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  • Alternate method to dependent, nested if statements to check multiple states

    - by octopusgrabbus
    Is there an easier way to process multiple true/false states than using nested if statements? I think there is, and it would be to create a sequence of states, and then use a function like when to determine if all states were true, and drop out if not. I am asking the question to make sure there is not a preferred Clojure way to do this. Here is the background of my problem: I have an application that depends on quite a few input files. The application depends on .csv data reports; column headers for each report (.csv files also), so each sequence in the sequence of sequences can be zipped together with its columns for the purposes of creating a smaller sequence; and column files for output data. I use the following functions to find out if a file is present: (defn kind [filename] (let [f (File. filename)] (cond (.isFile f) "file" (.isDirectory f) "directory" (.exists f) "other" :else "(cannot be found)" ))) (defn look-for [filename expected-type] (let [find-status (kind-stat filename expected-type)] find-status)) And here are the first few lines of a multiple if which looks ugly and is hard to maintain: (defn extract-re-values "Plain old-fashioned sub-routine to process real-estate values / 3rd Q re bills extract." [opts] (if (= (utl/look-for (:ifm1 opts) "f") 0) ; got re columns? (if (= (utl/look-for (:ifn1 opts) "f") 0) ; got re data? (if (= (utl/look-for (:ifm3 opts) "f") 0) ; got re values output columns? (if (= (utl/look-for (:ifm4 opts) "f") 0) ; got re_mixed_use_ratio columns? (let [re-in-col-nams (first (utl/fetch-csv-data (:ifm1 opts))) re-in-data (utl/fetch-csv-data (:ifn1 opts)) re-val-cols-out (first (utl/fetch-csv-data (:ifm3 opts))) mu-val-cols-out (first (utl/fetch-csv-data (:ifm4 opts))) chk-results (utl/chk-seq-len re-in-col-nams (first re-in-data) re-rec-count)] I am not looking for a discussion of the best way, but what is in Clojure that facilitates solving a problem like this.

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  • iOS chat application design, sending/relaying the message over to the end user

    - by AyBayBay
    I have a design question. Let us say you were tasked with building a chat application, specifically for iOS (iOS Chat Application). For simplicity let us say you can only chat with one person at a time (no group chat functionality). How then can you achieve sending a message directly to an end user from phone A to phone B? Obviously there is a web service layer with some API calls. One of the API calls available will be startChat(). After starting a chat, when you send a message, you make another async call, let us call it sendMessage() and pass in a string with your message. Once it goes to the web service layer, the message gets stored in a database. Here is where I am currently stuck. After the message gets sent to the web service layer, how do we then achieve sending/relaying the message over to the end user? Should the web server send out a message to the end user and notify them, or should each client call a receiveMessage() method periodically, and if the server side has some info for them it can then respond with that info? Finally, how can we handle the case in which the user you are trying to send a message to is offline? How can we make sure the end user gets the packet when he moves back to an area with signal?

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  • Forwarding ports with ssh on Linux

    - by Patrick Klingemann
    I have a database server, let's call it: dbserver I have a web server with access to my dbserver, let's call it: webserver I have a development machine that I'd like to use to access a database on dbserver, let's call it: dev dbserver has a firewall rule set to allow TCP requests from webserver to dbserver:1433 I'd like to set up a tunnel from dev:1433 to dbserver:1433, so all requests to 1433 on dev are passed along to dbserver:1433 My sshd_config on webserver has the following rules set: AllowTcpForwarding yes GatewayPorts yes This is what I've tried: ssh -v -L localhost:1433:dbserver:1433 webserver In another terminal: telnet localhost 1433 Results in: Trying ::1... Connected to localhost. Escape character is '^]'. Connection closed by foreign host. Any idea what I'm doing wrong here? Thanks in advance!

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  • Client-Server MMOG & data structures sync when joining / playing

    - by plang
    After reading a few articles on MMOG architecture, there is still one point on which I cannot find much information: it has to do with how you keep in sync server data on the client, when you join, and while you play. A pretty vague question, I agree. Let me refine it: Let's say we have an MMOG virtual world subdivided into geographical cells. A player in a cell is mostly interested in what happens in the cell itself, and all the surrounding cells, not more. When joining the game for the first time, the only thing we can do is send some sort of "database dump" of the interesting cells to the client. When playing, I guess it would be very inefficient to do the same thing regularly. I imagine the best thing to do is to send "deltas" to the client, which would allow keeping the local database in sync. Now let's say the player moves, and arrives in another cell. Surrounding cells change, and for all the new cells the player subscribes, the same technique as used when joining the game has to be used: some sort of "database dump". This mechanic of joining/moving in a cell-based MMOG virtual world interests me, and I was wondering if there were tried and tested techniques in this domain. Thanks!

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  • how to stop a driver from running - it self protected and rootkit hidden

    - by Aristos
    I have this serous problem For the first time I can not stop a program from running. Something is on one laptop computer that is run as system legacy driver, and self protected and hidden on service as rootkit. Anything I try to remove fails. When a program or anti toolkit try to remove the hidden registry setting for make it stop I get this error : "a device attached to the system is not functioning" So any idea that can help me stop it from running, or even delete it on start up ? My one limitation is that the hard drive is on a laptop and I can not remove it and attact it to somewhere else. This program not let me, touch the registry, do not let me touch the file, do not let me touch the file, The move on boot fail to delete it, the rootrepeal fail to delete it, the rootkiet reveal from sysinternals fail to reveal it ! everything fails. Do how have any experience on this, or do you have any suggestion how to stop this driver from run ?

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  • Avoiding spam filters on my CentOS 5.5 64bit server?

    - by Andrew Fashion
    I run a social network on my web server, with about 15,000 members right now. My administration section let's me Mass Email all my users. Currently it uses the built in PHP mail function. What is the best way to congfigure my server to bypass spam? Can I install anything on the server? Or should I just make the social network use SMTP? The admin panel lets me choose SMTP or built-in mail function. I'm not to familiar with mailing from servers, as I usually use Aweber for my mailing, but I cannot use Aweber for this as they will not let me just import 15,000 emails. Let me know, thanks.

