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  • How to build up a lookup table in microcontroller?

    - by GiGi
    Hi, I am so confused about how to build up a 3-dimension lookup table. Is the template as follows: create a 3 dimensional array to store data. Then create linked list. Then create function 'insert' to put all the data into the array? As some book said, linked list should be static const, is it need to create another function to expand the list? Because the lookup table should be used in a microcontroller, it only needs to finish the operation of putting the data into the array and whenever want to find the data, it will be fast and easy to search. Could you help me with that and give me some suggestions? Thank you.

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  • How to set alternate row color for an iterated table in php?

    - by chandru_cp
    I am using php and i am iterating a table with a result array ... I want to add row color and alternate row color to it.... How to do so? Any suggestion... <table id="chkbox" cellpadding="0" cellspacing="2" width="100%" class="table_Style_Border"> <tr> <td style="width:150px" class="grid_header" align="center">RackName</td> <td style="width:150px" class="grid_header" align="center">LibraryName</td> <td style="width:200px" class="grid_header" align="center">LibrarianName</td> <td style="width:200px" class="grid_header" align="center">Location</td> <td style="width:1%" class="grid_header"></td> </tr> <? if(isset($comment)) { echo '<tr> <td class=table_label colspan=5>'.$comment.'</td></tr>'; } ?> <?php foreach($rackData as $row) { ?> <tr> <td align="left" class="table_label"> <?=$row['rack_name']?> </td> <td align="left" class="table_label"> <?=$row['library_name']?> </td> <td align="center" class="table_label"> <?=$row['librarian']?> </td> <td align="center" class="table_label"> <?=$row['location']?> </td> <td align="center"> <input type="checkbox" name="group" id="group" value="<?=$row['rack_id']?>" onclick="display(this);" > </td> </tr> <? } ?> <table>

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

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

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  • How do you display a PHPmyadmin table onto a web browser/web page?

    - by user1390754
    Just a simple question, i've been searching around and for some reason i cannot find an answer to this. after creating a database/table in Phpmyadmin using xampp, what command do i need to put into my webpage (PHP) to show the table I made? I know the first step involves connecting to the database and i think i've done that properly. This is the code i found from somewhere about connecting (w3 tutorials I believe) $con = mysql_connect("localhost","xxxxxx,""); if (!$con) { die('Could not connect: ' . mysql_error()); }

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  • How to Export a Table to Excel File at Client Side with JQuery?

    - by kamaci
    I use java, jQuery and jsp at my web application. I want to learn that how can I import the values at my table to excel file with JQuery at client side. There are many examples and suggestions even at stackoverflow.com but I saw the solutions as server side as like Apache POI or something like that. There is a datable plug-in: http://www.datatables.net/ at that plug-in it can be done to export the table data into a excel file I think at client side and so I am searching for a solution as like that.

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  • How to Create Views for All Tables with Oracle SQL Developer

