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• Speaking in Omaha: December 7, 2011

  - by Bill Graziano

  I’m presenting in Omaha on Writing Faster SQL at 6PM on December 7th.  You can find meeting details on the Omaha SQL Server User Group page. The meeting location requires an RSVP so building security has a list of attendees. The presentation is a series of suggestions on improving performance.  It ranges from simple things like comparing indexed columns to scalar values up to tips for reducing query compiles and asynchronous processing patterns.  Nearly all of these come from specific issues I’ve encountered working on poorly performing SQL Servers.

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• Calculating angle between 2 vectors

  - by Error 454

  I am working on some movement AI where there are no obstacles and movement is restricted to the XY plane. I am calculating 2 vectors: v - the direction of ship 1 w - the vector pointing from the position of ship 1 to ship 2 I am then calculating the angle between these two vectors using the standard formula: arccos( v . w / ( |v| |w| ) ) The problem I'm having is the nature of arccos only returning values between 0 and 180. This makes it impossible to determine whether I should turn left or right to face the other ship. Is there a better way to do this?

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• Data structures for storing finger/stylus movements in drawing application?

  - by mattja?øb

  I have a general question about creating a drawing application, the language could be C++ or ObjectiveC with OpenGL. I would like to hear what are the best methods and practices for storing strokes data. Think of the many iPad apps that allow you to draw with your finger (or a stylus) or any other similar function on a desktop app. To summarize, the data structure must: be highly responsive to the movement store precise values (close in space / time) usable for rendering the strokes with complex textures (textures based on the dynamic of the stroke etc) exportable to a text file for saving/loading

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• Circular movement - eliminating speed ups near Y = 0

  - by Fibericon

  I have a basic algorithm to rotate an enemy around a 200 unit radius circle with center 0. This is how I'm achieving that: if (position.Y <= 0 && position.X > -200) { position.X -= 2; position.Y = 0 - (float)Math.Sqrt((200 * 200) - (position.X * position.X)); } else { position.X += 2; position.Y = (float)Math.Sqrt((200 * 200) - (position.X * position.X)); } It does work, and I've ensured that at no point does either X or Y equal NaN. However, when Y approaches 0, it seems to go significantly faster. This surprises me, because the Y values are locked to the X, which is being incremented by a steady amount. What can I do to smooth the speed?

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• Should I try to write simple key-value storage by myself?

  - by shabunc

  I need a key-value storage in a simplest form we can think of. Keys should be some fixed-length strings, values should be some texts. This key-value storage should have an HTTP-backed API. That's basically it. As you can see, there is no big difference between such storage and some web application with some upload functionality. The thing is - it'll take few hours (including tests and coffee drinking) to write something like this. "Something like this" will be fully under my control and can be tuned on demand. Should I, in this specific case, not try to reinvent bicycles? Is it better to use some of existing NoSQL solutions. If yes, which one exactly? If, say, I'd needed something SQL-like, I won't ask and won't try to write something by myself. But with NoSQL I just don't know what is adequate and what is not.

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• Hide GRUB2 menu UNLESS you hold down Shift key: how to make this happen?

  - by Shasteriskt

  I have a Ubuntu - Windows 7 dual-boot set-up, and I would like to have it that my laptop would boot up Windows 7 unless I press down the Shift key right after boot and bring up the Grub2 menu from which I can choose Ubuntu. I researched on Grub2 and options for etc/default/grub and I have tried playing around with combinations with the GRUB_TIMEOUT and GRUB_HIDDEN_TIMEOUT values, but to no avail. I tried setting the GRUB_HIDDEN_TIMEOUT higher than the GRUB_TIMEOUT thinking that both countdown start simultaneously, but no - GRUB_TIMEOUT only starts after the other is done. Is this behavior achievable? If so, how?

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• Data Source Security Part 4

