improvement - Page 41 - Developer IT

Developing Schema Compare for Oracle (Part 6): 9i Query Performance

- by Simon Cooper

All throughout the EAP and beta versions of Schema Compare for Oracle, our main request was support for Oracle 9i. After releasing version 1.0 with support for 10g and 11g, our next step was then to get version 1.1 of SCfO out with support for 9i. However, there were some significant problems that we had to overcome first. This post will concentrate on query execution time. When we first tested SCfO on a 9i server, after accounting for various changes to the data dictionary, we found that database registration was taking a long time. And I mean a looooooong time. The same database that on 10g or 11g would take a couple of minutes to register would be taking upwards of 30 mins on 9i. Obviously, this is not ideal, so a poke around the query execution plans was required. As an example, let's take the table population query - the one that reads ALL_TABLES and joins it with a few other dictionary views to get us back our list of tables. On 10g, this query takes 5.6 seconds. On 9i, it takes 89.47 seconds. The difference in execution plan is even more dramatic - here's the (edited) execution plan on 10g: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 108K| 939 || 1 | SORT ORDER BY | | 108K| 939 || 2 | NESTED LOOPS OUTER | | 108K| 938 ||* 3 | HASH JOIN RIGHT OUTER | | 103K| 762 || 4 | VIEW | ALL_EXTERNAL_LOCATIONS | 2058 | 3 ||* 20 | HASH JOIN RIGHT OUTER | | 73472 | 759 || 21 | VIEW | ALL_EXTERNAL_TABLES | 2097 | 3 ||* 34 | HASH JOIN RIGHT OUTER | | 39920 | 755 || 35 | VIEW | ALL_MVIEWS | 51 | 7 || 58 | NESTED LOOPS OUTER | | 39104 | 748 || 59 | VIEW | ALL_TABLES | 6704 | 668 || 89 | VIEW PUSHED PREDICATE | ALL_TAB_COMMENTS | 2025 | 5 || 106 | VIEW | ALL_PART_TABLES | 277 | 11 |------------------------------------------------------------------------------- And the same query on 9i: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 16P| 55G|| 1 | SORT ORDER BY | | 16P| 55G|| 2 | NESTED LOOPS OUTER | | 16P| 862M|| 3 | NESTED LOOPS OUTER | | 5251G| 992K|| 4 | NESTED LOOPS OUTER | | 4243M| 2578 || 5 | NESTED LOOPS OUTER | | 2669K| 1440 ||* 6 | HASH JOIN OUTER | | 398K| 302 || 7 | VIEW | ALL_TABLES | 342K| 276 || 29 | VIEW | ALL_MVIEWS | 51 | 20 ||* 50 | VIEW PUSHED PREDICATE | ALL_TAB_COMMENTS | 2043 | ||* 66 | VIEW PUSHED PREDICATE | ALL_EXTERNAL_TABLES | 1777K| ||* 80 | VIEW PUSHED PREDICATE | ALL_EXTERNAL_LOCATIONS | 1744K| ||* 96 | VIEW | ALL_PART_TABLES | 852K| |------------------------------------------------------------------------------- Have a look at the cost column. 10g's overall query cost is 939, and 9i is 55,000,000,000 (or more precisely, 55,496,472,769). It's also having to process far more data. What on earth could be causing this huge difference in query cost? After trawling through the '10g New Features' documentation, we found item 1.9.2.21. Before 10g, Oracle advised that you do not collect statistics on data dictionary objects. From 10g, it advised that you do collect statistics on the data dictionary; for our queries, Oracle therefore knows what sort of data is in the dictionary tables, and so can generate an efficient execution plan. On 9i, no statistics are present on the system tables, so Oracle has to use the Rule Based Optimizer, which turns most LEFT JOINs into nested loops. If we force 9i to use hash joins, like 10g, we get a much better plan: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 7587K| 3704 || 1 | SORT ORDER BY | | 7587K| 3704 ||* 2 | HASH JOIN OUTER | | 7587K| 822 ||* 3 | HASH JOIN OUTER | | 5262K| 616 ||* 4 | HASH JOIN OUTER | | 2980K| 465 ||* 5 | HASH JOIN OUTER | | 710K| 432 ||* 6 | HASH JOIN OUTER | | 398K| 302 || 7 | VIEW | ALL_TABLES | 342K| 276 || 29 | VIEW | ALL_MVIEWS | 51 | 20 || 50 | VIEW | ALL_PART_TABLES | 852K| 104 || 78 | VIEW | ALL_TAB_COMMENTS | 2043 | 14 || 93 | VIEW | ALL_EXTERNAL_LOCATIONS | 1744K| 31 || 106 | VIEW | ALL_EXTERNAL_TABLES | 1777K| 28 |------------------------------------------------------------------------------- That's much more like it. This drops the execution time down to 24 seconds. Not as good as 10g, but still an improvement. There are still several problems with this, however. 10g introduced a new join method - a right outer hash join (used in the first execution plan). The 9i query optimizer doesn't have this option available, so forcing a hash join means it has to hash the ALL_TABLES table, and furthermore re-hash it for every hash join in the execution plan; this could be thousands and thousands of rows. And although forcing hash joins somewhat alleviates this problem on our test systems, there's no guarantee that this will improve the execution time on customers' systems; it may even increase the time it takes (say, if all their tables are partitioned, or they've got a lot of materialized views). Ideally, we would want a solution that provides a speedup whatever the input. To try and get some ideas, we asked some oracle performance specialists to see if they had any ideas or tips. Their recommendation was to add a hidden hook into the product that allowed users to specify their own query hints, or even rewrite the queries entirely. However, we would prefer not to take that approach; as well as a lot of new infrastructure & a rewrite of the population code, it would have meant that any users of 9i would have to spend some time optimizing it to get it working on their system before they could use the product. Another approach was needed. All our population queries have a very specific pattern - a base table provides most of the information we need (ALL_TABLES for tables, or ALL_TAB_COLS for columns) and we do a left join to extra subsidiary tables that fill in gaps (for instance, ALL_PART_TABLES for partition information). All the left joins use the same set of columns to join on (typically the object owner & name), so we could re-use the hash information for each join, rather than re-hashing the same columns for every join. To allow us to do this, along with various other performance improvements that could be done for the specific query pattern we were using, we read all the tables individually and do a hash join on the client. Fortunately, this 'pure' algorithmic problem is the kind that can be very well optimized for expected real-world situations; as well as storing row data we're not using in the hash key on disk, we use very specific memory-efficient data structures to store all the information we need. This allows us to achieve a database population time that is as fast as on 10g, and even (in some situations) slightly faster, and a memory overhead of roughly 150 bytes per row of data in the result set (for schemas with 10,000 tables in that means an extra 1.4MB memory being used during population). Next: fun with the 9i dictionary views.

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iOS Support with Windows Azure Mobile Services – now with Push Notifications

- by ScottGu

A few weeks ago I posted about a number of improvements to Windows Azure Mobile Services. One of these was the addition of an Objective-C client SDK that allows iOS developers to easily use Mobile Services for data and authentication. Today I'm excited to announce a number of improvement to our iOS SDK and, most significantly, our new support for Push Notifications via APNS (Apple Push Notification Services). This makes it incredibly easy to fire push notifications to your iOS users from Windows Azure Mobile Service scripts. Push Notifications via APNS We've provided two complete tutorials that take you step-by-step through the provisioning and setup process to enable your Windows Azure Mobile Service application with APNS (Apple Push Notification Services), including all of the steps required to configure your application for push in the Apple iOS provisioning portal: Getting started with Push Notifications - iOS Push notifications to users by using Mobile Services - iOS Once you've configured your application in the Apple iOS provisioning portal and uploaded the APNS push certificate to the Apple provisioning portal, it's just a matter of uploading your APNS push certificate to Mobile Services using the Windows Azure admin portal: Clicking the “upload” within the “Push” tab of your Mobile Service allows you to browse your local file-system and locate/upload your exported certificate. As part of this you can also select whether you want to use the sandbox (dev) or production (prod) Apple service: Now, the code to send a push notification to your clients from within a Windows Azure Mobile Service is as easy as the code below: push.apns.send(deviceToken, { alert: 'Toast: A new Mobile Services task.', sound: 'default' }); This will cause Windows Azure Mobile Services to connect to APNS (Apple Push Notification Service) and send a notification to the iOS device you specified via the deviceToken: Check out our reference documentation for full details on how to use the new Windows Azure Mobile Services apns object to send your push notifications. Feedback Scripts An important part of working with any PNS (Push Notification Service) is handling feedback for expired device tokens and channels. This typically happens when your application is uninstalled from a particular device and can no longer receive your notifications. With Windows Notification Services you get an instant response from the HTTP server. Apple’s Notification Services works in a slightly different way and provides an additional endpoint you can connect to poll for a list of expired tokens. As with all of the capabilities we integrate with Mobile Services, our goal is to allow developers to focus more on building their app and less on building infrastructure to support their ideas. Therefore we knew we had to provide a simple way for developers to integrate feedback from APNS on a regular basis. This week’s update now includes a new screen in the portal that allows you to optionally provide a script to process your APNS feedback – and it will be executed by Mobile Services on an ongoing basis: This script is invoked periodically while your service is active. To poll the feedback endpoint you can simply call the apns object's getFeedback method from within this script: push.apns.getFeedback({ success: function(results) { // results is an array of objects with a deviceToken and time properties } }); This returns you a list of invalid tokens that can now be removed from your database. iOS Client SDK improvements Over the last month we've continued to work with a number of iOS advisors to make improvements to our Objective-C SDK. The SDK is being developed under an open source license (Apache 2.0) and is available on github. Many of the improvements are behind the scenes to improve performance and memory usage. However, one of the biggest improvements to our iOS Client API is the addition of an even easier login method. Below is the Objective-C code you can now write to invoke it: [client loginWithProvider:@"twitter" onController:self animated:YES completion:^(MSUser *user, NSError *error) { // if no error, you are now logged in via twitter }]; This code will automatically present and dismiss our login view controller as a modal dialog on the specified controller. This does all the hard work for you and makes login via Twitter, Google, Facebook and Microsoft Account identities just a single line of code. My colleague Josh just posted a short video demonstrating these new features which I'd recommend checking out: Summary The above features are all now live in production and are available to use immediately. If you don’t already have a Windows Azure account, you can sign-up for a free trial and start using Mobile Services today. Visit the Windows Azure Mobile Developer Center to learn more about how to build apps with Mobile Services. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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BeansBinding Across Modules in a NetBeans Platform Application

