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• BizTalk &ndash; Routing failure on Delivery Notifications (BizTalk 2006 R2 to 2013)

  - by S.E.R.

  Originally posted on: http://geekswithblogs.net/SERivas/archive/2013/11/11/biztalk-routing-failure-on-delivery-notifications.aspxThis is a detailed explanation of a something I posted a few month ago on stackoverflow, concerning a weird behavior (a bug, really…) of the delivery notifications in BizTalk. Reminder: what are delivery notifications Mechanism BizTalk has the ability to automatically publish positive acknowledgments (ACK) when it has succeeded transmitting a message or negative acknowledgments (NACK) in case of a transmission failure. Orchestrations can use delivery notifications to subscribe to those ACKs and NACKs in order to know if a message sent on a one-way send port has been successfully transmitted. Delivery Notifications can be “activated” in two ways: The most common and easy way is to set the Delivery Notification property of a logical send port (in the orchestration designer) to Transmitted: Another way is to set the BTS.AckRequired context property of the message to be sent to true: NOTE: fundamentally, those methods are strictly equivalent since the fact of setting the Delivery Notification to Transmitted on the send port only tells BizTalk the BTS.AckRequired context property has to be set to true on the outgoing message. Related context properties ACKs and NACKs have a common set of propoted context properties, which are : Propriété Description AckType Equals ACK when successful or NACK otherwise AckID MessageID of the message concerned by the acknowledgment AckOwnerID InstanceID of the instance associated with the acknowledgment AckSendPortID ID of the send port AckSendPortName Name of the send port AckOutboundTransportLocation URI of the send port AckReceivePortID ID of the port the message came from AckReceivePortName Name of the port the message came from AckInboundTransportLocation URI of the port the message came from Detailed behavior The way Delivery Notifications are handled by BizTalk is peculiar compared to the standard behavior of the Message Box: if no active subscription exists for the acknowledgment, it is simply discarded. The direct consequence of this is that there can be no routing failure for an acknowledgment, and an acknowledgment cannot be suspended. Moreover, when a message is sent to a send port where Delivery Notification = Transmitted, a correlation set is initialized and a correlation token is attached to the message (Context property: CorrelationToken). This correlation token will also be attached to the acknowledgment. So when the acknowledgment is issued, it is automatically routed to the source orchestration. Finally, when a NACK is received by the source orchestration, a DeliveryFailureException is thrown, which can be caught in Catch section. Context of the problem Consider this scenario: In an orchestration, Delivery Notifications are activated on a One-Way send port In case of a transmission failure, the messaging instance is suspended and the orchestration catches an exception (DeliveryFailureException). When the exception is caught, the orchestration does some logging and then terminates (thanks to a Terminate shape). So that leaves only the suspended messaging instance, waiting to be resumed. Symptoms Once the problem that caused the transmission failure is solved, the messaging instance is resumed. Considering what was said in the reminder, we would expect the instance to complete, leaving no active or suspended instance. Nevertheless, the result is that the messaging instance is once more suspended, this time because of a routing failure: The routing failure report shows that the suspended message has the following attached properties: Explanation Those properties clearly indicate that the message being suspended is an acknowledgment (ACK in this case), which was published in the message box and was supended because no subscribers were found. This makes sense, since the source orchestration was terminated before we resumed the messaging instance. So its subscription to the acknowledgments was no longer active when the ACK was published, which explains the routing failure. But this behavior is in direct contradiction with what was said earlier: an acknowledgment must be discarded when no subscriber is found and therefore should not be suspended. Cause It is indeed an outright bug, which appeared with the SP1 of BizTalk 2006 R2 and was never corrected since then: not in the next 4 CUs, not in BizTalk 2009, not in 2010 and not event in 2013 – though I haven’t tested CU1 and CU2 for this last edition, but I bet there is nothing to be expected from those CUs (on this particular point). Side effects This bug can have pretty nasty side effects: this behavior can be propagated to other ports, due to routing mechanisms. For instance: you have configured the ESB Toolkit and have activated the “Enable routing failure for failed messages”. The result will be that the ESB Exception SQL send port will also try and publish ACKs or NACKs concerning its own messaging instances. In itself, this is already messy, but remember that those acknowledgments will also have the source correlation token attached to them… See how far it goes? Well, actually there is more: in SQL send ports, transactions will be rolled back because of the routing failure (I guess it also happens with other adapters - like Oracle, but I haven’t tested them). Again, think of what happens when the send port is the ESB Exception send port: your BizTalk box is going mad, but you have no idea since no exception can be written in the exception database! All of this can be tricky to diagnose, I can tell you that… Solution There is no real solution, only a work-around, but it won’t solve all of the problems and side effects. The idea is to create an orchestration which subscribes to all acknowledgments. That is to say: The message type of the incoming message will be XmlDocument The BTS.AckType property exists The logical receive port will use direct binding By doing so, all acknowledgments will be consumed by an instance of this orchestration, thus avoiding the routing failure. Here is an example of what this orchestration could look like: In order not to pollute the HAT and the DTA Db (after all, this orchestration is only meant to be a palliative to some faulty internal BizTalk mechanism, so there should be no trace of its execution), all tracking must be deactivated:

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• Connecting to named Instances Using Port Number

  - by blakmk

  I came across an interesting situation where a developer was trying to connect to a named instance using a DNS alias without specifying the instance name. Coincidently though he remembered to include the port number and miraculously it worked. So it appears that sql server accepts connections to a specific instance based on its port number. While it may not seem to particularly useful, I can imagine it could be used in the following situations: To mirror to a server with a different instance name (but same port number) To hide the complexity of instance names from end users and just rely on port number (and optionally dns alias)

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• Why do I get an exception when playing multiple sound instances?

  - by Boreal

  Right now, I'm adding a rudimentary sound engine to my game. So far, I am able to load in a WAV file and play it once, then free up the memory when I close the game. However, the game crashes with a nice ArgumentOutOfBoundsException when I try to play another sound instance. Specified argument was out of the range of valid values. Parameter name: readLength I'm following this tutorial pretty much exactly, but I still keep getting the aforementioned error. Here's my sound-related code. /// <summary> /// Manages all sound instances. /// </summary> public static class Audio { static XAudio2 device; static MasteringVoice master; static List<SoundInstance> instances; /// <summary> /// The XAudio2 device. /// </summary> internal static XAudio2 Device { get { return device; } } /// <summary> /// Initializes the audio device and master track. /// </summary> internal static void Initialize() { device = new XAudio2(); master = new MasteringVoice(device); instances = new List<SoundInstance>(); } /// <summary> /// Releases all XA2 resources. /// </summary> internal static void Shutdown() { foreach(SoundInstance i in instances) i.Dispose(); master.Dispose(); device.Dispose(); } /// <summary> /// Registers a sound instance with the system. /// </summary> /// <param name="instance">Sound instance</param> internal static void AddInstance(SoundInstance instance) { instances.Add(instance); } /// <summary> /// Disposes any sound instance that has stopped playing. /// </summary> internal static void Update() { List<SoundInstance> temp = new List<SoundInstance>(instances); foreach(SoundInstance i in temp) if(!i.Playing) { i.Dispose(); instances.Remove(i); } } } /// <summary> /// Loads sounds from various files. /// </summary> internal class SoundLoader { /// <summary> /// Loads a .wav sound file. /// </summary> /// <param name="format">The decoded format will be sent here</param> /// <param name="buffer">The data will be sent here</param> /// <param name="soundName">The path to the WAV file</param> internal static void LoadWAV(out WaveFormat format, out AudioBuffer buffer, string soundName) { WaveStream wave = new WaveStream(soundName); format = wave.Format; buffer = new AudioBuffer(); buffer.AudioData = wave; buffer.AudioBytes = (int)wave.Length; buffer.Flags = BufferFlags.EndOfStream; } } /// <summary> /// Manages the data for a single sound. /// </summary> public class Sound : IAsset { WaveFormat format; AudioBuffer buffer; /// <summary> /// Loads a sound from a file. /// </summary> /// <param name="soundName">The path to the sound file</param> /// <returns>Whether the sound loaded successfully</returns> public bool Load(string soundName) { if(soundName.EndsWith(".wav")) SoundLoader.LoadWAV(out format, out buffer, soundName); else return false; return true; } /// <summary> /// Plays the sound. /// </summary> public void Play() { Audio.AddInstance(new SoundInstance(format, buffer)); } /// <summary> /// Unloads the sound from memory. /// </summary> public void Unload() { buffer.Dispose(); } } /// <summary> /// Manages a single sound instance. /// </summary> public class SoundInstance { SourceVoice source; bool playing; /// <summary> /// Whether the sound is currently playing. /// </summary> public bool Playing { get { return playing; } } /// <summary> /// Starts a new instance of a sound. /// </summary> /// <param name="format">Format of the sound</param> /// <param name="buffer">Buffer holding sound data</param> internal SoundInstance(WaveFormat format, AudioBuffer buffer) { source = new SourceVoice(Audio.Device, format); source.BufferEnd += (s, e) => playing = false; source.Start(); source.SubmitSourceBuffer(buffer); // THIS IS WHERE THE EXCEPTION IS THROWN playing = true; } /// <summary> /// Releases memory used by the instance. /// </summary> internal void Dispose() { source.Dispose(); } } The exception occurs on line 156 when I am playing the sound: source.SubmitSourceBuffer(buffer);

