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  • MySQL won't use index for query?

    - by Jack Sleight
    I have this table: CREATE TABLE `point` ( `id` INT(11) NOT NULL AUTO_INCREMENT, `siteid` INT(11) NOT NULL, `lft` INT(11) DEFAULT NULL, `rgt` INT(11) DEFAULT NULL, `level` SMALLINT(6) DEFAULT NULL, PRIMARY KEY (`id`), KEY `point_siteid_site_id` (`siteid`), CONSTRAINT `point_siteid_site_id` FOREIGN KEY (`siteid`) REFERENCES `site` (`id`) ON DELETE CASCADE ) ENGINE=INNODB AUTO_INCREMENT=35 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci And this query: SELECT * FROM `point` WHERE siteid = 1; Which results in this EXPLAIN information: +----+-------------+-------+------+----------------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+----------------------+------+---------+------+------+-------------+ | 1 | SIMPLE | point | ALL | point_siteid_site_id | NULL | NULL | NULL | 6 | Using where | +----+-------------+-------+------+----------------------+------+---------+------+------+-------------+ Question is, why isn't the query using the point_siteid_site_id index?

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  • Postgresql count+sort performance

    - by invictus
    I have built a small inventory system using postgresql and psycopg2. Everything works great, except, when I want to create aggregated summaries/reports of the content, I get really bad performance due to count()'ing and sorting. The DB schema is as follows: CREATE TABLE hosts ( id SERIAL PRIMARY KEY, name VARCHAR(255) ); CREATE TABLE items ( id SERIAL PRIMARY KEY, description TEXT ); CREATE TABLE host_item ( id SERIAL PRIMARY KEY, host INTEGER REFERENCES hosts(id) ON DELETE CASCADE ON UPDATE CASCADE, item INTEGER REFERENCES items(id) ON DELETE CASCADE ON UPDATE CASCADE ); There are some other fields as well, but those are not relevant. I want to extract 2 different reports: - List of all hosts with the number of items per, ordered from highest to lowest count - List of all items with the number of hosts per, ordered from highest to lowest count I have used 2 queries for the purpose: Items with host count: SELECT i.id, i.description, COUNT(hi.id) AS count FROM items AS i LEFT JOIN host_item AS hi ON (i.id=hi.item) GROUP BY i.id ORDER BY count DESC LIMIT 10; Hosts with item count: SELECT h.id, h.name, COUNT(hi.id) AS count FROM hosts AS h LEFT JOIN host_item AS hi ON (h.id=hi.host) GROUP BY h.id ORDER BY count DESC LIMIT 10; Problem is: the queries runs for 5-6 seconds before returning any data. As this is a web based application, 6 seconds are just not acceptable. The database is heavily populated with approximately 50k hosts, 1000 items and 400 000 host/items relations, and will likely increase significantly when (or perhaps if) the application will be used. After playing around, I found that by removing the "ORDER BY count DESC" part, both queries would execute instantly without any delay whatsoever (less than 20ms to finish the queries). Is there any way I can optimize these queries so that I can get the result sorted without the delay? I was trying different indexes, but seeing as the count is computed it is possible to utilize an index for this. I have read that count()'ing in postgresql is slow, but its the sorting that are causing me problems... My current workaround is to run the queries above as an hourly job, putting the result into a new table with an index on the count column for quick lookup. I use Postgresql 9.2.

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  • Sync Algorithms

    - by Kristopher Johnson
    Are there any good references out there for sync algorithms? I'm interested in algorithms that synchronize the following kinds of data between multiple users: calendars documents lists and outlines I'm not just looking for synchronization of contents of directories a la rsync; I am interested in merging the data within individual files.

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  • Mozilla addon- help needed with interfaces

    - by user303730
    Hi all , I am working on an Firefox - addon . To modify an url to another with all its parameters same .Could you please suggest me references.. I am struggling very hard to understand interfaces / services .Could you please help me with how and when and what interfaces-methods are called.. I want to know somewhat like this https://developer.mozilla.org/@api/deki/files/920/=Url_load.gif Thank you , Abhinav

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  • How do CUDA devices handle immediate operands?

    - by Jack Lloyd
    Compiling CUDA code with immediate (integer) operands, are they held in the instruction stream, or are they placed into memory? Specifically I'm thinking about 24 or 32 bit unsigned integer operands. I haven't been able to find information about this in any of the CUDA documentation I've examined so far. So references to any documents on specific uarch details like this would be perfect, as I don't currently have a good model for how CUDA works at this level.

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  • mono in production websites?

    - by sirmak
    Hi, I'm investigating the use of mono in real world high traffic web applications. There are some references on the mono site (companies using mono), but I couldn't find a high traffic website sample other than Deki powered ones. And I've read some mailings about mod_mono stability problems because of inexistence of compacting GC. Please reference your app and give some info, if is there anyone using mono in production. ...or do I have to look at Java ? Regards, sirmak

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  • nginx - redirect a certain path to another domain

    - by Eli
    Hey there. I am very unfamiliar with nginx, as a forewarning, and also can't find any actual references on the regex system they use. So right now it's a black box to me. All I want to do is redirect a user trying to go to www.mydomain.com/mydirectory/X to www.myotherdomain.com/X . Seems like I should be using the rewrite command but the syntax of the regex is eluding me. Thanks in advance.