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  • Why do most routers not include local DNS?

    - by user785194
    I need to change my firewall/router, and I'd prefer something with built-in DNS to resolve queries on the local subnets. I've got a mixed Linux/Windows system, often with only one computer turned on, and I frequently have problems resolving local names. I don't want to keep a Linux box permanently on just for DNS, and I'd prefer to have DNS in my router appliance, which is always on. I search Google for this occasionally but never find anything. You always get the obvious answers - it's not possible, put everything in /etc/hosts, NetBIOS, dedicated box, etc. So what am I missing? Why don't "cheap" routers let you do this? I'm pretty sure that Cisco kit does this. Almost all cheap routers will let you do MAC address reservation, to let them assign static IP addresses for DHCP. So why can't they simply do DNS as well for everything on the local subnets, just passing through remote domains to the ISP?

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  • FP for simulation and modelling

    - by heaptobesquare
    I'm about to start a simulation/modelling project. I already know that OOP is used for this kind of projects. However, studying Haskell made me consider using the FP paradigm for modelling a system of components. Let me elaborate: Let's say I have a component of type A, characterised by a set of data (a parameter like temperature or pressure,a PDE and some boundary conditions,etc.) and a component of type B, characterised by a different set of data(different or same parameter, different PDE and boundary conditions). Let's also assume that the functions/methods that are going to be applied on each component are the same (a Galerkin method for example). If I were to use an OOP approach, I would create two objects that would encapsulate each type's data, the methods for solving the PDE(inheritance would be used here for code reuse) and the solution to the PDE. On the other hand, if I were to use an FP approach, each component would be broken down to data parts and the functions that would act upon the data in order to get the solution for the PDE. This approach seems simpler to me assuming that linear operations on data would be trivial and that the parameters are constant. What if the parameters are not constant(for example, temperature increases suddenly and therefore cannot be immutable)? In OOP, the object's (mutable) state can be used. I know that Haskell has Monads for that. To conclude, would implementing the FP approach be actually simpler,less time consuming and easier to manage (add a different type of component or new method to solve the pde) compared to the OOP one? I come from a C++/Fortran background, plus I'm not a professional programmer, so correct me on anything that I've got wrong.

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  • Change Keybindings (hardware to software)

    - by Daniel
    I ran a search for this, but the answers I saw were referring to something altogether different than what I'm asking for. So let me clarify: I'm not asking how to change key-combo shortcuts. I'm asking--how do you actually change what your computer thinks you did when you press a given key? An example of what I mean (and the reason I'm asking). I'm a Chrome user, and I use Windows alongside Ubuntu. I own a Lenovo Thinkpad T61p--it came with my scholarship package, and I would have shopped for a nice computer if I could have. The T61p has two buttons above the left and right arrow keys that relate to browser commands to go back and forth one page. This is extremely frustrating for me, as I use the arrow keys, and a single accidental keystroke will catch me going back a page, losing temporary data, and yelling at my stupid keyboard. At the same time, I'm the type of person who keeps way too many tabs open. Chrome doesn't let me refigure keyboard shortcuts, and the only way it allows you to switch between tabs are ctrl+tab and ctrl+shift+tab, and ctrl+page up/down. I was using Notepad++, and they had finally found the solution to both problems! The page back and forth keys functioned as tab back and forth keys. I went through quite some effort to learn how to change the keybindings in Windows. The page back and page forward keys are now the page up and page down keys, respectively, and if I hit control, they let me switch tabs easily, and rather pleasantly. And if I hit the keys by accident, no harm, no foul. Alas, I'm in Ubuntu now, and I need to go through the process again. And while I couldn't just find the answer online, like I did for Windows, I know Ubuntu has nice, supportive communities like this one, where, hopefully, somebody can tell me how to do either what I did in Windows, or directly make it so that my computer changes tabs when I hit those buttons (removing the ctrl button from the tab-changing command).

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  • How to choose between using a Domain Event, or letting the application layer orchestrate everything

    - by Mr Happy
    I'm setting my first steps into domain driven design, bought the blue book and all, and I find myself seeing three ways to implement a certain solution. For the record: I'm not using CQRS or Event Sourcing. Let's say a user request comes into the application service layer. The business logic for that request is (for whatever reason) separated into a method on an entity, and a method on a domain service. How should I go about calling those methods? The options I have gathered so far are: Let the application service call both methods Use method injection/double dispatch to inject the domain service into the entity, letting the entity do it's thing and then let it call the method of the domain service (or the other way around, letting the domain service call the method on the entity) Raise a domain event in the entity method, a handler of which calls the domain service. (The kind of domain events I'm talking about are: http://www.udidahan.com/2009/06/14/domain-events-salvation/) I think these are all viable, but I'm unable to choose between them. I've been thinking about this a long time and I've come to a point where I no longer see the semantic differences between the three. Do you know of some guidelines when to use what?

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  • REST API wrapper - class design for 'lite' object responses

    - by sasfrog
    I am writing a class library to serve as a managed .NET wrapper over a REST API. I'm very new to OOP, and this task is an ideal opportunity for me to learn some OOP concepts in a real-life situation that makes sense to me. Some of the key resources/objects that the API returns are returned with different levels of detail depending on whether the request is for a single instance, a list, or part of a "search all resources" response. This is obviously a good design for the REST API itself, so that full objects aren't returned (thus increasing the size of the response and therefore the time taken to respond) unless they're needed. So, to be clear: .../car/1234.json returns the full Car object for 1234, all its properties like colour, make, model, year, engine_size, etc. Let's call this full. .../cars.json returns a list of Car objects, but only with a subset of the properties returned by .../car/1234.json. Let's call this lite. ...search.json returns, among other things, a list of car objects, but with minimal properties (only ID, make and model). Let's call this lite-lite. I want to know what the pros and cons of each of the following possible designs are, and whether there is a better design that I haven't covered: Create a Car class that models the lite-lite properties, and then have each of the more detailed responses inherit and extend this class. Create separate CarFull, CarLite and CarLiteLite classes corresponding to each of the responses. Create a single Car class that contains (nullable?) properties for the full response, and create constructors for each of the responses which populate it to the extent possible (and maybe include a property that returns the response type from which the instance was created). I expect among other things there will be use cases for consumers of the wrapper where they will want to iterate through lists of Cars, regardless of which response type they were created from, such that the three response types can contribute to the same list. Happy to be pointed to good resources on this sort of thing, and/or even told the name of the concept I'm describing so I can better target my research.

