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• Syncing data between devel/live databases in Django

  - by T. Stone

  With Django's new multi-db functionality in the development version, I've been trying to work on creating a management command that let's me synchronize the data from the live site down to a developer machine for extended testing. (Having actual data, particularly user-entered data, allows me to test a broader range of inputs.) Right now I've got a "mostly" working command. It can sync "simple" model data but the problem I'm having is that it ignores ManyToMany fields which I don't see any reason for it do so. Anyone have any ideas of either how to fix that or a better want to handle this? Should I be exporting that first query to a fixture first and then re-importing it? from django.core.management.base import LabelCommand from django.db.utils import IntegrityError from django.db import models from django.conf import settings LIVE_DATABASE_KEY = 'live' class Command(LabelCommand): help = ("Synchronizes the data between the local machine and the live server") args = "APP_NAME" label = 'application name' requires_model_validation = False can_import_settings = True def handle_label(self, label, **options): # Make sure we're running the command on a developer machine and that we've got the right settings db_settings = getattr(settings, 'DATABASES', {}) if not LIVE_DATABASE_KEY in db_settings: print 'Could not find "%s" in database settings.' % LIVE_DATABASE_KEY return if db_settings.get('default') == db_settings.get(LIVE_DATABASE_KEY): print 'Data cannot synchronize with self. This command must be run on a non-production server.' return # Fetch all models for the given app try: app = models.get_app(label) app_models = models.get_models(app) except: print "The app '%s' could not be found or models could not be loaded for it." % label for model in app_models: print 'Syncing %s.%s ...' % (model._meta.app_label, model._meta.object_name) # Query each model from the live site qs = model.objects.all().using(LIVE_DATABASE_KEY) # ...and save it to the local database for record in qs: try: record.save(using='default') except IntegrityError: # Skip as the record probably already exists pass

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• Why do my CouchDB databases grow so fast?

  - by konrad

  I was wondering why my CouchDB database was growing to fast so I wrote a little test script. This script changes an attributed of a CouchDB document 1200 times and takes the size of the database after each change. After performing these 1200 writing steps the database is doing a compaction step and the db size is measured again. In the end the script plots the databases size against the revision numbers. The benchmarking is run twice: The first time the default number of document revision (=1000) is used (_revs_limit). The second time the number of document revisions is set to 1. The first run produces the following plot The second run produces this plot For me this is quite an unexpected behavior. In the first run I would have expected a linear growth as every change produces a new revision. When the 1000 revisions are reached the size value should be constant as the older revisions are discarded. After the compaction the size should fall significantly. In the second run the first revision should result in certain database size that is then keeps during the following writing steps as every new revision leads to the deletion of the previous one. I could understand if there is a little bit of overhead needed to manage the changes but this growth behavior seems weird to me. Can anybody explain this phenomenon or correct my assumptions that lead to the wrong expectations?

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• Creating an SQL variable character column > 255 characters supporting multiple databases

  - by Piers

  I have an application that stores data through an ODBC data source of the user's choosing. So far it has worked well on a range of database systems (e.g. JET, Oracle, SQL Server), as the SQL syntax is fairly simple. Now I am running into a problem where I need to store more than 255 characters in my strings. Previously I created the table using column type VARCHAR (255). Now if I try to create a table using, e.g. VARCHAR (512) then it falls over on Access databases. I know that I can use the MEMO type for Access, but this is non-standard SQL and will thus likely fail on other database systems (e.g. Oracle). Is there any widely supported SQL standard for creating text columns wider than 255 characters, or do I need to find another solution? The alternatives seem to me to be: 1) Profile the database system and customise the SQL CREATE TABLE command based on the database system. I don't like this as it defeats the purpose of using ODBC. 2) Add extra columns of 255 chars as required (e.g. LONGSTRING1, LONGSTRING2, ...) and concatenate after reading. I don't like this because it means the number of columns can vary between tables and it complicates read/write. Are there any other viable alternatives to these two options? Or is it possible to have an SQL compliant CREATE TABLE command supported by the majority of database vendors, that supports strings longer than 255 chars?

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• PHP/MySQL - Working with two databases, one shared and one local to an instance of application

  - by Extrakun

  The situation: Using a off-the-shelf PHP application, I have to add in a new module for extra functionality. Today, it is made known that eventually four different instances of the application are to be deployed, but the data from the new functionality is to be shared among those 4 instances. Each instance should still have their own database for users, content and etc. So the data for the new functionality goes into a 'shared' database. The data for the application (user login, content, uploads) go into a 'local' database To make things more complex, the new module I am writing will fetch data from the local DB and the shared DB at the same time. A re-write of the base application will take too long. I only have control over the new module which I am writing. The ideal solution: Is there a way to encapsulate 2 databases into one name using MySQL? I do not wish to switch DB connections or specifically name the DB to query from inside my SQL statements. The application uses a DB wrapper, so I am able to change it somehow so I can invisibly attempt to read/write to two different DB. What is the best way to handle this problem?

