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• How to convert Vector Layer coordinates into Map Latitude and Longitude in Openlayers.

  - by Jenny

  I'm pretty confused. I have a point: x= -12669114.702301 y= 5561132.6760608 That I got from drawing a square on a vector layer with the DrawFeature controller. The numbers seem...erm...awfull large, but they seem to work, because if I later draw a square with all the same points, it's in the same position, so I figure they have to be right. The problem is when I try to convert this point to latitude and longitude. I'm using: map.getLonLatFromPixel(pointToPixel(points[0])); Where points[0] is a geometry Point, and the pointToPixel function takes any point and turns it into a pixel (since the getLonLatFromPixel needs a pixel). It does this by simply taking the point's x, and making it the pixels x, and so on. The latitude and longitude I get is on the order of: lat: -54402718463.864 lng: -18771380.353223 This is very clearly wrong. I'm left really confused. I try projecting this object, using: .transform(new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject()); But I don't really get it and am pretty sure I did it incorrectly, anyways. My code is here: http://pastie.org/909644 I'm sort of at a loss. The coordinates seem consistent, because I can reuse them to get the same result...but they seem way larger than any of the examples I'm seeing on the openLayers website...

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• could not execute a stored procedure(using DAAB) from a client(aspx page) to a wcf service

  - by user1144695

  i am trying to store data to sql database from a asp.net client website through a stored procedure(using DAAB) in a wcf service hosted in a asp.net empty website.When i try to store data to the DB i get the following error: ** - The server was unable to process the request due to an internal error. For more information about the error, either turn on IncludeExceptionDetailInFaults (either from ServiceBehaviorAttribute or from the <serviceDebug> configuration behavior) on the server in order to send the exception information back to the client, or turn on tracing as per the Microsoft .NET Framework SDK documentation and inspect the server trace logs. ** When i try to debug i get the following exception: Activation error occured while trying to get instance of type Database, key "" in the code-- Database db = EnterpriseLibraryContainer.Current.GetInstance<Database>("MyInstance"); where my app.config is <?xml version="1.0"?> <configuration> <configSections> <section name="dataConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Data.Configuration.DatabaseSettings, Microsoft.Practices.EnterpriseLibrary.Data, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="true"/> </configSections> <dataConfiguration defaultDatabase="MyInstance"/> <connectionStrings> <add name="MyInstance" connectionString="Data Source=BLRKDAS307581\KD;Integrated Security=True;User ID=SAPIENT\kdas3;Password=ilove0LINUX" providerName="System.Data.SqlClient" /> </connectionStrings> <startup> <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/> </startup> </configuration> Can anyone help me with it? Thanks in advance...

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• In Silverlight, what structures, aside of the ListBox, can be used for binding?

  - by Aidenn

  I need to simply provide the content of a property to a custom User Control in Silverlight. My control is something like this: <UserControl x:Class="SilverlightApplication.Header" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" d:DesignWidth="300" d:DesignHeight="120"> <Grid x:Name="Header_Layout"> <StackPanel x:Name="hiHeaderContent" Width="Auto" Margin="73,8,8,8"> <TextBlock x:Name="User:" Text="{Binding name}" /> </StackPanel> </Grid> I try to use this User Control from another control where I try to pass the parameter "name" to the previous UserControl ("Header"). I don't need to create a "ListBox" as I will only have 1 header, so I try to avoid doing: <ListBox x:Name="HeaderListBox" Grid.Row="0"> <ListBox.ItemTemplate> <DataTemplate> <SilverlightApplication:Header/> </DataTemplate> </ListBox.ItemTemplate> </ListBox> in order to send the "User" account using: HeaderListBox.ItemsSource = name; Is there any other structure I can use instead of the ListBox to pass the parameter just once? It won't be a list, it's just a header... Thank you!

