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• How do I Put Several Select Statements into Different Columns

  - by Russ Bradberry

  I basically have 7 select statement that I need to have the results output into separate columns. Normally I would use a crosstab for this but I need a fast efficient way to go about this as there are over 7 billion rows in the table. I am using the vertica database system. Below is an example of my statements: SELECT COUNT(user_id) AS '1' FROM event_log_facts WHERE date_dim_id=20100101 SELECT COUNT(user_id) AS '2' FROM event_log_facts WHERE date_dim_id=20100102 SELECT COUNT(user_id) AS '3' FROM event_log_facts WHERE date_dim_id=20100103 SELECT COUNT(user_id) AS '4' FROM event_log_facts WHERE date_dim_id=20100104 SELECT COUNT(user_id) AS '5' FROM event_log_facts WHERE date_dim_id=20100105 SELECT COUNT(user_id) AS '6' FROM event_log_facts WHERE date_dim_id=20100106 SELECT COUNT(user_id) AS '7' FROM event_log_facts WHERE date_dim_id=20100107

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• How many parameters in C# method are acceptable?

  - by Valentin Heinitz

  I am new to C# and have to maintain a C# Application. Now I'v found a method vaving 32 Parameters (not auto-generated code). From C/C++ I remember the rule of thumb "4 Parameters". It may be an old-fashioned rule rooting back to old 0x86 compilers, where 4 Parameters could be accomodated in registers (fast) or on stack otherwise. I am not concerning about performance, but I do have a feeling, that 32 parameters per functions are not easy to maintain even in C#. Or am I completly not up to date? What is the rule of thumb for C#? Thank you for any hint!

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• GCC/XCode equivalent of _CrtCheckMemory?

  - by Chris Becke

  When dealing with random memory overwrites, in MSVC it is possible to validate the state of the heap at various points with a call to _CrtCheckMemory, and know with at least a small level of confidence that the code up until the check was not responsible for any errors that might cause new or malloc to fail later. In XCode, whats the equivalent way to try and box in a memory overwrite? All I have at the moment is a random failure of a call to new, somewhere deep in the bowels of some code with no real idea of how long the code has been running with a corrupt heap up until that point.

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• Nested query to find details in table B for maximum value in table A

  - by jpatokal

  I've got a huge bunch of flights travelling between airports. Each airport has an ID and (x,y) coordinates. For a given list of flights, I want to find the northernmost (highest x) airport visited. Here's the query I'm currently using: SELECT name,iata,icao,apid,x,y FROM airports WHERE y=(SELECT MAX(y) FROM airports AS a , flights AS f WHERE (f.src_apid=a.apid OR f.dst_apid=a.apid) ) This works beautifully and reasonably fast as long as y is unique, but fails once it isn't. What I'd want to do instead is find the MAX(y) in the subquery, but return the unique apid for the airport with the highest y. Any suggestions?

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• How to ensure that a Serialized object is completely read over a Socket ?

  - by Amitd

  Hi guys, I am trying to write a socket server and Client that communicate with each other via serialized Objects.eg:To Login, Client sends server a serialized Login object and then the server deserialises the object to read login details. Similarly for other types of request/response. I just wanted to be sure if Socket.receive() can read(untill) large serialized objects completely. I have tried this code but seems to fail when a large object is serialised and sent over the internet.(seems to work fine in LAN situations.) http://stackoverflow.com/questions/2134356/sending-large-serialized-objects-over-sockets-is-failing-only-when-trying-to-grow using(MemoryStream ms = new MemoryStream()) { int bytesRead; while((bytesRead = m_socClient.Receive(buffer)) > 0) { ms.Write(buffer, 0, bytesRead); } // access ms.ToArray() or ms.GetBuffer() as desired, or // set Position to 0 and read } Are there any other ways to ensure that the object gets completely read.

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• do not use com.sun.xml.internal.*?

  - by sarah xia

  Hi all, Is this statement true: com.sun.xml.internal package is an internal package as the name suggestes. Users should not write code that depends on internal JDK implementation classes. Such classes are internal implementation details of the JDK and subject to change without notice One of my colleagues used one of the classes in his code, which caused javac task in Ant fail to compile our project as the compiler couldn't find the class. Answer from Sun/Oracle says that this is expected behavior of the compiler as user shouldn't use the package. Question is why the classes in the package made public in the first place? Thanks, Sarah

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• Should XML be used server-side, and JSON client-side?