- by Geertjan

Here's two TopComponents, each in a different NetBeans module. Let's use BeansBinding to synchronize the JTextField in TC2TopComponent with the data published by TC1TopComponent and received in TC2TopComponent by listening to the Lookup. The key to getting to the solution is to have the following in TC2TopComponent, which implements LookupListener: private BindingGroup bindingGroup = null; private AutoBinding binding = null; @Override public void resultChanged(LookupEvent le) { if (bindingGroup != null && binding != null) { bindingGroup.getBinding("customerNameBinding").unbind(); } if (!result.allInstances().isEmpty()){ Customer c = result.allInstances().iterator().next(); // put the customer into the lookup of this topcomponent, // so that it will remain in the lookup when focus changes // to this topcomponent: ic.set(Collections.singleton(c), null); bindingGroup = new BindingGroup(); binding = Bindings.createAutoBinding( // a two-way binding, i.e., a change in // one will cause a change in the other: AutoBinding.UpdateStrategy.READ_WRITE, // source: c, BeanProperty.create("name"), // target: jTextField1, BeanProperty.create("text"), // binding name: "customerNameBinding"); bindingGroup.addBinding(binding); bindingGroup.bind(); } } I must say that this solution is preferable over what I've been doing prior to getting to this solution: I would get the customer from the resultChanged, set a class-level field to that customer, add a document listener (or action listener, which is invoked when Enter is pressed) on the text field and, when a change is detected, set the new value on the customer. All that is not needed with the above bit of code. Then, in the node, make sure to use canRename, setName, and getDisplayName, so that when the user presses F2 on a node, the display name can be changed. In other words, when the user types something different in the node display name after pressing F2, the underlying customer name is changed, which happens, in the first place, because the customer name is bound to the text field's value, so that the text field's value will also change once enter is pressed on the changed node display name. Also set a PropertyChangeListener on the node (which implies you need to add property change support to the customer object), so that when the customer object changes (which happens, in the second place, via a change in the value of the text field, as defined in the binding defined above), the node display name is updated. In other words, there's still a bit of plumbing you need to include. But less than before and the nasty class-level field for storing the customer in the TC2TopComponent is no longer needed. And a listener on the text field, with a property change listener implented on the TC2TopComponent, isn't needed either. On the other hand, it's more code than I was using before and I've had to include the BeansBinding JAR, which adds a bit of overhead to my application, without much additional functionality over what I was doing originally. I'd lean towards not doing things this way. Seems quite expensive for essentially replacing a listener on a text field and a property change listener implemented on the TC2TopComponent for being notified of changes to the customer so that the text field can be updated. On the other other hand, it's kind of nice that all this listening-related code is centralized in one place now. So, here's a nice improvement over the above. Instead of listening for a customer, listen for a node, from which the customer can be obtained. Then, bind the node display name to the text field's value, so that when the user types in the text field, the node display name is updated. That saves you from having to listen in the node for changes to the customer's name. In addition to that binding, keep the previous binding, because the previous binding connects the customer name to the text field, so that when the customer display name is changed via F2 on the node, the text field will be updated. private BindingGroup bindingGroup = null; private AutoBinding nodeUpdateBinding; private AutoBinding textFieldUpdateBinding; @Override public void resultChanged(LookupEvent le) { if (bindingGroup != null && textFieldUpdateBinding != null) { bindingGroup.getBinding("textFieldUpdateBinding").unbind(); } if (bindingGroup != null && nodeUpdateBinding != null) { bindingGroup.getBinding("nodeUpdateBinding").unbind(); } if (!result.allInstances().isEmpty()) { Node n = result.allInstances().iterator().next(); Customer c = n.getLookup().lookup(Customer.class); ic.set(Collections.singleton(n), null); bindingGroup = new BindingGroup(); nodeUpdateBinding = Bindings.createAutoBinding( AutoBinding.UpdateStrategy.READ_WRITE, n, BeanProperty.create("name"), jTextField1, BeanProperty.create("text"), "nodeUpdateBinding"); bindingGroup.addBinding(nodeUpdateBinding); textFieldUpdateBinding = Bindings.createAutoBinding( AutoBinding.UpdateStrategy.READ_WRITE, c, BeanProperty.create("name"), jTextField1, BeanProperty.create("text"), "textFieldUpdateBinding"); bindingGroup.addBinding(textFieldUpdateBinding); bindingGroup.bind(); } } Now my node has no property change listener, while the customer has no property change support. As in the first bit of code, the text field doesn't have a listener either. All that listening is taken care of by the BeansBinding code. Thanks to Toni for help with this, though he can't be blamed for anything that is wrong with it, only thanked for anything that is right with it.

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Can I read an Outlook (2003/2007) PST file in C#?

- by Andy May

Is it possible to read a .PST file using C#? I would like to do this as a standalone application, not as an Outlook addin (if that is possible). If have seen other SO questions similar to this mention MailNavigator but I am looking to do this programmatically in C#. I have looked at the Microsoft.Office.Interop.Outlook namespace but that appears to be just for Outlook addins. LibPST appears to be able to read PST files, but this is in C (sorry Joel, I didn't learn C before graduating). Any help would be greatly appreciated, thanks! EDIT: Thank you all for the responses! I accepted Matthew Ruston's response as the answer because it ultimately led me to the code I was looking for. Here is a simple example of what I got to work (You will need to add a reference to Microsoft.Office.Interop.Outlook): using System; using System.Collections.Generic; using Microsoft.Office.Interop.Outlook; namespace PSTReader { class Program { static void Main () { try { IEnumerable<MailItem> mailItems = readPst(@"C:\temp\PST\Test.pst", "Test PST"); foreach (MailItem mailItem in mailItems) { Console.WriteLine(mailItem.SenderName + " - " + mailItem.Subject); } } catch (System.Exception ex) { Console.WriteLine(ex.Message); } Console.ReadLine(); } private static IEnumerable<MailItem> readPst(string pstFilePath, string pstName) { List<MailItem> mailItems = new List<MailItem>(); Application app = new Application(); NameSpace outlookNs = app.GetNamespace("MAPI"); // Add PST file (Outlook Data File) to Default Profile outlookNs.AddStore(pstFilePath); MAPIFolder rootFolder = outlookNs.Stores[pstName].GetRootFolder(); // Traverse through all folders in the PST file // TODO: This is not recursive, refactor Folders subFolders = rootFolder.Folders; foreach (Folder folder in subFolders) { Items items = folder.Items; foreach (object item in items) { if (item is MailItem) { MailItem mailItem = item as MailItem; mailItems.Add(mailItem); } } } // Remove PST file from Default Profile outlookNs.RemoveStore(rootFolder); return mailItems; } } } Note: This code assumes that Outlook is installed and already configured for the current user. It uses the Default Profile (you can edit the default profile by going to Mail in the Control Panel). One major improvement on this code would be to create a temporary profile to use instead of the Default, then destroy it once completed.

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WPF Animation FPS vs. CPU usage - Am I expecting too much?

- by Cory Charlton

Working on a screen saver for my wife, http://cchearts.codeplex.com/, and while I've been able to improve FPS on lower end machines (switch from Path to StreamGeometry, use DrawingVisual instead of UserControl, etc) the CPU usage still seems very high. Here's some numbers I ran from a few 5 minute sampling periods: ~60FPS 35% average CPU on Core 2 Duo T7500 @ 2.2GHz, 3GB ram, NVIDIA Quadro NVS 140M (128MB), Vista [My dev laptop] ~40FPS 50% average CPU on Pentium D @ 3.4GHz, 1.5GB ram, Standard VGA Graphics Adapter (unknown), 2003 Server [A crappy desktop] I can understand the lower frame rate and higher CPU usage on the crappy desktop but it still seems pretty high and 35% on my dev laptop seems high as well. I'd really like to analyze the application to get more details but I'm having issues there as well so I'm wondering if I'm doing something wrong (never profiled WPF before). WPF Performance Suite: Process Launch Error Unable to attach to process: CCHearts.exe Do you want to kill it? This error message occurs when I click cancel after attempting launch. If I don't click cancel it sits there idle, I guess waiting to attach. Performance Explorer: Could not launch C:\Projects2\CC.Hearts\CC.Hearts\bin\Debug (USEVISUAL)\CCHearts.exe. Previous attempt to profile the application finished unsuccessfully. Please restart the application. Output Window from Performance: Profiling started. Profiling process ID 5360 (CCHearts). Process ID 5360 has exited. Data written to C:\Projects2\CC.Hearts\CCHearts100608.vsp. Profiling finished. PRF0025: No data was collected. Profiling complete. So I'm stuck wanting to improve performance but have no concrete way to determine where the bottleneck is. Have been relatively successful throwing darts at this point but I'm beyond that now :) PS: Screensaver is hosted at CodePlex if you want to look at the source and missed the link above. Edit: My RenderOptions darts... // NOTE: Grasping at straws here ;-) RenderOptions.SetBitmapScalingMode(newHeart, BitmapScalingMode.LowQuality); RenderOptions.SetCachingHint(newHeart, CachingHint.Cache); RenderOptions.SetEdgeMode(newHeart, EdgeMode.Aliased); I threw those a little while back and didn't see much difference (not sure if the bitmap scaling even comes into play). Really wish I could get profiling working to know where I should try to optimize. For now I assume there is some overhead in creating a new HeartVisual and the DrawingVisual contained inside. Maybe if I reset and reused the hearts (tossed them in a queue once they completed or something) I'd see an improvement. Shrug Throwing darts while blindfolder is always fun.