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• Adding a ActionPerformed Array to a String Array

  - by user267490

  Hey, Before you guys ask, yes I've searched online for the answer, but everything I found just leaves a lil confuse and nothing is recent so asking in those forums won't really help. My problems is this: I have an array that holds my name for a menu. String[] fontColor = new String[] {"Red", "Blue", "Green"}; for (int i = 0; i < fontColors.length; i++) { JMenuItem fontC = new JMenuItem(fontColors[i]); fontC.addActionListener(new fontColorAction()); changeFontColor.add(fontC); } Then I have an array that holds my color change in a class called fontColorAction in that class I have another array that does the same thing as my string array except all thats in the statement is textarea.setForeground(colorArr[i]); that will set the setForeground() in order, but now how do I successfully attact the action listner in my class to my menuItems? my class looks like this private class fontColorAction implements ActionListener { Color[] colorArr - new Color[] {"Color.RED","Color.BLUE","Color.GREEN"}; public void actionPerformed(ActionEvent e){ for(i = 0; i < collorArr.length; i++){ textarea.setForeground(colorArr[i]); } } }

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• Create unique identifier for different row-groups

  - by Max van der Heijden

  I want to number certain combinations of row in a dataframe (which is ordered on ID and on Time) tc <- textConnection(' id time end_yn number abc 10 0 1 abc 11 0 2 abc 12 1 3 abc 13 0 1 def 10 0 1 def 15 1 2 def 16 0 1 def 17 0 2 def 18 1 3 ') test <- read.table(tc, header=TRUE) The goal is to create a new column ("journey_nr") that give a unique number to each row based on the journey it belongs to. Journeys are defined as a sequence of rows per id up until to end_yn == 1, also if end_ynnever becomes 1, the journey should also be numbered (see the expected outcome example). It is only possible to have end_yn == 0 journeys at the end of a collection of rows for an ID (as shown at row 4 for id 3). So either no end_yn == 1 has occured for that ID or that happened before the end_yn == 0-journey (see id == abc in the example). I know how to number using the data.table package, but I do not know which columns to combine in order to get the expected outcome. I've searched the data.table-tag on SO, but could not find a similar problem. Expected outcome: id time end_yn number journey abc 10 0 1 1 abc 11 0 2 1 abc 12 1 3 1 abc 13 0 1 2 def 10 0 1 3 def 15 1 2 3 def 16 0 1 4 def 17 0 2 4 def 18 1 3 4

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• C++ Declaring an enum within a class

  - by bporter

  In the following code snippet, the Color enum is declared within the Car class in order to limit the scope of the enum and to try not to "pollute" the global namespace. class Car { public: enum Color { RED, BLUE, WHITE }; void SetColor( Car::Color color ) { _color = color; } Car::Color GetColor() const { return _color; } private: Car::Color _color; }; (1) Is this a good way to limit the scope of the Color enum? Or, should I declare it outside of the Car class, but possibly within its own namespace or struct? I just came across this article today, which advocates the latter and discusses some nice points about enums: http://gamesfromwithin.com/stupid-c-tricks-2-better-enums. (2) In this example, when working within the class, is it best to code the enum as Car::Color, or would just Color suffice? (I assume the former is better, just in case there is another Color enum declared in the global namespace. That way, at least, we are explicit about the enum to we are referring.) Thanks in advance for any input on this.

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• Composing adaptors in Boost::range

  - by bruno nery

  I started playing with Boost::Range in order to have a pipeline of lazy transforms in C++]1. My problem now is how to split a pipeline in smaller parts. Suppose I have: int main(){ auto map = boost::adaptors::transformed; // shorten the name auto sink = generate(1) | map([](int x){ return 2*x; }) | map([](int x){ return x+1; }) | map([](int x){ return 3*x; }); for(auto i : sink) std::cout << i << "\n"; } And I want to replace the first two maps with a magic_transform, i.e.: int main(){ auto map = boost::adaptors::transformed; // shorten the name auto sink = generate(1) | magic_transform() | map([](int x){ return 3*x; }); for(auto i : sink) std::cout << i << "\n"; } How would one write magic_transform? I looked up Boost::Range's documentation, but I can't get a good grasp of it.

