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  • MySQL indexes: how do they work?

    - by bob-the-destroyer
    I'm a complete newbie with MySQL indexes. I have several MyISAM tables on MySQL 5.0x having utf8 charsets and collations with 100k+ records each. The primary keys are generally integer. Many columns on each table may have duplicate values. I need to quickly count, sum, average, or otherwise perform custom calculations on any number of fields in each table or joined on any number of others. I found this page giving an overview of MySQL index usage: http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html, but I'm still not sure I'm using indexes right. Just when I think I've made the perfect index out of a collection of fields I want to calculate against, I get the "index must be under 1000 bytes" error. Can anyone explain how to most efficiently create and use indexes to speed up queries? Caveat: upgrading Mysql is not possible in this case. Using Navicat Light for db administration, but this app isn't required.

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  • measuring performance - using real clicks vs "ab" command

    - by shanyu
    I have a web site in closed beta, developed in Django, runs with Mysql on Debian. In the last few days, the main page has been showing a slowdown. For every ten clicks, one or two receives extremely slow response (10 secs or more), others are as fast as they used to be. When I was searching for the problem, I ran into this issue that I couldn't grasp: top command shows that when I request the main page, mysql shoots up to 90% - 100% cpu usage. I get the page just as the cpu use gets back to normal. So, I thought, it is db. Then I called ab with parameters -n 1000 -c 5, I got decent performance, about 100 pages per second, just as it was before the slowdown. I would imagine a worse performance as 10-20% of requests take 10 secs to load. Is this conflict between ab and "real" clicks normal, or am I using ab in a wrong configuration?

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  • Writing datatable to database file, one record at a time in C#

    - by Kevin
    Hi! I want to write a C# program that will read a row from a datatable (named loadDT) and update a database file (named Forecasts.mdb). My datatable looks like this (each day's value is a number representing kilowatts usage forecast): Hour Day1 Day2 Day3 Day4 Day5 Day6 Day7 1 519 520 524 498 501 476 451 My database file looks like this: Day Hour KWForecast 1 1 519 2 1 520 3 1 524 ... and so on. Basically, I want to be able to read one row from the datatable, and then extrapolate that out to my database file, one record at a time. Each row from the datatable will result in seven records written to the database file. Any ideas on how to go about this? I can connect to my database, the connection string works, and I can update and delete from the database. I just can't wrap my head around how to do this one record at a time. Thanks in advance for any help and advice.

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  • Plugin architecture in .net: unloading

    - by henchman
    Hello everybody, I need to implement a plugin architecture within c#/.net in order to load custom user defined actions data type handling code for a custom data grid / conversion / ... from non-static linked assembly files. Because the application has to handle many custom user defined actions, Iam in need for unloading them once executed in order to reduce memory usage. I found several good articles about plugin architectures, eg: ExtensionManager PluginArchitecture ... but none of them gave me enough sausage for properly unloading an assembly. As the program is to be distributed and the user defined actions are (as the name states) user defined: how to i prevent the assembly from executing malicious code (eg. closing my progra, deleting files)? Are there any other pitfalls one of you has encountered?

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  • How to limit the number of the same Activity on the stack for an Android application

    - by johnrock
    Is this possible in an Android app? I want to make it so that no matter how many times a user starts activityA, when they hit the back button they will never get more than one occurence of activityA. What I am finding in my current code is that I have only two options: 1. I can call finish() in activityA which will prevent it from being accessible via the back button completely, or 2. I do not call finish(), and then if the user starts activityA (n) times during their usage, there will be (n) instances when hitting the back button. Again, I want to have activityA accessible by hitting the back button, but there is no reason to keep multiple instances of the same activity on the stack. Is there a way to limit the number of instances of an activity in the queue to only 1?

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  • Any difference between lazy loading Javascript files vs. placing just before </body>

    - by mhr
    Looked around, couldn't find this specific question discussed. Pretty sure the difference is negligible, just curious as to your thoughts. Scenario: All Javascript that doesn't need to be loaded before page render has been placed just before the closing </body> tag. Are there any benefits or detriments to lazy loading these instead through some Javascript code in the head that executes when the DOM load/ready event is fired? Let's say that this only concerns downloading one entire .js file full of functions and not lazy loading several individual files as needed upon usage. Hope that's clear, thanks.

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  • How can I catch a "catchable fatal error" on PHP type hinting?