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• Moving information between databases

  - by williamjones

  I'm on Postgres, and have two databases on the same machine, and I'd like to move some data from database Source to database Dest. Database Source: Table User has a primary key Table Comments has a primary key Table UserComments is a join table with two foreign keys for User and Comments Dest looks just like Source in structure, but already has information in User and Comments tables that needs to be retained. I'm thinking I'll probably have to do this in a few steps. Step 1, I would dump Source using the Postgres Copy command. Step 2, In Dest I would add a temporary second_key column to both User and Comments, and a new SecondUserComments join table. Step 3, I would import the dumped file into Dest using Copy again, with the keys input into the second_key columns. Step 4, I would add rows to UserComments in Dest based on the contents of SecondUserComments, only using the real primary keys this time. Could this be done with a SQL command or would I need a script? Step 5, delete the SecondUserComments table and remove the second_key columns. Does this sound like the best way to do this, or is there a better way I'm overlooking?

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• Fetch the most viewed data in databases

  - by Erik Edgren

  I want to get the most viewed photo from the database but I don't know how I shall accomplish this. Here's my SQL at the moment: SELECT * FROM photos AS p, viewers AS v WHERE p.id = v.id_photo GROUP BY v.id_photo The databases: CREATE TABLE IF NOT EXISTS `photos` ( `id` int(10) NOT NULL AUTO_INCREMENT, `photo_filename` varchar(50) NOT NULL, `photo_camera` varchar(150) NOT NULL, `photo_taken` datetime NOT NULL, `photo_resolution` varchar(10) NOT NULL, `photo_exposure` varchar(10) NOT NULL, `photo_iso` varchar(3) NOT NULL, `photo_fnumber` varchar(10) NOT NULL, `photo_focallength` varchar(10) NOT NULL, `post_coordinates` text NOT NULL, `post_description` text NOT NULL, `post_uploaded` datetime NOT NULL, `post_edited` datetime NOT NULL, `checkbox_approxcoor` enum('0','1') NOT NULL DEFAULT '0', PRIMARY KEY (`id`), UNIQUE KEY `id` (`id`) ) CREATE TABLE IF NOT EXISTS `viewers` ( `id` int(10) NOT NULL AUTO_INCREMENT, `id_photo` int(10) DEFAULT '0', `ipaddress` text NOT NULL, `date_viewed` datetime NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `id` (`id`) ) The data in viewers looks like this: (1, 85, '3892a0ab97d6ff325f285b27b847070f', '2012-06-21 22:49:25'), (2, 84, '3892a0ab97d6ff325f285b27b847070f', '2012-06-21 22:49:25'), (3, 85, '3892a0ab97d6ff325f285b27b847070f', '2012-06-21 22:49:25'); One single row from the database for photos to understand how the rows looks like in this database: (85, 'P1170986.JPG', 'Panasonic DMC-LX3', '2012-06-19 18:00:40', '3968x2232', '10/8000', '80', '50/10', '51/10', '', '', '2012-06-19 18:45:17', '0000-00-00 00:00:00', '0') At the moment the SQL only prints the photo with ID 84. In this case it's wrong - it should print out the photo with ID 85. How can I fix this problem? Thanks in advance.

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• MS SQL server: Single or multiple instances?

  - by Hugo Riley

  How costly (CPU or memory wise) is it to have multiple instances of SQL server 2005 instead of only one instance with prefixed databases? A company have three application providers. They each will install one application and they each require two or three databases. Should they all use the same instance or should every provider use it's own named instance? Is there any strong reason for one or other setup?

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• Using multiple column layout with HTML 5 and CSS 3