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• How to use PostgreSQL on AWS - Ubuntu 11.10

  - by That1Guy

  I'm extremely new to cloud-computing, Linux, and PostgreSQL, so if this is a stupid question, I apologize. I've managed to create an m1.large instance running Ubuntu 11.10, connect via Putty SSH, and install PostgreSQL (sudo apt-get install postgresql), but that is as far as I've gotten. My goal is to run several python web-scraping scripts that I've written on this instance (so as not to eat up all of our bandwidth (smaller company at the moment)) and insert the scraped data into a PostgreSQL table on the instance and later retrieve that data to store on our local server (as I've heard AWS EBS is unreliable and I don't want to take chances). How can I configure PostgreSQL on my AWS instance? How can I access the data from my machine? I currently use PgAdmin3 to manage PosgreSQL on our local server. Can I use this same interface to manage PostgreSQL on my AWS instance? Any suggestions, solutions, links, etc is greatly appreciated. And again, if this is a dumb question, I apologize.

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• How to loop through a javascript object and check each key exists in a separate multidimensional object

  - by Paul Atkins

  I have 2 javascript objects and I am trying to loop through one object and check whether the key exists in a second multidimensional object going one level deeper each time. Here are the two objects var check = {'scope':'instance', 'item':'body', 'property': 'background'}; var values = {'instance': {'body' : {'background': '000000'}}}; b.map(check, function(key){ console.log(values[key]); }); How am I able to check 1 level deeper in the values object each time? What I am trying to do is check the values object as follows: 1st values['instance'] 2nd values['instance']['body'] 3rd values['instance']['body']['background'] Thanks

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• does class reference itself static anti pattern in prism

  - by Michael Riva

  I have an application and my desing approach look like this: class Manager { public int State; static Manager _instance = null; public static Manager Instance { get { return _instance; } set { if (_instance == value) return; _instance = value; } } public Manager() { State = 0; Instance=this; } } class Module1 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } class Module2 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } class Module3 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } Manager class already registered in Bootstrapper like : protected override void ConfigureContainer() { base.ConfigureContainer(); Container.RegisterType<Manager>(new ContainerControlledLifetimeManager()); } protected override void InitializeModules() { Manager man= Container.Resolve<Manager>(); } Question is do I need to define my manager object as static in its field to be able to reach its state? Or this is anti pattern or bad for performance?

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• Pattern for loading and handling resources

  - by Enoon

  Many times there is the need to load external resources into the program, may they be graphics, audio samples or text strings. Is there a patten for handling the loading and the handling of such resources? For example: should I have a class that loads all the data and then call it everytime I need the data? As in: GraphicsHandler.instance().loadAllData() ...//and then later: draw(x,y, GraphicsHandler.instance().getData(WATER_IMAGE)) //or maybe draw(x,y, GraphicsHandler.instance().WATER_IMAGE) Or should I assign each resource to the class where it belongs? As in (for example, in a game): Graphics g = GraphicsLoader.load(CHAR01); Character c = new Character(..., g); ... c.draw(); Generally speaking which of these two is the more robust solution? GraphicsHandler.instance().getData(WATER_IMAGE) //or GraphicsHandler.instance().WATER_IMAGE //a constant reference

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• Django custom SQL returning single row of results when query returns 2?

  - by Alvin

  I have a custom SQL call that is returning different results to the template than I get when I run the same query against the database directly, 1 row vs 2 Query - copied from Django Debug Toolbar: SELECT ((Sum(new_recruit_interviews) / Sum(opportunities_offered)) * 100) as avg_recruit, ((Sum(inspections) / Sum(presentations)) * 100) as avg_inspect, ((Sum(contracts_signed) / Sum(roof_approvals)) * 100) as avg_contracts, ((Sum(adjusters) / Sum(contracts_signed)) * 100) as avg_adjusters, ((Sum(roof_approvals) / Sum(adjusters)) *100) as roof_approval_avg, ((Sum(roof_turned_in) / Sum(adjusters)) * 100) as roof_jobs_avg, Sum(roof_turned_in) as roof_jobs_total, ((Sum(siding_approvals) / Sum(adjusters)) *100) as siding_approval_avg, ((Sum(siding_turned_in) / Sum(adjusters)) * 100) as siding_jobs_avg, Sum(siding_turned_in) as siding_jobs_total, ((Sum(gutter_approvals) / Sum(adjusters)) *100) as gutter_approval_avg, ((Sum(gutter_turned_in) / Sum(adjusters)) * 100) as gutter_jobs_avg, Sum(gutter_turned_in) as gutter_jobs_total, ((Sum(window_approvals) / Sum(adjusters)) *100) as window_approval_avg, ((Sum(window_turned_in) / Sum(adjusters)) * 100) as window_jobs_avg, Sum(window_turned_in) as window_jobs_total, (Sum(roof_turned_in) + Sum(siding_turned_in) + Sum(gutter_turned_in) + Sum(window_turned_in)) as total_jobs, (((Sum(collections_jobs_new) + Sum(collections_jobs_previous)) / (Sum(roof_turned_in) + Sum(siding_turned_in) + Sum(gutter_turned_in) + Sum(window_turned_in))) * 100) as total_collections, sales_report_salesmen.location_id as detail_id, business_unit_location.title as title FROM sales_report_salesmen Inner Join auth_user ON sales_report_salesmen.user_id = auth_user.id Inner Join business_unit_location ON sales_report_salesmen.location_id = business_unit_location.id GROUP BY location_id Results from direct query running the above query: INSERT INTO `` (`avg_recruit`, `avg_inspect`, `avg_contracts`, `avg_adjusters`, `roof_approval_avg`, `roof_jobs_avg`, `roof_jobs_total`, `siding_approval_avg`, `siding_jobs_avg`, `siding_jobs_total`, `gutter_approval_avg`, `gutter_jobs_avg`, `gutter_jobs_total`, `window_approval_avg`, `window_jobs_avg`, `window_jobs_total`, `total_jobs`, `total_collections`, `detail_id`, `title`) VALUES (95.3968, 92.8178, 106.9622, 90.2928, 103.5420, 103.5670, 4152, 100.2494, 106.8845, 4285, 120.1297, 86.2559, 3458, 92.9658, 106.1611, 4256, 16151, 4.281469, 12, 'St Paul, MN'); VALUES (90.2982, 73.3723, 97.8474, 104.5433, 97.7585, 86.1848, 1884, 109.9268, 109.3321, 2390, 81.0156, 96.4318, 2108, 91.7200, 123.8792, 2708, 9090, 4.531573, 13, 'Denver, CO'); Results from template: {'roof_jobs_total': Decimal('4152'), 'gutter_jobs_total': Decimal('3458'), 'avg_adjusters': Decimal('90.2928'), 'title': u'St Paul, MN', 'window_approval_avg': Decimal('92.9658'), 'total_collections': Decimal('4.281469'), 'gutter_approval_avg': Decimal('120.1297'), 'avg_recruit': Decimal('95.3968'), 'siding_approval_avg': Decimal('100.2494'), 'window_jobs_total': Decimal('4256'), 'detail_id': 12L, 'siding_jobs_avg': Decimal('106.8845'), 'avg_inspect': Decimal('92.8178'), 'roof_approval_avg': Decimal('103.5420'), 'roof_jobs_avg': Decimal('103.5670'), 'total_jobs': Decimal('16151'), 'window_jobs_avg': Decimal('106.1611'), 'avg_contracts': Decimal('106.9622'), 'gutter_jobs_avg': Decimal('86.2559'), 'siding_jobs_total': Decimal('4285')} Tried tweaking it a few ways and running the results through various for loops, keep getting the same result where my results are a single row through the Django template and the expected results (through console) have 2 rows The row that is coming back is the same as the first row returned through the console query so I'm thinking that it is running correctly just a matter of passing the results through... for good measure this is the code I'm using to generate the query (yes it's a bit ugly, been playing with it) def sql_grouped(table, fields, group_by=False, where=False): from django.db import connection query = 'SELECT %s FROM %s' % (fields, table) if where: query = query + ' WHERE %s' % (where) if group_by: query = query + ' GROUP BY %s' % (group_by) cursor = connection.cursor() cursor.execute(query) desc = cursor.description data = [dict(zip([col[0] for col in desc], row)) for row in cursor.fetchall()] return data[0] any feedback is greatly appreciated - been tinkering with this since I realized I could skip a few steps by generating my averages directly within the SQL rather than post-process