  - by Michel Carroll

  As a personal project, I'm making an AJAX chatroom application using XML as a server-side storage, and JSON for client-side processing. Here's how it works: AJAX Request gets sent to PHP using GET (chat messages/logins/logouts) PHP fetches/modifies the XML file on the server PHP encodes the XML into JSON, and sends back JSON response Javascript handles JSON information (chat messages/logins/logouts) I want to eventually make this a larger-scale chatroom application. Therefore, I want to make sure it's fast and efficient. Was this a bad design choice? In this case, is switching between XML and JSON ok, or is there a better way?

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• Search filenames in MySQL database table restricted by filetype?

  - by ju

  Hello I have a MySQL database that I replicate from another server. The database contains a table with this columns ID, FileName and FileSize In the table there are more than 4'000'000 records. I want to make fast a search in FileName (varchar) column I found that I can use for this Sphinx search engine. The problem is that I want to restrict searches by filetype. Do I have to and how (trigers?) to extract file extensions for all rows? May be I have to create another table (because this one is replicated) and join them in 1:1 relation? Can you give me some advices please :)

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• Extracting Information from Images

  - by Khorkrak

  What are some fast and somewhat reliable ways to extract information about images? I've been tinkering with openCV and this seems so far to be the best route plus it has Python bindings. So to be more specific I'd like to determine what I can about what's in an image. So for example the haar face detection and full body detection classifiers are great - now I can tell that most likely there are faces and / or people in the image as well as about how many. okay - what else - how about whether there are any buildings and if so what do they seem to be - huts, office buildings etc? Is there sky visible, grass, trees and so forth. From what I've read about training classifiers to detect objects, it seems like a rather laborious process 10,000 or so wrong images and 5,000 or so correct samples to train a classifier. I'm hoping that there are some decent ones around already instead of having to do this all myself for a bunch of different objects - or is there some other way to go about this sort of thing?

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• Timeout with GAE Java

  - by user242153

  Hi, I am having some issues with an app I have deployed on GAE. Specifically, I am intermittently running into the DeadlineExceededException where the server is not responding within the 30 seconds required. What is odd is that the code is not overly complex, it should run in milliseconds. My guess is that the delay is in dealing with the persistence manager and accessing the datastore. 2 questions: 1) What is the best way to track where all of the CPU time on the server is being used up? Log files do not seem helpful and to make things more complicated the code runs very fast when I am running it locally 2) Any tips / best practices in dealing with the 30 second exception? What are the biggest drivers of this? Datastore? HTTP requests / responses? Thanks

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• Which event handler to use to record leaving page - onunload or onbeforeunload?

  - by symcbean

  Hi all, Having not any answers to my previous questions about using javascript to measure page turn times, I'm going to start writing my own code (!). To measure the length of tie it takes, I'm proposing dropping a cookie containing a timestamp when the user browses away from a page, then in a subsequent page, comparing that time with 'now' and sending back a request to a URL which will log the interval. It seems that there are 2 possible handlers I could associate the first block of code with - the onunload() handler or the onbeforeunload()? It's more important that it fail silently on browsers with no/broken support for the handler, than it be portable across every possible browser. Any pointers? Gotchas? TIA C.

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• Exception of Binding form data to object

  - by Captain Kidd

  I'm practising Spring MVC.But fail to populate command object in Controller when I use spring standard tag. For example: "form:input path="password"" But I perfectly do this with HTML standard tag. Like: "input type="text" name="password"" I wonder the way how to use Spring tag binding data. In addition, I think configuration and coding is right in my sample. protected ModelAndView onSubmit(HttpServletRequest request, HttpServletResponse response, Object command, BindException errors) throws Exception { UserFormBean b = (UserFormBean)command; System.out.println("s"); return super.onSubmit(request, response, command, errors); } <form:form commandName="command" action="/SpringFrame/register.html"> <form:input path="password"/> <!-- <input type="text" name="password"/> --> <input type="submit"/> </form:form>

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• Possible to InvalidateVisual() on a given region instead of entire WPF control?

  - by Scott Bilas

  I have a complex WPF control that draws a lot of primitives in its OnRender (it's sort of like a map). When a small portion of it changes, I'd only like to re-issue render commands for the affected elements, instead of running the entire OnRender over. While I'm fine with my OnRender function's performance on a resize or whatever, it's not fast enough for mouse hover-based highlighting of primitives. Currently the only way I know how to force a screen update is to call InvalidateVisual(). No way to send in a dirty rect region to invalidate. Is the lowest granularity of WPF screen composition the UI element? Will I need to do my renders of primitives into an intermediate target and then have that use InvalidateVisual() to update to the screen?