    - by thatjeffsmith
    Got this question over the weekend via a friend and Oracle ACE Director, so I thought I would share the answer here. If you want to quickly generate DDL to create VIEWs for all the tables in your system, the easiest way to do that with SQL Developer is to create a data model. Wait, why would I want to do this? StackOverflow has a few things to say on this subject… So, start with importing a data dictionary. Step One: Open of Create a Model In SQL Developer, go to View – Data Modeler – Browser. Then in the browser panel, expand your design and create a new Relational Model. Step Two: Import your Data Dictionary This is a fancy way of saying, ‘suck objects out of the database into my model’ This will open a wizard to connect, select your schema(s), objects, etc. Once they’re in your model, you’re ready to cook with gas I’m using HR (Human Resources) for this example. You should end up with something that looks like this. Our favorite HR model Now we’re ready to generate the views! Step Three: Auto-generate the Views Go to Tools – Data Modeler – Table to View Wizard. I don’t want all my tables included, and I want to change the naming standard Decide if you want to change the default generated view names By default the views will be created as ‘V_TABLE_NAME.’ If you don’t like the ‘V_’ you can enter your own. You also can reference the object and model name with variables as shown in the screenshot above. I’m going to go with something a little more personal. The views are the little green boxes in the diagram Can’t find your views? They should be grouped together in your diagram. Don’t forget to use the Navigator to easily find and navigate to those model diagram objects! Step Four: Generate the DDL Ok, let’s use the Generate DDL button on the toolbar. Un-check everything but your views If you used a prefix, take advantage of that to create a filter. You might have existing views in your model that you don’t want to include, right? Once you click ‘OK’ the DDL will be generated. -- Generated by Oracle SQL Developer Data Modeler 4.0.0.825 -- at: 2013-11-04 10:26:39 EST -- site: Oracle Database 11g -- type: Oracle Database 11g CREATE OR REPLACE VIEW HR.TJS_BLOG_COUNTRIES ( COUNTRY_ID , COUNTRY_NAME , REGION_ID ) AS SELECT COUNTRY_ID , COUNTRY_NAME , REGION_ID FROM HR.COUNTRIES ; CREATE OR REPLACE VIEW HR.TJS_BLOG_EMPLOYEES ( EMPLOYEE_ID , FIRST_NAME , LAST_NAME , EMAIL , PHONE_NUMBER , HIRE_DATE , JOB_ID , SALARY , COMMISSION_PCT , MANAGER_ID , DEPARTMENT_ID ) AS SELECT EMPLOYEE_ID , FIRST_NAME , LAST_NAME , EMAIL , PHONE_NUMBER , HIRE_DATE , JOB_ID , SALARY , COMMISSION_PCT , MANAGER_ID , DEPARTMENT_ID FROM HR.EMPLOYEES ; CREATE OR REPLACE VIEW HR.TJS_BLOG_JOBS ( JOB_ID , JOB_TITLE , MIN_SALARY , MAX_SALARY ) AS SELECT JOB_ID , JOB_TITLE , MIN_SALARY , MAX_SALARY FROM HR.JOBS ; CREATE OR REPLACE VIEW HR.TJS_BLOG_JOB_HISTORY ( EMPLOYEE_ID , START_DATE , END_DATE , JOB_ID , DEPARTMENT_ID ) AS SELECT EMPLOYEE_ID , START_DATE , END_DATE , JOB_ID , DEPARTMENT_ID FROM HR.JOB_HISTORY ; CREATE OR REPLACE VIEW HR.TJS_BLOG_LOCATIONS ( LOCATION_ID , STREET_ADDRESS , POSTAL_CODE , CITY , STATE_PROVINCE , COUNTRY_ID ) AS SELECT LOCATION_ID , STREET_ADDRESS , POSTAL_CODE , CITY , STATE_PROVINCE , COUNTRY_ID FROM HR.LOCATIONS ; CREATE OR REPLACE VIEW HR.TJS_BLOG_REGIONS ( REGION_ID , REGION_NAME ) AS SELECT REGION_ID , REGION_NAME FROM HR.REGIONS ; -- Oracle SQL Developer Data Modeler Summary Report: -- -- CREATE TABLE 0 -- CREATE INDEX 0 -- ALTER TABLE 0 -- CREATE VIEW 6 -- CREATE PACKAGE 0 -- CREATE PACKAGE BODY 0 -- CREATE PROCEDURE 0 -- CREATE FUNCTION 0 -- CREATE TRIGGER 0 -- ALTER TRIGGER 0 -- CREATE COLLECTION TYPE 0 -- CREATE STRUCTURED TYPE 0 -- CREATE STRUCTURED TYPE BODY 0 -- CREATE CLUSTER 0 -- CREATE CONTEXT 0 -- CREATE DATABASE 0 -- CREATE DIMENSION 0 -- CREATE DIRECTORY 0 -- CREATE DISK GROUP 0 -- CREATE ROLE 0 -- CREATE ROLLBACK SEGMENT 0 -- CREATE SEQUENCE 0 -- CREATE MATERIALIZED VIEW 0 -- CREATE SYNONYM 0 -- CREATE TABLESPACE 0 -- CREATE USER 0 -- -- DROP TABLESPACE 0 -- DROP DATABASE 0 -- -- REDACTION POLICY 0 -- -- ERRORS 0 -- WARNINGS 0 You can then choose to save this to a file or not. This has a few steps, but as the number of tables in your system increases, so does the amount of time this feature can save you!

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  • IE9 not rendering box-shadow Elements inside of Table Cells