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• MySQL query paralyzes site

  - by nute

  Once in a while, at random intervals, our website gets completely paralyzed. Looking at SHOW FULL PROCESSLIST;, I've noticed that when this happens, there is a specific query that is "Copying to tmp table" for a loooong time (sometimes 350 seconds), and almost all the other queries are "Locked". The part I don't understand is that 90% of the time, this query runs fine. I see it going through in the process list and it finishes pretty quickly most of the time. This query is being called by an ajax call on our homepage to display product recommendations based your browsing history (a la amazon). Just sometimes, randomly (but too often), it gets stuck at "copying to tmp table". Here is a caught instance of the query that was up 109 seconds when I looked: SELECT DISTINCT product_product.id, product_product.name, product_product.retailprice, product_product.imageurl, product_product.thumbnailurl, product_product.msrp FROM product_product, product_xref, product_viewhistory WHERE ( (product_viewhistory.productId = product_xref.product_id_1 AND product_xref.product_id_2 = product_product.id) OR (product_viewhistory.productId = product_xref.product_id_2 AND product_xref.product_id_1 = product_product.id) ) AND product_product.outofstock='N' AND product_viewhistory.cookieId = '188af1efad392c2adf82' AND product_viewhistory.productId IN (24976, 25873, 26067, 26073, 44949, 16209, 70528, 69784, 75171, 75172) ORDER BY product_xref.hits DESC LIMIT 10 Of course the "cookieId" and the list of "productId" changes dynamically depending on the request. I use php with PDO.

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• Is it possible to create a null function that will not produce warnings?

  - by bbazso

  I have a logger in a c++ application that uses defines as follows: #define FINEST(...) Logger::Log(FINEST, _FILE, __LINE, __func, __VA_ARGS_) However what I would like to do is to be able to switch off these logs since they have a serious performance impact on my system. And, it's not sufficient to simply have my Logger not write to the system log. I really need to get rid of the code produced by the logs. In order to do this, I changed the define to: #define FINEST(...) Which works, but this produces a whole bunch of warning in my code since variables are unused now. So what I would like to have is a sort of NULL FUNCTION that would not actually exist, but would not produce warnings for the unused variables. So, said another way, I would like it to compile with no warnings (i.e. the compiler thinks that the variables are used for a function) but the function does not actually exist in the application (i.e. produces no performance hit). Is this possible? Thanks!

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• Reordering fields in Django model

  - by Alex Lebedev

  I want to add few fields to every model in my django application. This time it's created_at, updated_at and notes. Duplicating code for every of 20+ models seems dumb. So, I decided to use abstract base class which would add these fields. The problem is that fields inherited from abstract base class come first in the field list in admin. Declaring field order for every ModelAdmin class is not an option, it's even more duplicate code than with manual field declaration. In my final solution, I modified model constructor to reorder fields in _meta before creating new instance: class MyModel(models.Model): # Service fields notes = my_fields.NotesField() created_at = models.DateTimeField(auto_now_add=True) updated_at = models.DateTimeField(auto_now=True) class Meta: abstract = True last_fields = ("notes", "created_at", "updated_at") def __init__(self, *args, **kwargs): new_order = [f.name for f in self._meta.fields] for field in self.last_fields: new_order.remove(field) new_order.append(field) self._meta._field_name_cache.sort(key=lambda x: new_order.index(x.name)) super(TwangooModel, self).__init__(*args, **kwargs) class ModelA(MyModel): field1 = models.CharField() field2 = models.CharField() #etc ... It works as intended, but I'm wondering, is there a better way to acheive my goal?

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• Where to add an overloaded operator for the tr1::array?

  - by phlipsy

  Since I need to add an operator& for the std::tr1::array<bool, N> I wrote the following lines template<std::size_t N> std::tr1::array<bool, N> operator& (const std::tr1::array<bool, N>& a, const std::tr1::array<bool, N>& b) { std::tr1::array<bool, N> result; std::transform(a.begin(), a.end(), b.begin(), result.begin(), std::logical_and<bool>()); return result; } Now I don't know in which namespace I've to put this function. I considered the std namespace as a restricted area. Only total specialization and overloaded function templates are allowed to be added by the user. Putting it into the global namespace isn't "allowed" either in order to prevent pollution of the global namespace and clashes with other declarations. And finally putting this function into the namespace of the project doesn't work since the compiler won't find it there. What had I best do? I don't want to write a new array class putted into the project namespace. Because in this case the compiler would find the right namespace via argument dependent name lookup. Or is this the only possible way because writing a new operator for existing classes means extending their interfaces and this isn't allowed either for standard classes?

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• How do I tell whether my IE is 64-bit? (For that matter, Java too?)