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  • Unable to start Ubuntu 12.04. The system is running in low-graphics

    - by kaleidoscpicsoul
    I am a newbie to Ubuntu. I installed Ubuntu 12.04 using a USB Stick and it was running all fine for a few weeks and this error popped up. According to one of my friend, the best way was to re-install Ubuntu. Being from a non unix background i thought the same too and after the second install it happened again, but only this time was much quicker, in 3 days. I don't want to re-install Ubuntu every time this happens. I am a complete newbie to Linux which means that i am really bad at using terminal. I know there are other people who fixed this issue using this very same forum, but unfortunately the answers provided are too complex for me to understand. Please let me know how to do this. Things I want to let you know: I would need help step by step if that is alright with you. After i get the error i get the options and i click exit to console login I get the following message in a black screen (which i think is a command line sort of thing): * Stopping save kernel messages [OK] apache2: Could not reliably determine the server's fully qualified domain name,using 127.0.1.1 for ServerName [OK] * Starting web server apache2 and a blinking cursor. So basically it looks like a dead end for my non unixy eye. And one final thing is before this issue had happened i had tried configuring Python to Apache2. For that i had uninstalled and installed LAMP server several time and edited the configuration files too. I don't know if this really is a concern, but I don't know.. I have a USB with Ubuntu 12.04 in it so i can install it anytime. (But i want to know what the issue is rather than running away) . I migrated to Ubuntu from Windows and i have no plans to go back. I think that's from my side. Please let me know if there are any questions.

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  • MATLAB: What is an appropriate Data Structure for a Matrix with Random Variable Entries?

    - by user12707
    I'm working in an area that is related to simulation and trying to design a data structure that can include random variables within matrices. I am currently coding in MATLAB. To motivate this let me say I have the following matrix: [a b; c d] I want to find a data structure that will allow for a, b, c, d to be either real numbers or random variables. As an example, let's say that a = 1, b = -1, c = 2 but let d be a normally distributed random variable with mean 20 and SD 40. The data structure that I have in mind will give no value to d. However, I also want to be able to design a function that can take in the structure, simulate an uniform(0,1), obtain a value for d using an inverse CDF and then spit out an actual matrix. I have several ideas to do this (all related to the MATLAB icdf function) but would like to know how more experienced programmers would do it. In this application, it's important that the structure is as "lean" as possible since I will be working with very very large matrices and memory will be an issue.

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  • Is it safe to assert a functions return type?

    - by wb
    This question is related to this question. I have several models stored in a collection. I loop through the collection and validate each field. Based on the input, a field can either be successful, have an error or a warning. Is it safe to unit test each decorator and assert that the type of object returned is what you would expect based on the given input? I could perhaps see this being an issue for a language with function return types since my validation function can return one of 3 types. This is the code I'm fiddling with: <!-- #include file = "../lib/Collection.asp" --> <style type="text/css"> td { padding: 4px; } td.error { background: #F00F00; } td.warning { background: #FC0; } </style> <% Class UserModel Private m_Name Private m_Age Private m_Height Public Property Let Name(value) m_Name = value End Property Public Property Get Name() Name = m_Name End Property Public Property Let Age(value) m_Age = value End Property Public Property Get Age() Age = m_Age End Property Public Property Let Height(value) m_Height = value End Property Public Property Get Height() Height = m_Height End Property End Class Class NameValidation Private m_Name Public Function Init(name) m_Name = name End Function Public Function Validate() Dim validationObject If Len(m_Name) < 5 Then Set validationObject = New ValidationError Else Set validationObject = New ValidationSuccess End If validationObject.CellValue = m_Name Set Validate = validationObject End Function End Class Class AgeValidation Private m_Age Public Function Init(age) m_Age = age End Function Public Function Validate() Dim validationObject If m_Age < 18 Then Set validationObject = New ValidationError ElseIf m_Age = 18 Then Set validationObject = New ValidationWarning Else Set validationObject = New ValidationSuccess End If validationObject.CellValue = m_Age Set Validate = validationObject End Function End Class Class HeightValidation Private m_Height Public Function Init(height) m_Height = height End Function Public Function Validate() Dim validationObject If m_Height > 400 Then Set validationObject = New ValidationError ElseIf m_Height = 324 Then Set validationObject = New ValidationWarning Else Set validationObject = New ValidationSuccess End If validationObject.CellValue = m_Height Set Validate = validationObject End Function End Class Class ValidationError Private m_CSSClass Private m_CellValue Public Property Get CSSClass() CSSClass = "error" End Property Public Property Let CellValue(value) m_CellValue = value End Property Public Property Get CellValue() CellValue = m_CellValue End Property End Class Class ValidationWarning Private m_CSSClass Private m_CellValue Public Property Get CSSClass() CSSClass = "warning" End Property Public Property Let CellValue(value) m_CellValue = value End Property Public Property Get CellValue() CellValue = m_CellValue End Property End Class Class ValidationSuccess Private m_CSSClass Private m_CellValue Public Property Get CSSClass() CSSClass = "" End Property Public Property Let CellValue(value) m_CellValue = value End Property Public Property Get CellValue() CellValue = m_CellValue End Property End Class Class ModelValidator Public Function ValidateModel(model) Dim modelValidation : Set modelValidation = New CollectionClass ' Validate name Dim name : Set name = New NameValidation name.Init model.Name modelValidation.Add name ' Validate age Dim age : Set age = New AgeValidation age.Init model.Age modelValidation.Add age ' Validate height Dim height : Set height = New HeightValidation height.Init model.Height modelValidation.Add height Dim validatedProperties : Set validatedProperties = New CollectionClass Dim modelVal For Each modelVal In modelValidation.Items() validatedProperties.Add modelVal.Validate() Next Set ValidateModel = validatedProperties End Function End Class Dim modelCollection : Set modelCollection = New CollectionClass Dim user1 : Set user1 = New UserModel user1.Name = "Mike" user1.Age = 12 user1.Height = 32 modelCollection.Add user1 Dim user2 : Set user2 = New UserModel user2.Name = "Phil" user2.Age = 18 user2.Height = 432 modelCollection.Add user2 Dim user3 : Set user3 = New UserModel user3.Name = "Michele" user3.Age = 32 user3.Height = 324 modelCollection.Add user3 ' Validate all models in the collection Dim modelValue Dim validatedModels : Set validatedModels = New CollectionClass For Each modelValue In modelCollection.Items() Dim objModelValidator : Set objModelValidator = New ModelValidator validatedModels.Add objModelValidator.ValidateModel(modelValue) Next %> <table> <tr> <td>Name</td> <td>Age</td> <td>Height</td> </tr> <% Dim r, c For Each r In validatedModels.Items() %><tr><% For Each c In r.Items() %><td class="<%= c.CSSClass %>"><%= c.CellValue %></td><% Next %></tr><% Next %> </table> Thank you.