    - by Rick Strahl
    Ran into an annoying problem today with IE 9. Slowly updating some older sites with CSS 3 tags and for the most part IE9 does a reasonably decent job of working with the new CSS 3 features. Not all by a long shot but at least some of the more useful ones like border-radius and box-shadow are supported. Until today I was happy to see that IE supported box-shadow just fine, but I ran into a problem with some old markup that uses tables for its main layout sections. I found that inside of a table cell IE fails to render a box-shadow. Below are images from Chrome (left) and IE 9 (right) of the same content: The download and purchase images are rendered with: <a href="download.asp" style="display:block;margin: 10px;"><img src="../images/download.gif" class="boxshadow roundbox" /></a> where the .boxshadow and .roundbox styles look like this:.boxshadow { -moz-box-shadow: 3px 3px 5px #535353; -webkit-box-shadow: 3px 3px 5px #535353; box-shadow: 3px 3px 5px #535353; } .roundbox { -moz-border-radius: 6px 6px 6px 6px; -webkit-border-radius: 6px; border-radius: 6px 6px 6px 6px; } And the Problem is… collapsed Table Borders Now normally these two styles work just fine in IE 9 when applied to elements. But the box-shadow doesn't work inside of this markup - because the parent container is a table cell.<td class="sidebar" style="border-collapse: collapse"> … <a href="download.asp" style="display:block;margin: 10px;"><img src="../images/download.gif" class="boxshadow roundbox" /></a> …</td> This HTML causes the image to not show a shadow. In actuality I'm not styling inline, but as part of my browser Reset I have the following in my master .css file:table { border-collapse: collapse; border-spacing: 0; } which has the same effect as the inline style. border-collapse by default inherits from the parent and so the TD inherits from table and tr - so TD tags are effectively collapsed. You can check out a test document that demonstrates this behavior here in this CodePaste.net snippet or run it here. How to work around this Issue To get IE9 to render the shadows inside of the TD tag correctly, I can just change the style explicitly NOT to use border-collapse:<td class="sidebar" style="border-collapse: separate; border-width: 0;"> Or better yet (thanks to David's comment below), you can add the border-collapse: separate to the .boxshadow style like this:.boxshadow { -moz-box-shadow: 3px 3px 5px #535353; -webkit-box-shadow: 3px 3px 5px #535353; box-shadow: 3px 3px 5px #535353; border-collapse: separate; } With either of these approaches IE renders the shadows correctly. Do you really need border-collapse? Should you bother with border-collapse? I think so! Collapsed borders render flat as a single fat line if a border-width and border-color are assigned, while separated borders render a thin line with a bunch of weird white space around it or worse render a old skool 3D raised border which is terribly ugly as well. So as a matter of course in any app my browser Reset includes the above code to make sure all tables with borders render the same flat borders. As you probably know, IE has all sorts of rendering issues in tables and on backgrounds (opacity backgrounds or image backgrounds) most of which is caused by the way that IE internally uses ActiveX filters to apply these effects. Apparently collapsed borders are yet one more item that causes problems with rendering. There you have it. Another crappy failure in IE we have to check for now, just one more reason to hate Internet Explorer. Luckily this one has a reasonably easy workaround. I hope this helps out somebody and saves them the hour I spent trying to figure out what caused this problem in the first place. Resources Sample HTML document that demonstrates the behavior Run the Sample© Rick Strahl, West Wind Technologies, 2005-2012Posted in HTML  Internet Explorer   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Single Key Multiple Values Data Structure for one to many mapping

    - by nijhawan.saurabh
    Dictionaries are good, they are great to store Key / Value pairs but what if you want to store multiple values for a single key? Dictionaries would not allow duplicate keys. I came across a nice way to represent such a Data Structure using one of the Extension Method (ToLookup) present in System.Linq Namespace which converts an IEnumerable<T> to an ILookup<TKey, TElement>.   Now, there are two parameters this method expects (The other overload expects 3 parameters): IEnumerable<TSource> - This list would contain the actual data. Func<TSource, TKey> keySelector - The Delegate which which computes the keys   The method returns the following: ILookup<TKey, TElement>   This DS would store Keys and multiple values along those keys.   Let's see a small example:        12  using System;    13     using System.Collections.Generic;    14     using System.Linq;    15     16     /// <summary>    17     /// </summary>    18     internal class Program    19     {    20         #region Methods    21     22         /// <summary>    23         /// </summary>    24         /// <param name="args">    25         /// The args.    26         /// </param>    27         private static void Main(string[] args)    28         {    29             // Create an array of strings.    30             var list = new List<string> { "IceCream1", "Chocolate Moose", "IceCream2" };    31     32             // Generate a lookup Data Structure    33             ILookup<int, string> lookupDs = list.ToLookup(item => item.Length);    34     35           // Enumerate groupings.    36             foreach (var group in lookupDs)    37             {    38                 foreach (string element in group)    39                 {    40                     Console.WriteLine(element);    41                 }    42             }    43         } Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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  • SQL Developer Quick Tip: Reordering Columns

    - by thatjeffsmith
    Do you find yourself always scrolling and scrolling and scrolling to get to the column you want to see when looking at a table or view’s data? Don’t do that! Instead, just right-click on the column headers, select ‘Columns’, and reorder as desired. Access the Manage Columns dialog Then move up the columns you want to see first… Put them in the order you want – it won’t affect the database. Now I see the data I want to see, when I want to see it – no scrolling. This will only change how the data is displayed for you, and SQL Developer will remember this ordering until you ‘Delete Persisted Settings…’ What IS Remembered Via These ‘Persisted Settings?’ Column Widths Column Sorts Column Positions Find/Highlights This means if you manipulate one of these settings, SQL Developer will remember them the next time you open the tool and go to that table or view. Don’t know what I mean by ‘Find/Highlight?’ Find and highlight values in a grid with Ctrl+F