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  • What was the single byte change to port WordStar from CP/M to DOS?

    - by amarillion
    I was re-reading Joel's Strategy Letter II: Chicken and Egg problems and came across this fun quote: In fact, WordStar was ported to DOS by changing one single byte in the code. (Real Programmers can tell you what that byte was, I've long since forgotten). I couldn't find any other references to this with a quick Google search. Is this true or just a figure of speech? In the interest of my quest to become a "Real Programmer", what was the single byte change?

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  • Left Outer Join on Many-to-One Mapping

    - by Colin Bowern
    I have a reference to call that may or may not be there. When I add the nullable option it still doing Inner Join when I want an Outer Left Join (show the left even if the right is null). Is this possible in the NH map? References(x => x.DefaultCategory, "CATEGORY_ID") .Nullable();

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  • Run time Debugging

    - by Prakash
    We have recently downloaded, installed and compiled gcc-3.0.4 code. gcc compiler has built successfully and we where able to compile some same test cpp file. I would like to know how we can modify gcc source code so that we add additional run time debugging statements like the binary in execution compiled by my gcc should print below statement in a log file: filename.cpp::FunctionName#linenumber-statement or any additional information that I can insert via this tailored compiler code Any references would be highly appreciable.

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  • Documentation on System.Deployment

    - by krisnam
    I have a Win Application which is publish using ClickOnce deployment (go though VS IDE). I want to develop another small application (Web) to do this deployment process without going though VS IDE. I heard about System.Deployment and Microsoft.Build.BuildEngine name spaces. But I count find good doc to solve my problem. If you have one please send me any references.

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  • get rid of red X in IE for non-existing images

    - by hubertg
    I have a 3rd website (Confluence) which references images which are secured by a login. If the current user is logged in the image is shown if not the image url would redirect to a login form. Example When you enter this url in the browser a redirect to the login page is done. The problem now: IE shows a the dreaded red X icon for the image even though there should be just nothing (like in Firefox). Anyone knows how to get around this?

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  • I get a "An attempt was made to load a program with an incorrect format" error on a SQL Server repli

    - by baldy
    The exact error is as follows "Could not load file or assembly 'Microsoft.SqlServer.Replication, Version=9.0.242.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91' or one of its dependencies. An attempt was made to load a program with an incorrect format." I've recently started working on this project again after a two month move to another project. It worked perfectly before, and I've double checked all the references.

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  • Why are enums considered compound types?

    - by FredOverflow
    Arrays, functions, pointers, references, classes, unions, enumerations and pointers to members are compound types. My understanding of a compound type is that is based on other type(s). For example, T[n], T* and T& are all based on T. Then what other type(s) is an enumeration based on? Or if my understanding of compound types is incorrect, what exactly is it about a type that makes it a compound type? Is compound simply a synonym for user-defined?

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  • Using single spring application context for web app

    - by Ramo
    Hi, I'm using org.springframework.web.servlet.DispatcherServlet and org.springframework.ws.transport.http.MessageDispatcherServlet In the same app but each is loading own application contexts, I need to load all beans in a single application context. The application consists of typical layers webappdao etc What I have tried is to use one single spring-root-context.xml by setting it in the contextConfigLocation. But didn't help, this has been an issue for me for a long time an I would appreciate any help with this. Any online references would be a great help. Regards Ramo

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  • Converting C source to C++

    - by Barry Kelly
    How would you go about converting a reasonably large (300K), fairly mature C codebase to C++? The kind of C I have in mind is split into files roughly corresponding to modules (i.e. less granular than a typical OO class-based decomposition), using internal linkage in lieu private functions and data, and external linkage for public functions and data. Global variables are used extensively for communication between the modules. There is a very extensive integration test suite available, but no unit (i.e. module) level tests. I have in mind a general strategy: Compile everything in C++'s C subset and get that working. Convert modules into huge classes, so that all the cross-references are scoped by a class name, but leaving all functions and data as static members, and get that working. Convert huge classes into instances with appropriate constructors and initialized cross-references; replace static member accesses with indirect accesses as appropriate; and get that working. Now, approach the project as an ill-factored OO application, and write unit tests where dependencies are tractable, and decompose into separate classes where they are not; the goal here would be to move from one working program to another at each transformation. Obviously, this would be quite a bit of work. Are there any case studies / war stories out there on this kind of translation? Alternative strategies? Other useful advice? Note 1: the program is a compiler, and probably millions of other programs rely on its behaviour not changing, so wholesale rewriting is pretty much not an option. Note 2: the source is nearly 20 years old, and has perhaps 30% code churn (lines modified + added / previous total lines) per year. It is heavily maintained and extended, in other words. Thus, one of the goals would be to increase mantainability. [For the sake of the question, assume that translation into C++ is mandatory, and that leaving it in C is not an option. The point of adding this condition is to weed out the "leave it in C" answers.]

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  • Big, Thick Reference Books (PHP / MySQL / Unix) [closed]

    - by Josh K
    I'm looking for in-depth reference books / guides in PHP, MySQL, and Unix. I'm aware there other other questions pertaining to good books for short references of function names, or detailed beginner guides to these systems. I'm looking for something different. I want a book that I can either use as a quick but in-depth (decent write up, not a pocket reference guide) reference to common functions (JOINS, string manipulation, Regular Expressions, etc) while also providing a detailed inner workings explanation on the system itself.

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