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• SQL Profiles showing high activity

  - by Wong Chi

  I am running my application locally -- ie. No external traffic and very low number of queries, fully under my control. I see tons of 'Audit Login' and 'Audit Logout' events. What are these and where are they actually stored (ie. Where is this audit log)? Are these a hint of a problem with connections, because I have only a simple connection string within my app and thought that connections would remain active throughout the operation of my app (ie. a single login at launch, and then a single logout when terminating).

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• How do I delete in Django? (mysql transactions)

  - by alex

  If you are familiar with Django, you know that they have a Authentication system with User model. Of course, I have many other tables that have a Foreign Key to this User model. If I want to delete this user, how do I architect a script (or through mysql itself) to delete every table that is related to this user? My only worry is that I can do this manually...but if I add a table , but I forget to add that table to my DELETE operation...then I have a row that links to a deleted, non-existing User.

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• How do I determine when two moving points become visible to each other?

  - by Devin Jeanpierre

  Suppose I have two points, Point1 and Point2. At any given time, these points may be at different positions-- they are not necessarily static. Point1 is located at some position at time t, and its position is defined by the continuous functions x1(t) and y1(t) giving the x and y coordinates at time t. These functions are not differentiable, they are constructed piecewise from line segments. Point2 is the same, with x2(t) and y2(t), each function having the same properties. The obstacles that might prevent visibility are simple (and immobile) polygons. How can I find the boundary points for visibility? i.e. there are two kinds of boundaries: where the points become visible, and become invisible. For a become-visible boundary i, there exists some ?0, such that for any real number a, a ? (i-?, i) , Point1 and Point2 are not visible (i.e. the line segment that connects (x1(a), y1(a)) to (x2(a), y2(x)) crosses some obstacles). For b ? (i, i+?) they are visible. And it is the other way around for becomes-invisible. But can I find such a precise boundary, and if so, how?

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• A good way to look back arbitrary number of items in the Array.Fold in F#

  - by tk

  In the folder function of the Array.Fold operation, i want to look back arbitrary number of items. The only way i can figure out is like this. let aFolder (dataArray, curIdx, result) (dataItem) = let N = numItemsToLookBack(result, dataItem) let recentNitems = dataArray.[curIdx - n .. curIdx - 1] let result = aCalc(result, dataItem, recentNitems ) dataArray, curIdx + 1, result myDataArray | Array.fold aFolder (myDataArray, 0, initResult) As you can see, I passed the whole dataArray and index to the folder function to get the "recentNitems". But this way allows the folder function to access not only preceding data, but also the following data. Is there a better (or more functional) way?

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• MySQL temp table issue

  - by AmyD

  Hi folks! I'm trying to use temp tables to speed up my MySQL 4.1.22-standard database and what seems like a simple operation is causing me all kinds of issues. My code is below.... CREATE TEMPORARY TABLE nonDerivativeTransaction_temp (accession_number varchar(30), transactionDateValue date)) TYPE=HEAP; INSERT INTO nonDerivativeTransaction_temp VALUES( SELECT accession_number, transactionDateValue FROM nonDerivativeTransaction WHERE transactionDateValue = "2010-06-15"); SELECT * FROM nonDerivativeTransaction_temp; The original table (nonDerivativeTransaction) has two fields, accession_number (varchar(30)) and transactionDateValue (date). Apparently I am getting an issue with the first two statements but I can't seem to nail down what it is. Any help would be appreciated. Amy D.

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• Endless saving of CoreData Context