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• <transport> tag within the ServicesReferences.ClientConfig

  - by jdiaz

  I've created a WCF service and added it to an existing Silverlight application that I am working on. When I run the silverlight application in debug mode it fails when I reference the WCF web service. Unrecognized element '' in service reference configuration. Note that only a subset of the Windows Communication Foundation configuration functionality is available in Silverlight. After searching around apparently the following line is causing the app to fail: <transport> <extendedProtectionPolicy policyEnforcement="Never" /> </transport> After removing the above lines everything works. What is the issue here? Should I believing this code in and configuring something else?

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• Maximum Possible File Name Length in Windows Kernel

  - by Lambert

  I was wondering, what is the longest possible name length allowed by the Windows kernel? E.g.: I know the kernel uses UNICODE_STRING structures to hold all object paths, and since the byte length of a wide-character string is stored inside a USHORT, that allows for a maximum path length of 2^15 - 1 characters. Is there a similar, hard restriction on a file name (rather than path)? (I don't care if NTFS or FAT32 imposes a particular restriction; I'm looking for the longest possible theoretically allowed name in the kernel, assuming no additional file system or shell restrictions.) (Edit: For those wondering why this even matters, consider that normally, traversing a directory is achieved by FindFirstFile/FindNextFile calls, one call per file. Given the function named NtQueryDirectoryFile, which is the underlying system call and which returns multiple file names per call, it's actually possible to take advantage of this maximum-length restriction on the path to make an extremely-fast directory traverser that uses solely the stack as a buffer. Now I'm trying to extend that concept, and I need to know the maximum size of a file name.)

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• Is ORM (Linq, Hibernate...) really that useful?

  - by Peter

  I have been playing with some LINQ ORM (LINQ directly to SQL) and I have to admit I like its expressive powers . For small utility-like apps, It also works quite fast: dropping a SQL server on some surface and you're set to linq away. For larger apps however, the DAL never was that big of an issue to me to setup, nor maintain, and more often than not, once it was set, all the programming was not happening there anyway... My, honest - I am an ORM newbie - question : what is the big advantage of ORM over writing a decent DAL by hand? (seems like a double, couldn't find it though) UPDATE : OK its a double :-) I found it myself eventually : ORM vs Handcoded Data Access Layer

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• Python fCGI + sqlAlchemy = malformed header from script. Bad header=FROM tags : index.py

  - by crgwbr

  I'm writing an Fast-CGI application that makes use of sqlAlchemy & MySQL for persistent data storage. I have no problem connecting to the DB and setting up ORM (so that tables get mapped to classes); I can even add data to tables (in memory). But, as soon as I query the DB (and push any changes from memory to storage) I get a 500 Internal Server Error and my error.log records malformed header from script. Bad header=FROM tags : index.py, when tags is the table name. Any idea what could be causing this? Also, I don't think it matters, but its a Linux development server talking to an off-site (across the country) MySQL server.

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• JQuery How to Uncheck A radio button

  - by user281867

  Hi, I have a list of data with a radio button. Users must select a date to edit. Then I load external dynamic form into a [div] using the jquery load() function. var ID = $('input[name=BookItem]:checked').val(); $("#EditFormWrapper").load("callEditData.cfm? ID="+ID); 2 Hours AM 2 Hours PM 2 Hours AM 2 Hours PM I am having trouble uncheck the radio button when user click on cancel button (editBTNcancel). The “BookItem” radio button is on the already on the webpage before the load() call. Here s my script: $("#editBTNcancel").live("click", function(event){ event.preventDefault(); $("#EditFormWrapper").slideUp("fast").empty(); //$('.TOR2Hours').removeAttr('checked'); $('.TOR2Hours').attr('checked', false); }); I hope I clearly state my problem, any suggestion would be greatly appreciated!

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• WCF Caching Solution - Need Advice

  - by Brandon

  The company I work for is looking to implement a caching solution. We have several WCF Web Services hosted and we need to cache certain values that can be persisted and fetched regardless of a client's session to a service. I am looking at the following technologies: Caching Application Block 4.1 WCF TCP Service using HttpRuntime Caching Memcached Win32 and Client Microsoft AppFabric Caching Beta 2 Our test server is a Windows Server 2003 with IIS6, but our production server is Windows Server 2008, so any of the above options would work (except for AppFabric Caching on our test server). Does anyone have any experience with any of these? This caching solution will not be used to store a lot of data, but it will need to be fetched from frequently and fast. Thanks in advance.