    - by Ho
    Hello, I am trying to implement Type Hinting of PHP5 on one of my class, class ClassA { public function method_a (ClassB $b) {} } class ClassB {} class ClassWrong{} Correct usage: $a = new ClassA; $a->method_a(new ClassB); producing error: $a = new ClassA; $a->method_a(new ClassWrong); Catchable fatal error: Argument 1 passed to ClassA::method_a() must be an instance of ClassB, instance of ClassWrong given... May I know if it is possible to catch that error(since it says "catchable")? and if yes, how? Thank you.

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  • Android on Eclipse - Adding jar files to an Eclipse Android Project

    - by Shalini
    I am developing an Android App that uses the Google APIs Client Library for Java version 1.12.0. I have added the jar files to the /libs folder (and not to a new /lib folder). I get the following error: Dx trouble processing "javax/xml/namespace/QName.class": Ill-advised or mistaken usage of a core class (java.* or javax.*) when not building a core library. I am NOT using Maven though, and all the answers by others seem to make use of Maven. Android version - 4.1.2 API level 16 Eclipse - Java EE Juno Any suggestions on how I can solve this?

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  • How can I use gnuplot to plot data that is in an un-friendly format?

    - by Zack
    I need to graph some data that is not exactly in the most friendly format, most examples or usage puts things in a nice column/table that is very easy to parse and graph. However I have the following format (and am a bit stuck as to how to tackle this): DATE1 label_1 xx yy DATE1 label_2 xx yy DATE1 label_3 xx yy DATE2 label_2 xx yy DATE2 label_3 xx yy DATE3 label_1 xx yy DATE3 label_2 xx yy DATE3 label_3 xx yy DATE4 label_2 xx yy DATE4 label_3 xx yy ...continues *I've added the extra space between the dates for readability. **Note: under DATE2,DATE4 label_1 is missing, i.e. the data file may have labels that come and go and should represent a discontinuity in the graph. I'd like to have the X-axis use the DATEX for the labels, and then create two lines for each label (xx and yy respectively). Does anyone have any suggestions on the best way to tackle this problem?

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  • Writing datatable to database file, one record at a time

    - by Kevin
    I want to write a C# program that will read a row from a datatable (named loadDT) and update a database file (named Forecasts.mdb). My datatable looks like this (each day's value is a number representing kilowatts usage forecast): Hour Day1 Day2 Day3 Day4 Day5 Day6 Day7 1 519 520 524 498 501 476 451 My database file looks like this: Day Hour KWForecast 1 1 519 2 1 520 3 1 524 ... and so on. Basically, I want to be able to read one row from the datatable, and then extrapolate that out to my database file, one record at a time. Each row from the datatable will result in seven records written to the database file. Any ideas on how to go about this? I can connect to my database, the connection string works, and I can update and delete from the database. I just can't wrap my head around how to do this one record at a time.

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  • What good software or scripts are available for managing users and subscriptions on our website?

    - by undefined
    hi all, Ok so it's not exactly a programing question but does anyone know or have experience with looking for a system for managing users on a website we are building? what is the shortlist of good feature rich secure solutions. we need Php and mysql integration and payment support for main credit cards. We will also want to be able to track users and generate reports about usage, subscription etc, create and send batch emails etc. It would also be great to have the ability to integrate customer support with this so we can view support tickets raised by users. cheers we are running PHP, mysql on an IIS server

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  • SciPy interp1d results are different than MatLab interp1

    - by LMO
    I'm converting a MatLab program to Python, and I'm having problems understanding why scipy.interpolate.interp1d is giving different results than MatLab interp1. In MatLab the usage is slightly different: yi = interp1(x,Y,xi,'cubic') SciPy: f = interp1d(x,Y,kind='cubic') yi = f(xi) For a trivial example the results are the same: MatLab: interp1([0 1 2 3 4], [0 1 2 3 4],[1.5 2.5 3.5],'cubic') 1.5000 2.5000 3.5000 Python: interp1d([1,2,3,4],[1,2,3,4],kind='cubic')([1.5,2.5,3.5]) array([ 1.5, 2.5, 3.5]) But for a real-world example they are not the same: x = 0.0000e+000 2.1333e+001 3.2000e+001 1.6000e+004 2.1333e+004 2.3994e+004 Y = -6 -6 20 20 -6 -6 xi = 0.00000 11.72161 23.44322 35.16484... (2048 data points) Matlab: -6.0000e+000 -1.2330e+001 -3.7384e+000 ... 7.0235e+000 7.0028e+000 6.9821e+000 SciPy: array([[ -6.00000000e+00], [ -1.56304101e+01], [ -2.04908267e+00], ..., [ 1.64475576e+05], [ 8.28360759e+04], [ -5.99999999e+00]]) Any thoughts as to how to can get results that are consistent with MatLab?