  - by user225626

  Millions of questions already on the web about how to tell whether the OS is 64-bit, but not whether IE and/or Java runtime is 64-bit. Some background: I installed 64-bit Win 7, and IE installed automatically with it from CD; I didn't download IE. I did download Java runtime. Mouseover tips in Control Panel!Programs shows it as: "Java 32-bit Java(TM) Control Panel" Then I went to http://java.com/en/download/manual.jsp and that page says... We have detected you may be viewing this page in a 32-bit browser. If you use 32-bit and 64-bit browsers interchangeably, you will need to install both 32-bit and 64-bit Java in order to have the Java plug-in for both browsers. But I cannot tell in the aftermath whether my Java is 64-bit. Evidently the "Java(TM) Control Panel" is, but I don't know if that's the same as the runtime. (I'm afraid to ask on the offical Java forums, because they're such a-holes.) Also, How do I issue a command to the OS to tell whether this IE is 64-bit? Help!About doesn't say on that. Thanks.

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• mySQL select and group by values

  - by Foo

  I'd like to count and group rows by specific values. This seems fairly simple, but I can't seem to do it. I have a table set up similar to this: Table: Ratings id pID uID rating 1 1 2 7 2 1 7 7 3 1 5 4 4 1 1 1 id is the primary key, piD and uID are foreign-keys. Rating contains values between 1 and 10, and only between 1 and 10. I want to run some statistics and count the number of ratings with a certain value. In the example above, two have left a rating of 7. So I wrote the following query: SELECT COUNT(*) AS 'count' , 'rating' FROM 'ratings' WHERE pID= '1' GROUP BY `rating` ORDER BY `rating` Which yields the nice result as: count ratings 1 1 1 4 2 7 I'd like to get the mySQL query to include values between 1 and 10 as well. For example: Desired Result count ratings 1 1 0 2 0 3 1 4 0 5 0 6 2 7 0 8 0 9 0 10 Unfortunately, I'm relatively new to SQL and I've been reading through everything I could get my hands on for the past hour, but I can't get it to work. I've been leaning along the lines of a some type of JOIN. If anyone can point me in the right direction, it'd be appreciated. Thanks.

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• C++ and Dependency Injection in unit testing

  - by lhumongous

  Suppose I have a C++ class like so: class A { public: A() { } void SetNewB( const B& _b ) { m_B = _b; } private: B m_B; } In order to unit test something like this, I would have to break A's dependency on B. Since class A holds onto an actual object and not a pointer, I would have to refactor this code to take a pointer. Additionally, I would need to create a parent interface class for B so I can pass in my own fake of B when I test SetNewB. In this case, doesn't unit testing with dependency injection further complicate the existing code? If I make B a pointer, I'm now introducing heap allocation, and some piece of code is now responsible for cleaning it up (unless I use ref counted pointers). Additionally, if B is a rather trivial class with only a couple of member variables and functions, why introduce a whole new interface for it instead of just testing with an instance of B? I suppose you could make the argument that it would be easier to refactor A by using an interface. But are there some cases where two classes might need to be tightly coupled?

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• How reference popup object when opener page changes?

  - by achairapart

  This is driving me crazy! Scenario: The main page opens a pop-up window and later calls a function in it: newWin = window.open(someurl,'newWin',options); ...some code later... newWin.remoteFunction(options); and it's ok. Now, popup is still open and Main Page changes to Page 2. In Page 2 newWin doesn't exist anymore and I need to recreate the popup window object reference in order to call again the remote function (newWin.remoteFunction) I tried something like: newWin = open('','newWin', options); if (!newWin || newWin.closed || !newWin.remoteFunction) { newWin = window.open(someurl,'newWin',options); } And it works, I can call newWin.remoteFunction again BUT Safari for some reason gives Focus() to the popup window everytime the open() method is called breaking the navigation (I absolutely need the popup working in the background). Only workaround I can think to solve this is to create an interval in the popup with: if(window.opener && !window.opener.newWin) window.opener.newWin = self; and then set another interval in the opener Page with some try/catch but it is inelegant and very inefficient. so, I wonder, it's really so hard to get the popup object reference between different pages in the opener window?