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• Select columns from join table only without requiring a join

  - by Kent Boogaart

  Given these tables: create table Orders ( Id INT IDENTITY NOT NULL, primary key (Id) ) create table Items ( Id INT IDENTITY NOT NULL, primary key (Id) ) create table OrdersItems ( OrderId INT not null, ItemId INT not null, primary key (OrderId, ItemId) ) Is it possible to use HQL/criteria API to contruct a query that results in the following SQL: SELECT [OrderId], [ItemId] FROM [OrdersItems] I've tried both of these approaches: var hqlResults = session .CreateQuery("select order.id, item.id from Order order inner join order.Items item") .List(); var criteriaResults = session .CreateCriteria<Order>() .CreateAlias("Items", "item", NHibernate.SqlCommand.JoinType.None) .SetProjection(Projections.Property("id"), Projections.Property("item.id")) .List(); But both approaches insist on generating a join (or fail because the join isn't present, in using criteria), resulting in SQL such as: select order.Id, item.Id from Orders order inner join OrdersItems ordersItems on order.Id = ordersItems.ArticleId inner join Items item on ordersItems.CategoryId = item.Id Is there any way to have NHibernate generate a query that selects columns only from the join table, without requiring a join?

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• Displaying/scrolling through heaps of pictures in the browser

  - by user347256

  I want to be able to browse through heaps of images in the browser, fast. THe easy way (just load 2000 images and scroll) slows down the scrolling a lot, assumedly because there's too much images to be kept in memory. I'd love to hear thoughts on strategies to be able to quickly scroll through 10000s of images (as if you were on your desktop) in the browser. What would expected bottlenecks be? How to address them? How to fake things so that the user experience is still good? Examples in the wild?

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• When not to use a Drupal node?

  - by stotastic

  I've recently created a very simple CRUD table where the user stores some data. For the data, I created a custom node. The functionality works great for creating, editing, and deleting data in the CRUD table using the basic node functionality (I'm actually amazed how fast and easy it was to program the basic functionality with proper access controls using only a tiny bit of code).... Since the data isn't meant to be treated the same way as 'content' such as a blog post (no title, no body, no commments, no revisions, shouldn't show up on ?q=node page, no previews, no teasers, etc)... I find that I'm spending most of my time 'turning off' and modifying the stuff that drupal does automatically for nodes. I know its a matter of taste, but where should one draw the line on what should be treated as a node and what shouldn't? In other words, would it be better to program this stuff from scratch without using nodes?

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• NoSQL or Ehcache caching ?

  - by paddydub

  I'm building a Route Planner Webapp using Spring/Hibernate/Tomcat and a mysql database, I have a database containing read only data, such as Bus Stop Coordinates, Bus times which is never updated. I'm trying to make the app run faster, each time the application is run it will preform approx 1000 reads to the database to calculate a route. I have setup a Ehcache which greatly improves the read from database times. I'm now setting terracotta + Ehcache distributed caching to share the cache with multiple Tomcat JVMs. This seems a bit complicated. I've tried memcached but it was not performing as fast as ehcache. I'm wondering if a MongoDb or Redis would be better suited. I have no experience with nosql but I would appreciate if anyone has any ideas. What i need is quick access to the read only database.

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• Can I mix compile time string comparison with MPL templates?

  - by Negative Zero

  I got this compile time string comparison from another thread using constexpr and C++11 (http://stackoverflow.com/questions/5721813/compile-time-assert-for-string-equality). It works with constant strings like "OK" constexpr bool isequal(char const *one, char const *two) { return (*one && *two) ? (*one == *two && isequal(one + 1, two + 1)) : (!*one && !*two); } I am trying to use it in the following context: static_assert(isequal(boost::mpl::c_str<boost::mpl::string<'ak'>>::value, "ak"), "should not fail"); But it gives me an compilation error of static_assert expression is not an constant integral expression. Can I do this?

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• mysql - filtering a list against keywords, both list and keywords > 20 million records

  - by threecheeseopera

  I have two tables, both having more than 20 million records; table1 is a list of terms, and table2 is a list of keywords that may or may not appear in those terms. I need to identify the terms that contain a keyword. My current strategy is: SELECT table1.term, table2.keyword FROM table1 INNER JOIN table2 ON table1.term LIKE CONCAT('%', table2.keyword, '%'); This is not working, it takes f o r e v e r. It's not the server (see notes). How might I rewrite this so that it runs in under a day? Notes: As for server optimization: both tables are myisam and have unique indexes on the matching fields; the myisam key buffer is greater than the sum of both index file sizes, and it is not even being fully taxed (key_blocks_unused is ... large); the server is a dual-xeon 2U beast with fast sas drives and 8G of ram, fine-tuned for the mysql workload.

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