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  • Easiest Way To Get Started In Dot Net

    - by Avery Payne
    Ok, so the initial search in StackOverflow shows nothing related for this question. So here it goes: Let's pretend for a moment that you're just getting started in a career in computer programming. Let's say that, for whatever reason, you decide to use the .Net framework as a basis for your programming. Let's also say that you've been exposed to some programming background, but not one in .Net, so it seems foreign to you at first. And lastly, you don't have the benefit of 25 years of exposure to the Win32 API, which explains why it seems so foreign to you when you start looking at it. So the questions are: What is a comprehensive overview of what .Net is? It appears to be a combination of a runtime environment, a set of languages, a common set of libraries, and perhaps a few other things...so it's about as clear as mud. Specifically, what are the key components to .Net? What is the easiest way to understand .Net programming with regard to available APIs? Which language would best suit beginning programming out of the "stock" languages that Microsoft has to offer? (C++, C#, VB, etc.) What are some differences between .Net programming and programming in a procedural language (aka Pascal, Modula, etc.) What are some differences between .Net programming and programming in a "traditional" object-oriented language? (aka Smalltalk, Java, Python, Ruby, etc.) As I currently understand it, the CLR provides a foundation for all of the other languages to run on. What are some of the inherent limitations of the CLR? Given the enormous amount of API to cover, would it even be worth learning a .Net language (using the Microsoft APIs) given that you would not have prior exposure to Win32 programming? Let's say you write a for-profit program with .Net. Can you resell the program without running afoul of licensing issues? Let's say you write a gratis (free) program with .Net. Can you offer the program to the public under a "free" license (GPL, BSD, Artistic, etc.) without running afoul of licensing issues? Thank you in advance for your patience.

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  • Can parser combination be made efficient?

    - by Jon Harrop
    Around 6 years ago, I benchmarked my own parser combinators in OCaml and found that they were ~5× slower than the parser generators on offer at the time. I recently revisited this subject and benchmarked Haskell's Parsec vs a simple hand-rolled precedence climbing parser written in F# and was surprised to find the F# to be 25× faster than the Haskell. Here's the Haskell code I used to read a large mathematical expression from file, parse and evaluate it: import Control.Applicative import Text.Parsec hiding ((<|>)) expr = chainl1 term ((+) <$ char '+' <|> (-) <$ char '-') term = chainl1 fact ((*) <$ char '*' <|> div <$ char '/') fact = read <$> many1 digit <|> char '(' *> expr <* char ')' eval :: String -> Int eval = either (error . show) id . parse expr "" . filter (/= ' ') main :: IO () main = do file <- readFile "expr" putStr $ show $ eval file putStr "\n" and here's my self-contained precedence climbing parser in F#: let rec (|Expr|) (P(f, xs)) = Expr(loop (' ', f, xs)) and shift oop f op (P(g, xs)) = let h, xs = loop (op, g, xs) loop (oop, f h, xs) and loop = function | ' ' as oop, f, ('+' | '-' as op)::P(g, xs) | (' ' | '+' | '-' as oop), f, ('*' | '/' as op)::P(g, xs) | oop, f, ('^' as op)::P(g, xs) -> let h, xs = loop (op, g, xs) let op = match op with | '+' -> (+) | '-' -> (-) | '*' -> (*) | '/' -> (/) | '^' -> pown loop (oop, op f h, xs) | _, f, xs -> f, xs and (|P|) = function | '-'::P(f, xs) -> let f, xs = loop ('~', f, xs) P(-f, xs) | '('::Expr(f, ')'::xs) -> P(f, xs) | c::xs when '0' <= c && c <= '9' -> P(int(string c), xs) My impression is that even state-of-the-art parser combinators waste a lot of time back tracking. Is that correct? If so, is it possible to write parser combinators that generate state machines to obtain competitive performance or is it necessary to use code generation?