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• Android: How to periodically check current location without draining the battery

  - by uyahalom

  I have a background service which works periodically by timer.scheduleAtFixedRate. It wakes up every amount of time (let's say 60 seconds for example) and checks for the location. The location is checked by locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 60000, 5, listener); and the actual location is collected from the listener's onLocationChanged. Now, when the phone is outside and GPS reception is good, this works fine. But, if the phone is inside, the GPS is almost always active - looking for a signal, and the battery is drained rapidly. I created another thread using a Handler and a Runnable in order to conrol the GPS active time accurately: I used locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, listener); and locManager.removeUpdates(listener); so I can open and close the GPS as I want. In this case, I can open the GPS for the exact amount of time, but found out that it doesn't lock in an area with good reception even after 10 seconds. So here I'm draining the battery again... I'm using API level 7, hence I cannot use locationManager.requestSingleUpdate. I have two questions: Is there any way to optimize this process? Will upgrading to API level 9 (and use locationManager.requestSingleUpdate) improve the process significantly? I mean, does it worth upgrading?

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• How to do this in a smart way

  - by Azzyh

  Hello SO. My websystem im coding with now is integrated from the originally phpBB system. With this i mean when you log on my websystem, you have actually logged into the forum from the login page. Now i came to the "log out" part, and i want to make it smart. Right now its a simply link with logout: <a href="<?php echo BASEDIR; ?>../../ucp.php?mode=logout&sid=<? echo $user->data['session_id']; ?>" style="margin-left: 14px; font-size: 10px;">- Log Out</a> As you see in the link it refers to the forum´s ucp.php?mode=logout, and you need to have the SID variable in it in order to log out right.. anyway.. I want to do this log out part in a smart way, i mean, not so you land on the forum´s "you have now been logged out", i want something maybe like run this page in background when you click, and then it refreshes the current page your on. Or should it be smarter just try to modify the phpbb file ucp.php? I think its hard coded, and not the way I am coding, so thats why i find it abit tricky. Thank you for your answers and examples on how this could be done, in a smart way..

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• iOS - is it possible to cache CGContextDrawImage?

  - by woot586

  I used the timing profile tool to identify that 95% of the time is spent calling the function CGContextDrawImage. In my app there are a lot of duplicate images repeatably being chopped from a sprite map and drawn to the screen. I was wondering if it was possible to cache the output of CGContextDrawImage in an NSMutableDictionay, then if the same sprite is requested again it can be just pull it from the cache rather than doing all the work of clipping and rendering it again. This is what i’ve got but I have not been to successful: Definitions if(cache == NULL) cache = [[NSMutableDictionary alloc]init]; //Identifier based on the name of the sprite and location within the sprite. NSString* identifier = [NSString stringWithFormat:@"%@-%d",filename,frame]; Adding to cache CGRect clippedRect = CGRectMake(0, 0, clipRect.size.width, clipRect.size.height); CGContextClipToRect( context, clippedRect); //create a rect equivalent to the full size of the image //offset the rect by the X and Y we want to start the crop //from in order to cut off anything before them CGRect drawRect = CGRectMake(clipRect.origin.x * -1, clipRect.origin.y * -1, atlas.size.width, atlas.size.height); //draw the image to our clipped context using our offset rect CGContextDrawImage(context, drawRect, atlas.CGImage); [cache setValue:UIGraphicsGetImageFromCurrentImageContext() forKey:identifier]; UIGraphicsEndImageContext(); Rendering a cached sprite There is probably a better way to render CGImage which is my ultimate caching goal but at the moment I’m just looking to successfully render the cached image out however this has not been successful. UIImage* cachedImage = [cache objectForKey:identifier]; if(cachedImage){ NSLog(@"Cached %@",identifier); CGRect imageRect = CGRectMake(0, 0, cachedImage.size.width, cachedImage.size.height); if (NULL != UIGraphicsBeginImageContextWithOptions) UIGraphicsBeginImageContextWithOptions(imageRect.size, NO, 0); else UIGraphicsBeginImageContext(imageRect.size); //Use draw for now just to see if the image renders out ok CGContextDrawImage(context, imageRect, cachedImage.CGImage); UIGraphicsEndImageContext(); }

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• Tree iterator, can you optimize this any further?