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  • SQL SERVER – Removing Leading Zeros From Column in Table

    - by pinaldave
    Some questions surprises me and make me write code which I have never explored before. Today was similar experience as well. I have always received the question regarding how to reserve leading zeroes in SQL Server while displaying them on the SSMS or another application. I have written articles on this subject over here. SQL SERVER – Pad Ride Side of Number with 0 – Fixed Width Number Display SQL SERVER – UDF – Pad Ride Side of Number with 0 – Fixed Width Number Display SQL SERVER – Preserve Leading Zero While Coping to Excel from SSMS Today I received a very different question where the user wanted to remove leading zero and white space. I am using the same sample sent by user in this example. USE tempdb GO -- Create sample table CREATE TABLE Table1 (Col1 VARCHAR(100)) INSERT INTO Table1 (Col1) SELECT '0001' UNION ALL SELECT '000100' UNION ALL SELECT '100100' UNION ALL SELECT '000 0001' UNION ALL SELECT '00.001' UNION ALL SELECT '01.001' GO -- Original data SELECT * FROM Table1 GO -- Remove leading zeros SELECT SUBSTRING(Col1, PATINDEX('%[^0 ]%', Col1 + ' '), LEN(Col1)) FROM Table1 GO -- Clean up DROP TABLE Table1 GO Here is the resultset of above script. It will remove any leading zero or space and will display the number accordingly. This problem is a very generic problem and I am confident there are alternate solutions to this problem as well. If you have an alternate solution or can suggest a sample data which does not satisfy the SUBSTRING solution proposed, I will be glad to include them in follow up blog post with due credit. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Page Zipper Unpacks Multi-Page Articles for Single-Page Display

    - by ETC
    It’s annoying when you find an article worth reading but it’s diced up into little segments. Skip clicking next-next-next to read; use Page Zipper to unpack multi-page articles and read them all on one page. Page Zipper is available as both a bookmarklet and a Firefox extension. You simply click on the bookmarklet (or extension icon) when you’re looking at a segmented article or gallery. Page Zipper renders the page with all the individual pages laid out for easy reading. No more clicking next a dozen times to get to the end of the article or gallery. In addition unpacking long articles it also rocks keyboard shortcuts for viewing galleries and automatically resizes images to best-fit your browser window. Check the video above to see the article and gallery features in action. Visit the link below to read more and grab a copy of Page Zipper for your browser. Page Zipper [PrintWhatYouLike] Latest Features How-To Geek ETC How to Get Amazing Color from Photos in Photoshop, GIMP, and Paint.NET Learn To Adjust Contrast Like a Pro in Photoshop, GIMP, and Paint.NET Have You Ever Wondered How Your Operating System Got Its Name? Should You Delete Windows 7 Service Pack Backup Files to Save Space? What Can Super Mario Teach Us About Graphics Technology? Windows 7 Service Pack 1 is Released: But Should You Install It? Page Zipper Unpacks Multi-Page Articles for Single-Page Display Minty Bug: Build an FM Bug Inside a Mint Container Get the MakeUseOf eBook Guide to Hacker Proofing Your PC Sync Your Windows Computer with Your Ubuntu One Account [Desktop Client] Awesome 10 Meter Curved Touchscreen at the University of Groningen [Video] TV Antenna Helper Makes HDTV Antenna Calibration a Snap

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  • SQL SERVER – Removing Leading Zeros From Column in Table – Part 2