  - by nikolaosk

  This is going to be the fourth post in a series of posts regarding HTML 5. You can find the other posts here , here and here.In this post I will provide a hands-on example with HTML 5 and CSS 3 on how to create a page with multiple columns and proper layout.I will show you how to use CSS 3 to create columns much easier than relying on DIV elements and the float CSS rule.I will also show you how to use browser-specific prefix rules (-ms for Internet Explorer and -moz for Firefox ) for browsers that do not fully support CSS 3.In order to be absolutely clear this is not (and could not be) a detailed tutorial on HTML 5. There are other great resources for that.Navigate to the excellent interactive tutorials of W3School.Another excellent resource is HTML 5 Doctor.Two very nice sites that show you what features and specifications are implemented by various browsers and their versions are http://caniuse.com/ and http://html5test.com/. At this times Chrome seems to support most of HTML 5 specifications.Another excellent way to find out if the browser supports HTML 5 and CSS 3 features is to use the Javascript lightweight library Modernizr.In this hands-on example I will be using Expression Web 4.0.This application is not a free application. You can use any HTML editor you like.You can use Visual Studio 2012 Express edition. You can download it here.I will create a simple page with information about HTML 5, CSS 3 and JQuery. This is the full HTML 5 code. <!DOCTYPE html><html lang="en">  <head>    <title>HTML 5, CSS3 and JQuery</title>    <meta http-equiv="Content-Type" content="text/html;charset=utf-8" >    <link rel="stylesheet" type="text/css" href="style.css">       </head>  <body>    <div id="header">      <h1>Learn cutting edge technologies</h1>      <p>HTML 5, JQuery, CSS3</p>    </div>    <div id="main">      <div id="mainnews">        <div>          <h2>HTML 5</h2>        </div>        <div>          <p>            HTML5 is the latest version of HTML and XHTML. The HTML standard defines a single language that can be written in HTML and XML. It attempts to solve issues found in previous iterations of HTML and addresses the needs of Web Applications, an area previously not adequately covered by HTML.          </p>          <div class="quote">            <h4>Do More with Less</h4>            <p>             jQuery is a fast and concise JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development.             </p>            </div>          <p>            The HTML5 test(html5test.com) score is an indication of how well your browser supports the upcoming HTML5 standard and related specifications. Even though the specification isn't finalized yet, all major browser manufacturers are making sure their browser is ready for the future. Find out which parts of HTML5 are already supported by your browser today and compare the results with other browsers.                      The HTML5 test does not try to test all of the new features offered by HTML5, nor does it try to test the functionality of each feature it does detect. Despite these shortcomings we hope that by quantifying the level of support users and web developers will get an idea of how hard the browser manufacturers work on improving their browsers and the web as a development platform.</p>        </div>      </div>              <div id="CSS">        <div>          <h2>CSS 3 Intro</h2>        </div>        <div>          <p>          Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation semantics (the look and formatting) of a document written in a markup language. Its most common application is to style web pages written in HTML and XHTML, but the language can also be applied to any kind of XML document, including plain XML, SVG and XUL.          </p>        </div>      </div>            <div id="CSSmore">        <div>          <h2>CSS 3 Purpose</h2>        </div>        <div>          <p>            CSS is designed primarily to enable the separation of document content (written in HTML or a similar markup language) from document presentation, including elements such as the layout, colors, and fonts.[1] This separation can improve content accessibility, provide more flexibility and control in the specification of presentation characteristics, enable multiple pages to share formatting, and reduce complexity and repetition in the structural content (such as by allowing for tableless web design).          </p>        </div>      </div>                </div>    <div id="footer">        <p>Feel free to google more about the subject</p>      </div>     </body>  </html>  The markup is very easy to follow. I have used some HTML 5 tags and the relevant HTML 5 doctype.The CSS code (style.css) follows  body{        line-height: 30px;        width: 1024px;        background-color:#eee;      }            p{        font-size:17px;    font-family:"Comic Sans MS"      }      p,h2,h3,h4{        margin: 0 0 20px 0;      }            #main, #header, #footer{        width: 100%;        margin: 0px auto;        display:block;      }            #header{        text-align: center;         border-bottom: 1px solid #000;         margin-bottom: 30px;      }            #footer{        text-align: center;         border-top: 1px solid #000;         margin-bottom: 30px;      }            .quote{        width: 200px;       margin-left: 10px;       padding: 5px;       float: right;       border: 2px solid #000;       background-color:#F9ACAE;      }            .quote :last-child{        margin-bottom: 0;      }            #main{        column-count:2;        column-gap:20px;        column-rule: 1px solid #000;        -moz-column-count: 2;        -webkit-column-count: 2;        -moz-column-gap: 20px;        -webkit-column-gap: 20px;        -moz-column-rule: 1px solid #000;        -webkit-column-rule: 1px solid #000;      }       All the rules in the css code are pretty simple. The layout is achieved with that CSS rule #main{        column-count:2;        column-gap:20px;        column-rule: 1px solid #000;        -moz-column-count: 2;        -webkit-column-count: 2;        -moz-column-gap: 20px;        -webkit-column-gap: 20px;        -moz-column-rule: 1px solid #000;        -webkit-column-rule: 1px solid #000; Do note the column-count,column-gap and column-rule properties. These properties make the two column layout possible.Please have a look at the picture below to see why I used prefixes for Chrome (webkit) and Firefox(moz).It clearly indicates that the CSS 3 column layout are not supported from Firefox and Chrome.   Finally I test my simple HTML 5 page using the latest versions of Firefox,Internet Explorer and Chrome. In my machine I have installed Firefox 15.0.1.Have a look at the picture below to see how the page looks  I have installed Google Chrome 21.0 in my machine.Have a look at the picture below to see how the page looks Have a look at the picture below to see how my page looks in IE 10.  My page looks the same in all browsers. Hope it helps!!!

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• Best Practices for Sanitizing SQL inputs Using JavaScript?