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  • f# types' properties in inconsistent order and of slightly differing types

    - by philbrowndotcom
    I'm trying to iterate through an array of objects and recursively print out each objects properties. Here is my object model: type firmIdentifier = { firmId: int ; firmName: string ; } type authorIdentifier = { authorId: int ; authorName: string ; firm: firmIdentifier ; } type denormalizedSuggestedTradeRecommendations = { id: int ; ticker: string ; direction: string ; author: authorIdentifier ; } Here is how I am instantiating my objects: let getMyIdeasIdeas = [| {id=1; ticker="msfqt"; direction="buy"; author={authorId=0; authorName="john Smith"; firm={firmId=12; firmName="Firm1"}};}; {id=2; ticker="goog"; direction="sell"; author={authorId=1; authorName="Bill Jones"; firm={firmId=13; firmName="ABC Financial"}};}; {id=3; ticker="DFHF"; direction="buy"; author={authorId=2; authorName="Ron James"; firm={firmId=2; firmName="DEFFirm"}};}|] And here is my algorithm to iterate, recurse and print: let rec recurseObj (sb : StringBuilder) o= let props : PropertyInfo [] = o.GetType().GetProperties() sb.Append( o.GetType().ToString()) |> ignore for x in props do let getMethod = x.GetGetMethod() let value = getMethod.Invoke(o, Array.empty) ignore <| match value with | :? float | :? int | :? string | :? bool as f -> sb.Append(x.Name + ": " + f.ToString() + "," ) |> ignore | _ -> recurseObj sb value for x in getMyIdeas do recurseObj sb x sb.Append("\r\n") |> ignore If you couldnt tell, I'm trying to create a csv file and am printing out the types for debugging purposes. The problem is, the first element comes through in the order you'd expect, but all subsequent elements come through with a slightly different (and confusing) ordering of the "child" properties like so: RpcMethods+denormalizedSuggestedTradeRecommendationsid: 1,ticker: msfqt,direction: buy,RpcMethods+authorIdentifierauthorId: 0,authorName: john Smith,RpcMethods+firmIdentifierfirmId: 12,firmName: Firm1, RpcMethods+denormalizedSuggestedTradeRecommendationsid: 2,ticker: goog,direction: sell,RpcMethods+authorIdentifierauthorName: Bill Jones,RpcMethods+firmIdentifierfirmName: ABC Financial,firmId: 13,authorId: 1, RpcMethods+denormalizedSuggestedTradeRecommendationsid: 3,ticker: DFHF,direction: buy,RpcMethods+authorIdentifierauthorName: Ron James,RpcMethods+firmIdentifierfirmName: DEFFirm,firmId: 2,authorId: 2, Any idea what is going on here?

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  • Problem determining how to order F# types due to circular references

    - by James Black
    I have some types that extend a common type, and these are my models. I then have DAO types for each model type for CRUD operations. I now have a need for a function that will allow me to find an id given any model type, so I created a new type for some miscellaneous functions. The problem is that I don't know how to order these types. Currently I have models before dao, but I somehow need DAOMisc before CityDAO and CityDAO before DAOMisc, which isn't possible. The simple approach would be to put this function in each DAO, referring to just the types that can come before it, so, State comes before City as State has a foreign key relationship with City, so the miscellaneous function would be very short. But, this just strikes me as wrong, so I am not certain how to best approach this. Here is my miscellaneous type, where BaseType is a common type for all my models. type DAOMisc = member internal self.FindIdByType item = match(item:BaseType) with | :? StateType as i -> let a = (StateDAO()).Retrieve i a.Head.Id | :? CityType as i -> let a = (CityDAO()).Retrieve i a.Head.Id | _ -> -1 Here is one dao type. CommonDAO actually has the code for the CRUD operations, but that is not important here. type CityDAO() = inherit CommonDAO<CityType>("city", ["name"; "state_id"], (fun(reader) -> [ while reader.Read() do let s = new CityType() s.Id <- reader.GetInt32 0 s.Name <- reader.GetString 1 s.StateName <- reader.GetString 3 ]), list.Empty ) This is my model type: type CityType() = inherit BaseType() let mutable name = "" let mutable stateName = "" member this.Name with get() = name and set restnameval=name <- restnameval member this.StateName with get() = stateName and set stateidval=stateName <- stateidval override this.ToSqlValuesList = [this.Name;] override this.ToFKValuesList = [StateType(Name=this.StateName);] The purpose for this FindIdByType function is that I want to find the id for a foreign key relationship, so I can set the value in my model and then have the CRUD functions do the operations with all the correct information. So, City needs the id for the state name, so I would get the state name, put it into the state type, then call this function to get the id for that state, so my city insert will also include the id for the foreign key. This seems to be the best approach, in a very generic way to handle inserts, which is the current problem I am trying to solve.

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  • SQL SERVER – Merge Operations – Insert, Update, Delete in Single Execution