  - by Steve Felts

  So far, I have covered Client Identity and Oracle Proxy Session features, with WLS or database credentials.  This article will cover one more feature, Identify-based pooling.  Then, there is one more topic to cover - how these options play with transactions.Identity-based Connection Pooling An identity based pool creates a heterogeneous pool of connections.  This allows applications to use a JDBC connection with a specific DBMS credential by pooling physical connections with different DBMS credentials.  The DBMS credential is based on either the WebLogic user mapped to a database user or the database user directly, based on the “use database credentials” setting as described earlier. Using this feature enabled with “use database credentials” enabled seems to be what is proposed in the JDBC standard, basically a heterogeneous pool with users specified by getConnection(user, password). The allocation of connections is more complex if Enable Identity Based Connection Pooling attribute is enabled on the data source.  When an application requests a database connection, the WebLogic Server instance selects an existing physical connection or creates a new physical connection with requested DBMS identity. The following section provides information on how heterogeneous connections are created:1. At connection pool initialization, the physical JDBC connections based on the configured or default “initial capacity” are created with the configured default DBMS credential of the data source.2. An application tries to get a connection from a data source.3a. If “use database credentials” is not enabled, the user specified in getConnection is mapped to a DBMS credential, as described earlier.  If the credential map doesn’t have a matching user, the default DBMS credential is used from the datasource descriptor.3b. If “use database credentials” is enabled, the user and password specified in getConnection are used directly.4. The connection pool is searched for a connection with a matching DBMS credential.5. If a match is found, the connection is reserved and returned to the application.6. If no match is found, a connection is created or reused based on the maximum capacity of the pool: - If the maximum capacity has not been reached, a new connection is created with the DBMS credential, reserved, and returned to the application.- If the pool has reached maximum capacity, based on the least recently used (LRU) algorithm, a physical connection is selected from the pool and destroyed. A new connection is created with the DBMS credential, reserved, and returned to the application. It should be clear that finding a matching connection is more expensive than a homogeneous pool.  Destroying a connection and getting a new one is very expensive.  If you can use a normal homogeneous pool or one of the light-weight options (client identity or an Oracle proxy connection), those should be used instead of identity based pooling. Regardless of how physical connections are created, each physical connection in the pool has its own DBMS credential information maintained by the pool. Once a physical connection is reserved by the pool, it does not change its DBMS credential even if the current thread changes its WebLogic user credential and continues to use the same connection. To configure this feature, select Enable Identity Based Connection Pooling.  See http://docs.oracle.com/cd/E24329_01/apirefs.1211/e24401/taskhelp/jdbc/jdbc_datasources/EnableIdentityBasedConnectionPooling.html  "Enable identity-based connection pooling for a JDBC data source" in Oracle WebLogic Server Administration Console Help. You must make the following changes to use Logging Last Resource (LLR) transaction optimization with Identity-based Pooling to get around the problem that multiple users will be accessing the associated transaction table.- You must configure a custom schema for LLR using a fully qualified LLR table name. All LLR connections will then use the named schema rather than the default schema when accessing the LLR transaction table.  - Use database specific administration tools to grant permission to access the named LLR table to all users that could access this table via a global transaction. By default, the LLR table is created during boot by the user configured for the connection in the data source. In most cases, the database will only allow access to this user and not allow access to mapped users. Connections within Transactions Now that we have covered the behavior of all of these various options, it’s time to discuss the exception to all of the rules.  When you get a connection within a transaction, it is associated with the transaction context on a particular WLS instance. When getting a connection with a data source configured with non-XA LLR or 1PC (using the JTS driver) with global transactions, the first connection obtained within the transaction is returned on subsequent connection requests regardless of the values of username/password specified and independent of the associated proxy user session, if any. The connection must be shared among all users of the connection when using LLR or 1PC. For XA data sources, the first connection obtained within the global transaction is returned on subsequent connection requests within the application server, regardless of the values of username/password specified and independent of the associated proxy user session, if any.  The connection must be shared among all users of the connection within a global transaction within the application server/JVM.

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• arrays format (Javascript)

  - by João Melo

  i have a list of users, with minions, something like this: User52: minion10 minion12 User32: minion13 minion11 i've been keeping in an array where the "location" is the id, like this: Users: [52]User minions: [10]minion [12]minion [32]User minions: [13]minion [11]minion so i can access them easily like this: user[UserID].minions[MinionID] (ex: user[32].minions[11]) but when i print it or send it by json i get something like this: {,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,minion,,,,,,,,,,,,,,minion} but should i keep using like this or should i change to something like this: User = function(){ this.minions = ...; this.getMinion = function(value){ for(var m in this.minions){ if(this.minions[m].id == value){ return this.minions[m]; break; } } } } and get it like this: user.getMinion(MinionID); Question: i get better performance using a "short" array but using loops every time i need a minion, or using "long" arrays, but no need for loop and getting values directly from the id "name"?

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• What kind of performance issues does multiple instances of the exact same object have on a game?

  - by lggmonclar

  I'm fairly new to programming, and I've pretty much learned all the things I know on the go, while working on projects. The problem is that there some things that I just don't know where to begin searching. My question is about performance, and how can multiple instances of the same object affect it -- Specifically, I'm talking about XNA's "GraphicsDevice" class. I have it instanced on four different parts of my game, and in three of those, the object has the exact same values for all the attributes. So, in that case, should I be using the same instance of GraphicsDevice, passing it as a parameter, even if I use it in different classes? I apologize if the question seems redundant, but like I said, I've taught myself most of what I know, so there are quite a few "holes" in my learning process.