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Featureful commercial text editors?

- by wrp

I'm willing to buy tools if they add genuine value over a FOSS equivalent. One thing I wouldn't mind having is an editor with the power of Emacs, but made more user-friendly. There seem to be several commercial editors out there, but I can't find much discussion of them online. Maybe it's because the kind of people who use commercial software don't have time to do much blogging. ;-) If you have used any, what was your evaluation? I'd especially like to hear how you would compare them to Emacs. I'm thinking of editors like VEDIT, Boxer, Crisp, UltraEdit, SlickEdit, etc. To get things started, I tried EditPad Pro because I needed something on a Win98SE box. I was attracted by its powerful support for regexps, but I didn't use it for long. One annoyance was that find-in-files was only available in a separate product you had to buy. The main problem, though, was stability. It sometimes hung and I lost a few files because it corrupted them while editing. After a couple weeks, I found that I was avoiding using it, so I just uninstalled. Edit: Ah...I need to remove some ambiguity. With reference to Emacs, "power" often means its potential for customization. This malleability comes from having an architecture in which most of the functionality is written in a scripting language that runs on a compiled core. Emacs (with elisp) is by far the most widely known such system among home users, but there have been other heavily used editors such as Freemacs (MINT), JED (S-Lang), XEDIT (Rexx), ADAM (TPU), and SlickEdit (Slick-C). In this case, by "power" I'm not referring to extensibility but to realized features. There are three main areas which I think a commercial text editor might be an improvement over Emacs: Stability The only apps I regularly use on Linux that give me flaky behavior are Emacs, Gedit, and Geany. On Windows, I like the look and features of Notepad++, but I find it extremely unstable, especially if I try to use the plugins. Whatever I happen to be doing, I'm using some text editor practically all day long. If I could switch to an editor that never gave me problems, it would definitely lower my stress level. Tools When I started using Emacs, I searched the manual cover to cover to gleam ideas for clever, useful things I could do with it. I'd like to see lots of useful features for editing code, based on detailed knowledge of what the system can do and the accumulated feedback of users. Polish The rule of threes goes that if you develop something for yourself, it's three times harder to make it usable in-house, and three times harder again to make it a viable product for sale. It's understandable, but free software development doesn't seem to benefit from much usability testing. BTW, texteditors.org is a fantastic resource for researching text editors.

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Smooth animation using MatrixTransform?

- by Mattias Konradsson

I'm trying to do an Matrix animation where I both scale and transpose a canvas at the same time. The only approach I found was using a MatrixTransform and MatrixAnimationUsingKeyFrames. Since there doesnt seem to be any interpolation for matrices built in (only for path/rotate) it seems the only choice is to try and build the interpolation and DiscreteMatrixKeyFrame's yourself. I did a basic implementation of this but it isnt exactly smooth and I'm not sure if this is the best way and how to handle framerates etc. Anyone have suggestions for improvement? Here's the code: MatrixAnimationUsingKeyFrames anim = new MatrixAnimationUsingKeyFrames(); int duration = 1; anim.KeyFrames = Interpolate(new Point(0, 0), centerPoint, 1, factor,100,duration); this.matrixTransform.BeginAnimation(MatrixTransform.MatrixProperty, anim,HandoffBehavior.Compose); public MatrixKeyFrameCollection Interpolate(Point startPoint, Point endPoint, double startScale, double endScale, double framerate,double duration) { MatrixKeyFrameCollection keyframes = new MatrixKeyFrameCollection(); double steps = duration * framerate; double milliSeconds = 1000 / framerate; double timeCounter = 0; double diffX = Math.Abs(startPoint.X- endPoint.X); double xStep = diffX / steps; double diffY = Math.Abs(startPoint.Y - endPoint.Y); double yStep = diffY / steps; double diffScale= Math.Abs(startScale- endScale); double scaleStep = diffScale / steps; if (endPoint.Y < startPoint.Y) { yStep = -yStep; } if (endPoint.X < startPoint.X) { xStep = -xStep; } if (endScale < startScale) { scaleStep = -scaleStep; } Point currentPoint = new Point(); double currentScale = startScale; for (int i = 0; i < steps; i++) { keyframes.Add(new DiscreteMatrixKeyFrame(new Matrix(currentScale, 0, 0, currentScale, currentPoint.X, currentPoint.Y), KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(timeCounter)))); currentPoint.X += xStep; currentPoint.Y += yStep; currentScale += scaleStep; timeCounter += milliSeconds; } keyframes.Add(new DiscreteMatrixKeyFrame(new Matrix(endScale, 0, 0, endScale, endPoint.X, endPoint.Y), KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(0)))); return keyframes; }

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Using commit monitors as a form of code review

- by Jeff Dege

I'm working in a small company - four developers, working on a variety of projects. We've been looking at what we can do as cost-effective methods of process improvement, and an idea came up. Given what we do, we often have single developers working on parts of a system, independently of the other developers. This can have a number of negative affects: A developer might not be fully aware of the context in which a change is being implemented, and make the change in a way that will meet the current customer's needs, but will break functionality that other customers depend on. A developer might make a change that breaks the current architectural design, introducing a dependency that will cause problems in future development. Other developers might not be aware of how the system has changed, in areas that they have not worked on. We've talked about doing code reviews, as a way of dealing with these issues. But we've not had much success when we tried. It takes a lot of time to prepare a change for a code review, and it takes everybody out of production while the review is being performed. And the benefits of any review we've tried has been minimal. We're using Subversion (with TortioseSVN) as our VCS. I've been looking at the SubVersion CommitMonitor tool, and wondering whether it might work as a sort of poor-man's code review. It lists every commit made on the repository, allowing someone to see the changes that have been made, the log messages made for that change, the files that were included in the change, and the specific lines in each file that were changed. Rather than scheduling a meeting, trying to get everybody together to review every change, we could just have every developer review every other developer's commits, at whatever time was convenient. This would keep every developer abreast of what changes were being made elsewhere in the system, and would have every change reviewed for customer conflicts and design consistency, at a fairly low cost. If someone saw a problem with the code that was being checked in, he could discuss it with the developer who did the commit, or more likely, schedule a meeting to discuss how the new feature could be implemented in a way that would not impact other users or screw up the architecture. Anyone else doing anything like this, using commit monitors for such a purpose?

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SQL Server to PostgreSQL - Migration and design concerns

- by youwhut

Currently migrating from SQL Server to PostgreSQL and attempting to improve a couple of key areas on the way: I have an Articles table: CREATE TABLE [dbo].[Articles]( [server_ref] [int] NOT NULL, [article_ref] [int] NOT NULL, [article_title] [varchar](400) NOT NULL, [category_ref] [int] NOT NULL, [size] [bigint] NOT NULL ) Data (comma delimited text files) is dumped on the import server by ~500 (out of ~1000) servers on a daily basis. Importing: Indexes are disabled on the Articles table. For each dumped text file Data is BULK copied to a temporary table. Temporary table is updated. Old data for the server is dropped from the Articles table. Temporary table data is copied to Articles table. Temporary table dropped. Once this process is complete for all servers the indexes are built and the new database is copied to a web server. I am reasonably happy with this process but there is always room for improvement as I strive for a real-time (haha!) system. Is what I am doing correct? The Articles table contains ~500 million records and is expected to grow. Searching across this table is okay but could be better. i.e. SELECT * FROM Articles WHERE server_ref=33 AND article_title LIKE '%criteria%' has been satisfactory but I want to improve the speed of searching. Obviously the "LIKE" is my problem here. Suggestions? SELECT * FROM Articles WHERE article_title LIKE '%criteria%' is horrendous. Partitioning is a feature of SQL Server Enterprise but $$$ which is one of the many exciting prospects of PostgreSQL. What performance hit will be incurred for the import process (drop data, insert data) and building indexes? Will the database grow by a huge amount? The database currently stands at 200 GB and will grow. Copying this across the network is not ideal but it works. I am putting thought into changing the hardware structure of the system. The thought process of having an import server and a web server is so that the import server can do the dirty work (WITHOUT indexes) while the web server (WITH indexes) can present reports. Maybe reducing the system down to one server would work to skip the copying across the network stage. This one server would have two versions of the database: one with the indexes for delivering reports and the other without for importing new data. The databases would swap daily. Thoughts? This is a fantastic system, and believe it or not there is some method to my madness by giving it a big shake up. UPDATE: I am not looking for help with relational databases, but hoping to bounce ideas around with data warehouse experts.

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CSS selectors : should I make my CSS easier to read or optimise the speed

- by Laurent Bourgault-Roy

As I was working on a small website, I decided to use the PageSpeed extension to check if their was some improvement I could do to make the site load faster. However I was quite surprise when it told me that my use of CSS selector was "inefficient". I was always told that you should keep the usage of the class attribute in the HTML to a minimum, but if I understand correctly what PageSpeed tell me, it's much more efficient for the browser to match directly against a class name. It make sense to me, but it also mean that I need to put more CSS classes in my HTML. It make my .css file harder to read. I usually tend to mark my CSS like this : #mainContent p.productDescription em.priceTag { ... } Which make it easy to read : I know this will affect the main content and that it affect something in a paragraph tag (so I wont start to put all sort of layout code in it) that describe a product and its something that need emphasis. However it seem I should rewrite it as .priceTag { ... } Which remove all context information about the style. And if I want to use differently formatted price tag (for example, one in a list on the sidebar and one in a paragraph), I need to use something like that .paragraphPriceTag { ... } .listPriceTag { ... } Which really annoy me since I seem to duplicate the semantic of the HTML in my classes. And that mean I can't put common style in an unqualified .priceTag { ... } and thus I need to replicate the style in both CSS rule, making it harder to make change. (Altough for that I could use multiple class selector, but IE6 dont support them) I believe making code harder to read for the sake of speed has never been really considered a very good practice . Except where it is critical, of course. This is why people use PHP/Ruby/C# etc. instead of C/assembly to code their site. It's easier to write and debug. So I was wondering if I should stick with few CSS classes and complex selector or if I should go the optimisation route and remove my fancy CSS selectors for the sake of speed? Does PageSpeed make over the top recommandation? On most modern computer, will it even make a difference?