  - by Robert

  Sometimes I noticed that a 'save:' operation an a ManagedObjectContext never returns and consumes 100% CPU. I'm using an SQL Store in a GarbageCollected environment (Mac OS X 10.6.3). The disk activity shows about 700 KB/s writing. While having a look at the folder that contains the sqlite database file the "-journal" file appears and disappears, appears and disappears, ... This is part of the call graph from the process analysis: 2203 -[NSManagedObjectContext save:] 1899 -[NSPersistentStoreCoordinator(_NSInternalMethods) executeRequest:withContext:] 1836 -[NSSQLCore executeRequest:withContext:] 1836 -[NSSQLCore saveChanges:] 1479 -[NSSQLCore performChanges] ... 335 -[NSSQLCore recordChangesInContext:] ... 20 -[NSSQLCore rollbackChanges] ... 2 -[NSSQLCore prepareForSave:] ... 62 -[NSPersistentStoreCoordinator(_NSInternalMethods) _checkRequestForStore:originalRequest:andOptimisticLocking:] ... 1 -[NSPersistentStore(_NSInternalMethods) _preflightCrossCheck] ... 184 -[NSMergePolicy resolveConflicts:] ... 120 -[NSManagedObjectContext(_NSInternalChangeProcessing) _prepareForPushChanges:] ... Everything a happening in the main GUI thread. Any ideas what I can to do to resolve the problem?

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• Can using non primitive Integer/ Long datatypes too frequently in the application, hurt the performance??

  - by Marcos

  I am using Long/Integer data types very frequently in my application, to build Generic datatypes. I fear that using these wrapper objects instead of primitive data types may be harmful for performance since each time it needs to create objects which is an expensive operation. but also it seems that I have no other choice(when I have to use primtives with generics) rather than just using them. However, still it would be great if you can suggest if there is anything I could do to make it better. or any way if I could just avoid it ?? Also What may be the downsides of this ? Suggestions welcomed!

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• Reading files with Java

  - by sikas

  I would like to know how can I read a file byte by byte then perform some operation every n bytes. for example: Say I have a file of size = 50 bytes, I want to divide it into blocks each of n bytes. Then each block is sent to a function for some operations to be done on those bytes. The blocks are to be created during the read process and sent to the function when the block reaches n bytes so that I don`t use much memory for storing all blocks. I want the output of the function to be written/appended on a new file. This is what I've reached to read, yet I don't know it it is right: fc = new JFileChooser(); File f = fc.getSelectedFile(); FileInputStream in = new FileInputStream(f); byte[] b = new byte[16]; in.read(b); I haven't done anything yet for the write process.

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• which is better, creating a view or a new table?

  - by Carson

  I have some demanding mysql queries that are needed to grap same datasets from several mysql tables. I am thinking of creating a table or view to gather all demanding columns from other tables, so as to increase performance. If I create that table, I may need to do extra insert / update / delete operation each time other tables updated. if I create view, I am worrying if the performance can be greatly improved. Because data from other tables are changing very frequently. Most likely, the view may need to be created first everytime before selecting it. Any ideas? e.g. how to cache? other extra measures I can do?

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• Appengine backreferences - need composite index?

  - by davezor

  I have a query that is very recently starting to throw: "The built-in indices are not efficient enough for this query and your data. Please add a composite index for this query." I checked the line on which this exception is being thrown, and the problem query is this one: count = self.vote_set.filter("direction =", 1).count() This is literally a one-filter operation using appengine's built-in backreferences. I have no idea how to optimize this query...anyone have any suggestions? I tried to add this index: - kind: Vote properties: - name: direction direction: desc - kind: Vote properties: - name: direction And I got a message (obviously) saying this was an unnecessary index. Thanks for your help in advance.

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• Can I use Cassandra to store objects?

  - by Sandeep

  Hi, My application works like this. A database(Mysql) where there is a command. The command is an object(consists of fields many fields like ints ans strings). There is a webservice which interact with the database and get the command from the db and performs some operation. The way how I am storing the command into db is by stripping all the fields and inserting them in to the db. Can I use cassandra in place of mysql and store the command object?

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• In SQL, a Join is actually an Intersection? And it is also a linkage or a "Sideway Union"?

  - by Jian Lin

  I always thought of a Join in SQL as some kind of linkage between two tables. For example, select e.name, d.name from employees e, departments d where employees.deptID = departments.deptID In this case, it is linking two tables, to show each employee with a department name instead of a department ID. And kind of like a "linkage" or "Union" sideway". But, after learning about inner join vs outer join, it shows that a Join (Inner join) is actually an intersection. For example, when one table has the ID 1, 2, 7, 8, while another table has the ID 7 and 8 only, the way we get the intersection is: select * from t1, t2 where t1.ID = t2.ID to get the two records of "7 and 8". So it is actually an intersection. So we have the "Intersection" of 2 tables. Compare this with the "Union" operation on 2 tables. Can a Join be thought of as an "Intersection"? But what about the "linking" or "sideway union" aspect of it?