    - by pinaldave
    This blog post is written in response to T-SQL Tuesday hosted by Jorge Segarra (aka SQLChicken). I have been very active using these Merge operations in my development. However, I have found out from my consultancy work and friends that these amazing operations are not utilized by them most of the time. Here is my attempt to bring the necessity of using the Merge Operation to surface one more time. MERGE is a new feature that provides an efficient way to do multiple DML operations. In earlier versions of SQL Server, we had to write separate statements to INSERT, UPDATE, or DELETE data based on certain conditions; however, at present, by using the MERGE statement, we can include the logic of such data changes in one statement that even checks when the data is matched and then just update it, and similarly, when the data is unmatched, it is inserted. One of the most important advantages of MERGE statement is that the entire data are read and processed only once. In earlier versions, three different statements had to be written to process three different activities (INSERT, UPDATE or DELETE); however, by using MERGE statement, all the update activities can be done in one pass of database table. I have written about these Merge Operations earlier in my blog post over here SQL SERVER – 2008 – Introduction to Merge Statement – One Statement for INSERT, UPDATE, DELETE. I was asked by one of the readers that how do we know that this operator was doing everything in single pass and was not calling this Merge Operator multiple times. Let us run the same example which I have used earlier; I am listing the same here again for convenience. --Let’s create Student Details and StudentTotalMarks and inserted some records. USE tempdb GO CREATE TABLE StudentDetails ( StudentID INTEGER PRIMARY KEY, StudentName VARCHAR(15) ) GO INSERT INTO StudentDetails VALUES(1,'SMITH') INSERT INTO StudentDetails VALUES(2,'ALLEN') INSERT INTO StudentDetails VALUES(3,'JONES') INSERT INTO StudentDetails VALUES(4,'MARTIN') INSERT INTO StudentDetails VALUES(5,'JAMES') GO CREATE TABLE StudentTotalMarks ( StudentID INTEGER REFERENCES StudentDetails, StudentMarks INTEGER ) GO INSERT INTO StudentTotalMarks VALUES(1,230) INSERT INTO StudentTotalMarks VALUES(2,255) INSERT INTO StudentTotalMarks VALUES(3,200) GO -- Select from Table SELECT * FROM StudentDetails GO SELECT * FROM StudentTotalMarks GO -- Merge Statement MERGE StudentTotalMarks AS stm USING (SELECT StudentID,StudentName FROM StudentDetails) AS sd ON stm.StudentID = sd.StudentID WHEN MATCHED AND stm.StudentMarks > 250 THEN DELETE WHEN MATCHED THEN UPDATE SET stm.StudentMarks = stm.StudentMarks + 25 WHEN NOT MATCHED THEN INSERT(StudentID,StudentMarks) VALUES(sd.StudentID,25); GO -- Select from Table SELECT * FROM StudentDetails GO SELECT * FROM StudentTotalMarks GO -- Clean up DROP TABLE StudentDetails GO DROP TABLE StudentTotalMarks GO The Merge Join performs very well and the following result is obtained. Let us check the execution plan for the merge operator. You can click on following image to enlarge it. Let us evaluate the execution plan for the Table Merge Operator only. We can clearly see that the Number of Executions property suggests value 1. Which is quite clear that in a single PASS, the Merge Operation completes the operations of Insert, Update and Delete. I strongly suggest you all to use this operation, if possible, in your development. I have seen this operation implemented in many data warehousing applications. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Joins, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Merge

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  • SQL SERVER – SOS_SCHEDULER_YIELD – Wait Type – Day 8 of 28

    - by pinaldave
    This is a very interesting wait type and quite often seen as one of the top wait types. Let us discuss this today. From Book On-Line: Occurs when a task voluntarily yields the scheduler for other tasks to execute. During this wait the task is waiting for its quantum to be renewed. SOS_SCHEDULER_YIELD Explanation: SQL Server has multiple threads, and the basic working methodology for SQL Server is that SQL Server does not let any “runnable” thread to starve. Now let us assume SQL Server OS is very busy running threads on all the scheduler. There are always new threads coming up which are ready to run (in other words, runnable). Thread management of the SQL Server is decided by SQL Server and not the operating system. SQL Server runs on non-preemptive mode most of the time, meaning the threads are co-operative and can let other threads to run from time to time by yielding itself. When any thread yields itself for another thread, it creates this wait. If there are more threads, it clearly indicates that the CPU is under pressure. You can fun the following DMV to see how many runnable task counts there are in your system. SELECT scheduler_id, current_tasks_count, runnable_tasks_count, work_queue_count, pending_disk_io_count FROM sys.dm_os_schedulers WHERE scheduler_id < 255 GO If you notice a two-digit number in runnable_tasks_count continuously for long time (not once in a while), you will know that there is CPU pressure. The two-digit number is usually considered as a bad thing; you can read the description of the above DMV over here. Additionally, there are several other counters (%Processor Time and other processor related counters), through which you can refer to so you can validate CPU pressure along with the method explained above. Reducing SOS_SCHEDULER_YIELD wait: This is the trickiest part of this procedure. As discussed, this particular wait type relates to CPU pressure. Increasing more CPU is the solution in simple terms; however, it is not easy to implement this solution. There are other things that you can consider when this wait type is very high. Here is the query where you can find the most expensive query related to CPU from the cache Note: The query that used lots of resources but is not cached will not be caught here. SELECT SUBSTRING(qt.TEXT, (qs.statement_start_offset/2)+1, ((CASE qs.statement_end_offset WHEN -1 THEN DATALENGTH(qt.TEXT) ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)+1), qs.execution_count, qs.total_logical_reads, qs.last_logical_reads, qs.total_logical_writes, qs.last_logical_writes, qs.total_worker_time, qs.last_worker_time, qs.total_elapsed_time/1000000 total_elapsed_time_in_S, qs.last_elapsed_time/1000000 last_elapsed_time_in_S, qs.last_execution_time, qp.query_plan FROM sys.dm_exec_query_stats qs CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) qt CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) qp ORDER BY qs.total_worker_time DESC -- CPU time You can find the most expensive queries that are utilizing lots of CPU (from the cache) and you can tune them accordingly. Moreover, you can find the longest running query and attempt to tune them if there is any processor offending code. Additionally, pay attention to total_worker_time because if that is also consistently higher, then  the CPU under too much pressure. You can also check perfmon counters of compilations as they tend to use good amount of CPU. Index rebuild is also a CPU intensive process but we should consider that main cause for this query because that is indeed needed on high transactions OLTP system utilized to reduce fragmentations. Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All of the discussions of Wait Stats in this blog is generic and varies from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • PetaPoco with parameterised stored procedure and Asp.Net MVC