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Learning MVC - Maintaining model state

- by GenericTypeTea

First of all, I'm very new to MVC. Bought the books, but not got the T-Shirt yet. I've put together my first little application, but I'm looking at the way I'm maintaining my model and I don't think it looks right. My form contains the following: <% using (Html.BeginForm("Reconfigured", null, FormMethod.Post, new { id = "configurationForm" })) { %> <%= Html.DropDownList("selectedCompany", new SelectList(Model.Companies, Model.SelectedCompany), new { onchange = "$('#configurationForm').submit()" })%> <%= Html.DropDownList("selectedDepartment", new SelectList(Model.Departments, Model.SelectedDepartment), new { onchange = "$('#configurationForm').submit()" })%> <%=Html.TextArea("comment", Model.Comment) %> <%} %> My controller has the following: public ActionResult Index(string company, string department, string comment) { TestModel form = new TestModel(); form.Departments = _someRepository.GetList(); form.Companies = _someRepository.GetList(); form.Comment = comment; form.SelectedCompany = company; form.SelectedDepartment = department; return View(form); } [HttpPost] public ActionResult Reconfigured(string selectedCompany, string selectedDepartment, string comment) { return RedirectToAction("Index", new { company = selectedCompany, department = selectedDepartment, comment = comment}); } And finally, this is my route: routes.MapRoute( "Default", "{controller}/{company}/{department}", new { controller = "CompanyController", action = "Index", company="", department="" } ); Now, every time I change DropDownList value, all my values are maintained. I end up with a URL like the following after the Reconfigure action is called: http://localhost/Main/Index/Company/Sales?comment=Foo%20Bar Ideally I'd like the URL to remain as: http://localhost/Main/Index My routing object is probably wrong. This can't be the right way? It seems totally wrong to me as for each extra field I add, I have to add the property into the Index() method? I had a look at this answer where the form is passed through TempData. This is obviously an improvement, but it's not strongly typed? Is there a way to do something similar but have it strongly typed? This may be a simple-enough question, but the curse of 10 years of WinForms/WebForms makes this MVC malarky hard to get your head 'round.

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Function Point Analysis -- a seriously over-estimating technique?

- by kizzx2

I know questions about FPA has been asked numerous times before, but this time I'm taking a more analytical angle at it, backed up with data. 1. First, some data This question is based on a tutorial. He had a "Sample Count" section where he demonstrated it step by step. You can see some screenshots of his sample application here. In the end, he calculated the unadjusted FP to be 99. There is another article on InformIT with industry data on typical hour/FP. It ranges from 2 hours/FP to 27.4 hours/FP. Let's try to stick with 2 for the moment (since SO readers are probably the more efficient crowd :p). 2. Reality check!? Now just check out the screenshots again. Do a little math here 99 * 2 = 198 hours 198 hours / 40 hours per week = 5 weeks Seriously? That sample application is going to take 5 weeks to implement? Is it just my feeling that it wouldn't take any decent programmer longer than one week to have it completed? Now let's try estimating the cost of the project. We'll use New York's minimum wage at the moment (Wikipedia), which is $7.25 198 * 7.25 = $1435.5 From what I could see from the screenshots, this application is a small excel-improvement app. I could have bought MS Office Pro for 200 bucks which gives me greater interoperability (.xls files) and flexibility (spreadsheets). (For the record, that same Web site has another article discussing productivity. It seems like they typically use 4.2 hours/FP, which gives us even more shocking stats: 99 * 4.2 = 415 hours = 10 weeks = almost 3 whopping months! 415 hours * $7.25 = $3000 zomg (That's even assuming that all our poor coders get the minimum wage!) 3. Am I missing something here? Right now, I could come up with several possible explanation: FPA is really only suited for bigger projects (1000+ FPs) so it becomes extremely inaccurate at smaller scale. The hours/FP metric fluctuates abruptly from team to team, project to project. For a small project like this, we could have used something like 0.5 hour/FP or something. (Now this kind of makes the whole estimation thing pointless, unless my firm does the same type of projects for several years with the same team, not really common.) From my experience with several software metrics, Function Point is really not a lightweight metric. If the hour/FP thing fluctuates so much, then what's the point, maybe I could have gone with User Story Points which is a lot faster to get and arguably almost as uncertain. What would be the FP experts' answers to this?

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What is the best way get and hold property reference by name in c#

- by Jeff Weber

I want to know if there is a better way (than what I'm currently doing) to obtain and hold a reference to a property in another object using only the object and property string names. Particularly, is there a better way to do this with the new dynamic functionality of .Net 4.0? Here is what I have right now. I have a "PropertyReference<T>" object that takes an object name and property name in the constructor. An Initialize() method uses reflection to find the object and property and stores the property Getter as an Action<T> and the property Setter as an Func<T>. When I want to actually call the property I do something like this: int x = _propertyReference.Get(); or _propertyReference.Set(2); Here is my PropertyReference<T> code. Please dissect and make suggestions for improvement. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Reflection; using System.Xml; namespace WindowsFormsApplication2 { public class PropertyReference<T> : IPropertyReference { public string ComponentName { get; set; } public string PropertyName { get; set; } public bool IsInitialized { get { return (_action != null && _func != null); } } Action<T> _action; Func<T> _func; public PropertyReference() { } public PropertyReference(string componentName, string propertyName) { ComponentName = componentName; PropertyName = propertyName; } public void Initialize(IEntity e) { Object component = e.GetByName(ComponentName); if (component == null) return; Type t = e.GetByName(ComponentName).GetType(); PropertyInfo pi = t.GetProperty(PropertyName); _action = (T a) => pi.SetValue(component, a, null); _func = () => (T)pi.GetValue(component, null); } public void Reset() { _action = null; _func = null; } public void Set(T value) { _action.Invoke(value); } public T Get() { return _func(); } } } Note: I can't use the "Emit" functionality as I need this code to work on the new Windows Phone 7 and that does not support Emit.

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Function Point Analysis -- a seriously overestimating technique?

- by kizzx2

I know questions about FPA has been asked numerous times before, but this time I'm taking a more analytical angle at it, backed up with data. 1. First, some data This question is based on a tutorial. He had a "Sample Count" section where he demonstrated it step by step. You can see some screenshots of his sample application here. In the end, he calculated the unadjusted FP to be 99. There is another article on InformIT with industry data on typical hour/FP. It ranges from 2 hours/FP to 27.4 hours/FP. Let's try to stick with 2 for the moment (since SO readers are probably the more efficient crowd :p). 2. Reality check!? Now just check out the screenshots again. Do a little math here 99 * 2 = 198 hours 198 hours / 40 hours per week = 5 weeks Seriously? That sample application is going to take 5 weeks to implement? Is it just my feeling that it wouldn't take any decent programmer longer than one week (I"m not even saying weekend) to have it completed? Now let's try estimating the cost of the project. We'll use New York's minimum wage at the moment (Wikipedia), which is $7.25 198 * 7.25 = $1435.5 From what I could see from the screenshots, this application is a small excel-improvement app. I could have bought MS Office Pro for 200 bucks which gives me greater interoperability (.xls files) and flexibility (spreadsheets). (For the record, that same Web site has another article discussing productivity. It seems like they typically use 4.2 hours/FP, which gives us even more shocking stats: 99 * 4.2 = 415 hours = 10 weeks = almost 3 whopping months! 415 hours * $7.25 = $3000 zomg (That's even assuming that all our poor coders get the minimum wage!) 3. Am I missing something here? Right now, I could come up with several possible explanation: FPA is really only suited for bigger projects (1000+ FPs) so it becomes extremely inaccurate at smaller scale. The hours/FP metric fluctuates abruptly from team to team, project to project. For a small project like this, we could have used something like 0.5 hour/FP or something. (Now this kind of makes the whole estimation thing pointless, unless my firm does the same type of projects for several years with the same team, not really common.) From my experience with several software metrics, Function Point is really not a lightweight metric. If the hour/FP thing fluctuates so much, then what's the point, maybe I could have gone with User Story Points which is a lot faster to get and arguably almost as uncertain. What would be the FP experts' answers to this?