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• Are the atomic builtins provided by gcc actually translated into the example code, or is that just f

  - by Jared P

  So I was reading http://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/Atomic-Builtins.html, and came across this: type __sync_and_and_fetch (type *ptr, type value, ...) type __sync_xor_and_fetch (type *ptr, type value, ...) type __sync_nand_and_fetch (type *ptr, type value, ...) These builtins perform the operation suggested by the name, and return the new value. That is, { *ptr op= value; return *ptr; } { *ptr = ~*ptr & value; return *ptr; } // nand Is this code literal? or is it just to explain what gcc is doing atomically using c-like syntax? And if this is the direct translation, can someone explain how it is atomic?

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• Javascript function returning number with two decimals...?

  - by muzzledBYbrass

  I have a function to return points along a line and my return comes back with two decimal points...? For example, a return of my variable px will be something like -88.4029.032940598. vx is the x vector and mult is the distance of the line plus distance to calculate the point. Here is the operation that is returning these values: var mult = parseFloat(mag + theUnit); var px = coord_one.x_point + (vx * mult); console.log(px); Never have seen this before- I appreciate any and all help!

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• Different RegisterWindowMessage() names appear the same

  - by Mike Trader

  Using the C/C++ Windows API RegisterWindowMessage() I am using the name of the application as the message name. Next I call CreatMutex() using the same name so that I can tell if it already exists. If it does, I know this application is already running and not to launch a second instance of it. THis is the operation of my function Running() My confusion is over the message name. It seems that "AutoConvert.exe" and "AutoAppend.exe" are interpreted as the same name. Why?

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• not inserting data into database from jsf web module connecting with ejb module..

  - by krazyk

  hello.. in my application i had taken ejbmodule and web module seprately. in ejb module there is one entity and session bean with remote interface. in web module i had taken jsf and used managed bean for calling method of session bean. and used jsf page with .jsp extension where m had put 2 textboxes and one commandbutton.which mapped to managed bean. my database table has only 2 field. bt when i run the application and entered data then click on button no operation is done.no data inserted into database table. i m nt given any error.so couldn't found any problem.. also dnt knw clear abt faces-config.xml file i had written abt managed bean into tht file.. plz guide me wht will be the actual problem?. thanks in advance.. waiting for positive reply..

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• Should filters write to the response during or after filtering?

  - by Mark

  I have a filter which processes generated HTML and rewrites certain elements. For example, it adds class attributes to some anchors. Finally, it writes the processed HTML to the response (a subclass of HttpServletResponseWrapper). Naturally, this means that the processed HTML is a different length after it has passed through the filter. I can see two ways of approaching this. One is to iterate over the HTML, using a StringBuilder to build up the processed HTML, and write the processed HTML to the response once all filtering is complete. The other is to iterate over the HTML but to write it to the response as soon as each element has been processed. Which is the better way for this operation, or is there another option which would be preferable? I am looking to minimise temporary memory usage primarily.

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• how to get a sub list from a list in ocaml

  - by romerun

  Hi, I'm looking at the List document. It seems the library does not provide a sublist function. I'm trying to get list of elements from i to j. Now I have to write it as: let rec sublist list i j = if i j then [] else (List.nth list i) :: (sublist list (i+1) j) which is quite concise but I'm questioning the efficiency of List.nth, because if it's O(n), I would rather have to write it in a less concise way. I'm wondering why didn't they provide List.sublist func, if List.nth is not O(1), because it's such a quite common operation..

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• How to create a Mutex with security attribute to share resource from different application?

  - by Antony Tess

  How to create a Mutex with security attribute rigth to share resource from different application? In according with Microsoft SDK documentation the CreateMutex API accept as first parameter a SECURITY_ATTRIBUTES pointer. HANDLE WINAPI CreateMutex( __in LPSECURITY_ATTRIBUTES lpMutexAttributes, __in BOOL bInitialOwner, __in LPCTSTR lpName ); I want to create the rigth security attribute so only my application group can open the MUTEX and access to a specific resource (a file) where my application gruop read/write data operation. The target opertaing system are XP, Vista and Seven. The feature must working in both, administrator/standard user, login shenario.