    - by Jalpesh P. Vadgama
    I have been playing with Micro ORMs as this is very interesting things that are happening in developer communities and I already liked the concept of it. It’s tiny easy to use and can do performance tweaks. PetaPoco is also one of them I have written few blog post about this. In this blog post I have explained How we can use the PetaPoco with stored procedure which are having parameters.  I am going to use same Customer table which I have used in my previous posts. For those who have not read my previous post following is the link for that. Get started with ASP.NET MVC and PetaPoco PetaPoco with stored procedures Now our customer table is ready. So let’s Create a simple process which will fetch a single customer via CustomerId. Following is a code for that. CREATE PROCEDURE mysp_GetCustomer @CustomerId as INT AS SELECT * FROM [dbo].Customer where CustomerId=@CustomerId Now  we are ready with our stored procedures. Now lets create code in CustomerDB class to retrieve single customer like following. using System.Collections.Generic; namespace CodeSimplified.Models { public class CustomerDB { public IEnumerable<Customer> GetCustomers() { var databaseContext = new PetaPoco.Database("MyConnectionString"); databaseContext.EnableAutoSelect = false; return databaseContext.Query<Customer>("exec mysp_GetCustomers"); } public Customer GetCustomer(int customerId) { var databaseContext = new PetaPoco.Database("MyConnectionString"); databaseContext.EnableAutoSelect = false; var customer= databaseContext.SingleOrDefault<Customer>("exec mysp_GetCustomer @customerId",new {customerId}); return customer; } } } Here in above code you can see that I have created a new method call GetCustomer which is having customerId as parameter and then I have written to code to use stored procedure which we have created to fetch customer Information. Here I have set EnableAutoSelect=false because I don’t want to create Select statement automatically I want to use my stored procedure for that. Now Our Customer DB class is ready and now lets create a ActionResult Detail in our controller like following using System.Web.Mvc; namespace CodeSimplified.Controllers { public class HomeController : Controller { public ActionResult Index() { ViewBag.Message = "Welcome to ASP.NET MVC!"; return View(); } public ActionResult About() { return View(); } public ActionResult Customer() { var customerDb = new Models.CustomerDB(); return View(customerDb.GetCustomers()); } public ActionResult Details(int id) { var customerDb = new Models.CustomerDB(); return View(customerDb.GetCustomer(id)); } } } Now Let’s create view based on that ActionResult Details method like following. Now everything is ready let’s test it in browser. So lets first goto customer list like following. Now I am clicking on details for first customer and Let’s see how we can use the stored procedure with parameter to fetch the customer details and below is the output. So that’s it. It’s very easy. Hope you liked it. Stay tuned for more..Happy Programming

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  • SQL SERVER – Data Pages in Buffer Pool – Data Stored in Memory Cache

    - by pinaldave
    This will drop all the clean buffers so we will be able to start again from there. Now, run the following script and check the execution plan of the query. Have you ever wondered what types of data are there in your cache? During SQL Server Trainings, I am usually asked if there is any way one can know how much data in a table is stored in the memory cache? The more detailed question I usually get is if there are multiple indexes on table (and used in a query), were the data of the single table stored multiple times in the memory cache or only for a single time? Here is a query you can run to figure out what kind of data is stored in the cache. USE AdventureWorks GO SELECT COUNT(*) AS cached_pages_count, name AS BaseTableName, IndexName, IndexTypeDesc FROM sys.dm_os_buffer_descriptors AS bd INNER JOIN ( SELECT s_obj.name, s_obj.index_id, s_obj.allocation_unit_id, s_obj.OBJECT_ID, i.name IndexName, i.type_desc IndexTypeDesc FROM ( SELECT OBJECT_NAME(OBJECT_ID) AS name, index_id ,allocation_unit_id, OBJECT_ID FROM sys.allocation_units AS au INNER JOIN sys.partitions AS p ON au.container_id = p.hobt_id AND (au.type = 1 OR au.type = 3) UNION ALL SELECT OBJECT_NAME(OBJECT_ID) AS name, index_id, allocation_unit_id, OBJECT_ID FROM sys.allocation_units AS au INNER JOIN sys.partitions AS p ON au.container_id = p.partition_id AND au.type = 2 ) AS s_obj LEFT JOIN sys.indexes i ON i.index_id = s_obj.index_id AND i.OBJECT_ID = s_obj.OBJECT_ID ) AS obj ON bd.allocation_unit_id = obj.allocation_unit_id WHERE database_id = DB_ID() GROUP BY name, index_id, IndexName, IndexTypeDesc ORDER BY cached_pages_count DESC; GO Now let us run the query above and observe the output of the same. We can see in the above query that there are four columns. Cached_Pages_Count lists the pages cached in the memory. BaseTableName lists the original base table from which data pages are cached. IndexName lists the name of the index from which pages are cached. IndexTypeDesc lists the type of index. Now, let us do one more experience here. Please note that you should not run this test on a production server as it can extremely reduce the performance of the database. DBCC DROPCLEANBUFFERS This will drop all the clean buffers and we will be able to start again from there. Now run following script and check the execution plan for the same. USE AdventureWorks GO SELECT UnitPrice, ModifiedDate FROM Sales.SalesOrderDetail WHERE SalesOrderDetailID BETWEEN 1 AND 100 GO The execution plans contain the usage of two different indexes. Now, let us run the script that checks the pages cached in SQL Server. It will give us the following output. It is clear from the Resultset that when more than one index is used, datapages related to both or all of the indexes are stored in Memory Cache separately. Let me know what you think of this article. I had a great pleasure while writing this article because I was able to write on this subject, which I like the most. In the next article, we will exactly see what data are cached and those that are not cached, using a few undocumented commands. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: DMV, Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL DMV

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  • SQL SERVER – How to Compare the Schema of Two Databases with Schema Compare