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  • Is It Possible To Spring Autowire the same Instance of a protoype scoped class in two places

    - by Mark
    Hi ** changed the example to better express the situation i am using spring 2.5 and have the following situation @Component @Scope("prototype") Class Foo { } class A { @Autowired Foo fooA; } class B { @Autowired Foo fooB; } class C { @Autowired Foo fooC; } i am trying to understand if there is some way to use @Autowired and bind the same instance of FOO onto fooA and fooB while binding a different instance to fooC i understand that if the scope of FOO will be singleton it will work but i am wandering if there is a way to achieve the same goal while using a protoype scope. also please explain is this the correct usage of the autowiring concept ? am i trying to abuse the spring framework purpose

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  • Why implement DB connection pointer object as a reference counting pointer? (C++)

    - by DVK
    At our company one of the core C++ classes (Database connection pointer) is implemented as a reference counting pointer. To be clear, the objects are NOT DB connections themselves, but pointers to a DB connection object. The library is very old, and nobody who designed is around anymore. So far, nether I, nor any C++ experts in the company that I asked have come up with a good reason for why this particular design was chosen. Any ideas? It is introducing some problems (partially due to awful reference pointer implementation used), and I'm trying to understand if this design actually has some deep underlying reasons? The usage pattern these days seems to be that the DB connection pointer object is returned by a DB connection manager class, and it's somewhat unclear whether DB connection pointers were designed to be able to be used independently of DB connection manager.

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  • stripe payment issue ruby on rails

    - by Admir Huric
    So I have made a stripe payment option in my app. When I click the button pay now, it shows me that the payment is successful. and when I go to my stripe account and go to stripe-test and check logs, I can see my test payment with the code 200 OK. But this payment doesn't show in stripe-test events, or in stripe-test payments. Are the payments from logs processed the next day or am I doing something wrong? def charge Stripe.api_key = "some_test_api_key" customer = Stripe::Customer.retrieve(stripe_customer_id) if stripe_customer_id.nil? Stripe::Charge.create( :amount => 2500, :currency => "cad", :customer => stripe_customer_id, :description => "Usage charges for #{name}" ) end rescue Stripe::StripeError => e logger.error "Stripe Error: " + e.message errors.add :base, "Unable to process charge. #{e.message}." false end

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  • Are there any C++ tools that detect misuse of static_cast, dynamic_cast, and reinterpret_cast?

    - by chrisp451
    The answers to the following question describe the recommended usage of static_cast, dynamic_cast, and reinterpret_cast in C++: http://stackoverflow.com/questions/332030/when-should-static-cast-dynamic-cast-and-reinterpret-cast-be-used Do you know of any tools that can be used to detect misuse of these kinds of cast? Would a static analysis tool like PC-Lint or Coverity Static Analysis do this? The particular case that prompted this question was the inappropriate use of static_cast to downcast a pointer, which the compiler does not warn about. I'd like to detect this case using a tool, and not assume that developers will never make this mistake.

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  • Parsing getopts in bash

    - by ABach
    I've got a bash function that I'm trying to use getopts with and am having some trouble. The function is designed to be called by itself (getch), with an optional -s flag (getch -s), or with an optional string argument afterward (so getch master and getch -s master are both valid). The snippet below is where my problem lies - it isn't the entire function, but it's what I'm focusing on: getch() { if [ "$#" -gt 2 ] || [ "$1" = "-h" ] || [ "$1" = "--help" ]; then echo "Usage: $0 [-s] [branch-name]" >&2 return 1 fi while getopts "s" opt; do echo $opt # This line is here to test how many times we go through the loop case $opt in s) squash=true shift ;; *) ;; esac done } The getch -s master case is where the strangeness happens. The above should spit out s once, but instead, I get this: [user@host:git-repositories/temp]$ getch -s master s s [user@host:git-repositories/temp]$ Why is it parsing the -s opt twice?

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  • Does a program exist for checking two similar directories for file differences?

    - by John Sullivan
    Is there a program to compare one folder and all subfolders to another folder and all subfolders for differences in the files contained therein (presence, absence of files, size and list of filenames)? Example of usage: I have 100 DLL files from environment 1 and I want to check if any of them are different (in size and date modified) from the 100 DLL files in environment 2. So I copy and paste all the DLLs in environment 1 into directory A, and all the DLLs in environment 2 into directory B. I then run my "directory comparison" program on directories A and B and find out that, aha, here is a list of 7 DLLs that have different modified dates and times between the two directories. EDIT: OS is windows XP

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  • Uses for static generic classes?