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• Multi-threaded random_r is slower than single threaded version.

  - by Nixuz

  The following program is essentially the same the one described here. When I run and compile the program using two threads (NTHREADS == 2), I get the following run times: real 0m14.120s user 0m25.570s sys 0m0.050s When it is run with just one thread (NTHREADS == 1), I get run times significantly better even though it is only using one core. real 0m4.705s user 0m4.660s sys 0m0.010s My system is dual core, and I know random_r is thread safe and I am pretty sure it is non-blocking. When the same program is run without random_r and a calculation of cosines and sines is used as a replacement, the dual-threaded version runs in about 1/2 the time as expected. #include <pthread.h> #include <stdlib.h> #include <stdio.h> #define NTHREADS 2 #define PRNG_BUFSZ 8 #define ITERATIONS 1000000000 void* thread_run(void* arg) { int r1, i, totalIterations = ITERATIONS / NTHREADS; for (i = 0; i < totalIterations; i++){ random_r((struct random_data*)arg, &r1); } printf("%i\n", r1); } int main(int argc, char** argv) { struct random_data* rand_states = (struct random_data*)calloc(NTHREADS, sizeof(struct random_data)); char* rand_statebufs = (char*)calloc(NTHREADS, PRNG_BUFSZ); pthread_t* thread_ids; int t = 0; thread_ids = (pthread_t*)calloc(NTHREADS, sizeof(pthread_t)); /* create threads */ for (t = 0; t < NTHREADS; t++) { initstate_r(random(), &rand_statebufs[t], PRNG_BUFSZ, &rand_states[t]); pthread_create(&thread_ids[t], NULL, &thread_run, &rand_states[t]); } for (t = 0; t < NTHREADS; t++) { pthread_join(thread_ids[t], NULL); } free(thread_ids); free(rand_states); free(rand_statebufs); } I am confused why when generating random numbers the two threaded version performs much worse than the single threaded version, considering random_r is meant to be used in multi-threaded applications.

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• Scheduling runtime-specified Activity in Workflow 4 RC

  - by johnny g

  Hi, so I have this requirement to kick off Activities provided to me at run-time. To facilitate this, I have set up a WorkflowService that receives Activities as Xaml, hydrates them, and kicks them off. Sounds simple enough ... ... this is my WorkflowService in Xaml <Activity x:Class="Workflow.Services.WorkflowService.WorkflowService" ... xmlns:local1="clr-namespace:Workflow.Activities" > <Sequence sap:VirtualizedContainerService.HintSize="277,272"> <Sequence.Variables> <Variable x:TypeArguments="local:Workflow" Name="Workflow" /> </Sequence.Variables> <sap:WorkflowViewStateService.ViewState> <scg3:Dictionary x:TypeArguments="x:String, x:Object"> <x:Boolean x:Key="IsExpanded">True</x:Boolean> </scg3:Dictionary> </sap:WorkflowViewStateService.ViewState> <p:Receive CanCreateInstance="True" DisplayName="ReceiveSubmitWorkflow" sap:VirtualizedContainerService.HintSize="255,86" OperationName="SubmitWorkflow" ServiceContractName="IWorkflowService"> <p:ReceiveParametersContent> <OutArgument x:TypeArguments="local:Workflow" x:Key="workflow">[Workflow]</OutArgument> </p:ReceiveParametersContent> </p:Receive> <local1:InvokeActivity Activity="[ActivityXamlServices.Load(New System.IO.StringReader(Workflow.Xaml))]" sap:VirtualizedContainerService.HintSize="255,22" /> </Sequence> </Activity> ... which, except for repetitive use of "Workflow" is pretty straight forward. In fact, it's just a Sequence with a Receive and [currently] a custom Activity called InvokeActivity. Get to that in a bit. Receive Activity accepts a custom type, [DataContract] public class Workflow { [DataMember] public string Xaml { get; set; } } which contains a string whose contents are to be interpreted as Xaml. You can see the VB expression that then converts this Xaml to an Activity and passes it on. Now this second bit, the custom InvokeActivity is where I have questions. First question: 1) given an arbitrary task, provided at runtime [as described above] is it possible to kick off this Activity using Activities that ship with WF4RC, out of the box? I'm fairly new, and thought I did a good job going through the API and existing documentation, but may as well ask :) Second: 2) my first attempt at implementing a custom InvokeActivity looked like this public sealed class InvokeActivity : NativeActivity { private static readonly ILog _log = LogManager.GetLogger (typeof (InvokeActivity)); public InArgument<Activity> Activity { get; set; } public InvokeActivity () { _log.DebugFormat ("Instantiated."); } protected override void Execute (NativeActivityContext context) { Activity activity = Activity.Get (context); _log.DebugFormat ("Scheduling activity [{0}]...", activity.DisplayName); // throws exception to lack of metadata! :( ActivityInstance instance = context.ScheduleActivity (activity, OnComplete, OnFault); _log.DebugFormat ( "Scheduled activity [{0}] with instance id [{1}].", activity.DisplayName, instance.Id); } protected override void CacheMetadata (NativeActivityMetadata metadata) { // how does one add InArgument<T> to metadata? not easily // is my first guess base.CacheMetadata (metadata); } // private methods private void OnComplete ( NativeActivityContext context, ActivityInstance instance) { _log.DebugFormat ( "Scheduled activity [{0}] with instance id [{1}] has [{2}].", instance.Activity.DisplayName, instance.Id, instance.State); } private void OnFault ( NativeActivityFaultContext context, Exception exception, ActivityInstance instance) { _log.ErrorFormat ( @"Scheduled activity [{0}] with instance id [{1}] has faulted in state [{2}] {3}", instance.Activity.DisplayName, instance.Id, instance.State, exception.ToStringFullStackTrace ()); } } Which attempts to schedule the specified Activity within the current context. Unfortunately, however, this fails. When I attempt to schedule said Activity, the runtime returns with the following exception The provided activity was not part of this workflow definition when its metadata was being processed. The problematic activity named 'DynamicActivity' was provided by the activity named 'InvokeActivity'. Right, so the "dynamic" Activity provided at runtime is not a member of InvokeActivitys metadata. Googled and came across this. Couldn't sort out how to specify an InArgument<Activity> to metadata cache, so my second question is, naturally, how does one address this issue? Is it ill advised to use context.ScheduleActivity (...) in this manner? Third and final, 3) I have settled on this [simpler] solution for the time being, public sealed class InvokeActivity : NativeActivity { private static readonly ILog _log = LogManager.GetLogger (typeof (InvokeActivity)); public InArgument<Activity> Activity { get; set; } public InvokeActivity () { _log.DebugFormat ("Instantiated."); } protected override void Execute (NativeActivityContext context) { Activity activity = Activity.Get (context); _log.DebugFormat ("Invoking activity [{0}] ...", activity.DisplayName); // synchronous execution ... a little less than ideal, this // seems heavy handed, and not entirely semantic-equivalent // to what i want. i really want to invoke this runtime // activity as if it were one of my own, not a separate // process - wrong mentality? WorkflowInvoker.Invoke (activity); _log.DebugFormat ("Invoked activity [{0}].", activity.DisplayName); } } Which simply invokes specified task synchronously within its own runtime instance thingy [use of WF4 vernacular is certainly questionable]. Eventually, I would like to tap into WF's tracking and possibly persistance facilities. So my third and final question is, in terms of what I would like to do [ie kick off arbitrary workflows inbound from client applications] is this the preferred method? Alright, thanks in advance for your time and consideration :)