  - by Greg Bulmash

  So, with HTML5 giving us local SQL databases on the client side, if you want to write a select or insert, you no longer have the ability to sanitize third party input by saying $buddski = mysql_real_escape_string($tuddski) because the PHP parser and MySQL bridge are far away. It's a whole new world of SQLite where you compose your queries and parse your results with JavaScript. But while you may not have your whole site's database go down, the user who gets his/her database corrupted or wiped due to a malicious injection attack is going to be rather upset. So, what's the best way, in pure JavaScript, to escape/sanitize your inputs so they will not wreak havoc with your user's built-in database? Scriptlets? specifications? Anyone?

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• Storing Templates and Object-Oriented vs Relational Databases

  - by syrion

  I'm designing some custom blog software, and have run into a conundrum regarding database design. The software requires that there be multiple content types, each of which will require different entry forms and presentation templates. My initial instinct is to create these content types as objects, then serialize them and store them in the database as JSON or YAML, with the entry forms and templates as simple strings attached to the "contentTypes" table. This seems cumbersome, however. Are there established best practices for dealing with this design? Is this a use case where I should consider an object database? If I should be using an object database, which should I consider? I am currently working in Python and would prefer a capable Python library, but can move to Java if need be.

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• Dynamic Multiple Choice (Like a Wizard) - How would you design it? (e.g. Schema, AI model, etc.)

  - by henry74

  This question can probably be broken up into multiple questions, but here goes... In essence, I'd like to allow users to type in what they would like to do and provide a wizard-like interface to ask for information which is missing to complete a requested query. For example, let's say a user types: "What is the weather like in Springfield?" We recognize the user is interested in weather, but it could be Springfield, Il or Springfield in another state. A follow-up question would be: What Springfield did you want weather for? 1 - Springfield, Il 2 - Springfield, Wi You can probably think of a million examples where a request is missing key data or its ambiguous. Make the assumption the gist of what the user wants can be understood, but there are missing pieces of data required to complete the request. Perhaps you can take it as far back as asking what the user wants to do and "leading" them to a query. This is not AI in the sense of taking any input and truly understanding it. I'm not referring to having some way to hold a conversation with a user. It's about inferring what a user wants, checking to see if there is an applicable service to be provided, identifying the inputs needed and overlaying that on top of what's missing from the request, then asking the user for the remaining information. That's it! :-) How would you want to store the information about services? How would you go about determining what was missing from the input data? My thoughts: Use regex expressions to identify clear pieces of information. These will be matched to the parameters of a service. Figure out which parameters do not have matching data and look up the associated question for those parameters. Ask those questions and capture answers. Re-run the service passing in the newly captured data. These would be more free-form questions. For multiple choice, identify the ambiguity and search for potential matches ranked in order of likelihood (add in user history/preferences to help decide). Provide the top 3 as choices. Thoughts appreciated. Cheers, Henry

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• Can in-memory SQLite databases be used concurrently?

  - by Kent Boogaart

  In order to prevent a SQLite in-memory database from being cleaned up, one must use the same connection to access the database. However, using the same connection causes SQLite to synchronize access to the database. Thus, if I have many threads performing reads against an in-memory database, it is slower on a multi-core machine than the exact same code running against a file-backed database. Is there any way to get the best of both worlds? That is, an in-memory database that permits multiple, concurrent calls to the database?

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• Can in-memory SQLite databases scale with concurrency?

  - by Kent Boogaart

  In order to prevent a SQLite in-memory database from being cleaned up, one must use the same connection to access the database. However, using the same connection causes SQLite to synchronize access to the database. Thus, if I have many threads performing reads against an in-memory database, it is slower on a multi-core machine than the exact same code running against a file-backed database. Is there any way to get the best of both worlds? That is, an in-memory database that permits multiple, concurrent calls to the database?

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• Dividing web.config into multiple files in asp.net

  - by Jalpesh P. Vadgama

  When you are having different people working on one project remotely you will get some problem with web.config, as everybody was having different version of web.config. So at that time once you check in your web.config with your latest changes the other people have to get latest that web.config and made some specific changes as per their local environment. Most of people who have worked things from remotely has faced that problem. I think most common example would be connection string and app settings changes. For this kind of situation this will be a best solution. We can divide particular section of web.config into the multiple files. For example we could have separate ConnectionStrings.config file for connection strings and AppSettings.config file for app settings file. Most of people does not know that there is attribute called ‘configSource’ where we can  define the path of external config file and it will load that section from that external file. Just like below. <configuration> <appSettings configSource="AppSettings.config"/> <connectionStrings configSource="ConnectionStrings.config"/> </configuration> And you could have your ConnectionStrings.config file like following. <connectionStrings> <add name="DefaultConnection" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=aspnet-WebApplication1-20120523114732;Integrated Security=True" providerName="System.Data.SqlClient" /> </connectionStrings> Same way you have another AppSettings.Config file like following. <appSettings> <add key="aspnet:UseTaskFriendlySynchronizationContext" value="true" /> <add key="ValidationSettings:UnobtrusiveValidationMode" value="WebForms" /> </appSettings> That's it. Hope you like this post. Stay tuned for more..

