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  • Data aggregation mongodb vs mysql

    - by Dimitris Stefanidis
    I am currently researching on a backend to use for a project with demanding data aggregation requirements. The main project requirements are the following. Store millions of records for each user. Users might have more than 1 million entries per year so even with 100 users we are talking about 100 million entries per year. Data aggregation on those entries must be performed on the fly. The users need to be able to filter on the entries by a ton of available filters and then present summaries (totals , averages e.t.c) and graphs on the results. Obviously I cannot precalculate any of the aggregation results because the filter combinations (and thus the result sets) are huge. Users are going to have access on their own data only but it would be nice if anonymous stats could be calculated for all the data. The data is going to be most of the time in batch. e.g the user will upload the data every day and it could like 3000 records. In some later version there could be automated programs that upload every few minutes in smaller batches of 100 items for example. I made a simple test of creating a table with 1 million rows and performing a simple sum of 1 column both in mongodb and in mysql and the performance difference was huge. I do not remember the exact numbers but it was something like mysql = 200ms , mongodb = 20 sec. I have also made the test with couchdb and had much worse results. What seems promising speed wise is cassandra which I was very enthusiastic about when I first discovered it. However the documentation is scarce and I haven't found any solid examples on how to perform sums and other aggregate functions on the data. Is that possible ? As it seems from my test (Maybe I have done something wrong) with the current performance its impossible to use mongodb for such a project although the automated sharding functionality seems like a perfect fit for it. Does anybody have experience with data aggregation in mongodb or have any insights that might be of help for the implementation of the project ? Thanks, Dimitris

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  • How to change the cursor type

    - by Jessy
    This question is related to the previous post. http://stackoverflow.com/questions/2532936/how-to-save-file-and-read How can I change the cursor to "Hand" only when the mouse pointed on grid which is not Null (contained images)? So far the cursor turn to "Hand" all over the grids (null or not null). public GUI() { .... JPanel pDraw = new JPanel(); .... for(Component component: pDraw.getComponents()){ JLabel lbl = (JLabel)component; //add mouse listener to grid box which contained image if (lbl.getIcon() != null) lbl.addMouseListener(this); } public void mouseEntered(MouseEvent e) { Cursor cursor = Cursor.getDefaultCursor(); //change cursor appearance to HAND_CURSOR when the mouse pointed on images cursor = Cursor.getPredefinedCursor(Cursor.HAND_CURSOR); setCursor(cursor); }

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  • PHP scripts owned by www-data

    - by matnagel
    I am always running php scripts on a dedicated server as user "webroot". It would be easier for coding and administration if the scripts were owned by www-data, the apache2 user. Also feels more simple and clean. There is no ftp on this box and there are no other users or sites. Why not have the php scripts owned by www-data? If there is anything against it, what is the worst that can happen?

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  • XMLReader in silverlight <test /> type tag problem

    - by Ummar
    Hi I am parsing XML in silverlight, in my XML I have one tag is like <test attribute1="123" /> <test1 attribute2="345">abc text</test1> I am using XMLReader to parse xml like using (XmlReader reader = XmlReader.Create(new StringReader(xmlString))) { // Parse the file and display each of the nodes. while (reader.Read()) { switch (reader.NodeType) { case XmlNodeType.Element: //process start tag here break; case XmlNodeType.Text: //process text here break; case XmlNodeType.XmlDeclaration: case XmlNodeType.ProcessingInstruction: break; case XmlNodeType.Comment: break; case XmlNodeType.EndElement: //process end tag here break; } } } but the problem is that for test tag no EndElement is received? which is making my whole program logic wrong. (for test1 tag all works fine). Please help me out.

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  • XmlSchemaElement type

    - by user305287
    Hi, I'm generating WSDL of my web service dynamically, but when I set the XmlSchemaType of my elements, the ServiceDescriptor writes the element as an element rather than message, as I need. The code looks like this: XmlSchemaElement schemaElement = new XmlSchemaElement(); XmlSchemaComplexType complexType = new XmlSchemaComplexType(); XmlSchemaSequence sequence = new XmlSchemaSequence(); foreach (XmlSchemaComplexElementParameter param in element.Parameters) { XmlSchemaElement paramElement = new XmlSchemaElement(); paramElement.Name = param.ParameterName; paramElement.SchemaTypeName = new XmlQualifiedName(param.ParameterType, "http://www.w3.org/2001/XMLSchema"); paramElement.MaxOccurs = param.MaxOccurs; paramElement.MinOccurs = param.MinOccurs; sequence.Items.Add(paramElement); } complexType.Particle = sequence; schemaElement.Name = element.MessageName; schemaElement.SchemaType = complexType; Any ideas about this?