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• BIT of a Problem

  The BIT data type is an awkward fit for a SQL database. It doesn't have just two values, and it can do unexpected things in expressions. What is worse, it is a flag rather than a predicate, and so its overuse, along with bit masks, is a prime candidate for being listed as a 'SQL Code Smell'. Joe Celko makes the case. Free trial of SQL Backup™“SQL Backup was able to cut down my backup time significantly AND achieved a 90% compression at the same time!” Joe Cheng. Download a free trial now.

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• And if I ask the job interviewer for reasons to join the company?

  - by Oscar

  In job interviews I am frequently asked if I know the company, explain why do I think I would be the best choice for this company, etc and I have never liked this kinds of questions. Using your experiences in job interviewing, what do you think it would happen if I ask the interviewer to explain me why he think the company is the best company for me and why I should accept their answer? Do you think it would be a good think or bad thing to do? Edit: the idea of the question would not be to "challenge" the interviewer. The idea of the question would be to see what he thinks about the company, what values he thinks are given importance inside the company and what are the strong points of the company.

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• Using Microsoft&apos;s Chart Controls In An ASP.NET Application: Serializing Chart Data

  In most usage scenarios, the data displayed in a Microsoft Chart control comes from some dynamic source, such as from a database query. The appearance of the chart can be modified dynamically, as well; past installments in this article series showed how to programmatically customize the axes, labels, and other appearance-related settings. However, it is possible to statically define the chart's data and appearance strictly through the control's declarative markup. One of the demos examined in the <a href="http://www.4guysfromrolla.com/articles/072209-1.aspx">Getting Started</a> article rendered a column chart with seven columns whose labels and values were defined statically in the <code>&lt;asp:Series&gt;</code> tag's

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• Easy QueryBuilder - A User-Friendly Ad-Hoc Advanced Search Solution

  Constructing an easy and powerful QueryBuilder interface becomes more important for complex data grid filtering and accurate reporting services. In this article, I'll discuss how to build a query search engine using ASP.NET AJAX and dynamic SQL. The main goal is to provide an interactive interface to allow users select query attributes, operators, attribute values, and T-SQL operators so that the data context query list can be easily composed and a search engine is invoked.Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Calculating the force of an impact?

  - by meds

  I'm trying to figure out a way to determine the force two objects collide in. I have two vectors defining their linear velocity at the time of impact, their mass and their angular velocity. Keep in mind this is all for a 2D physics engine. I don't think it's as simple as adding up these values and figuring out if it's large enogh it makes a large impact since that doesn't take into account if the two objects are travelling in the same direction (as an example). Any ideas?

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• Data Conversion in SQL Server

  Most of the time, you do not have to worry about implicit conversion in SQL expressions, or when assigning a value to a column. Just occasionally, though, you'll find that data gets truncated, queries run slowly, or comparisons just seem plain wrong. Robert Sheldon explains why you sometimes need to be very careful if you mix data types when manipulating values. Free trial of SQL Backup™“SQL Backup was able to cut down my backup time significantly AND achieved a 90% compression at the same time!” Joe Cheng. Download a free trial now.

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• JavaOne 2012: JDBC Community Discussion

  - by sowmya

  At JavaOne2012, Mark Biamonte of DataDirect Technologies and Lance Andersen of Oracle organized a discussion about JDBC. To learn more about using JDBC to develop database applications, see the JDBC trail in the Java Tutorials. You will know how to use the basic JDBC API to * create tables * insert values into them * query the tables * retrieve the results of the queries * update the tables In this process, you will learn how to use simple statements and prepared statements, and see an example of a stored procedure. You will also learn how to perform transactions and how to catch exceptions and warnings. - Sowmya

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• Which is the appropriate content-type meta tag value?

  - by Argoron

  I have a question about the meta tag content-type. When starting to build my site (HTML+PHP+JS), I copied a lot of the meta tags over from elsewhere, and I have, amongst others, the following: <meta http-equiv="content-type" content="application/xhtml+xml; charset=iso-8859-1" /> Now, I've seen that tag is being used a lot with the value "text/html". I've been searching the web but could not find a comprehensive explanation regarding what the difference between both is. The "text/html" intuitively sounds more straightforward to me. Should I change my tag to that, or might the "application/xhtml+xml" be an equivalent solution ? Alternatively, can anyone point me to a resource where the different values for these tags are listed and explained in a clear manner? Thanks in advance

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• I'm looking for websites with programming problems that I can practice [on hold]

  - by Spentak

  I want to become a more skilled programmer. I also want to do it through Objective-C and iOS. What websites or programs that you know of have problems that I can solve (with the answers)? I have failed some programming tests for jobs (such as "Given 2 values in a Binary Tree - how do you find the lowest common ancestor?) and I want to become a better engineer. I have developed 54 iOS/Android apps to date, but my core CS Skills apparently are rusty/bad. I have looked at TopCoder - but there aren't very many competitions going on, the website is terrible, and there does not appear to be anything that really supports Objective-C/iOS Websites?