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• Running Multiple Queries in Oracle SQL Developer

  - by thatjeffsmith

  There are two methods for running queries in SQL Developer: Run Statement Run Statement, Shift+Enter, F9, or this button Run Script No grids, just script (SQL*Plus like) ouput is fine, thank you very much! What’s the Difference? There are some obvious differences between the two features, the most obvious being the format of the output delivered. But there are some other, more subtle differences here, primarily around fetching. What is Fetch? After you run send your query to Oracle, it has to do 3 things: Parse Execute Fetch Technically it has to do at least 2 things, and sometimes only 1. But, to get the data back to the user, the fetch must occur. If you have a 10 row query or a 1,000,000 row query, this can mean 1 or many fetches in groups of records. Ok, before I went on the Fetch tangent, I said there were two ways to run statements in SQL Developer: Run Statement Run statement brings your query results to a grid with a single fetch. The user sees 50, 100, 500, etc rows come back, but SQL Developer and the database know that there are more rows waiting to be retrieved. The process on the server that was used to execute the query is still hanging around too. To alleviate this, increase your fetch size to 500. Every query ran will come back with the first 500 rows, and rows will be continued to be fetched in 500 row increments. You’ll then see most of your ad hoc queries complete with a single fetch. Scroll down, or hit Ctrl+End to force a full fetch and get all your rows back. Run Script Run Script runs the contents of the worksheet (or what’s highlighted) as a ‘script.’ What does that mean exactly? Think of this as being equivalent to running this in SQL*Plus: @my_script.sql; Each statement is executed. Also, ALL rows are fetched. So once it’s finished executing, there are no open cursors left around. The more obvious difference here is that the output comes back formatted as plain old text. Run one or more commands plus SQL*Plus commands like SET and SPOOL The Trick: Run Statement Works With Multiple Statements! It says ‘run statement,’ but if you select more than one with your mouse and hit the button – it will run each and throw the results to 1 grid for each statement. If you mouse hover over the Query Result panel tab, SQL Developer will tell you the query used to populate that grid. This will work regardless of what you have this preference set to: DATABASE – WORKSHEET – SHOW QUERY RESULTS IN NEW TABS Mind the fetch though! Close those cursors by bring back all the records or closing the grids when you’re done with them.

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• Draw multiple objects with textures

  - by Simplex

  I want to draw cubes using textures. void OperateWithMainMatrix(ESContext* esContext, GLfloat offsetX, GLfloat offsetY, GLfloat offsetZ) { UserData *userData = (UserData*) esContext->userData; ESMatrix modelview; ESMatrix perspective; //Manipulation with matrix ... glVertexAttribPointer(userData->positionLoc, 3, GL_FLOAT, GL_FALSE, 0, cubeFaces); //in cubeFaces coordinates verticles cube glVertexAttribPointer(userData->normalLoc, 3, GL_FLOAT, GL_FALSE, 0, cubeFaces); //for normals (use in fragment shaider for textures) glEnableVertexAttribArray(userData->positionLoc); glEnableVertexAttribArray(userData->normalLoc); // Load the MVP matrix glUniformMatrix4fv(userData->mvpLoc, 1, GL_FALSE, (GLfloat*)&userData->mvpMatrix.m[0][0]); //Bind base map glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_CUBE_MAP, userData->baseMapTexId); //Set the base map sampler to texture unit to 0 glUniform1i(userData->baseMapLoc, 0); // Draw the cube glDrawArrays(GL_TRIANGLES, 0, 36); } (coordinates transformation is in OperateWithMainMatrix() ) Then Draw() function is called: void Draw(ESContext *esContext) { UserData *userData = esContext->userData; // Set the viewport glViewport(0, 0, esContext->width, esContext->height); // Clear the color buffer glClear(GL_COLOR_BUFFER_BIT); // Use the program object glUseProgram(userData->programObject); OperateWithMainMatrix(esContext, 0.0f, 0.0f, 0.0f); eglSwapBuffers(esContext->eglDisplay, esContext->eglSurface); } This work fine, but if I try to draw multiple cubes (next code for example): void Draw(ESContext *esContext) { ... // Use the program object glUseProgram(userData->programObject); OperateWithMainMatrix(esContext, 2.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, 1.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, 0.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, -1.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, -2.0f, 0.0f, 0.0f); eglSwapBuffers(esContext->eglDisplay, esContext->eglSurface); } A side faces overlapes frontal face. The side face of the right cube overlaps frontal face of the center cube. How can i remove this effect and display miltiple cubes without it?

