.setFBML? Here is the code:

I’ve added control to the Controls collection to get events fired. If you would call this snippet from OnLoad, only OnInit would be fired in ProfileFBML, so do not forget to call DataBind method to force data binding from OnInit in this case.

Please note: my solution is just copy/past of the XmlHttpExecutor code with two small changes:

• I have passed false as third parameter of the XMLHttpRequest.open method to make synchronous call.
• I have cached request results in XMLHttpSyncExecutor members before freeing XMLHttpRequest in the _onReadyStateChange function.

So let’s get started. First of all we would define XMLHttpSyncExecutor class, descendant of the WebRequestExecutor.

This is very simple and clean, so I’ll just show you other methods of the XMLHttpSyncExecutor.

And finally we will notify ASP.NET AJAX that script have been loaded.

Usage is not so simple as wanted, but it’s still quite easy to understand:

When you are using ScriptService, you will not see these difficulties, because ASP.NET will generate wrappers by itself. But if you need synchronous AJAX call — sorry, but in this case you should do it manually. Sample solution could be found here.

So, little more about the video. Luis von Ahn, an assistant professor in the Computer Science Department at Carnegie Mellon University, explains idea of how to use resources of millions people absolutely free, and get results unachievable by today’s high end computers. He is very smart, and I took a delight in watching his performance (yeah, performance, because his jokes were no worse than jokes of the best comic actors I’ve seen). I strongly recommend you to watch it, even if you hate artificial intelligence.

Here is an abstract:

Tasks like image recognition are trivial for humans, but continue to challenge even the most sophisticated computer programs. This talk introduces a paradigm for utilizing human processing power to solve problems that computers cannot yet solve. Traditional approaches to solving such problems focus on improving software. I advocate a novel approach: constructively channel human brainpower using computer games. For example, the ESP Game, described in this talk, is an enjoyable online game — many people play over 40 hours a week — and when people play, they help label images on the Web with descriptive keywords. These keywords can be used to significantly improve the accuracy of image search. People play the game not because they want to help, but because they enjoy it.

I describe other examples of “games with a purpose”: Peekaboom, which helps determine the location of objects in images, and Verbosity, which collects common-sense knowledge. I also explain a general approach for constructing games with a purpose.

And the video itself:

Stop playing solitaire! Help Google to grab the World!

BTW, “Peekaboom” is consonant to my current project name. No, I’m not developing another clone of the “game with a purpose”. No, I won’t tell you what the project is, at least now. Have other questions?