    - by Pinal Dave
    Earlier I wrote about An Efficiency Tool to Compare and Synchronize SQL Server Databases and it was very much well received. Since the blog post I have received quite a many question that just like data how we can also compare schema and synchronize it. If you think about comparing the schema manually, it is almost impossible to do so. Table Schema has been just one of the concept but if you really want the all the schema of the database (triggers, views, stored procedure and everything else) it is just impossible task. If you are developer or database administrator who works in the production environment than you know that there are so many different occasions when we have to compare schema of the database. Before deploying any changes to the production server, I personally like to make note of the every single schema change and document it so in case of any issue , I can always go back and refer my documentation. As discussed earlier it is absolutely impossible to do this task without the help of third party tools. I personally use Devart Schema Compare for this task. This is an extremely easy tool. Let us see how it works. First I have two different databases – a) AdventureWorks2012 and b) AdventureWorks2012-V1. There are total three changes between these databases. Here is the list of the same. One of the table has additional column One of the table have new index One of the stored procedure is changed Now let see how dbForge Schema Compare works in this scenario. First open dbForge Schema Compare studio. Click on New Schema Comparison. It will bring you to following screen where we have to configure the database needed to configure. I have selected AdventureWorks2012 and AdventureWorks-V1 databases. In the next screen we can verify various options but for this demonstration we will keep it as it is. We will not change anything in schema mapping screen as in our case it is not required but generically if you are comparing across schema you may need this. This is the most important screen as on this screen we select which kind of object we want to compare. You can see the options which are available to select. The screen lets you select the objects from SQL Server 2000 to SQL Server 2012. Once you click on compare in previous screen it will bring you to this screen, which will essentially display the comparative difference between two of the databases which we had selected in earlier screen. As mentioned above there are three different changes in the database and the same has been listed over here. Two of the changes belongs to the tables and one changes belong to the procedure. Let us click each of them one by one to see what is the difference between them. In very first option we can see that there is an additional column in another database which did not exist earlier. In this example we can see that AdventureWorks2012 database have an additional index. Following example is very interesting as in this case, we have changed the definition of the stored procedure and the result pan contains the same. dbForget Schema Compare very effectively identify the changes in schema and lists them neatly to developers. Here is one more screen. This software not only compares the schema but also provides the options to update or drop them as per the choice. I think this is brilliant option. Well, I have been using schema compare for quite a while and have found it very useful. Here are few of the things which dbForge Schema Compare can do for developers and DBAs. Compare and synchronize SQL Server database schemas Compare schemas of live database and SQL Server backup Generate comparison reports in Excel and HTML formats Eliminate mistakes in schema changes propagation across environments Track production database changes and customizations Automate migration of schema changes using command line interface I suggest that you try out dbForge Schema Compare and let me know what you think of this product. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, T SQL

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  • Technology vs. Antiquated Methods

    - by AreYouSerious
    So Here I am talking with my Program lead, about technology, and how while my father is the VP of a major company, he still doesn't have a blackberry, or a smart phone. and I think it's funny. Most people would say it's a generational thing. That because he's older, he dosen't accept technology, and that's why. I have trouble swallowing that because this is the same man, who bought a satellite radio for his car, and made sure that the printer for the house was networked so that his and my mom's laptop could print wirelessly from the living room through their wireless network. I think it has to do with more with necessity, and partially with finical responsibility. My father is very financially conciencious. Think about it yourself. you pay for internet at your home. You have internet access at your office. But if you get a smart phone you're going to pay almost the same amount just for that access. A lot of people take it as just another fixed cost... I'm one of those. I don't even think about it, as I check my facebook from the bus, train, or even while sitting in traffic... The convience of having connection everywhere outweigh the financial responsible person screaming at in the back of my mind. However This conversation lead us to another venue of discussion.... what happens when the power dies. if you left your charger at home, or you phone or navi just stops working... are you going to be able to continue on as you did when it was working... let take the navi as an example... if your navi stops working, how many of you know how to use a map, and navigate? can you even find where you are on a map using the cross streets that your stopped at? This is a skill that unfortunatelly is overlooked these days in the child rearing process. Most people don't see the value, while some others can't do it themselves, so how can they teach their offspring? Take another example.... what if your phone gets lost... or stolen, or you drive over it? do you have the numbers in their memorized? are they recorded somewhere? I know that if it weren't for google sync I wouldn't have them backed up... not sufficiently. And what good does that do if you're in timbuckto and your phone dies, think you can get on the internet to look up those numbers? Don't get me wrong. I'm the first to see the value in technology, and am willing to pay the price to not have to wait for prices to come down. I will pay extra to have that newest thing right now. but let me tell you what.... I know that should I ever procreate it will be a requirement for my offspring (children) to learn how to do something manually before I'll let them use technology. Food for thought?? Let everyone else know what you think.... just sayin'

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  • SQL SERVER – Read Only Files and SQL Server Management Studio (SSMS)

    - by pinaldave
    Just like any other Developer or DBA SQL Server Management Studio is my favorite application. Any any moment of the time I have multiple instances of the same application are open and I am working on it. Recently, I have come across a very interesting feature in SSMS related to “Read Only” files. I believe it is a little unknown feature as well so decided to write a blog about the same. First create a read only SQL file. You can make any file read by Right Click >> Properties >> Select Attribute Read Only. Now open the same file in SQL Server Management Studio. You will find that besides the file name there is a small ‘lock’ icon. This small icon indicates that the file is read only. Now let us attempt to edit the read only file. It will let us edit the file any way we want, however when we attempt to save it, it gives following pop-up value. The options in the pop-up are self explanatory and I liked it. The goal of the read only file is to prevent users to make un-intended changes. However, when a user should have complete control over the user file. User should be aware that the file is read only but if he wants to edit the file or save as a new file the choices should be present in front of it and the pop-up menu precisely captures the same. Now let us check option related to this feature in SSMS. Go to Menu >> Options >> Environment >> Documents You will find the third option which is “Allow editing of read-only files; warn when attempt to save”. In the above scenario it was already checked. Let us uncheck the same and do the same exercise which we have done earlier. I closed all the earlier window to avoid confusion. With the new option selected when I attempt to even modify the Read Only file, it gives me totally different pop up screen. It gives me an option like “Edit In-Memory”, “Make Writeable” etc. When you select “Edit In-Memory” it allows you to edit the file and later you can save as new file – just like the earlier scenario which we have discussed. . If clicked on the Make Writeable it will remove the restriction of the Read Only and file can be edited as pleased. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology

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