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• Django: testing get query

  - by Brant

  Okay, so I am sick of writing this... res = Something.objects.filter(asdf=something) if res: single = res[0] else: single = None if single: # do some stuff I would much rather be able to do something like this: single = Something.objects.filter(asdf=something) if single: #do some stuff I want to be able to grab a single object without testing the filtered results. In other words, when i know there is either going to be 1 or 0 matching entries, I would like to jump right to that entry, otherwise just get a 'None'. The DoesNotExist error that goes along with .get does not always work so well when trying to compress these queries into a single line. Is there any way to do what I have described?

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• Why are alloc and init called separately in Objective-C?

  - by André Hoffmann

  Note: I'm relatively new to Objective-C and am coming from Java and PHP. Could someone explain to me why I always have to first allocate and then initialize an instance? Couldn't this be done in the init methods like this: + (MyClass*)init { MyClass *instance = [MyClass alloc]; [instance setFoo:@"bla"]; return instance; } + (MyClass*)initWithString:(NSString*)text { MyClass *instance = [MyClass init]; [instance setFoo:text]; return instance; } ... Is this just a relict from the old C days or is there something that I'm not seeing? I know this isn't a problem as I could as well always call alloc and init, but since it's a bit tedious I'd like to at least know why I'm doing it. I'm liking the expressiveness of the language so far, but this is something that I want to fully understand in order to think the Objective-C way. Thank you!

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• PostgreSQL pgdb driver raises "can't rollback" exception

  - by David Parunakian

  Hello, for some reason I'm experiencing the Operational Error with "can't rollback" message when I attempt to roll back my transaction in the following context: try: cursors[instance].execute("lock revision, app, timeout IN SHARE MODE") cursors[instance].execute("insert into app (type, active, active_revision, contents, z) values ('session', true, %s, %s, 0) returning id", (cRevision, sessionId)) sAppId = cursors[instance].fetchone()[0] cursors[instance].execute("insert into revision (app_id, type) values (%s, 'active')", (sAppId,)) cursors[instance].execute("insert into timeout (app_id, last_seen) values (%s, now())", (sAppId,)) connections[instance].commit() except pgdb.DatabaseError, e: connections[instance].rollback() return "{status: 'error', errno:4, errmsg: \"%s\"}"%(str(e).replace('\"', '\\"').replace('\n', '\\n').replace('\r', '\\r')) The driver in use is PGDB. What is fundamentally wrong here?

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• Isn't it better to use a single try catch instead of tons of TryParsing and other error handling sometimes?

  - by Ryan Peschel

  I know people say it's bad to use exceptions for flow control and to only use exceptions for exceptional situations, but sometimes isn't it just cleaner and more elegant to wrap the entire block in a try-catch? For example, let's say I have a dialog window with a TextBox where the user can type input in to be parsed in a key-value sort of manner. This situation is not as contrived as you might think because I've inherited code that has to handle this exact situation (albeit not with farm animals). Consider this wall of code: class Animals { public int catA, catB; public float dogA, dogB; public int mouseA, mouseB, mouseC; public double cow; } class Program { static void Main(string[] args) { string input = "Sets all the farm animals CAT 3 5 DOG 21.3 5.23 MOUSE 1 0 1 COW 12.25"; string[] splitInput = input.Split(' '); string[] animals = { "CAT", "DOG", "MOUSE", "COW", "CHICKEN", "GOOSE", "HEN", "BUNNY" }; Animals animal = new Animals(); for (int i = 0; i < splitInput.Length; i++) { string token = splitInput[i]; if (animals.Contains(token)) { switch (token) { case "CAT": animal.catA = int.Parse(splitInput[i + 1]); animal.catB = int.Parse(splitInput[i + 2]); break; case "DOG": animal.dogA = float.Parse(splitInput[i + 1]); animal.dogB = float.Parse(splitInput[i + 2]); break; case "MOUSE": animal.mouseA = int.Parse(splitInput[i + 1]); animal.mouseB = int.Parse(splitInput[i + 2]); animal.mouseC = int.Parse(splitInput[i + 3]); break; case "COW": animal.cow = double.Parse(splitInput[i + 1]); break; } } } } } In actuality there are a lot more farm animals and more handling than that. A lot of things can go wrong though. The user could enter in the wrong number of parameters. The user can enter the input in an incorrect format. The user could specify numbers too large or too small for the data type to handle. All these different errors could be handled without exceptions through the use of TryParse, checking how many parameters the user tried to use for a specific animal, checking if the parameter is too large or too small for the data type (because TryParse just returns 0), but every one should result in the same thing: A MessageBox appearing telling the user that the inputted data is invalid and to fix it. My boss doesn't want different message boxes for different errors. So instead of doing all that, why not just wrap the block in a try-catch and in the catch statement just display that error message box and let the user try again? Maybe this isn't the best example but think of any other scenario where there would otherwise be tons of error handling that could be substituted for a single try-catch. Is that not the better solution?

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• S#harp architecture mapping many to many and ado.net data services: A single resource was expected f

  - by Leg10n

  Hi, I'm developing an application that reads data from a SQL server database (migrated from a legacy DB) with nHibernate and s#arp architecture through ADO.NET Data services. I'm trying to map a many-to-many relationship. I have a Error class: public class Error { public virtual int ERROR_ID { get; set; } public virtual string ERROR_CODE { get; set; } public virtual string DESCRIPTION { get; set; } public virtual IList<ErrorGroup> GROUPS { get; protected set; } } And then I have the error group class: public class ErrorGroup { public virtual int ERROR_GROUP_ID {get; set;} public virtual string ERROR_GROUP_NAME { get; set; } public virtual string DESCRIPTION { get; set; } public virtual IList<Error> ERRORS { get; protected set; } } And the overrides: public class ErrorGroupOverride : IAutoMappingOverride<ErrorGroup> { public void Override(AutoMapping<ErrorGroup> mapping) { mapping.Table("ERROR_GROUP"); mapping.Id(x => x.ERROR_GROUP_ID, "ERROR_GROUP_ID"); mapping.IgnoreProperty(x => x.Id); mapping.HasManyToMany<Error>(x => x.Error) .Table("ERROR_GROUP_LINK") .ParentKeyColumn("ERROR_GROUP_ID") .ChildKeyColumn("ERROR_ID").Inverse().AsBag(); } } public class ErrorOverride : IAutoMappingOverride<Error> { public void Override(AutoMapping<Error> mapping) { mapping.Table("ERROR"); mapping.Id(x => x.ERROR_ID, "ERROR_ID"); mapping.IgnoreProperty(x => x.Id); mapping.HasManyToMany<ErrorGroup>(x => x.GROUPS) .Table("ERROR_GROUP_LINK") .ParentKeyColumn("ERROR_ID") .ChildKeyColumn("ERROR_GROUP_ID").AsBag(); } } When I view the Data service in the browser like: http://localhost:1905/DataService.svc/Errors it shows the list of errors with no problems, and using it like http://localhost:1905/DataService.svc/Errors(123) works too. The Problem When I want to see the Errors in a group or the groups form an error, like: "http://localhost:1905/DataService.svc/Errors(123)?$expand=GROUPS" I get the XML Document, but the browser says: The XML page cannot be displayed Cannot view XML input using XSL style sheet. Please correct the error and then click the Refresh button, or try again later. -------------------------------------------------------------------------------- Only one top level element is allowed in an XML document. Error processing resource 'http://localhost:1905/DataServic... <error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"> -^ I view the sourcecode, and I get the data. However it comes with an exception: <error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"> <code></code> <message xml:lang="en-US">An error occurred while processing this request.</message> <innererror xmlns="xmlns"> <message>A single resource was expected for the result, but multiple resources were found.</message> <type>System.InvalidOperationException</type> <stacktrace> at System.Data.Services.Serializers.Serializer.WriteRequest(IEnumerator queryResults, Boolean hasMoved)&#xD; at System.Data.Services.ResponseBodyWriter.Write(Stream stream)</stacktrace> </innererror> </error> A I missing something??? Where does this error come from?