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• Drawing multiple objects from one Vertex Buffer Object in OpenGL/OpenTK

  - by stoney78us

  I am trying to experimenting drawing method using VBO in OpenGL. Many people normally use 1 vbo to store one object data array. I was trying to do something quite opposite which is storing multiple object data into 1 vbo then drawing it. There is story behind why i want to do this. I want to group many of objects as a single object sometime. However my code doesn't do the justice. Following is my pseudo code: //Data double[] vertices = {line strip 1, line strip 2, line strip 3}; //series of vertices int linestrip1offset = index of the first vertex in line strip 1; int linestrip2offset = index of the first vertex in line strip 2; int linestrip3offset = index of the first vertex in line strip 3; int linestrip1VertexNum = number of vertices in linestrip 1; int linestrip2VertexNum = number of vertices in linestrip 2; int linestrip3VertexNum = number of vertices in linestrip 3; //Setting Up void init() { int[] vBO = new int[1]; GL.GenBuffer(1, vBO); GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.BufferData(BufferTarget.ArrayBuffer, new IntPtr(_vertices.Length * sizeof(double)), _vertices, BufferUsageHint.StaticDraw); GL.EnableClientState(Array.VertexArray); } //Drawing void draw() { GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.EnableClientState(ArrayCap.VertexArray); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip1offset); //drawing first linestrip GL.DrawArrays(drawMode, linestrip1offset , linestrip1VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip2offset); //drawing second linestrip GL.DrawArrays(drawMode, linestrip2offset , linestrip2VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip3offset); //drawing third linestrip GL.DrawArrays(drawMode, linestrip3offset , linestrip3VertexNum ); GL.DisableClientState(ArrayCap.VertexArray); GL.BindBuffer(BufferTarget.ArrayBuffer, 0); } I don't know what i did wrong but i think technically it should work where we can tell OpenGL which part of the data in the vBO to be drawn.

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• How to send multiple MVP matrices to a vertex shader in OpenGL ES 2.0

  - by Carbon Crystal

  I'm working my way through optimizing the rendering of sprites in a 2D game using OpenGL ES and I've hit the limit of my knowledge when it comes to GLSL and vertex shaders. I have two large float buffers containing my vertex coordinates and texture coordinates (eventually this will be one buffer) for multiple sprites in order to perform a single glDrawArrays call. This works but I've hit a snag when it comes to passing the transformation matrix into the vertex shader. My shader code is: uniform mat4 u_MVPMatrix; attribute vec4 a_Position; attribute vec2 a_TexCoordinate; varying vec2 v_TexCoordinate; void main() { v_TexCoordinate = a_TexCoordinate; gl_Position = u_MVPMatrix * a_Position; } In Java (Android) I am using a FloatBuffer to store the vertex/texture data and this is provided to the shader like so: mGlEs20.glVertexAttribPointer(mVertexHandle, Globals.GL_POSITION_VERTEX_COUNT, GLES20.GL_FLOAT, false, 0, mVertexCoordinates); mGlEs20.glVertexAttribPointer(mTextureCoordinateHandle, Globals.GL_TEXTURE_VERTEX_COUNT, GLES20.GL_FLOAT, false, 0, mTextureCoordinates); (The Globals.GL_POSITION_VERTEX_COUNT etc are just integers with the value of 2 right now) And I'm passing the MVP (Model/View/Projection) matrix buffer like this: GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mModelCoordinates); (mModelCoordinates is a FloatBuffer containing 16-float sequences representing the MVP matrix for each sprite) This renders my scene but all the sprites share the same transformation, so it's obviously only picking the first 16 elements from the buffer which makes sense since I am passing in "1" as the second parameter. The documentation for this method says: "This should be 1 if the targeted uniform variable is not an array of matrices, and 1 or more if it is an array of matrices." So I tried modifying the shader with a fixed size array large enough to accomodate most of my scenarios: uniform mat4 u_MVPMatrix[1000]; But this lead to an error in the shader: cannot convert from 'uniform array of 4X4 matrix of float' to 'Position 4-component vector of float' This just seems wrong anyway as it's not clear to me how the shader would know when to transition to the next matrix anyway. Anyone have an idea how I can get my shader to pick up a different MVP matrix (i.e. the NEXT 16 floats) from my MVP buffer for every 4 vertices it encounters? (I am using GL_TRIANGLE_STRIP so each sprite has 4 vertices). Thanks!