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IP address numbers in MySQL subquery

- by Iain Collins

I have a problem with a subquery involving IPV4 addresses stored in MySQL (MySQL 5.0). The IP addresses are stored in two tables, both in network number format - e.g. the format output by MySQL's INET_ATON(). The first table ('events') contains lots of rows with IP addresses associated with them, the second table ('network_providers') contains a list of provider information for given netblocks. events table (~4,000,000 rows): event_id (int) event_name (varchar) ip_address (unsigned 4 byte int) network_providers table (~60,000 rows): ip_start (unsigned 4 byte int) ip_end (unsigned 4 byte int) provider_name (varchar) Simplified for the purposes of the problem I'm having, the goal is to create an export along the lines of: event_id,event_name,ip_address,provider_name If do a query along the lines of either of the following, I get the result I expect: SELECT provider_name FROM network_providers WHERE INET_ATON('192.168.0.1') >= network_providers.ip_start ORDER BY network_providers.ip_start DESC LIMIT 1 SELECT provider_name FROM network_providers WHERE 3232235521 >= network_providers.ip_start ORDER BY network_providers.ip_start DESC LIMIT 1 That is to say, it returns the correct provider_name for whatever IP I look up (of course I'm not really using 192.168.0.1 in my queries). However, when performing this same query as a subquery, in the following manner, it doesn't yield the result I would expect: SELECT event.id, event.event_name, (SELECT provider_name FROM network_providers WHERE event.ip_address >= network_providers.ip_start ORDER BY network_providers.ip_start DESC LIMIT 1) as provider FROM events Instead the a different (incorrect) value for network_provider is returned - over 90% (but curiously not all) values returned in the provider column contain the wrong provider information for that IP. Using event.ip_address in a subquery just to echo out the value confirms it contains the value I'd expect and that the subquery can parse it. Replacing event.ip_address with an actual network number also works, just using it dynamically in the subquery in this manner that doesn't work for me. I suspect the problem is there is something fundamental and important about subqueries in MySQL that I don't get. I've worked with IP addresses like this in MySQL quite a bit before, but haven't previously done lookups for them using a subquery. The question: I'd really appreciate an example of how I could get the output I want, and if someone here knows, some enlightenment as to why what I'm doing doesn't work so I can avoid making this mistake again. Notes: The actual real-world usage I'm trying to do is considerably more complicated (involving joining two or three tables). This is a simplified version, to avoid overly complicating the question. Additionally, I know I'm not using a between on ip_start & ip_end - that's intentional (the DB's can be out of date, and such cases the owner in the DB is almost always in the next specified range and 'best guess' is fine in this context) however I'm grateful for any suggestions for improvement that relate to the question. Efficiency is always nice, but in this case absolutely not essential - any help appreciated.

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Live search results as you type... am I going about this the right way? jQuery + PHP

- by dallen

This is my first time building a tool like this, so please bare with me. I'm doing this to learn more about jQuery and AJAX. Basically, I have a search input and a hidden div. When you start typing in the search input, the hidden div becomes visible and results are brought in. In this case, I'm searching for client names. It all works fine, however I think my code could be better but I'm not sure exactly where to begin. Each keyup requests a PHP script which accesses a table in a database to find a like string. But in my PHP script, I'm echo'ing some JS/jQuery which I'm not sure is good practice. Below is my code. Am I going about this the right way or am I totally off base? Any suggestions for improvement? Javascript $("#search").keyup(function() { $("#search_results").show("fast"); $.ajax ({ type: "POST", url: "http://localhost:8888/index.php/welcome/search/" + $("#search").val(), success: function(html) { $("#search_results").html(html); } }); }); PHP function search($search_string = false) { if ($search_string) { $this->db->like('name', $search_string); $query = $this->db->get('clients'); if ($query->num_rows() == 0) { echo "No client exists."; } else { foreach ($query->result() as $row) { echo '<script>'; echo ' $("#client_results_'.$row->id.'").hide(); $("#'.$row->id.'").toggle(function() { $.ajax ({ type: "POST", url: "http://localhost:8888/index.php/welcome/search_client_ads/" + '.$row->id.', success: function(html) { $("#client_results_'.$row->id.'").html(html).show("fast"); } }); }, function() { $("#client_results_'.$row->id.'").hide("fast").html(""); });'; echo '</script>'; echo '<p><span id="'.$row->id.'">'.$row->name.'</span></p>'; echo '<div id="client_results_'.$row->id.'"></div>'; } } } else { echo ''; } } function search_client_ads($client_id) { $query = $this->db->get_where('online_ads', array('client' => $client_id)); if ($query->num_rows() == 0) { echo "No ads exist."; } else { foreach ($query->result() as $row) { echo $row->id; } } }

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CSS selectors : should I minimise my use of the class attribute in the HTML or optimise the speed

- by Laurent Bourgault-Roy

As I was working on a small website, I decided to use the PageSpeed extension to check if their was some improvement I could do to make the site load faster. However I was quite surprise when it told me that my use of CSS selector was "inefficient". I was always told that you should keep the usage of the class attribute in the HTML to a minimum, but if I understand correctly what PageSpeed tell me, it's much more efficient for the browser to match directly against a class name. It make sense to me, but it also mean that I need to put more CSS classes in my HTML. It also make my .css file a little harder to read. I usually tend to mark my CSS like this : #mainContent p.productDescription em.priceTag { ... } Which make it easy to read : I know this will affect the main content and that it affect something in a paragraph tag (so I wont start to put all sort of layout code in it) that describe a product and its something that need emphasis. However it seem I should rewrite it as .priceTag { ... } Which remove all context information about the style. And if I want to use differently formatted price tag (for example, one in a list on the sidebar and one in a paragraph), I need to use something like that .paragraphPriceTag { ... } .listPriceTag { ... } Which really annoy me since I seem to duplicate the semantic of the HTML in my classes. And that mean I can't put common style in an unqualified .priceTag { ... } and thus I need to replicate the style in both CSS rule, making it harder to make change. (Altough for that I could use multiple class selector, but IE6 dont support them) I believe making code harder to read for the sake of speed has never been really considered a very good practice . Except where it is critical, of course. This is why people use PHP/Ruby/C# etc. instead of C/assembly to code their site. It's easier to write and debug. So I was wondering if I should stick with few CSS classes and complex selector or if I should go the optimisation route and remove my fancy CSS selectors for the sake of speed? Does PageSpeed make over the top recommandation? On most modern computer, will it even make a difference?

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Are there any modern GUI toolkits which implement a heirarchical menu buffer zone?

- by scomar

In Bruce Tognazzini's quiz on Fitt's Law, the question discussing the bottleneck in the hierarchical menu (as used in almost every modern desktop UI), talks about his design for the original Mac: The bottleneck is the passage between the first-level menu and the second-level menu. Users first slide the mouse pointer down to the category menu item. Then, they must carefully slide the mouse directly across (horizontally) in order to move the pointer into the secondary menu. The engineer who originally designed hierarchicals apparently had his forearm mounted on a track so that he could move it perfectly in a horizontal direction without any vertical component. Most of us, however, have our forarms mounted on a pivot we like to call our elbow. That means that moving our hand describes an arc, rather than a straight line. Demanding that pivoted people move a mouse pointer along in a straight line horizontally is just wrong. We are naturally going to slip downward even as we try to slide sideways. When we are not allowed to slip downward, the menu we're after is going to slam shut just before we get there. The Windows folks tried to overcome the pivot problem with a hack: If they see the user move down into range of the next item on the primary menu, they don't instantly close the second-level menu. Instead, they leave it open for around a half second, so, if users are really quick, they can be inaccurate but still get into the second-level menu before it slams shut. Unfortunately, people's reactions to heightened chance of error is to slow down, rather than speed up, a well-established phenomenon. Therefore, few users will ever figure out that moving faster could solve their problem. Microsoft's solution is exactly wrong. When I specified the Mac hierarchical menu algorthm in the mid-'80s, I called for a buffer zone shaped like a <, so that users could make an increasingly-greater error as they neared the hierarchical without fear of jumping to an unwanted menu. As long as the user's pointer was moving a few pixels over for every one down, on average, the menu stayed open, no matter how slow they moved. (Cancelling was still really easy; just deliberately move up or down.) This just blew me away! Such a simple idea which would result in a huge improvement in usability. I'm sure I'm not the only one who regularly has the next level of a menu slam shut because I don't move the mouse pointer in a perfectly horizontal line. So my question is: Are there any modern UI toolkits which implement this brilliant idea of a < shaped buffer zone in hierarchical menus? And if not, why not?!

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Adding a clustered index to a SQL table: what dangers exist for a live production system?

- by MoSlo

Right, keep in mind i need to describe this by abstracting all possible confidential info: I've been put in charge of a 10-year old transactional system of which the majority business logic is implemented at database level (triggers, stored procedures etc). Win2000 server, MSSQL 2000 Enterprise. No immediate plans for replacing/updating the system are being considered :( The core process is a program that executes transactions - specifically, it executes a stored procedure with various parameters, lets call it sp_ProcessTrans. The program executes the stored procedure at asynchronous intervals. By itself, things work fine. But there are 30 instances of this program on remotely located workstations, all of them asynchronously executing sp_ProcessTrans and then retrieving data from the SQL server (execution is pretty regular - ranging 0 to 60 times a minute, depending on what items the program instance is responsible for) . Performance of the system has dropped considerably with 10 yrs of data growth: the reason is the deadlocks and specifically deadlock wait times. The deadlock is on the Employee table. I have discovered: In sp_ProcessTrans' execution, it selects from an Employee table 7 times (dont ask) The select is done on a field that is NOT the primary key No index exists on this field. Thus a table scan is performed. 7 times. per transaction So the reason for deadlocks is clear. I created a non-unique ordered clustered index on the field (field looks good, almost unique, NUM(7), very rarely changes). Immediate improvement in the test environment. The problem is that i cannot simulate the deadlocks in a test environment (I'd need 30 workstations; i'd need to simulate 'realistic' activity on those stations, so visualization is out). I need to know if i must schedule downtime. Creating an index shouldn't be a risky operation for MSSQL, but is there any danger (data corruption in transactions/select statements/extra wait time etc) to create this field index on the production database while the transactions are still taking place? (although i can select a time when transactions are fairly quiet through the 30 stations) Are there any hidden dangers i'm not seeing (not looking forward to needing to restore the DB if something goes wrong, restoring would take a lot of time with 10yrs of data).