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• WCF - Define multiple services in a single APP.Config file?

  - by Goober

  Scenario I have a windows forms application. I want to use two different WCF Services that are in no way connected. HOWEVER, I'm not sure how to go about defining the services in my APP.CONFIG file. From what I have read, it is possible to do what I have done below, but I cannot be sure that the syntax is correct or the tags are all present where necessary and I needed some clarification. Question. So is the below the correct way to setup two services in A SINGLE APP.CONFIG FILE? I.E: <configuration> <system.serviceModel> <services> <service> <!--SERVICE ONE--> <endpoint> </endpoint> <binding> </binding> </service> <service> <!--SERVICE TWO--> <endpoint> </endpoint> <binding> </binding> </service> </services> </system.serviceModel> </configuration> CODE <configuration> <system.serviceModel> <services> <!--SERVICE ONE--> <service> <endpoint address="" binding="netTcpBinding" bindingConfiguration="tcpServiceEndPoint" contract="ListenerService.IListenerService" name="tcpServiceEndPoint" /> <binding name="tcpServiceEndPoint" closeTimeout="00:01:00" openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00" transactionFlow="false" transferMode="Buffered" transactionProtocol="OleTransactions" hostNameComparisonMode="StrongWildcard" listenBacklog="10" maxBufferPoolSize="524288" maxBufferSize="65536" maxConnections="10" maxReceivedMessageSize="65536"> <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384" maxBytesPerRead="4096" maxNameTableCharCount="16384" /> <reliableSession ordered="true" inactivityTimeout="00:05:00" enabled="true" /> <security mode="None"> <transport clientCredentialType="Windows" protectionLevel="EncryptAndSign" /> <message clientCredentialType="Windows" /> </security> </binding> </service> <!--SERVICE TWO--> <service> <endpoint address="" binding="netTcpBinding" contract="UploadObjects.IResponseService" bindingConfiguration="TransactedBinding" name="UploadObjects.ResponseService"/> <binding name="TransactedBinding"> <security mode="None" /> </binding> </service> </services> </system.serviceModel> </configuration> EDIT What do the BEHAVIOURS represent? How do they relate to the service definitions?

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• LLBLGen Pro feature highlights: grouping model elements

  - by FransBouma

  (This post is part of a series of posts about features of the LLBLGen Pro system) When working with an entity model which has more than a few entities, it's often convenient to be able to group entities together if they belong to a semantic sub-model. For example, if your entity model has several entities which are about 'security', it would be practical to group them together under the 'security' moniker. This way, you could easily find them back, yet they can be left inside the complete entity model altogether so their relationships with entities outside the group are kept. In other situations your domain consists of semi-separate entity models which all target tables/views which are located in the same database. It then might be convenient to have a single project to manage the complete target database, yet have the entity models separate of each other and have them result in separate code bases. LLBLGen Pro can do both for you. This blog post will illustrate both situations. The feature is called group usage and is controllable through the project settings. This setting is supported on all supported O/R mapper frameworks. Situation one: grouping entities in a single model. This situation is common for entity models which are dense, so many relationships exist between all sub-models: you can't split them up easily into separate models (nor do you likely want to), however it's convenient to have them grouped together into groups inside the entity model at the project level. A typical example for this is the AdventureWorks example database for SQL Server. This database, which is a single catalog, has for each sub-group a schema, however most of these schemas are tightly connected with each other: adding all schemas together will give a model with entities which indirectly are related to all other entities. LLBLGen Pro's default setting for group usage is AsVisualGroupingMechanism which is what this situation is all about: we group the elements for visual purposes, it has no real meaning for the model nor the code generated. Let's reverse engineer AdventureWorks to an entity model. By default, LLBLGen Pro uses the target schema an element is in which is being reverse engineered, as the group it will be in. This is convenient if you already have categorized tables/views in schemas, like which is the case in AdventureWorks. Of course this can be switched off, or corrected on the fly. When reverse engineering, we'll walk through a wizard which will guide us with the selection of the elements which relational model data should be retrieved, which we can later on use to reverse engineer to an entity model. The first step after specifying which database server connect to is to select these elements. below we can see the AdventureWorks catalog as well as the different schemas it contains. We'll include all of them. After the wizard completes, we have all relational model data nicely in our catalog data, with schemas. So let's reverse engineer entities from the tables in these schemas. We select in the catalog explorer the schemas 'HumanResources', 'Person', 'Production', 'Purchasing' and 'Sales', then right-click one of them and from the context menu, we select Reverse engineer Tables to Entity Definitions.... This will bring up the dialog below. We check all checkboxes in one go by checking the checkbox at the top to mark them all to be added to the project. As you can see LLBLGen Pro has already filled in the group name based on the schema name, as this is the default and we didn't change the setting. If you want, you can select multiple rows at once and set the group name to something else using the controls on the dialog. We're fine with the group names chosen so we'll simply click Add to Project. This gives the following result:   (I collapsed the other groups to keep the picture small ;)). As you can see, the entities are now grouped. Just to see how dense this model is, I've expanded the relationships of Employee: As you can see, it has relationships with entities from three other groups than HumanResources. It's not doable to cut up this project into sub-models without duplicating the Employee entity in all those groups, so this model is better suited to be used as a single model resulting in a single code base, however it benefits greatly from having its entities grouped into separate groups at the project level, to make work done on the model easier. Now let's look at another situation, namely where we work with a single database while we want to have multiple models and for each model a separate code base. Situation two: grouping entities in separate models within the same project. To get rid of the entities to see the second situation in action, simply undo the reverse engineering action in the project. We still have the AdventureWorks relational model data in the catalog. To switch LLBLGen Pro to see each group in the project as a separate project, open the Project Settings, navigate to General and set Group usage to AsSeparateProjects. In the catalog explorer, select Person and Production, right-click them and select again Reverse engineer Tables to Entities.... Again check the checkbox at the top to mark all entities to be added and click Add to Project. We get two groups, as expected, however this time the groups are seen as separate projects. This means that the validation logic inside LLBLGen Pro will see it as an error if there's e.g. a relationship or an inheritance edge linking two groups together, as that would lead to a cyclic reference in the code bases. To see this variant of the grouping feature, seeing the groups as separate projects, in action, we'll generate code from the project with the two groups we just created: select from the main menu: Project -> Generate Source-code... (or press F7 ;)). In the dialog popping up, select the target .NET framework you want to use, the template preset, fill in a destination folder and click Start Generator (normal). This will start the code generator process. As expected the code generator has simply generated two code bases, one for Person and one for Production: The group name is used inside the namespace for the different elements. This allows you to add both code bases to a single solution and use them together in a different project without problems. Below is a snippet from the code file of a generated entity class. //... using System.Xml.Serialization; using AdventureWorks.Person; using AdventureWorks.Person.HelperClasses; using AdventureWorks.Person.FactoryClasses; using AdventureWorks.Person.RelationClasses; using SD.LLBLGen.Pro.ORMSupportClasses; namespace AdventureWorks.Person.EntityClasses { //... /// <summary>Entity class which represents the entity 'Address'.<br/><br/></summary> [Serializable] public partial class AddressEntity : CommonEntityBase //... The advantage of this is that you can have two code bases and work with them separately, yet have a single target database and maintain everything in a single location. If you decide to move to a single code base, you can do so with a change of one setting. It's also useful if you want to keep the groups as separate models (and code bases) yet want to add relationships to elements from another group using a copy of the entity: you can simply reverse engineer the target table to a new entity into a different group, effectively making a copy of the entity. As there's a single target database, changes made to that database are reflected in both models which makes maintenance easier than when you'd have a separate project for each group, with its own relational model data. Conclusion LLBLGen Pro offers a flexible way to work with entities in sub-models and control how the sub-models end up in the generated code.