    - by pinaldave
    Earlier I wrote a blog post about Remvoing Leading Zeros from Column In Table. It was a great co-incident that my friend Madhivanan (no need of introduction for him) also post a similar article over on BeyondRelational.com. I strongly suggest to read his blog as well as he has suggested some cool solutions to the same problem. On original blog post asked two questions 1) if my sample for testing is correct and 2) If there is any better method to achieve the same. The response was amazing. I am proud on our SQL Community that we all keep on improving on each other’s contribution. There are some really good suggestions as a comment. Let us go over them right now. Improving the ResultSet I had missed including all zeros in my sample set which was an overlook. Here is the new sample which includes all zero values as well. USE tempdb GO -- Create sample table CREATE TABLE Table1 (Col1 VARCHAR(100)) INSERT INTO Table1 (Col1) SELECT '0001' UNION ALL SELECT '000100' UNION ALL SELECT '100100' UNION ALL SELECT '000 0001' UNION ALL SELECT '00.001' UNION ALL SELECT '01.001' UNION ALL SELECT '0000' GO Now let us go over some of the fantastic solutions which we have received. Response from Rainmaker SELECT CASE PATINDEX('%[^0 ]%', Col1 + ' ‘') WHEN 0 THEN '' ELSE SUBSTRING(Col1, PATINDEX('%[^0 ]%', Col1 + ' '), LEN(Col1)) END FROM Table1 Response from Harsh Solution 1 SELECT SUBSTRING(Col1, PATINDEX('%[^0 ]%', Col1 + 'a'), LEN(Col1)) FROM Table1 Response from Harsh Solution 2 SELECT RIGHT(Col1, LEN(Col1)+1 -PATINDEX('%[^0 ]%', Col1 + 'a' )) FROM Table1 Response from lucazav SELECT T.Col1 , label = CAST( CAST(REPLACE(T.Col1, ' ', '') AS FLOAT) AS VARCHAR(10)) FROM Table1 AS T Response from iamAkashSingh SELECT REPLACE(LTRIM(REPLACE(col1,'0',' ')),' ','0') FROM table1 Here is the resultset of above scripts. It will remove any leading zero or space and will display the number accordingly. If you believe there is a better solution, please leave a comment. I am just glad to see so many various responses and all of them teach us something new. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Multi MVC processing vs Single MVC process

    - by lordg
    I've worked fairly extensively with the MVC framework cakephp, however I'm finding that I would rather have my pages driven by the multiple MVC than by just one MVC. My reason is primarily to maintain an a more DRY principle. In CakePHP MVC: you call a URL which calls a single MVC, which then calls the layout. What I want is: you call a URL, it processes a layout, which then calls multiple MVC's per component/block of html on the page. When you compare JavaScript components, AJAX, and server side HTML rendering, it seems the most consistent method for building pages is through blocks of components or HTML views. That way, the view block could be situated either on the server or the client. This is technically my ONLY disagreement with the MVC model. Outside of this, IMHO MVC rocks! My question is: What other RAD frameworks follow the same principles as MVC but are driven rather by the View side of MVC? I've looked at Django and Ruby on Rails, yet they seems to be more Controller driven. Lift/Scala appears to be somewhat of a good fit, but i'm interested to see what others exist.

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  • New Enhancements for InnoDB Memcached