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• Efficient way to find unique elements in a vector compared against multiple vectors

  - by SyncMaster

  I am trying find the number of unique elements in a vector compared against multiple vectors using C++. Suppose I have, v1: 5, 8, 13, 16, 20 v2: 2, 4, 6, 8 v3: 20 v4: 1, 2, 3, 4, 5, 6, 7 v5: 1, 3, 5, 7, 11, 13, 15 The number of unique elements in v1 is 1 (i.e. number 16). I tried two approaches. Added vectors v2,v3,v4 and v5 into a vector of vector. For each element in v1, checked if the element is present in any of the other vectors. Combined all the vectors v2,v3,v4 and v5 using merge sort into a single vector and compared it against v1 to find the unique elements. Note: sample_vector = v1 and all_vectors_merged contains v2,v3,v4,v5 //Method 1 unsigned int compute_unique_elements_1(vector<unsigned int> sample_vector,vector<vector<unsigned int> > all_vectors_merged) { unsigned int duplicate = 0; for (unsigned int i = 0; i < sample_vector.size(); i++) { for (unsigned int j = 0; j < all_vectors_merged.size(); j++) { if (std::find(all_vectors_merged.at(j).begin(), all_vectors_merged.at(j).end(), sample_vector.at(i)) != all_vectors_merged.at(j).end()) { duplicate++; } } } return sample_vector.size()-duplicate; } // Method 2 unsigned int compute_unique_elements_2(vector<unsigned int> sample_vector, vector<unsigned int> all_vectors_merged) { unsigned int unique = 0; unsigned int i = 0, j = 0; while (i < sample_vector.size() && j < all_vectors_merged.size()) { if (sample_vector.at(i) > all_vectors_merged.at(j)) { j++; } else if (sample_vector.at(i) < all_vectors_merged.at(j)) { i++; unique ++; } else { i++; j++; } } if (i < sample_vector.size()) { unique += sample_vector.size() - i; } return unique; } Of these two techniques, I see that Method 2 gives faster results. 1) Method 1: Is there a more efficient way to find the elements than running std::find on all the vectors for all the elements in v1. 2) Method 2: Extra overhead in comparing vectors v2,v3,v4,v5 and sorting them. How can I do this in a better way?

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• Looking a lightweight PHP ORM

  - by allenskd

  At first I was going to use doctrine ORM as the main one but it was an overkill, unneeded features and probably excessive calls. One of the main reasons was the "helper" that handled traverse trees (the hierarchy tree) easily but I'm starting to prefer building my own class. This is what I'm looking for: 1) Can manage multiple database connections, (sort of like doctrine manager) 2) Models 3) flexible All suggestions are welcome

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• Do Websites need Local Databases Anymore?

  - by viatropos

  If there's a better place to ask this, please let me know. Every time I build a new website/blog/shopping-cart/etc., I keep trying to do the following: Extract out common functionality into reusable code (Rubygems and jQuery plugins mostly) If possible, convert that gem into a small service so I never have to deal with a database for the objects involved (by service, I mean something lean and mean, usually built with the Sinatra Web Framework with a few core models). My assumption is, if I can remove dependencies on local databases, that will make it easier and more scalable in the long run (scalable in terms of reusability and manageability, not necessarily database/performance). I'm not sure if that's a good or bad assumption yet. What do you think? I've made this assumption because of the following reason: Most serious database/model functionality has been built on the internet somewhere. Just to name a few: Social Network API: Facebook Messaging API: Twitter Mailing API: Google Event API: Eventbrite Shopping API: Shopify Comment API: Disqus Form API: Wufoo Image API: Picasa Video API: Youtube ... Each of those things are fairly complicated to build from scratch and to make as optimized, simple, and easy to use as those companies have made them. So if I build an app that shows pictures (picasa) on an Event page (eventbrite), and you can see who joined the event (facebook events), and send them emails (google apps api), and have them fill out monthly surveys (wufoo), and watch a video when they're done (youtube), all integrated into a custom, easy to use website, and I can do that without ever creating a local database, is that a good thing? I ask because there's two things missing from the puzzle that keep forcing me to create that local database: Post API RESTful/Pretty Url API While there's plenty of Blogging systems and APIs for them, there is no one place where you can just write content and have it part of some massive thing. For every app, I have to use code for creating pretty/restful urls, and that saves posts. But it seems like that should be a service! Question is, is that what the website is? ...That place to integrate the worlds services for my specific cause... and, sigh, to store posts that only my site has access to. Will everyone always need "their own blog"? Why not just have a profile and write lots of content on an established platform like StackOverflow or Facebook? ... That way I can write apps entirely without a database and know that I'm doing it right. Note: Of course at some point you'd need a database, if you were doing something unique or new. But for the case where you're just rewiring information or creating things like videos, events, and products, is it really necessary anymore??

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• B-trees, databases, sequential inputs, and speed.