    - by Hightechrider
    What are the key uses of a Static Generic Class in C#? When should they be used? What examples best illustrate their usage? e.g. public static class Example<T> { public static ... } Since you can't define extension methods in them they appear to be somewhat limited in their utility. Web references on the topic are scarce so clearly there aren't a lot of people using them. Here's a couple:- http://ayende.com/Blog/archive/2005/10/05/StaticGenericClass.aspx http://stackoverflow.com/questions/686630/static-generic-class-as-dictionary

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  • Database design: Using hundred of fields for little values

    - by user964260
    I'm planning to develop a PHP Web App, it will mainly be used by registered users(sessions) While thinking about the DB design, I was contemplating that in order to give the best user experience possible there would be lots of options for the user to activate, deactivate, specify, etc. For example: - Options for each layout elements, dialog boxes, dashboard, grid, etc. - color, size, stay visible, invisible, don't ask again, show everytime, advanced mode, simple mode, etc. This would get like 100s of fields ranging from simple Yes/No or 1 to N values..., for each user. So, is it having a field for each of these options the way to go? or how do those CRMs or CMS or other Web Apps do it to store lots of 1-2 char long values? Do they group them on Text fields separated by a special char and then "explode" them as an array for runtime usage? thank you

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  • Is it valid syntax to have ordered and unordered lists in sequence in markdown?

    - by nfm
    I just wrote some markdown and it doesn't seem to render correctly. Is it legal syntax to have an ordered list, followed by newlines, then followed by an unordered list? Or is this a bug in bluecloth? For example: 1. One 2. Two 3. Three * Apple * Banana * Carrot Bluecloth creates a single <ul> and nests apple, banana and carrot as <li>'s under it. Stackoverflow's markdown parser does this too. Am I just doing it wrong? Surely this is a common usage case...

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  • Do invariant assertions fit into C# programming?

    - by P.Brian.Mackey
    In the book coders at work, the author asks "How do you use invariants in your code". Please explain what this question means. I saw class invariants on wiki, but the example is in Java and I am not skilled enough in Java to relate this example to C#. .NET 4.0 introduces invariance, covariance, and contravariance and is well explained here. Invariance is so broad. The authors usage of the word seems unit test related. For those that read the book, what does the author mean? Are we talking about making an assumption and simply testing the validity after the unit test?

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  • Intersection of sets Mongodb

    - by afvasd
    Hi everyone I am new to mongo, this is my db design: product := { name: str group: ref, comments: [ ref, ref, ref, ref ] } comments := { ... a bunch of comments stuff } tag := { _id: int, #Need this for online requests tag: str, products: [ {product: ref, score: float}, ... ], comments: [ {comment: ref, score: float}, ...], } So my usage pattern is: GIVEN a product, find comments that have certain tag and sort them accordingly. My current approach involves: Look for that tag object that has tag=myTag pull all the comments out, sorted look for that product where product.name=myProduct pull all the comments out (which are dbrefs by the way) loop through the result of 2, and checking if they are in 4, (this I can do a limit 10) etc. It's pretty inefficient. Any better methods?

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  • View a SYS.XMLTYPE returned from an Oracle function, using PL/SQL

    - by caerphilly
    I have an Oracle function that dynamically creates an XML document, and returns it in a SYS.XMLTYPE value. I want to run a query from SQL Developer that calls that function and prints the document (either via a select, or dbms_output - I don't care). But all the examples/documentation seem to refer to querying XML columns in tables, and I can't seem to get the syntax right for my particular usage. I'd like something like this: declare x SYS.XMLTYPE; begin x := my_package.my_function(); select x.getclobval() from x; -- doesn't work! end; How can I print out the value of the XML type variable 'x' in the above code?

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  • Is Webhooks a style/pattern or a specification?

    - by Emilio
    I've been reading about Webhooks and I'm trying to determine if it's a specification vs a style/pattern. By "specification" I mean that the implementation details, e.g. headers, payload and so on are well defined. By "style" or "pattern" I mean in the sense that REST is a style (as opposed to a spec) or a pattern which describes usage but doesn't define implementation details. From what I see, Webhooks is a style/pattern. That the event(s) which triggers the http callbacks are generated however the developer wants, and that the http callbacks have no specific implementation requirements except to be an http post. Is this correct?

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