  - by Ron

  As a follow up to my original question about a small piece of this code I decided to ask a follow up to see if you can do better then what we came up with so far. The code below iterates over a binary tree (left/right = child/next ). I do believe there is room for one less conditional in here (the down boolean). The fastest answer wins! The cnt statement can be multiple statements so lets make sure this appears only once The child() and next() member functions are about 30x as slow as the hasChild() and hasNext() operations. Keep it iterative <-- dropped this requirement as the recursive solution presented was faster. This is C++ code visit order of the nodes must stay as they are in the example below. ( hit parents first then the children then the 'next' nodes). BaseNodePtr is a boost::shared_ptr as thus assignments are slow, avoid any temporary BaseNodePtr variables. Currently this code takes 5897ms to visit 62200000 nodes in a test tree, calling this function 200,000 times. void processTree (BaseNodePtr current, unsigned int & cnt ) { bool down = true; while ( true ) { if ( down ) { while (true) { cnt++; // this can/will be multiple statesments if (!current->hasChild()) break; current = current->child(); } } if ( current->hasNext() ) { down = true; current = current->next(); } else { down = false; current = current->parent(); if (!current) return; // done. } } }

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• Anything wrong with this MySQL quert? takes 10 seconds+ to load

  - by user345426

  I have a search that is taking 10 seconds+ to execute! Keep in mind it is also searching over 200,000 products in the database. I posted the explain and MySQL query here. 1 SIMPLE p ref PRIMARY,products_status,prod_prodid_status,product... products_status 1 const 9048 Using where; Using temporary; Using filesort 1 SIMPLE v ref PRIMARY,vendors_id,vendors_vendorid vendors_vendorid 4 rhinomar_rhinomartnew.p.vendors_id 1 1 SIMPLE s ref products_id products_id 4 rhinomar_rhinomartnew.p.products_id 1 1 SIMPLE pd ref PRIMARY,products,prod_desc_prodid_prodname prod_desc_prodid_prodname 4 rhinomar_rhinomartnew.p.products_id 1 1 SIMPLE p2c ref PRIMARY,ptc_catidx PRIMARY 4 rhinomar_rhinomartnew.p.products_id 1 Using where; Using index 1 SIMPLE c eq_ref PRIMARY PRIMARY 4 rhinomar_rhinomartnew.p2c.categories_id 1 Using where MySQL Query: select p.products_id, p.products_image, p.products_price, p.products_weight, p.products_unit_quantity, s.specials_new_products_price, s.status, pd.products_name, pd.products_img_alt from products p left join vendors v ON v.vendors_id = p.vendors_id left join specials s on s.products_id = p.products_id left join products_description pd on pd.products_id = p.products_id left join products_to_categories p2c on p2c.products_id = p.products_id left join categories c on c.categories_id = p2c.categories_id where ( ( pd.products_name like '%apparel%' ) or p2c.categories_id IN (773, 132, 135, 136, 119, 122, 124, 125, 126, 1749, 1753, 1747, 123, 127, 130, 131, 178, 137, 140, 164, 165, 166, 167, 168, 169, 832, 2045 ) or p.products_id = 'apparel' or p.products_model = 'apparel' or CONCAT(v.vendors_prefix, '-') = 'apparel' or CONCAT( v.vendors_prefix, '-', p.products_id ) = 'apparel' ) and p.products_status = '1' and c.categories_status = '1' group by p.products_id order by pd.products_name

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• Stable/repeatable random sort (MySQL, Rails)

  - by Matt Rogish

  I'd like to paginate through a randomly sorted list of ActiveRecord models (rows from MySQL database). However, this randomization needs to persist on a per-session basis, so that other people that visit the website also receive a random, paginate-able list of records. Let's say there are enough entities (tens of thousands) that storing the randomly sorted ID values in either the session or a cookie is too large, so I must temporarily persist it in some other way (MySQL, file, etc.). Initially I thought I could create a function based on the session ID and the page ID (returning the object IDs for that page) however since the object ID values in MySQL are not sequential (there are gaps), that seemed to fall apart as I was poking at it. The nice thing is that it would require no/minimal storage but the downsides are that it is likely pretty complex to implement and probably CPU intensive. My feeling is I should create an intersection table, something like: random_sorts( sort_id, created_at, user_id NULL if guest) random_sort_items( sort_id, item_id, position ) And then simply store the 'sort_id' in the session. Then, I can paginate the random_sorts WHERE sort_id = n ORDER BY position LIMIT... as usual. Of course, I'd have to put some sort of a reaper in there to remove them after some period of inactivity (based on random_sorts.created_at). Unfortunately, I'd have to invalidate the sort as new objects were created (and/or old objects being removed, although deletion is very rare). And, as load increases the size/performance of this table (even properly indexed) drops. It seems like this ought to be a solved problem but I can't find any rails plugins that do this... Any ideas? Thanks!!