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  • Java: matching two different type of array

    - by sling
    Hi, I am doing a password login that requires me to match two array: User and Pass. If user key in "mark" and "pass", it should show successfully. However I have trouble with the String[] input = pass.getPassword(); and the matching of the two arrays. String[] User = {"mark", "susan", "bobo"}; String[] Pass = {"pass", "word", "password"}; String[] input = pass.getPassword(); if(Pass.length == input.length && user.getText().equals(User)) { lblstat.setForeground(Color.GREEN); lblstat.setText("Successful"); } else { lblstat.setForeground(Color.RED); lblstat.setText("Failed"); }

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  • How to group data changes by operation with MySQL triggers

    - by Jan-Henk
    I am using triggers in MySQL to log changes to the data. These changes are recorded on a row level. I can now insert an entry in my log table for each row that is changed. However, I also need to record the operation to which the changes belong. For example, a delete operation like "DELETE * FROM table WHERE type=x" can delete multiple rows. With the trigger I can insert an entry for each deleted row into the log table, but I would like to also provide a unique identifier for the operation as a whole, so that the log table looks something like: log_id operation_id tablename fieldname oldvalue newvalue 1 1 table id 1 null 2 1 table type a null 3 1 table id 2 null 4 1 table type a null 5 2 table id 3 null 6 2 table type b null 7 2 table id 4 null 8 2 table type b null Is there a way in MySQL to identify the higher level operation to which the row changes belong? Or is this only possible by means of application level code? In the future it would also be nice to be able to record the transaction to which an operation belongs. Another question is if it is possible to capture the actual SQL query, besides using the query log. I don't think so myself, but maybe I am missing something. It is of course possible to capture these at the application level, but the goal is to keep intrusions to the application level code as minimal as possible. When this is not possible with MySQL, how is this with other database systems? For the current project it is not an option to use something other than MySQL, but it would be nice to know for future projects.

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  • Is this way of storing typed objects in memory good?

    - by Pindatjuh
    This is an "is this okay, or can it be done better" question. Topic: Storing typed objects in memory. Background information: I'm building a compiler for the x86-32 platform for my language. My goal includes typed objects. Idea: Every primitive is a semi-class (it can be used as if it was a normal class, but it's stored more compact). Every class is represented by primitives and some meta-data (containing class-properties, inheritance stuff, etc.). The meta-data is complex: it doesn't use fields but instead context-switches. For primitives, the meta-data is very small, compared to a "real" class, which is alot bigger. This enables another idea that "primitives are objects", in my language, which I found nessecairy. Example: If I have an array of 32 booleans, then the pure content of this array is exactly 4 byte (32 bits of booleans). The meta-data will contain flags that the type is an array of booleans, which contains 32 entries. The meta-data is very compacted, on bit-level: using a sort of "packing" mechanism, which is read by a FSM at runtime, when doing inspection of the type (like when passing the object to methods for checking, etc.) For instance (read from left to right, top to bottom, remember vertical possition when going to the right, and check nearest column header for meaning of switch): Primitive? Array? Type-Meta 1 Byte? || Size (1 byte) 1 1 [...] 1 [...] done 0 2 Bytes? || Size (2 bytes) 1 [...] done || Size (4 bytes) 0 [...] done Integer? 1 Byte? 2 Bytes? 0 1 0 1 done 1 done 0 done Boolean? Byte? 0 1 0 done 1 done More-Primitives 0 .... Class-Stuff (Huge) 0 ... (After reaching done the data is inserted. || = byte alignement. [...] is variable sized. ... is not described here, for simplicity. And let's call them cost-based-data-structures.) For an array of 32 booleans containing all true values, the memory for this type would be (read top-down): 1 Primitive 1 Array 1 ArrayType: Primitive 0 Not-Array 0 Not-Integer 1 Boolean 0 Not-Byte (thus bit) 1 Integer Size: 1 Byte 00100000 Array size 11111111 11111111 11111111 11111111 Data Thus, 8 bytes represent 32 booleans in an array: 11100101 00100000 11111111 11111111 11111111 11111111 Is this okay, or can it be done better?