    - by Calvin Sun
    In MySQL 5.6, we continued our development on InnoDB Memcached and completed a few widely desirable features that make InnoDB Memcached a competitive feature in more scenario. Notablely, they are 1) Support multiple table mapping 2) Added background thread to auto-commit long running transactions 3) Enhancement in binlog performance  Let’s go over each of these features one by one. And in the last section, we will go over a couple of internally performed performance tests. Support multiple table mapping In our earlier release, all InnoDB Memcached operations are mapped to a single InnoDB table. In the real life, user might want to use this InnoDB Memcached features on different tables. Thus being able to support access to different table at run time, and having different mapping for different connections becomes a very desirable feature. And in this GA release, we allow user just be able to do both. We will discuss the key concepts and key steps in using this feature. 1) "mapping name" in the "get" and "set" command In order to allow InnoDB Memcached map to a new table, the user (DBA) would still require to "pre-register" table(s) in InnoDB Memcached “containers” table (there is security consideration for this requirement). If you would like to know about “containers” table, please refer to my earlier blogs in blogs.innodb.com. Once registered, the InnoDB Memcached will then be able to look for such table when they are referred. Each of such registered table will have a unique "registration name" (or mapping_name) corresponding to the “name” field in the “containers” table.. To access these tables, user will include such "registration name" in their get or set commands, in the form of "get @@new_mapping_name.key", prefix "@@" is required for signaling a mapped table change. The key and the "mapping name" are separated by a configurable delimiter, by default, it is ".". So the syntax is: get [@@mapping_name.]key_name set [@@mapping_name.]key_name  or  get @@mapping_name set @@mapping_name Here is an example: Let's set up three tables in the "containers" table: The first is a map to InnoDB table "test/demo_test" table with mapping name "setup_1" INSERT INTO containers VALUES ("setup_1", "test", "demo_test", "c1", "c2", "c3", "c4", "c5", "PRIMARY");  Similarly, we set up table mappings for table "test/new_demo" with name "setup_2" and that to table "mydatabase/my_demo" with name "setup_3": INSERT INTO containers VALUES ("setup_2", "test", "new_demo", "c1", "c2", "c3", "c4", "c5", "secondary_index_x"); INSERT INTO containers VALUES ("setup_3", "my_database", "my_demo", "c1", "c2", "c3", "c4", "c5", "idx"); To switch to table "my_database/my_demo", and get the value corresponding to “key_a”, user will do: get @@setup_3.key_a (this will also output the value that corresponding to key "key_a" or simply get @@setup_3 Once this is done, this connection will switch to "my_database/my_demo" table until another table mapping switch is requested. so it can continue issue regular command like: get key_b  set key_c 0 0 7 These DMLs will all be directed to "my_database/my_demo" table. And this also implies that different connections can have different bindings (to different table). 2) Delimiter: For the delimiter "." that separates the "mapping name" and key value, we also added a configure option in the "config_options" system table with name of "table_map_delimiter": INSERT INTO config_options VALUES("table_map_delimiter", "."); So if user wants to change to a different delimiter, they can change it in the config_option table. 3) Default mapping: Once we have multiple table mapping, there should be always a "default" map setting. For this, we decided if there exists a mapping name of "default", then this will be chosen as default mapping. Otherwise, the first row of the containers table will chosen as default setting. Please note, user tables can be repeated in the "containers" table (for example, user wants to access different columns of the table in different settings), as long as they are using different mapping/configure names in the first column, which is enforced by a unique index. 4) bind command In addition, we also extend the protocol and added a bind command, its usage is fairly straightforward. To switch to "setup_3" mapping above, you simply issue: bind setup_3 This will switch this connection's InnoDB table to "my_database/my_demo" In summary, with this feature, you now can direct access to difference tables with difference session. And even a single connection, you can query into difference tables. Background thread to auto-commit long running transactions This is a feature related to the “batch” concept we discussed in earlier blogs. This “batch” feature allows us batch the read and write operations, and commit them only after certain calls. The “batch” size is controlled by the configure parameter “daemon_memcached_w_batch_size” and “daemon_memcached_r_batch_size”. This could significantly boost performance. However, it also comes with some disadvantages, for example, you will not be able to view “uncommitted” operations from SQL end unless you set transaction isolation level to read_uncommitted, and in addition, this will held certain row locks for extend period of time that might reduce the concurrency. To deal with this, we introduce a background thread that “auto-commits” the transaction if they are idle for certain amount of time (default is 5 seconds). The background thread will wake up every second and loop through every “connections” opened by Memcached, and check for idle transactions. And if such transaction is idle longer than certain limit and not being used, it will commit such transactions. This limit is configurable by change “innodb_api_bk_commit_interval”. Its default value is 5 seconds, and minimum is 1 second, and maximum is 1073741824 seconds. With the help of such background thread, you will not need to worry about long running uncommitted transactions when set daemon_memcached_w_batch_size and daemon_memcached_r_batch_size to a large number. This also reduces the number of locks that could be held due to long running transactions, and thus further increase the concurrency. Enhancement in binlog performance As you might all know, binlog operation is not done by InnoDB storage engine, rather it is handled in the MySQL layer. In order to support binlog operation through InnoDB Memcached, we would have to artificially create some MySQL constructs in order to access binlog handler APIs. In previous lab release, for simplicity consideration, we open and destroy these MySQL constructs (such as THD) for each operations. This required us to set the “batch” size always to 1 when binlog is on, no matter what “daemon_memcached_w_batch_size” and “daemon_memcached_r_batch_size” are configured to. This put a big restriction on our capability to scale, and also there are quite a bit overhead in creating destroying such constructs that bogs the performance down. With this release, we made necessary change that would keep MySQL constructs as long as they are valid for a particular connection. So there will not be repeated and redundant open and close (table) calls. And now even with binlog option is enabled (with innodb_api_enable_binlog,), we still can batch the transactions with daemon_memcached_w_batch_size and daemon_memcached_r_batch_size, thus scale the write/read performance. Although there are still overheads that makes InnoDB Memcached cannot perform as fast as when binlog is turned off. It is much better off comparing to previous release. And we are continuing optimize the solution is this area to improve the performance as much as possible. Performance Study: Amerandra of our System QA team have conducted some performance studies on queries through our InnoDB Memcached connection and plain SQL end. And it shows some interesting results. The test is conducted on a “Linux 2.6.32-300.7.1.el6uek.x86_64 ix86 (64)” machine with 16 GB Memory, Intel Xeon 2.0 GHz CPU X86_64 2 CPUs- 4 Core Each, 2 RAID DISKS (1027 GB,733.9GB). Results are described in following tables: Table 1: Performance comparison on Set operations Connections 5.6.7-RC-Memcached-plugin ( TPS / Qps) with memcached-threads=8*** 5.6.7-RC* X faster Set (QPS) Set** 8 30,000 5,600 5.36 32 59,000 13,000 4.54 128 68,000 8,000 8.50 512 63,000 6.800 9.23 * mysql-5.6.7-rc-linux2.6-x86_64 ** The “set” operation when implemented in InnoDB Memcached involves a couple of DMLs: it first query the table to see whether the “key” exists, if it does not, the new key/value pair will be inserted. If it does exist, the “value” field of matching row (by key) will be updated. So when used in above query, it is a precompiled store procedure, and query will just execute such procedures. *** added “–daemon_memcached_option=-t8” (default is 4 threads) So we can see with this “set” query, InnoDB Memcached can run 4.5 to 9 time faster than MySQL server. Table 2: Performance comparison on Get operations Connections 5.6.7-RC-Memcached-plugin ( TPS / Qps) with memcached-threads=8 5.6.7-RC* X faster Get (QPS) Get 8 42,000 27,000 1.56 32 101,000 55.000 1.83 128 117,000 52,000 2.25 512 109,000 52,000 2.10 With the “get” query (or the select query), memcached performs 1.5 to 2 times faster than normal SQL. Summary: In summary, we added several much-desired features to InnoDB Memcached in this release, allowing user to operate on different tables with this Memcached interface. We also now provide a background commit thread to commit long running idle transactions, thus allow user to configure large batch write/read without worrying about large number of rows held or not being able to see (uncommit) data. We also greatly enhanced the performance when Binlog is enabled. We will continue making efforts in both performance enhancement and functionality areas to make InnoDB Memcached a good demo case for our InnoDB APIs. Jimmy Yang, September 29, 2012