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Issue with SQL query for activity stream/feed

- by blabus

I'm building an application that allows users to recommend music to each other, and am having trouble building a query that would return a 'stream' of recommendations that involve both the user themselves, as well as any of the user's friends. This is my table structure: Recommendations ID Sender Recipient [other columns...] -- ------ --------- ------------------ r1 u1 u3 ... r2 u3 u2 ... r3 u4 u3 ... Users ID Email First Name Last Name [other columns...] --- ----- ---------- --------- ------------------ u1 ... ... ... ... u2 ... ... ... ... u3 ... ... ... ... u4 ... ... ... ... Relationships ID Sender Recipient Status [other columns...] --- ------ --------- -------- ------------------ rl1 u1 u2 accepted ... rl2 u3 u1 accepted ... rl3 u1 u4 accepted ... rl4 u3 u2 accepted ... So for user 'u4' (who is friends with 'u1'), I want to query for a 'stream' of recommendations relevant to u4. This stream would include all recommendations in which either the sender or recipient is u4, as well as all recommendations in which the sender or recipient is u1 (the friend). This is what I have for the query so far: SELECT * FROM recommendations WHERE recommendations.sender IN ( SELECT sender FROM relationships WHERE recipient='u4' AND status='accepted' UNION SELECT recipient FROM relationships WHERE sender='u4' AND status='accepted') OR recommendations.recipient IN ( SELECT sender FROM relationships WHERE recipient='u4' AND status='accepted' UNION SELECT recipient FROM relationships WHERE sender='u4' AND status='accepted') UNION SELECT * FROM recommendations WHERE recommendations.sender='u4' OR recommendations.recipient='u4' GROUP BY recommendations.id ORDER BY datecreated DESC Which seems to work, as far as I can see (I'm no SQL expert). It returns all of the records from the Recommendations table that would be 'relevant' to a given user. However, I'm now having trouble also getting data from the Users table as well. The Recommendations table has the sender's and recipient's ID (foreign keys), but I'd also like to get the first and last name of each as well. I think I require some sort of JOIN, but I'm lost on how to proceed, and was looking for help on that. (And also, if anyone sees any areas for improvement in my current query, I'm all ears.) Thanks!

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Difficulty with jQuery and input keydown event

- by Rosarch

I am making a simple JavaScript enhanced list. I want it to be a list of inputs, each with an 'Add' and 'Remove' button. If the user clicks 'Add', a new li will be added. If the user clicks 'Remove', that li will be removed. It works fine, except for hitting "enter" in an <input>. Currently, it always causes the Remove.click event handler to fire, unless there's only one item in the list. I'm not sure why. How can I suppress this? Here is the complete jQuery. My attempt to fix the "enter" issue is commented out, and it doesn't work. I suspect that I could be designing this code better; if you see an improvement I'd love to hear it. function make_smart_list(list) { var ADD_CLASS = 'foo-widget-Add'; var REMOVE_CLASS = 'foo-widget-Remove'; var jq_list = $(list); jq_list.parents('form').submit(function() { return false; }); function refresh_handlers() { jq_list.find(sprintf('.%s, .%s', REMOVE_CLASS, ADD_CLASS)).unbind('click'); // jq_list.find('input').unbind('submit'); // // jq_list.find('input').submit(function() { // var jq_this = $(this); // var next_button = jq_this.nextAll('button'); // if (next_button.hasClass(ADD_CLASS)) { // next_button.nextAll('button').click(); // return; // } // // if (next_button.hasClass(REMOVE_CLASS)) { // return false; // } // // }); jq_list.find("." + REMOVE_CLASS).click(function() { var jq_this = $(this); jq_this.parent().remove(); refresh_handlers(); return false; }); jq_list.find("." + ADD_CLASS).click(function() { var jq_this = $(this); if (jq_this.prevAll('input').val() == '') { return; } jq_this.parent().clone().appendTo(jq_this.parent().parent()); jq_this.parent().next().find('input').val('').focus(); jq_this.removeClass(ADD_CLASS).addClass(REMOVE_CLASS); jq_this.text('Remove'); refresh_handlers(); return false; }); } refresh_handlers(); } (sprintf is another script I have.)

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The dynamic Type in C# Simplifies COM Member Access from Visual FoxPro

- by Rick Strahl

I’ve written quite a bit about Visual FoxPro interoperating with .NET in the past both for ASP.NET interacting with Visual FoxPro COM objects as well as Visual FoxPro calling into .NET code via COM Interop. COM Interop with Visual FoxPro has a number of problems but one of them at least got a lot easier with the introduction of dynamic type support in .NET. One of the biggest problems with COM interop has been that it’s been really difficult to pass dynamic objects from FoxPro to .NET and get them properly typed. The only way that any strong typing can occur in .NET for FoxPro components is via COM type library exports of Visual FoxPro components. Due to limitations in Visual FoxPro’s type library support as well as the dynamic nature of the Visual FoxPro language where few things are or can be described in the form of a COM type library, a lot of useful interaction between FoxPro and .NET required the use of messy Reflection code in .NET. Reflection is .NET’s base interface to runtime type discovery and dynamic execution of code without requiring strong typing. In FoxPro terms it’s similar to EVALUATE() functionality albeit with a much more complex API and corresponiding syntax. The Reflection APIs are fairly powerful, but they are rather awkward to use and require a lot of code. Even with the creation of wrapper utility classes for common EVAL() style Reflection functionality dynamically access COM objects passed to .NET often is pretty tedious and ugly. Let’s look at a simple example. In the following code I use some FoxPro code to dynamically create an object in code and then pass this object to .NET. An alternative to this might also be to create a new object on the fly by using SCATTER NAME on a database record. How the object is created is inconsequential, other than the fact that it’s not defined as a COM object – it’s a pure FoxPro object that is passed to .NET. Here’s the code: *** Create .NET COM InstanceloNet = CREATEOBJECT('DotNetCom.DotNetComPublisher') *** Create a Customer Object Instance (factory method) loCustomer = GetCustomer() loCustomer.Name = "Rick Strahl" loCustomer.Company = "West Wind Technologies" loCustomer.creditLimit = 9999999999.99 loCustomer.Address.StreetAddress = "32 Kaiea Place" loCustomer.Address.Phone = "808 579-8342" loCustomer.Address.Email = "[email protected]" *** Pass Fox Object and echo back values ? loNet.PassRecordObject(loObject) RETURN FUNCTION GetCustomer LOCAL loCustomer, loAddress loCustomer = CREATEOBJECT("EMPTY") ADDPROPERTY(loCustomer,"Name","") ADDPROPERTY(loCustomer,"Company","") ADDPROPERTY(loCUstomer,"CreditLimit",0.00) ADDPROPERTY(loCustomer,"Entered",DATETIME()) loAddress = CREATEOBJECT("Empty") ADDPROPERTY(loAddress,"StreetAddress","") ADDPROPERTY(loAddress,"Phone","") ADDPROPERTY(loAddress,"Email","") ADDPROPERTY(loCustomer,"Address",loAddress) RETURN loCustomer ENDFUNC Now prior to .NET 4.0 you’d have to access this object passed to .NET via Reflection and the method code to do this would looks something like this in the .NET component: public string PassRecordObject(object FoxObject) { // *** using raw Reflection string Company = (string) FoxObject.GetType().InvokeMember( "Company", BindingFlags.GetProperty,null, FoxObject,null); // using the easier ComUtils wrappers string Name = (string) ComUtils.GetProperty(FoxObject,"Name"); // Getting Address object – then getting child properties object Address = ComUtils.GetProperty(FoxObject,"Address"); string Street = (string) ComUtils.GetProperty(FoxObject,"StreetAddress"); // using ComUtils 'Ex' functions you can use . Syntax string StreetAddress = (string) ComUtils.GetPropertyEx(FoxObject,"AddressStreetAddress"); return Name + Environment.NewLine + Company + Environment.NewLine + StreetAddress + Environment.NewLine + " FOX"; } Note that the FoxObject is passed in as type object which has no specific type. Since the object doesn’t exist in .NET as a type signature the object is passed without any specific type information as plain non-descript object. To retrieve a property the Reflection APIs like Type.InvokeMember or Type.GetProperty().GetValue() etc. need to be used. I made this code a little simpler by using the Reflection Wrappers I mentioned earlier but even with those ComUtils calls the code is pretty ugly requiring passing the objects for each call and casting each element. Using .NET 4.0 Dynamic Typing makes this Code a lot cleaner Enter .NET 4.0 and the dynamic type. Replacing the input parameter to the .NET method from type object to dynamic makes the code to access the FoxPro component inside of .NET much more natural: public string PassRecordObjectDynamic(dynamic FoxObject) { // *** using raw Reflection string Company = FoxObject.Company; // *** using the easier ComUtils class string Name = FoxObject.Name; // *** using ComUtils 'ex' functions to use . Syntax string Address = FoxObject.Address.StreetAddress; return Name + Environment.NewLine + Company + Environment.NewLine + Address + Environment.NewLine + " FOX"; } As you can see the parameter is of type dynamic which as the name implies performs Reflection lookups and evaluation on the fly so all the Reflection code in the last example goes away. The code can use regular object ‘.’ syntax to reference each of the members of the object. You can access properties and call methods this way using natural object language. Also note that all the type casts that were required in the Reflection code go away – dynamic types like var can infer the type to cast to based on the target assignment. As long as the type can be inferred by the compiler at compile time (ie. the left side of the expression is strongly typed) no explicit casts are required. Note that although you get to use plain object syntax in the code above you don’t get Intellisense in Visual Studio because the type is dynamic and thus has no hard type definition in .NET . The above example calls a .NET Component from VFP, but it also works the other way around. Another frequent scenario is an .NET code calling into a FoxPro COM object that returns a dynamic result. Assume you have a FoxPro COM object returns a FoxPro Cursor Record as an object: DEFINE CLASS FoxData AS SESSION OlePublic cAppStartPath = "" FUNCTION INIT THIS.cAppStartPath = ADDBS( JustPath(Application.ServerName) ) SET PATH TO ( THIS.cAppStartpath ) ENDFUNC FUNCTION GetRecord(lnPk) LOCAL loCustomer SELECT * FROM tt_Cust WHERE pk = lnPk ; INTO CURSOR TCustomer IF _TALLY < 1 RETURN NULL ENDIF SCATTER NAME loCustomer MEMO RETURN loCustomer ENDFUNC ENDDEFINE If you call this from a .NET application you can now retrieve this data via COM Interop and cast the result as dynamic to simplify the data access of the dynamic FoxPro type that was created on the fly: int pk = 0; int.TryParse(Request.QueryString["id"],out pk); // Create Fox COM Object with Com Callable Wrapper FoxData foxData = new FoxData(); dynamic foxRecord = foxData.GetRecord(pk); string company = foxRecord.Company; DateTime entered = foxRecord.Entered; This code looks simple and natural as it should be – heck you could write code like this in days long gone by in scripting languages like ASP classic for example. Compared to the Reflection code that previously was necessary to run similar code this is much easier to write, understand and maintain. For COM interop and Visual FoxPro operation dynamic type support in .NET 4.0 is a huge improvement and certainly makes it much easier to deal with FoxPro code that calls into .NET. Regardless of whether you’re using COM for calling Visual FoxPro objects from .NET (ASP.NET calling a COM component and getting a dynamic result returned) or whether FoxPro code is calling into a .NET COM component from a FoxPro desktop application. At one point or another FoxPro likely ends up passing complex dynamic data to .NET and for this the dynamic typing makes coding much cleaner and more readable without having to create custom Reflection wrappers. As a bonus the dynamic runtime that underlies the dynamic type is fairly efficient in terms of making Reflection calls especially if members are repeatedly accessed. © Rick Strahl, West Wind Technologies, 2005-2010Posted in COM FoxPro .NET CSharp