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• Indexing table with duplicates MySQL/MSSQL with millions of records

  - by Tesnep

  I need help in indexing in MySQL. I have a table in MySQL with following rows: ID Store_ID Feature_ID Order_ID Viewed_Date Deal_ID IsTrial The ID is auto generated. Store_ID goes from 1 - 8. Feature_ID from 1 - let's say 100. Viewed Date is Date and time on which the data is inserted. IsTrial is either 0 or 1. You can ignore Order_ID and Deal_ID from this discussion. There are millions of data in the table and we have a reporting backend that needs to view the number of views in a certain period or overall where trial is 0 for a particular store id and for a particular feature. The query takes the form of: select count(viewed_date) from theTable where viewed_date between '2009-12-01' and '2010-12-31' and store_id = '2' and feature_id = '12' and Istrial = 0 In MSSQL you can have a filtered index to use for Istrial. Is there anything similar to this in MySQL? Also, Store_ID and Feature_ID have a lot of duplicate data. I created an index using Store_ID and Feature_ID. Although this seems to have decreased the search period, I need better improvement than this. Right now I have more than 4 million rows. To search for a particular query like the one above, it looks at 3.5 million rows in order to give me the count of 500k rows. PS. I forgot to add view_date filter in the query. Now I have done this.

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• INotifyPropertyChanged Setter Style

  - by Ivovic

  In order to reflect changes in your data to the UI you have to implement INotifyPropertyChanged, okay. If I look at examples, articles, tutorials etc most of the time the setters look like something in that manner: public string MyProperty { //get [...] set { if (_correspondingField == value) { return; } _correspondingField = value; OnPropertyChanged("MyProperty"); } } No problem so far, only raise the event if you have to, cool. But you could rewrite this code to this: public string MyProperty { //get [...] set { if (_correspondingField != value) { _correspondingField = value; OnPropertyChanged("MyProperty"); } } } It should do the same (?), you only have one place of return, it is less code, it is less boring code and it is more to the point ("only act if necessary" vs "if not necessary do nothing, the other way round act"). So if the second version has its pros compared to the first one, why I see this style rarely? I don't consider myself being smarter than those people that write frameworks, published articles etc, therefore the second version has to have drawbacks. Or is it wrong? Or do I think too much? Thanks in advance

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• formatting mysql data for ouptut into a table

  - by bsandrabr

  Following on from a question earlier today this answer was given to read the data into an array and separate it to print vehicle type and then some data for each vehicle. <?php $sql = "SELECT * FROM apparatus ORDER BY vehicleType"; $getSQL = mysql_query($sql); // transform the result set: $data = array(); while ($row = mysql_fetch_assoc($getSQL)) { $data[$row['vehicleType']][] = $row; } ?> <?php foreach ($data as $type => $rows): ?> <h2><?php echo $type?></h2> <ul> <?php foreach ($rows as $vehicleData):?> <li><?php echo $vehicleData['name'];?></li> <?php endforeach ?> </ul> <?php endforeach ?> This is almost perfect for what I want to do but I need to print out two columns from the database ie ford and mondeo before going into the second foreach loop. I've tried print $rows['model'] and all the other combinations I can think of but that doesn't work. Any help much appreciated

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• Iteratively creating multiple file input fields in Rails

  - by David

  I have a column of product views in a database (e.g. top, bottom, front, back). I'm trying to generate a series of file inputs to allow the user to upload an image for each view. This is the result I'm after: ... <label>Top</label> <input type="file" name="image[Top]"><br> <label>Bottom</label> <input type="file" name="image[Bottom]"><br> <label>Front</label> <input type="file" name="image[Front']"><br> ... This is what I'm trying: <%= views = View.order('name ASC').all.map { |view| [view.name, view.id] } %> <%= views.each { |view| label(view); file_field('image', view) } %> However, all this does is print out the views array a couple of times. Hopefully you Rails experts can point me in the right direction. (I apologize in advance if I'm butchering Ruby.)

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