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• Structuring an input file

  - by Ricardo

  I am in the process of structuring a small program to perform some hydraulic analysis of pipe flow. As I am envisioning this, the program will read an input file, store the input parameters in a suitable way, operate on them and finally output results. I am struggling with how to structure the input file in a sane way; that is, in a way that a human can write it easily and a machine can parse it easily. A sample input file made available to me for a similar program is just a stream of comma-separated numbers that don't make much sense on their own, so that's the scenario I am trying to avoid. Though I am giving the details of my particular problem, I am more interested in general input-file structuring strategies. Is a stream of comma-separated values my best bet? Would I be better off using some sort of key:value structure? I don't know much about this, so any help will probably put me in a better track than I am now.

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• align to the bottom of the div [closed]

  - by dole

  I need to arange the value and the lorem ipsum text to the bottom of the div as in the following image, but everything I've tryed until now doesn't work. My html looks like this: <div class="product"> <span class="title">Lorem Ipsum</span> <div class="values"> <span class="price">$29,225</span> <span class="description">Lorem ipsum dolor sit amet, consectetur ...</span> </div> </div>

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• How can I acheive a smooth 2D lighting effect?

  - by Cyral

  I'm making a tile based game in XNA. So currently my lightning looks like this: How can I get it to look like this? Instead of each block having its own tint, it has a smooth overlay. I'm assuming some sort of shader, and to tell it the lighting and blur it some how. But im not an expert with shaders. My current lighting calculates the light, and then passes it to a spritebatch and draws with a color parameter. EDIT: No longer uses spritebatch tint, I was testing and now pass parameters to set the light values. But still looking for a way to smooth it.

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• Variable names for Contact Information bits

  - by RustyTheBoyRobot

  I am in the middle of refactoring code and would like to get some ideas on variable naming so that my new names clearly represent the data they hold. I have a class called ContactMethod which makes sense to me; each instance is a different way to contact someone. My problem comes when naming the properties of ContactMethod. For example, one instance might be a Fax number of 555-555-5555 while another could be an Email address of [email protected]; I've got a property called contactMethodType to hold the values "fax" or "email", but I don't know what to call the "555-555-5555" or "[email protected]" part. Has anyone here created a good generic name for this piece of contact information? (PS - the old convention was to call it a "Phone" with fields "phoneType" holding the "fax"/"email" value and "phoneId" holding the number/address. Yuck.)

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• Relative Positions Of Player And Enemy Are Different In XNA 3D Game

  - by CoOlDud3

  I am having a problem in my 3D Jet Fighter Game using XNA. I have a Player Jet and a few enemy drones built from a separate class. The problem is that when I set Player position and a drone's position to a height 10f in y direction. They aren't at the same height. But if i move Drone's Position up 500f in the y direction then it is pretty much close to the player. Relatively They are supposedly at the same height but with different position values. Can Any One Help Please?

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• WPF Release History : Q1 2010 SP1 (version 2010.1.0422)

  Q1 2010 SP1 Changes: RadGrid Important Changes: The enumerator of RadGridView.Items now enumerates data items only (use RadGridView.Items.Groups to retrieve group items). What's New: Added support for BorderBrush and BorderThickness for GridViewRow. Editable field filter logical composition operator (And/Or). New overload of the GridViewDataContro.GetDistinctValues method that accepts the number of distinct values to return as a parameter. Group footer row now uses its Item as aggregate...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Dynamic Fields/Columns

  - by DanMark

  What is the best way to allow for dynamic fields/database columns? For example, let's say we have a payroll system that allows a user to create unique salary structures for each employee. How could/should one handle this scenario? I thought of using a "salary" table that hold the salary component fields and joining these columns to a "salary_values" table that hold the actual values. Does this make sense? Example Salary Structures: Notice how the components of the salary can be shared or unique. -- Jon's Salary -- Basic 100 Annual Bonus 25 Tel. Allowances 15 -- Jane's Salary -- Basic 100 Travel Allowances 10 Bi-annual Bonus 30

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