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C#: System.Collections.Concurrent.ConcurrentQueue vs. Queue

- by James Michael Hare

I love new toys, so of course when .NET 4.0 came out I felt like the proverbial kid in the candy store! Now, some people get all excited about the IDE and it’s new features or about changes to WPF and Silver Light and yes, those are all very fine and grand. But me, I get all excited about things that tend to affect my life on the backside of development. That’s why when I heard there were going to be concurrent container implementations in the latest version of .NET I was salivating like Pavlov’s dog at the dinner bell. They seem so simple, really, that one could easily overlook them. Essentially they are implementations of containers (many that mirror the generic collections, others are new) that have either been optimized with very efficient, limited, or no locking but are still completely thread safe -- and I just had to see what kind of an improvement that would translate into. Since part of my job as a solutions architect here where I work is to help design, develop, and maintain the systems that process tons of requests each second, the thought of extremely efficient thread-safe containers was extremely appealing. Of course, they also rolled out a whole parallel development framework which I won’t get into in this post but will cover bits and pieces of as time goes by. This time, I was mainly curious as to how well these new concurrent containers would perform compared to areas in our code where we manually synchronize them using lock or some other mechanism. So I set about to run a processing test with a series of producers and consumers that would be either processing a traditional System.Collections.Generic.Queue or a System.Collection.Concurrent.ConcurrentQueue. Now, I wanted to keep the code as common as possible to make sure that the only variance was the container, so I created a test Producer and a test Consumer. The test Producer takes an Action<string> delegate which is responsible for taking a string and placing it on whichever queue we’re testing in a thread-safe manner: 1: internal class Producer 2: { 3: public int Iterations { get; set; } 4: public Action<string> ProduceDelegate { get; set; } 5: 6: public void Produce() 7: { 8: for (int i = 0; i < Iterations; i++) 9: { 10: ProduceDelegate(“Hello”); 11: } 12: } 13: } Then likewise, I created a consumer that took a Func<string> that would read from whichever queue we’re testing and return either the string if data exists or null if not. Then, if the item doesn’t exist, it will do a 10 ms wait before testing again. Once all the producers are done and join the main thread, a flag will be set in each of the consumers to tell them once the queue is empty they can shut down since no other data is coming: 1: internal class Consumer 2: { 3: public Func<string> ConsumeDelegate { get; set; } 4: public bool HaltWhenEmpty { get; set; } 5: 6: public void Consume() 7: { 8: bool processing = true; 9: 10: while (processing) 11: { 12: string result = ConsumeDelegate(); 13: 14: if(result == null) 15: { 16: if (HaltWhenEmpty) 17: { 18: processing = false; 19: } 20: else 21: { 22: Thread.Sleep(TimeSpan.FromMilliseconds(10)); 23: } 24: } 25: else 26: { 27: DoWork(); // do something non-trivial so consumers lag behind a bit 28: } 29: } 30: } 31: } Okay, now that we’ve done that, we can launch threads of varying numbers using lambdas for each different method of production/consumption. First let's look at the lambdas for a typical System.Collections.Generics.Queue with locking: 1: // lambda for putting to typical Queue with locking... 2: var productionDelegate = s => 3: { 4: lock (_mutex) 5: { 6: _mutexQueue.Enqueue(s); 7: } 8: }; 9: 10: // and lambda for typical getting from Queue with locking... 11: var consumptionDelegate = () => 12: { 13: lock (_mutex) 14: { 15: if (_mutexQueue.Count > 0) 16: { 17: return _mutexQueue.Dequeue(); 18: } 19: } 20: return null; 21: }; Nothing new or interesting here. Just typical locks on an internal object instance. Now let's look at using a ConcurrentQueue from the System.Collections.Concurrent library: 1: // lambda for putting to a ConcurrentQueue, notice it needs no locking! 2: var productionDelegate = s => 3: { 4: _concurrentQueue.Enqueue(s); 5: }; 6: 7: // lambda for getting from a ConcurrentQueue, once again, no locking required. 8: var consumptionDelegate = () => 9: { 10: string s; 11: return _concurrentQueue.TryDequeue(out s) ? s : null; 12: }; So I pass each of these lambdas and the number of producer and consumers threads to launch and take a look at the timing results. Basically I’m timing from the time all threads start and begin producing/consuming to the time that all threads rejoin. I won't bore you with the test code, basically it just launches code that creates the producers and consumers and launches them in their own threads, then waits for them all to rejoin. The following are the timings from the start of all threads to the Join() on all threads completing. The producers create 10,000,000 items evenly between themselves and then when all producers are done they trigger the consumers to stop once the queue is empty. These are the results in milliseconds from the ordinary Queue with locking: 1: Consumers Producers 1 2 3 Time (ms) 2: ---------- ---------- ------ ------ ------ --------- 3: 1 1 4284 5153 4226 4554.33 4: 10 10 4044 3831 5010 4295.00 5: 100 100 5497 5378 5612 5495.67 6: 1000 1000 24234 25409 27160 25601.00 And the following are the results in milliseconds from the ConcurrentQueue with no locking necessary: 1: Consumers Producers 1 2 3 Time (ms) 2: ---------- ---------- ------ ------ ------ --------- 3: 1 1 3647 3643 3718 3669.33 4: 10 10 2311 2136 2142 2196.33 5: 100 100 2480 2416 2190 2362.00 6: 1000 1000 7289 6897 7061 7082.33 Note that even though obviously 2000 threads is quite extreme, the concurrent queue actually scales really well, whereas the traditional queue with simple locking scales much more poorly. I love the new concurrent collections, they look so much simpler without littering your code with the locking logic, and they perform much better. All in all, a great new toy to add to your arsenal of multi-threaded processing!

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CodePlex Daily Summary for Monday, February 22, 2010