  - by IanC

  I know from experience that b-trees have awful performance when data is added to them sequentially (regardless of the direction). However, when data is added randomly, best performance is obtained. This is easy to demonstrate with the likes of an RB-Tree. Sequential writes cause a maximum number of tree balances to be performed. I know very few databases use binary trees, but rather used n-order balanced trees. I logically assume they suffer a similar fate to binary trees when it comes to sequential inputs. This sparked my curiosity. If this is so, then one could deduce that writing sequential IDs (such as in IDENTITY(1,1)) would cause multiple re-balances of the tree to occur. I have seen many posts argue against GUIDs as "these will cause random writes". I never use GUIDs, but it struck me that this "bad" point was in fact a good point. So I decided to test it. Here is my code: SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[T1]( [ID] [int] NOT NULL CONSTRAINT [T1_1] PRIMARY KEY CLUSTERED ([ID] ASC) ) GO CREATE TABLE [dbo].[T2]( [ID] [uniqueidentifier] NOT NULL CONSTRAINT [T2_1] PRIMARY KEY CLUSTERED ([ID] ASC) ) GO declare @i int, @t1 datetime, @t2 datetime, @t3 datetime, @c char(300) set @t1 = GETDATE() set @i = 1 while @i < 2000 begin insert into T2 values (NEWID(), @c) set @i = @i + 1 end set @t2 = GETDATE() WAITFOR delay '0:0:10' set @t3 = GETDATE() set @i = 1 while @i < 2000 begin insert into T1 values (@i, @c) set @i = @i + 1 end select DATEDIFF(ms, @t1, @t2) AS [Int], DATEDIFF(ms, @t3, getdate()) AS [GUID] drop table T1 drop table T2 Note that I am not subtracting any time for the creation of the GUID nor for the considerably extra size of the row. The results on my machine were as follows: Int: 17,340 ms GUID: 6,746 ms This means that in this test, random inserts of 16 bytes was almost 3 times faster than sequential inserts of 4 bytes. Would anyone like to comment on this? Ps. I get that this isn't a question. It's an invite to discussion, and that is relevant to learning optimum programming.

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• Android multiple email attachment using Intent question

  - by yyyy1234

  Hi, I've been working on Android program to send email with attachment (image file , audio file , etc) using Intent with (ACTION_SEND) . THe program is working when email has a single attachment. I used Intent.putExtra( android.content.Intent.EXTRA_STREAM, uri) to attach the designated image file to the mail and it is wokring fine , the mail can be delivered through Gmail . However, when I tried to have multiple images attached to the same mail by calling Intent.putExtra( android.content.Intent.EXTRA_STREAM, uri) multiple times, it failed to work. None of the attachment show up in the email . I searched the SDK documentation and Android programming user group about email attachment but cannot find any related info. However, I've discovered that there's another intent constnat ACTION_SEND_MULTIPLE (available since API level 4 ) which might meet my requirement. Based on SDK documentation, it simply states that it deliver multiple data to someone else , it works like ACTION_SEND , excpet the data is multiple. But I still could not figure out the correct usage for this command. I tried to delcare intent with ACTION_SEND_MULTIPLE , then call putExtra(EXTRA_STREAM, uri) multiple times to attach multiple images , but I got the same errnoenous result just like before, none of the attachment show up in the email. Has anyone tried with ACTION_SEND_MULTIPLE and got it working with multiple email attachment ? Thanks very much for your help. Regards, yyyy1234

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• Synchronizing one or more databases with a master database - Foreign keys

  - by Ikke

  I'm using Google Gears to be able to use an application offline (I know Gears is deprecated). The problem I am facing is the synchronization with the database on the server. The specific problem is the primary keys or more exactly, the foreign keys. When sending the information to the server, I could easily ignore the primary keys, and generate new ones. But then how would I know what the relations are. I had one sollution in mind, bet the I would need to save all the pk for every client. What is the best way to synchronize multiple client with one server db. Edit: I've been thinking about it, and I guess seqential primary keys are not the best solution, but what other possibilities are there? Time based doesn't seem right because of collisions which could happen. A GUID comes to mind, is that an option? It looks like generating a GUID in javascript is not that easy. I can do something with natural keys or composite keys. As I'm thinking about it, that looks like the best solution. Can I expect any problems with that?

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• Mapping relationships from multiple databases in NHibernate

  - by mannish

  I have a multi-database application configured with NHibernate. The entities that correspond to tables from each database are in their own separate assemblies (an assembly per database if you will). I have a need/desire to relate an entity from one database to an entity of another database. Everything up to this point works as I want it to (the application handles multiple session factories, etc.). The relationship I want is many-to-one, but in reality my application only cares about one side of the relationship (for reasons that aren't relevant). The relevant entities are Project and PMProject, where a Project HAS A PMProject. When I map the many-to-one, I get the following error: NHibernate.MappingException: An association from the table PROJECTS refers to an unmapped class: SDMS.PPRM.PMProject The Project mapping itself reads (ignore the funky column naming; it's an Oracle db): <many-to-one name="PMProject" class="SDMS.PPRM.PMProject" column="PM_PROJECT_ID" cascade="none" /> In the class attribute, I'm referencing the appropriate assembly, but I get that error which seems to tell me it simply can't find the mapping file for PMProject. But that file exists (it's set as embedded resource), the session factory instantiation works without fail; so I'm at a loss on how to tell the Project mapping how/where to look for the appropriate mapping. Is there something I'm missing? A better way to go about this? Thanks in advance.

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