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  • What are the advantages of Maven when it comes to single man, educational projects

    - by Leron
    I've spend a few hours playing around with Maven + reading some stuff on the apache official site and also a few random googled articles. By this I mean that I really tried to find the answers myself - both by reading and by doing things on my own. Also maybe worth to mention that I installed the m2e plugin so most of the time I've tried things out from Eclipse and not using the command line too much. However aside from the generated project that for example prevent me from using the default package I didn't see that much of a difference with the standard way I've created my projects before try Maven. In fact I've almost decided to skip Maven for now and move on to the other technology I wanted to learn more in-depth - Hibernate, but when I start with opening the official page the first thing I've read was the recommendation to use Hibernate with Maven. That get me confused and made me taking a step back and trying once more to find what I'm obviously missing right now. As it's said in the maven.apache.. site, the true strength of Maven is shown when you work on large projects with other people, but I lack the option to see how Maven is really used in this scenario, still i think that there are maybe advantages even when it comes to working with small projects alone, but I really have difficulties to point them out. So what do you think are the advantages of Maven when it's used for small projects writing from a single person. What are the things that I should be aware of and try to exploit (I mean features offered by Maven) that can come in handy in this situations?

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  • Gathering all data in single iteration vs using functions for readable code

    - by user828584
    Say I have an array of runners with which I need to find the tallest runner, the fastest runner, and the lightest runner. It seems like the most readable solution would be: runners = getRunners(); tallestRunner = getTallestRunner(runners); fastestRunner = getFastestRunner(runners); lightestRunner = getLightestRunner(runners); ..where each function iterates over the runners and keeps track of the largest height, greatest speed, and lowest weight. Iterating over the array three times, however, doesn't seem like a very good idea. It would instead be better to do: int greatestHeght, greatestSpeed, leastWeight; Runner tallestRunner, fastestRunner, lightestRunner; for(runner in runners){ if(runner.height > greatestHeight) { greatestHeight = runner.height; tallestRunner = runner; } if(runner.speed > ... } While this isn't too unreadable, it can get messy when there is more logic for each piece of information being extracted in the iteration. What's the middle ground here? How can I use only a single iteration while still keeping the code divided into logical units?

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  • Merging multiple top-level domains into a single domain

    - by user23089
    My client had multiple top-level-domains. Each one represented an insurance program within a specific vertical. For all the sites at these alternate domains, there was a 30/70 mix of duplicate vs. original content. Some of the alternate domains ranked very well for their target keyphrase groups, where others were absent in results pages. We advised the client to merge multiple domains into their existing main domain, for usability and SEO reasons. We recently ran the merger. Here was our process: On the main domain, transfer the content such that it matches 1-for-1 content on the various alternate domains Setup Google Webmaster Tools on the main domain Push the new content on the main domain live and submit a corresponding sitemap to Google Establish 301 redirects on the alternate domains, such that each alternate domain URL points to its respective page on the main domain We did this 12 days ago, and pages (previously on the alternate domains) that had ranked well on Google have now plummeted or are entirely non-existent. Did we do the right thing by merging multiple top-level domains into a single domain? Is this initial dip in rankings normal? How soon should we expect to see it return to its normal rankings?