CodePlex Daily Summary for Monday, February 22, 2010New ProjectsAVDB: System to keep track of orders and the inventory of televisions, DVDs, VCRs etcBooky: Booky is an online Bookmark Management Tool. Gear Up for Lord of the Rings Online (lotro): Windows utility for checking what your LOTRO character currently has equipped and figuring out gear you should get to improve your stats.GotSharp Extensions: GotSharp Extensions is a set of helpful classes and extension methods that can make your coding experience easier and cleaner. Halfwit: A minimalist WPF Twitter client.HOA Starter Kit: A community subdivision website starter kit. First draft.Lua For Irony: Project to define the Lua language using the Irony (http://irony.codeplex.com/) development kit. This work is based heavily on the work done for V...MimeCloud: Scalable .NET Digital Asset & Media Management: MimeCloud is a scalable digital asset library & media management toolset. Founded by Alex Norcliffe and Peter Miller Written by people who have b...Parallel Mandelbrot Set solver: Solving the Mandelbrot set using the Parallel class in .NET 4.0. Showing the resulting image in a WPF application. The solution file requires VS 2010.Pomogad - Pomodoro Windows Gadget: Você usa Pomodoro Technique? Não sabe o que é? Veja aqui http://www.pomodorotechnique.com Agora que você já sabe, que tal usar essa técnica? E p...PostCrap - flyweight .NET AOP post compiler: PostCrap is a flyweight attribute based aspect injection .NET post compiler It is written in C# and uses Mono.Cecil to modify assemblies and injec...Software + Service Reference Demo Kit: MS China Developer and Platform Evangelism team created an End-2-End demo for Software + Service. Yet Another SharePoint Tool: YEAST provides you with a simple to integrate approach to generating SharePoint solution packages as part of a Visual Studio project. Zen Coding Visual Studio Plugin: Zen Coding for Visual Studio is plugin for HTML and CSS hi-speed codingNew Releases.Net MSBuild Google Closure Compiler Task: .Net MSBuild Google Closure Compiler Task 1.1: - Corrected issue with regular expression source file and renamingdotNails: dotNails_0.5.9: NOTE - the latest source code has been moved to google code to take advantage of Mercurial source control - http://code.google.com/p/dotnails/sourc...EasyWFUnit: EasyWFUnit-2.2: Release 2.2 of EasyWFUnit, an extension library to support unit testing of Windows Workflow, includes a revised WinForm GUI Test Builder that utili...Fluent Ribbon Control Suite: Fluent Ribbon Control Suite BETA2 (for .NET 4.0RC): Includes Fluent.dll (with .pdb and .xml) and test application compiled with .NET 4.0 RC.FolderSize: FolderSize.Win32.1.0.3.0: FolderSize.Win32.1.0.3.0 A simple utility intended to be used to scan harddrives for the folders that take most place and display this to the user...Fusion Charts Free for SharePoint: 1.3: Fix release for issue #11833 : Feature Must Be Activated on Root of Web Application.GotSharp Extensions: 1.0: First release, containing only a few extension methods for the System.String and System.IO.Stream classes, and a Range utility class.Jeremy's Experimental Repository: FluentValidation with IoC Sample: Sample code for the blog post Using FluentValidation with an IoC containerMiniTwitter: 1.08: MiniTwitter 1.08 更新内容修正自動更新が CodePlex の変更で動いていなかった問題を修正自動更新に失敗すると落ちるバグを修正通知領域アイコン右クリックで表示されるメニューが消えないバグを修正変更ハッシュタグの抽出条件を変更 API のエンドポイ...MSTS Editors & Tools: Simis Editor v0.3: Simis Editor v0.3 Enabled Edit > Undo and Edit > Redo. Undoing/redoing back to last saved state is identified as saved (no prompt on exit, etc.)....Parallel Mandelbrot Set solver: Alpha 1: First releaseParallelTasks: ParallelTasks 2.0 beta1: ParallelTasks 2.0 is a total re-write of the original version. Featuring improved performance and stability and a more consistent API.Personal Expense Tracker: Personal Expense Tracker v0.1 beta: This is the first beta release. Please provide me with your feedback.PostCrap - flyweight .NET AOP post compiler: PostCrap 1.0 AOP source and binaries: PostCrap 1.0 source and binaries (the unit test project contains sample interceptor attributes for exception handling & logging)Protoforma | Tactica Adversa: Skilful 0.1.3.276: AlphaRawr: Rawr 2.3.10: - More improvements to the default filters - Further improvement on avoiding useless gem swaps from the Optimizer. - Normal/Heroic ICC items shou...Reusable Library: v1.0.2: A collection of reusable abstractions for enterprise application developer.Sem.Sync: 2010-02-21 - Synchronization Manager - Beta: This release is not tested very well, so you should use this version only to evaluate new features. - Changed way of handling source-ids in order ...Survey - web survey & form engine: Survey 1.1.0: Release Survey v. 1.1.0.0 Major changes: - layout & graphics completely overhauled - several technical changes & repairs (e.g. matrix question iss...Yet Another SharePoint Tool: Version 1: Version 1Zeta Resource Editor: Release 2010-02-21: New source code release.Most Popular ProjectsWBFS ManagerRawrAJAX Control ToolkitMicrosoft SQL Server Product Samples: DatabaseSilverlight ToolkitWindows Presentation Foundation (WPF)Image Resizer Powertoy Clone for WindowsASP.NETDotNetNuke® Community EditionMicrosoft SQL Server Community & SamplesMost Active ProjectsDinnerNow.netRawrBlogEngine.NETNB_Store - Free DotNetNuke Ecommerce Catalog ModuleSharpyjQuery Library for SharePoint Web ServicesSharePoint ContribInfoServicepatterns & practices – Enterprise LibraryPHPExcel

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C# 4: The Curious ConcurrentDictionary

- by James Michael Hare

In my previous post (here) I did a comparison of the new ConcurrentQueue versus the old standard of a System.Collections.Generic Queue with simple locking. The results were exactly what I would have hoped, that the ConcurrentQueue was faster with multi-threading for most all situations. In addition, concurrent collections have the added benefit that you can enumerate them even if they're being modified. So I set out to see what the improvements would be for the ConcurrentDictionary, would it have the same performance benefits as the ConcurrentQueue did? Well, after running some tests and multiple tweaks and tunes, I have good and bad news. But first, let's look at the tests. Obviously there's many things we can do with a dictionary. One of the most notable uses, of course, in a multi-threaded environment is for a small, local in-memory cache. So I set about to do a very simple simulation of a cache where I would create a test class that I'll just call an Accessor. This accessor will attempt to look up a key in the dictionary, and if the key exists, it stops (i.e. a cache "hit"). However, if the lookup fails, it will then try to add the key and value to the dictionary (i.e. a cache "miss"). So here's the Accessor that will run the tests: 1: internal class Accessor 2: { 3: public int Hits { get; set; } 4: public int Misses { get; set; } 5: public Func<int, string> GetDelegate { get; set; } 6: public Action<int, string> AddDelegate { get; set; } 7: public int Iterations { get; set; } 8: public int MaxRange { get; set; } 9: public int Seed { get; set; } 10: 11: public void Access() 12: { 13: var randomGenerator = new Random(Seed); 14: 15: for (int i=0; i<Iterations; i++) 16: { 17: // give a wide spread so will have some duplicates and some unique 18: var target = randomGenerator.Next(1, MaxRange); 19: 20: // attempt to grab the item from the cache 21: var result = GetDelegate(target); 22: 23: // if the item doesn't exist, add it 24: if(result == null) 25: { 26: AddDelegate(target, target.ToString()); 27: Misses++; 28: } 29: else 30: { 31: Hits++; 32: } 33: } 34: } 35: } Note that so I could test different implementations, I defined a GetDelegate and AddDelegate that will call the appropriate dictionary methods to add or retrieve items in the cache using various techniques. So let's examine the three techniques I decided to test: Dictionary with mutex - Just your standard generic Dictionary with a simple lock construct on an internal object. Dictionary with ReaderWriterLockSlim - Same Dictionary, but now using a lock designed to let multiple readers access simultaneously and then locked when a writer needs access. ConcurrentDictionary - The new ConcurrentDictionary from System.Collections.Concurrent that is supposed to be optimized to allow multiple threads to access safely. So the approach to each of these is also fairly straight-forward. Let's look at the GetDelegate and AddDelegate implementations for the Dictionary with mutex lock: 1: var addDelegate = (key,val) => 2: { 3: lock (_mutex) 4: { 5: _dictionary[key] = val; 6: } 7: }; 8: var getDelegate = (key) => 9: { 10: lock (_mutex) 11: { 12: string val; 13: return _dictionary.TryGetValue(key, out val) ? val : null; 14: } 15: }; Nothing new or fancy here, just your basic lock on a private object and then query/insert into the Dictionary. Now, for the Dictionary with ReadWriteLockSlim it's a little more complex: 1: var addDelegate = (key,val) => 2: { 3: _readerWriterLock.EnterWriteLock(); 4: _dictionary[key] = val; 5: _readerWriterLock.ExitWriteLock(); 6: }; 7: var getDelegate = (key) => 8: { 9: string val; 10: _readerWriterLock.EnterReadLock(); 11: if(!_dictionary.TryGetValue(key, out val)) 12: { 13: val = null; 14: } 15: _readerWriterLock.ExitReadLock(); 16: return val; 17: }; And finally, the ConcurrentDictionary, which since it does all it's own concurrency control, is remarkably elegant and simple: 1: var addDelegate = (key,val) => 2: { 3: _concurrentDictionary[key] = val; 4: }; 5: var getDelegate = (key) => 6: { 7: string s; 8: return _concurrentDictionary.TryGetValue(key, out s) ? s : null; 9: }; Then, I set up a test harness that would simply ask the user for the number of concurrent Accessors to attempt to Access the cache (as specified in Accessor.Access() above) and then let them fly and see how long it took them all to complete. Each of these tests was run with 10,000,000 cache accesses divided among the available Accessor instances. All times are in milliseconds. 1: Dictionary with Mutex Locking 2: --------------------------------------------------- 3: Accessors Mostly Misses Mostly Hits 4: 1 7916 3285 5: 10 8293 3481 6: 100 8799 3532 7: 1000 8815 3584 8: 9: 10: Dictionary with ReaderWriterLockSlim Locking 11: --------------------------------------------------- 12: Accessors Mostly Misses Mostly Hits 13: 1 8445 3624 14: 10 11002 4119 15: 100 11076 3992 16: 1000 14794 4861 17: 18: 19: Concurrent Dictionary 20: --------------------------------------------------- 21: Accessors Mostly Misses Mostly Hits 22: 1 17443 3726 23: 10 14181 1897 24: 100 15141 1994 25: 1000 17209 2128 The first test I did across the board is the Mostly Misses category. The mostly misses (more adds because data requested was not in the dictionary) shows an interesting trend. In both cases the Dictionary with the simple mutex lock is much faster, and the ConcurrentDictionary is the slowest solution. But this got me thinking, and a little research seemed to confirm it, maybe the ConcurrentDictionary is more optimized to concurrent "gets" than "adds". So since the ratio of misses to hits were 2 to 1, I decided to reverse that and see the results. So I tweaked the data so that the number of keys were much smaller than the number of iterations to give me about a 2 to 1 ration of hits to misses (twice as likely to already find the item in the cache than to need to add it). And yes, indeed here we see that the ConcurrentDictionary is indeed faster than the standard Dictionary here. I have a strong feeling that as the ration of hits-to-misses gets higher and higher these number gets even better as well. This makes sense since the ConcurrentDictionary is read-optimized. Also note that I tried the tests with capacity and concurrency hints on the ConcurrentDictionary but saw very little improvement, I think this is largely because on the 10,000,000 hit test it quickly ramped up to the correct capacity and concurrency and thus the impact was limited to the first few milliseconds of the run. So what does this tell us? Well, as in all things, ConcurrentDictionary is not a panacea. It won't solve all your woes and it shouldn't be the only Dictionary you ever use. So when should we use each? Use System.Collections.Generic.Dictionary when: You need a single-threaded Dictionary (no locking needed). You need a multi-threaded Dictionary that is loaded only once at creation and never modified (no locking needed). You need a multi-threaded Dictionary to store items where writes are far more prevalent than reads (locking needed). And use System.Collections.Concurrent.ConcurrentDictionary when: You need a multi-threaded Dictionary where the writes are far more prevalent than reads. You need to be able to iterate over the collection without locking it even if its being modified. Both Dictionaries have their strong suits, I have a feeling this is just one where you need to know from design what you hope to use it for and make your decision based on that criteria.

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