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• Can an installation of SSRS be used for other reports if the SCOM Reporting Role is installed?

  - by Pete Davis

  I'm currently in the process of planing a SCOM 2007 R2 deployment and would like to deploy the OperationsManagerDW and Reporting Server to a shared SQL 2008 cluster which is used for reporting across multiple solutions. However in the in the deployment guide for SCOM 2007 R2 it says: Due to changes that the Operations Manager 2007 Reporting component makes to SQL Server Reporting Services security, no other applications that make use of SQL Server Reporting Services can be installed on this server. Which concerns me that it may interfere with existing or future (non SCOM) reports in some way even if deployed as a separate SSRS instance. Later in the same guide it states: Installing Operations Manager 2007 Reporting Services integrates the security of the instance of SQL Reporting Services with the Operations Manager role-based security. Do not install any other Reporting Services applications in this same instance of SQL Server. Does this mean that I can install a new SSRS instance and use this on the shared cluster for SCOM reporting or that I'd also need to create a whole new SQL Server instance as well as SSRS instance or I'd need a whole separate server for SCOM OperationsManagerDW and Reporitng Server?

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• So…is it a Seek or a Scan?

  - by Paul White

  You’re probably most familiar with the terms ‘Seek’ and ‘Scan’ from the graphical plans produced by SQL Server Management Studio (SSMS).  The image to the left shows the most common ones, with the three types of scan at the top, followed by four types of seek.  You might look to the SSMS tool-tip descriptions to explain the differences between them: Not hugely helpful are they?  Both mention scans and ranges (nothing about seeks) and the Index Seek description implies that it will not scan the index entirely (which isn’t necessarily true). Recall also yesterday’s post where we saw two Clustered Index Seek operations doing very different things.  The first Seek performed 63 single-row seeking operations; and the second performed a ‘Range Scan’ (more on those later in this post).  I hope you agree that those were two very different operations, and perhaps you are wondering why there aren’t different graphical plan icons for Range Scans and Seeks?  I have often wondered about that, and the first person to mention it after yesterday’s post was Erin Stellato (twitter | blog): Before we go on to make sense of all this, let’s look at another example of how SQL Server confusingly mixes the terms ‘Scan’ and ‘Seek’ in different contexts.  The diagram below shows a very simple heap table with two columns, one of which is the non-clustered Primary Key, and the other has a non-unique non-clustered index defined on it.  The right hand side of the diagram shows a simple query, it’s associated query plan, and a couple of extracts from the SSMS tool-tip and Properties windows. Notice the ‘scan direction’ entry in the Properties window snippet.  Is this a seek or a scan?  The different references to Scans and Seeks are even more pronounced in the XML plan output that the graphical plan is based on.  This fragment is what lies behind the single Index Seek icon shown above: You’ll find the same confusing references to Seeks and Scans throughout the product and its documentation. Making Sense of Seeks Let’s forget all about scans for a moment, and think purely about seeks.  Loosely speaking, a seek is the process of navigating an index B-tree to find a particular index record, most often at the leaf level.  A seek starts at the root and navigates down through the levels of the index to find the point of interest: Singleton Lookups The simplest sort of seek predicate performs this traversal to find (at most) a single record.  This is the case when we search for a single value using a unique index and an equality predicate.  It should be readily apparent that this type of search will either find one record, or none at all.  This operation is known as a singleton lookup.  Given the example table from before, the following query is an example of a singleton lookup seek: Sadly, there’s nothing in the graphical plan or XML output to show that this is a singleton lookup – you have to infer it from the fact that this is a single-value equality seek on a unique index.  The other common examples of a singleton lookup are bookmark lookups – both the RID and Key Lookup forms are singleton lookups (an RID lookup finds a single record in a heap from the unique row locator, and a Key Lookup does much the same thing on a clustered table).  If you happen to run your query with STATISTICS IO ON, you will notice that ‘Scan Count’ is always zero for a singleton lookup. Range Scans The other type of seek predicate is a ‘seek plus range scan’, which I will refer to simply as a range scan.  The seek operation makes an initial descent into the index structure to find the first leaf row that qualifies, and then performs a range scan (either backwards or forwards in the index) until it reaches the end of the scan range. The ability of a range scan to proceed in either direction comes about because index pages at the same level are connected by a doubly-linked list – each page has a pointer to the previous page (in logical key order) as well as a pointer to the following page.  The doubly-linked list is represented by the green and red dotted arrows in the index diagram presented earlier.  One subtle (but important) point is that the notion of a ‘forward’ or ‘backward’ scan applies to the logical key order defined when the index was built.  In the present case, the non-clustered primary key index was created as follows: CREATE TABLE dbo.Example ( key_col INTEGER NOT NULL, data INTEGER NOT NULL, CONSTRAINT [PK dbo.Example key_col] PRIMARY KEY NONCLUSTERED (key_col ASC) ) ; Notice that the primary key index specifies an ascending sort order for the single key column.  This means that a forward scan of the index will retrieve keys in ascending order, while a backward scan would retrieve keys in descending key order.  If the index had been created instead on key_col DESC, a forward scan would retrieve keys in descending order, and a backward scan would return keys in ascending order. A range scan seek predicate may have a Start condition, an End condition, or both.  Where one is missing, the scan starts (or ends) at one extreme end of the index, depending on the scan direction.  Some examples might help clarify that: the following diagram shows four queries, each of which performs a single seek against a column holding every integer from 1 to 100 inclusive.  The results from each query are shown in the blue columns, and relevant attributes from the Properties window appear on the right: Query 1 specifies that all key_col values less than 5 should be returned in ascending order.  The query plan achieves this by seeking to the start of the index leaf (there is no explicit starting value) and scanning forward until the End condition (key_col < 5) is no longer satisfied (SQL Server knows it can stop looking as soon as it finds a key_col value that isn’t less than 5 because all later index entries are guaranteed to sort higher). Query 2 asks for key_col values greater than 95, in descending order.  SQL Server returns these results by seeking to the end of the index, and scanning backwards (in descending key order) until it comes across a row that isn’t greater than 95.  Sharp-eyed readers may notice that the end-of-scan condition is shown as a Start range value.  This is a bug in the XML show plan which bubbles up to the Properties window – when a backward scan is performed, the roles of the Start and End values are reversed, but the plan does not reflect that.  Oh well. Query 3 looks for key_col values that are greater than or equal to 10, and less than 15, in ascending order.  This time, SQL Server seeks to the first index record that matches the Start condition (key_col >= 10) and then scans forward through the leaf pages until the End condition (key_col < 15) is no longer met. Query 4 performs much the same sort of operation as Query 3, but requests the output in descending order.  Again, we have to mentally reverse the Start and End conditions because of the bug, but otherwise the process is the same as always: SQL Server finds the highest-sorting record that meets the condition ‘key_col < 25’ and scans backward until ‘key_col >= 20’ is no longer true. One final point to note: seek operations always have the Ordered: True attribute.  This means that the operator always produces rows in a sorted order, either ascending or descending depending on how the index was defined, and whether the scan part of the operation is forward or backward.  You cannot rely on this sort order in your queries of course (you must always specify an ORDER BY clause if order is important) but SQL Server can make use of the sort order internally.  In the four queries above, the query optimizer was able to avoid an explicit Sort operator to honour the ORDER BY clause, for example. Multiple Seek Predicates As we saw yesterday, a single index seek plan operator can contain one or more seek predicates.  These seek predicates can either be all singleton seeks or all range scans – SQL Server does not mix them.  For example, you might expect the following query to contain two seek predicates, a singleton seek to find the single record in the unique index where key_col = 10, and a range scan to find the key_col values between 15 and 20: SELECT key_col FROM dbo.Example WHERE key_col = 10 OR key_col BETWEEN 15 AND 20 ORDER BY key_col ASC ; In fact, SQL Server transforms the singleton seek (key_col = 10) to the equivalent range scan, Start:[key_col >= 10], End:[key_col <= 10].  This allows both range scans to be evaluated by a single seek operator.  To be clear, this query results in two range scans: one from 10 to 10, and one from 15 to 20. Final Thoughts That’s it for today – tomorrow we’ll look at monitoring singleton lookups and range scans, and I’ll show you a seek on a heap table. Yes, a seek.  On a heap.  Not an index! If you would like to run the queries in this post for yourself, there’s a script below.  Thanks for reading! IF OBJECT_ID(N'dbo.Example', N'U') IS NOT NULL BEGIN DROP TABLE dbo.Example; END ; -- Test table is a heap -- Non-clustered primary key on 'key_col' CREATE TABLE dbo.Example ( key_col INTEGER NOT NULL, data INTEGER NOT NULL, CONSTRAINT [PK dbo.Example key_col] PRIMARY KEY NONCLUSTERED (key_col) ) ; -- Non-unique non-clustered index on the 'data' column CREATE NONCLUSTERED INDEX [IX dbo.Example data] ON dbo.Example (data) ; -- Add 100 rows INSERT dbo.Example WITH (TABLOCKX) ( key_col, data ) SELECT key_col = V.number, data = V.number FROM master.dbo.spt_values AS V WHERE V.[type] = N'P' AND V.number BETWEEN 1 AND 100 ; -- ================ -- Singleton lookup -- ================ ; -- Single value equality seek in a unique index -- Scan count = 0 when STATISTIS IO is ON -- Check the XML SHOWPLAN SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col = 32 ; -- =========== -- Range Scans -- =========== ; -- Query 1 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col <= 5 ORDER BY E.key_col ASC ; -- Query 2 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col > 95 ORDER BY E.key_col DESC ; -- Query 3 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col >= 10 AND E.key_col < 15 ORDER BY E.key_col ASC ; -- Query 4 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col >= 20 AND E.key_col < 25 ORDER BY E.key_col DESC ; -- Final query (singleton + range = 2 range scans) SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col = 10 OR E.key_col BETWEEN 15 AND 20 ORDER BY E.key_col ASC ; -- === TIDY UP === DROP TABLE dbo.Example; © 2011 Paul White email: [email protected] twitter: @SQL_Kiwi