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• PropertyInfo.GetValue() - how do you index into a generic parameter using reflection in C#?

  - by flesh

  This (shortened) code.. for (int i = 0; i < count; i++) { object obj = propertyInfo.GetValue(Tcurrent, new object[] { i }); } .. is throwing a 'TargetParameterCountException : Parameter count mismatch' exception. The underlying type of 'propertyInfo' is a Collection of some T. 'count' is the number of items in the collection. I need to iterate through the collection and perform an operation on obj. Advice appreciated.

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• Cross-referencing UML models in VS 2010

  - by cheaster

  I am just starting to explore/use the UML modeling support in Visual Studio 2010 Umltimate. I have created two model projects within a single solution. Let's call them Model A and Model B. I have some data types (classes) defined in Model B. I want to use them as return types for operations in Model A. However, I cannot figure out how to make the types defined in Model B show up in Model A when attempting to set return type on an operation. Any help/suggestions would be greatly appreciated! Thanks!

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• Python: Access members of a set

  - by emu

  Say I have a set myset of custom objects that may be equal although their references are different (a == b and a is not b). Now if I add(a) to the set, Python correctly assumes that a in myset and b in myset even though there is only len(myset) == 1 object in the set. That is clear. But is it now possible to extract the value of a somehow out from the set, using b only? Suppose that the objects are mutable and I want to change them both, having forgotten the direct reference to a. Put differently, I am looking for the myset[b] operation, which would return exactly the member a of the set. It seems to me that the type set cannot do this (faster than iterating through all its members). If so, is there at least an effective work-around?

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• How can I write faster JavaScript?

  - by a paid nerd

  I'm writing an HTML5 canvas visualization. According to the Chrome Developer Tools profiler, 90% of the work is being done in (program), which I assume is the V8 interpreter at work calling functions and switching contexts and whatnot. Other than logic optimizations (e.g., only redrawing parts of the visualization that have changed), what can I do to optimize the CPU usage of my JavaScript? I'm willing to sacrifice some amount of readability and extensibility for performance. Is there a big list I'm missing because my Google skills suck? I have some ideas but I'm not sure if they're worth it: Limit function calls When possible, use arrays instead of objects and properties Use variables for math operation results as much as possible Cache common math operations such as Math.PI / 180 Use sin and cos approximation functions instead of Math.sin() and Math.cos() Reuse objects when passing around data instead of creating new ones Replace Math.abs() with ~~ Study jsperf.com until my eyes bleed Use a preprocessor on my JavaScript to do some of the above operations

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• Oracle global_names DELETE problem

  - by jyzuz

  I'm using a database link to execute a DELETE statement on another DB, but the DB link name doesn't conform to global naming, and this requirement cannot change. Also I have global_names set to false, and cannot be changed either. When I try to use these links however, I receive: ORA-02069: - global_names parameter must be set to TRUE for this operation Cause: A remote mapping of the statement is required but cannot be achieved because GLOBAL_NAMES should be set to TRUE for it to be achieved. - Action: Issue `ALTER SESSION SET GLOBAL_NAMES = TRUE` (if possible) What is the alternative action when setting global_names=true is not possible? Cheers, Jean

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• Is this the best way to get the size of a Paper via CUPS?

  - by Lawrence Johnston

  I've got a CUPS job control file. I need to get the actual dimensions of the print that was made. This is the way I've figure out to do it: Get the paper name using the media attribute. (e.g. Letter) Get the printer uri from the printer-uri attribute. (e.g. ipp://localhost/printers/MyPrinter) Get the printer name by passing the printer uri to the IPP_GET_PRINTER_ATTRIBUTES operation and getting the printer-name attribute. (e.g. MyPrinter) Get the path to the PPD passing the printer name to the the cupsGetPPD method. Open the PPD passing the path to the PPD to the ppdOpenFile method. Get the paper size by passing the PPD and paper name to the ppdPageSize method. This will work, but it seems a bit roundabout. Is there a more efficient way of getting what I need?

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