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  • SQL SERVER – Validating Unique Columnname Across Whole Database

    - by pinaldave
    I sometimes come across very strange requirements and often I do not receive a proper explanation of the same. Here is the one of those examples. Asker: “Our business requirement is when we add new column we want it unique across current database.” Pinal: “Why do you have such requirement?” Asker: “Do you know the solution?” Pinal: “Sure I can come up with the answer but it will help me to come up with an optimal answer if I know the business need.” Asker: “Thanks – what will be the answer in that case.” Pinal: “Honestly I am just curious about the reason why you need your column name to be unique across database.” (Silence) Pinal: “Alright – here is the answer – I guess you do not want to tell me reason.” Option 1: Check if Column Exists in Current Database IF EXISTS (  SELECT * FROM sys.columns WHERE Name = N'NameofColumn') BEGIN SELECT 'Column Exists' -- add other logic END ELSE BEGIN SELECT 'Column Does NOT Exists' -- add other logic END Option 2: Check if Column Exists in Current Database in Specific Table IF EXISTS (  SELECT * FROM sys.columns WHERE Name = N'NameofColumn' AND OBJECT_ID = OBJECT_ID(N'tableName')) BEGIN SELECT 'Column Exists' -- add other logic END ELSE BEGIN SELECT 'Column Does NOT Exists' -- add other logic END I guess user did not want to share the reason why he had a unique requirement of having column name unique across databases. Here is my question back to you – have you faced a similar situation ever where you needed unique column name across a database. If not, can you guess what could be the reason for this kind of requirement?  Additional Reference: SQL SERVER – Query to Find Column From All Tables of Database Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL System Table, SQL Tips and Tricks, T SQL, Technology

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  • Animating DOM elements vs refreshing a single Canvas

    - by mgibsonbr
    A few years ago, when the HTML Canvas element was still kinda fresh, I wrote a small game in a rather "unusual" way: each game element had its own canvas, and frequently animated elements even had multiple canvases, one for each animation sprite. This way, the translation would be done by manipulating the DOM position of the canvases, while the sprite animation would consist of altering the visibility of the already drawn canvases. (z-indexes, of course, were the tricky part) It worked like a charm: even in IE6 with excanvas it showed a decent performance, and everything was rather consistent between browsers, including some smartphones. Now I'm thinking in writing a larger game engine in the same fashion, so I'm wondering whether it would be a good idea to do so in the current context (with all the advances in browsers and so on). I know I'm trading memory for time, so this needs to be customizable (even at runtime) for each machine the game will be running. But I believe using separate canvases would also help to avoid the game "freezing" on CPU spikes, since the translation would still happen even if the redraws lag for a while. Besides, the browsers' rendering engines are already optimized in may ways, so I'm guessing this scheme would also reduce the load on the CPU (in contrast to doing everything in JavaScript - specially the less optimized ones). It looks good in my head, but I'd like to hear the opinion of more experienced people before proceeding further. Is there any known drawback of doing this? I'm particulartly unexperienced in dealing with the GPU, so I wonder whether this "trick" would nullify any benefit of using a single, big canvas. Or maybe on modern devices it's overkill (though I'm skeptic about the claims that canvas+js - especially WebGL - will ever be a good alternative to native code). Any thoughts?

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  • Determinism in multiplayer simulation with Box2D, and single computer

    - by Jake
    I wrote a small test car driving multiplayer game with Box2D using TCP server-client communcations. I ran 1 instance of server.exe and 2 instance of client.exe on the same machine that I code and compile the executables. I type inputs (WASD for a simple car movement) into one of the 2 clients and I can get both clients to update the simulation. There are 2 cars in the simulation. As long as the cars do not collide, I get the same identical output on both client.exe. I can run the car(s) around for as long as I could they still update the same. However, if I start to collide the cars, very quickly they go out of sync. My tools: Windows 7, C++, MSVS 2010, Box2D, freeGlut. My Psuedocode: // client.exe void timer(int value) { tcpServer.send(my_inputs); foreach(i = player including myself) inputs[i] = tcpServer.receive(); foreach(i = player including myself) players[i].process(inputs[i]); myb2World.step(33, 8, 6); // Box2D world step simulation foreach(i = player including myself) renderer.render(player[i]); glutTimerFunc(33, timer, 0); } // server.exe void serviceloop { while(all clients alive) { foreach(c = clients) tcpClients[c].receive(&inputs[c]); // send input of each client to all clients foreach(source = clients) { foreach(dest = clients) { tcpClients[dest].send(inputs[source]); } } } } I have read all over the internet and SE the following claims (paraphrased): Box2D is deterministic as long as floating point architecture/implementation is the same. (For any deterministic engine) Determinism is gauranteed if playback of recorded inputs is on the same machine with exe compiled using same compiler and machine. Additionally my server.exe and client.exe gameloop is single thread with blocking socket calls and fixed time step. Question: Can anyone explain what I did wrong to get different Box2D output?

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