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• Imperative vs. LINQ Performance on WP7

  - by Bil Simser

  Jesse Liberty had a nice post presenting the concepts around imperative, LINQ and fluent programming to populate a listbox. Check out the post as it’s a great example of some foundational things every .NET programmer should know. I was more interested in what the IL code that would be generated from imperative vs. LINQ was like and what the performance numbers are and how they differ. The code at the instruction level is interesting but not surprising. The imperative example with it’s creating lists and loops weighs in at about 60 instructions. .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } 1: .method private hidebysig instance void ImperativeMethod() cil managed 2: { 3: .maxstack 3 4: .locals init ( 5: [0] class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> someData, 6: [1] class [mscorlib]System.Collections.Generic.List`1<int32> inLoop, 7: [2] int32 n, 8: [3] class [mscorlib]System.Collections.Generic.IEnumerator`1<int32> CS$5$0000, 9: [4] bool CS$4$0001) 10: L_0000: nop 11: L_0001: ldc.i4.1 12: L_0002: ldc.i4.s 50 13: L_0004: call class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> [System.Core]System.Linq.Enumerable::Range(int32, int32) 14: L_0009: stloc.0 15: L_000a: newobj instance void [mscorlib]System.Collections.Generic.List`1<int32>::.ctor() 16: L_000f: stloc.1 17: L_0010: nop 18: L_0011: ldloc.0 19: L_0012: callvirt instance class [mscorlib]System.Collections.Generic.IEnumerator`1<!0> [mscorlib]System.Collections.Generic.IEnumerable`1<int32>::GetEnumerator() 20: L_0017: stloc.3 21: L_0018: br.s L_003a 22: L_001a: ldloc.3 23: L_001b: callvirt instance !0 [mscorlib]System.Collections.Generic.IEnumerator`1<int32>::get_Current() 24: L_0020: stloc.2 25: L_0021: nop 26: L_0022: ldloc.2 27: L_0023: ldc.i4.5 28: L_0024: cgt 29: L_0026: ldc.i4.0 30: L_0027: ceq 31: L_0029: stloc.s CS$4$0001 32: L_002b: ldloc.s CS$4$0001 33: L_002d: brtrue.s L_0039 34: L_002f: ldloc.1 35: L_0030: ldloc.2 36: L_0031: ldloc.2 37: L_0032: mul 38: L_0033: callvirt instance void [mscorlib]System.Collections.Generic.List`1<int32>::Add(!0) 39: L_0038: nop 40: L_0039: nop 41: L_003a: ldloc.3 42: L_003b: callvirt instance bool [mscorlib]System.Collections.IEnumerator::MoveNext() 43: L_0040: stloc.s CS$4$0001 44: L_0042: ldloc.s CS$4$0001 45: L_0044: brtrue.s L_001a 46: L_0046: leave.s L_005a 47: L_0048: ldloc.3 48: L_0049: ldnull 49: L_004a: ceq 50: L_004c: stloc.s CS$4$0001 51: L_004e: ldloc.s CS$4$0001 52: L_0050: brtrue.s L_0059 53: L_0052: ldloc.3 54: L_0053: callvirt instance void [mscorlib]System.IDisposable::Dispose() 55: L_0058: nop 56: L_0059: endfinally 57: L_005a: nop 58: L_005b: ldarg.0 59: L_005c: ldfld class [System.Windows]System.Windows.Controls.ListBox PerfTest.MainPage::LB1 60: L_0061: ldloc.1 61: L_0062: callvirt instance void [System.Windows]System.Windows.Controls.ItemsControl::set_ItemsSource(class [mscorlib]System.Collections.IEnumerable) 62: L_0067: nop 63: L_0068: ret 64: .try L_0018 to L_0048 finally handler L_0048 to L_005a 65: } 66:   67: Compare that to the IL generated for the LINQ version which has about half of the instructions and just gets the job done, no fluff. .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } 1: .method private hidebysig instance void LINQMethod() cil managed 2: { 3: .maxstack 4 4: .locals init ( 5: [0] class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> someData, 6: [1] class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> queryResult) 7: L_0000: nop 8: L_0001: ldc.i4.1 9: L_0002: ldc.i4.s 50 10: L_0004: call class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> [System.Core]System.Linq.Enumerable::Range(int32, int32) 11: L_0009: stloc.0 12: L_000a: ldloc.0 13: L_000b: ldsfld class [System.Core]System.Func`2<int32, bool> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate6 14: L_0010: brtrue.s L_0025 15: L_0012: ldnull 16: L_0013: ldftn bool PerfTest.MainPage::<LINQProgramming>b__4(int32) 17: L_0019: newobj instance void [System.Core]System.Func`2<int32, bool>::.ctor(object, native int) 18: L_001e: stsfld class [System.Core]System.Func`2<int32, bool> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate6 19: L_0023: br.s L_0025 20: L_0025: ldsfld class [System.Core]System.Func`2<int32, bool> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate6 21: L_002a: call class [mscorlib]System.Collections.Generic.IEnumerable`1<!!0> [System.Core]System.Linq.Enumerable::Where<int32>(class [mscorlib]System.Collections.Generic.IEnumerable`1<!!0>, class [System.Core]System.Func`2<!!0, bool>) 22: L_002f: ldsfld class [System.Core]System.Func`2<int32, int32> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate7 23: L_0034: brtrue.s L_0049 24: L_0036: ldnull 25: L_0037: ldftn int32 PerfTest.MainPage::<LINQProgramming>b__5(int32) 26: L_003d: newobj instance void [System.Core]System.Func`2<int32, int32>::.ctor(object, native int) 27: L_0042: stsfld class [System.Core]System.Func`2<int32, int32> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate7 28: L_0047: br.s L_0049 29: L_0049: ldsfld class [System.Core]System.Func`2<int32, int32> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate7 30: L_004e: call class [mscorlib]System.Collections.Generic.IEnumerable`1<!!1> [System.Core]System.Linq.Enumerable::Select<int32, int32>(class [mscorlib]System.Collections.Generic.IEnumerable`1<!!0>, class [System.Core]System.Func`2<!!0, !!1>) 31: L_0053: stloc.1 32: L_0054: ldarg.0 33: L_0055: ldfld class [System.Windows]System.Windows.Controls.ListBox PerfTest.MainPage::LB2 34: L_005a: ldloc.1 35: L_005b: callvirt instance void [System.Windows]System.Windows.Controls.ItemsControl::set_ItemsSource(class [mscorlib]System.Collections.IEnumerable) 36: L_0060: nop 37: L_0061: ret 38: } Again, not surprising here but a good indicator that you should consider using LINQ where possible. In fact if you have ReSharper installed you’ll see a squiggly (technical term) in the imperative code that says “Hey Dude, I can convert this to LINQ if you want to be c00L!” (or something like that, it’s the 2010 geek version of Clippy). What about the fluent version? As Jon correctly pointed out in the comments, when you compare the IL for the LINQ code and the IL for the fluent code it’s the same. LINQ and the fluent interface are just syntactical sugar so you decide what you’re most comfortable with. At the end of the day they’re both the same. Now onto the numbers. Again I expected the imperative version to be better performing than the LINQ version (before I saw the IL that was generated). Call it womanly instinct. A gut feel. Whatever. Some of the numbers are interesting though. For Jesse’s example of 50 items, the numbers were interesting. The imperative sample clocked in at 7ms while the LINQ version completed in 4. As the number of items went up, the elapsed time didn’t necessarily climb exponentially. At 500 items they were pretty much the same and the results were similar up to about 50,000 items. After that I tried 500,000 items where the gap widened but not by much (2.2 seconds for imperative, 2.3 for LINQ). It wasn’t until I tried 5,000,000 items where things were noticeable. Imperative filled the list in 20 seconds while LINQ took 8 seconds longer (although personally I wouldn’t suggest you put 5 million items in a list unless you want your users showing up at your door with torches and pitchforks). Here’s the table with the full results. Method/Items 50 500 5,000 50,000 500,000 5,000,000 Imperative 7ms 7ms 38ms 223ms 2230ms 20974ms LINQ/Fluent 4ms 6ms 41ms 240ms 2310ms 28731ms Like I said, at the end of the day it’s not a huge difference and you really don’t want your users waiting around for 30 seconds on a mobile device filling lists. In fact if Windows Phone 7 detects you’re taking more than 10 seconds to do any one thing, it considers the app hung and shuts it down. The results here are for Windows Phone 7 but frankly they're the same for desktop and web apps so feel free to apply it generally. From a programming perspective, choose what you like. Some LINQ statements can get pretty hairy so I usually fall back with my simple mind and write it imperatively. If you really want to impress your friends, write it old school then let ReSharper do the hard work for! Happy programming!

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• Static NAT in AWS's Virtual Private Cloud (VPC)

  - by user1050797

  Currently in a VPC with a public and a private subnet, all internet bound traffic from the private subnet could be routed via an NAT instance. The NAT instance will port address translate the packet's source IP to use the NAT instance's elastic IP, so the public server can reply to this public address. This is a PAT mechanism. My question is there a way for me to do a static NAT on my NAT instance -- Using the same NAT instance to static NAT an unassociated but reserved elastic IP to a private subnet host. This NAT instance will behave like a physical firewall doing static nat'ing for a bunch of private ip's.

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• MMO Data Persistence Question

  - by JasonG

  I wanted to ask a question regarding data persistence strategies for an MMO. I have some experience in the games industry with social synchronous games. At Zynga, we stored static proto data in XML on both the client and the server and stored instance/runtime data in membase. For clarity sake, proto data for a Potion would be PotionName or MaxCharges, while runtime/instance data would be something like ChargesRemaining. So basically, if a player picks up a potion the instance is (via prediction) created from XML data on the client, the request gets sent to the server where the instance is created from XML and then added to membase. Is the same strategy that would be used for soemthing like an MMO? Would it be feasible to have static proto data in some kind of in-memory no-sql database on both client and server with instance data being stored on the server in a more enterprise level database? Or should all data (proto/instance) be stored on the server and the client gets everything from server? I know a lot of this might on certain game requirements, however, i'm basically looking for some general opinion/best practices here if there are any.

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• MySQL multiple instances: can you specify a separate general_log/general_log_file option?

  - by gravyface

  Have two working MySQL instances as well as the default instance. I have general logging enabled on the default; this is working fine. On the second instance, I've added: general_log = 1 general_log_file = /path/to/log/file under [mysqld1]. Restarted the instance (using mysqladmin and confirmed it was not running with mysqld_multi report 1), started it back up again, and the only data in the log file are the connect statements from when mysqld_multi report 1 was executed. Are all the instance #1 queries just being logged to the default instance general log file? The default instance is quite busy and has identical database names, tables, etc. so it's difficult to figure out right now.

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• Hosting a site on amazon ec2

  - by Khalid Mushtaq

  I have recently bought an amazon ec2 instance. Now I want to host a website. I have googled and found some useful info but there is some confusion in my mind. Suppose domain name is "http://www.example.com" That's what I have done so far. I have configured my domain locally on amazon ec2 instance and it's working fine when I open that url in amazon ec2 instance's browser. I have used http://www.example.com in /etc/hosts file point it to 127.0.0.1 to open locally on instance. I have got one elastic ip address and associated it with the instance. I have changed http://www.example.com A's record with the elastic IP that I have got in above step. Now what should I do? When some user will open my website anywhere in the world, will it get pointed to my instanace's ip address? Have I done proper configurations for website on instance?

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• Switch or a Dictionary when assigning to new object

  - by KChaloux

  Recently, I've come to prefer mapping 1-1 relationships using Dictionaries instead of Switch statements. I find it to be a little faster to write and easier to mentally process. Unfortunately, when mapping to a new instance of an object, I don't want to define it like this: var fooDict = new Dictionary<int, IBigObject>() { { 0, new Foo() }, // Creates an instance of Foo { 1, new Bar() }, // Creates an instance of Bar { 2, new Baz() } // Creates an instance of Baz } var quux = fooDict[0]; // quux references Foo Given that construct, I've wasted CPU cycles and memory creating 3 objects, doing whatever their constructors might contain, and only ended up using one of them. I also believe that mapping other objects to fooDict[0] in this case will cause them to reference the same thing, rather than creating a new instance of Foo as intended. A solution would be to use a lambda instead: var fooDict = new Dictionary<int, Func<IBigObject>>() { { 0, () => new Foo() }, // Returns a new instance of Foo when invoked { 1, () => new Bar() }, // Ditto Bar { 2, () => new Baz() } // Ditto Baz } var quux = fooDict[0](); // equivalent to saying 'var quux = new Foo();' Is this getting to a point where it's too confusing? It's easy to miss that () on the end. Or is mapping to a function/expression a fairly common practice? The alternative would be to use a switch: IBigObject quux; switch(someInt) { case 0: quux = new Foo(); break; case 1: quux = new Bar(); break; case 2: quux = new Baz(); break; } Which invocation is more acceptable? Dictionary, for faster lookups and fewer keywords (case and break) Switch: More commonly found in code, doesn't require the use of a Func< object for indirection.

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