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  • pdf errors with php, apache2

    - by julio
    Hi-- I'm seeing some strange behavior from some dynamically generated PDFs using the TCPDF library in PHP. Standard lamp stack-- however, if you try to open the PDF from Windows with Acrobat Reader, it gives an error that the "file is damaged and could not be repaired". From Mac, Linux, etc. the file works fine, and opens fine. It also opens fine in Google Docs-- so clearly the PDF itself is ok. Is it possible that the mime type (application/pdf) is causing problems in Windows? Thanks

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  • IValidator.Validate method and adding error message to a custom type

    - by user102533
    I have several server controls that implement the IValidator interface. As such, they have their own Validate() methods that look like this. public void Validate() { this.IsValid = true; if (someConditionFails()) { ErrorMessage = "Condition failed!"; this.IsValid = false; } } I understand that these Validate() methods are executed on postback before the load completed event that is executed before the save button's event handler. What I would like to do is pass in a reference to an instance of a custom class that collects all the error messages that I can access from Save button event handler. In other words, I would like to do something like this: public void Validate(ref SummaryOfErrorMessages sum) I guess I can't do this as the signature is different from what the IValidator interface has. The other option I can think of is on Load Completed event, I would iterate through all the validators on page, get the ones with IsValid = false and create my SummaryOfErrorMessages there. Does this sound right? Is there a better way of doing it?

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  • Deserializing a type at the current stream position with protobuf-net

    - by Arne Claassen
    I'm serializing several objects into a single stream, but when i try to read them back, i can't seem to get anything but the last object: ProtoBuf.Serializer.Serialize(stream, postA1); ProtoBuf.Serializer.Serialize(stream, postB2); stream.Position = 0; var postA2 = ProtoBuf.Serializer.Deserialize<Post>(stream); var postB2 = ProtoBuf.Serializer.Deserialize<Post>(stream); The first deserialize moves the stream to the end and postA2 contains the value of postB2, while postB2 is just an uninitialized instance. Is this expected behavior, and if so, how do you deserialize an object from a random position in a stream?

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  • Migrate data from SQL Compact to SQL Server 2008

    - by Martin
    I need to do a one-time migration of data from SQL Server Compact Edition to SQL Server 2008 Express Edition. I'm looking for a tool to do this kind of migration. I've tried using Import and Export Data in SQL Server, but it doesn't let me import from SQL Server Compact Edition. Anyone knows of a easy way to do it?

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  • Better type safety in Java collections

    - by Paul Tomblin
    In my java coding, I often end up with several Map<String,Map<String,foo>> or Map<String,List<String>> and then I have trouble remembering which String is which key. I comment the declaration with //Map<capabiltyId,Map<groupId,foo>> or //Map<groupId,List<capabilityId>, but it's not the greatest solution. If String wasn't final, I would make new classes CapabilityId extends String and GroupId extends String, but I can't. Is there a better way to keep track of which thing is the key and maybe have the compiler enforce it?

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  • Generic function to handle DataType Conversion

    - by Tommo1977
    I have the following function in C#, that I want to pass a MySQL DataReader value/object. If the value of the object passed is a DBNull I need to handle it and return a Null value of that data type e.g null int. Otherwise I want to convert the returned value like Convert.ToInt32(value) or similar. public static T ConvertFromDB<T>(object value) { return value == DBNull.Value ? default(T) : (T)value; } Can anyone offer any help on this ?

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  • jquery to check if returned data object is empty

    - by user253530
    $("#post").live("click",function() { $("input:checkbox[name='bookmarkid']:checked").each(function() { $.post("php/socialbookmark-post.php", {bookmarkID: $(this).val()},function(data) { if(data != "") alert(data); }); }); }); the php file outputs some text only if something goes wrong. The checking that I do fails if the data is empty and displays an empty message. I need to fix this. Any ideas?

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  • Castle Windsor - Resolving a generic implementation to a base type

    - by arootbeer
    I'm trying to use Windsor as a factory to provide specification implementations based on subtypes of XAbstractBase (an abstract message base class in my case). I have code like the following: public abstract class XAbstractBase { } public class YImplementation : XAbstractBase { } public class ZImplementation : XAbstractBase { } public interface ISpecification<T> where T : XAbstractBase { bool PredicateLogic(); } public class DefaultSpecificationImplementation : ISpecification<XAbstractBase> { public bool PredicateLogic() { return true; } } public class SpecificSpecificationImplementation : ISpecification<YImplementation> { public bool PredicateLogic() { /*do real work*/ } } My component registration code looks like this: container.Register( AllTypes.FromAssembly(Assembly.GetExecutingAssembly()) .BasedOn(typeof(ISpecification<>)) .WithService.FirstInterface() ) This works fine when I try to resolve ISpecification<YImplementation>; it correctly resolves SpecificSpecificationImplementation. However, when I try to resolve ISpecification<ZImplementation> Windsor throws an exception: "No component for supporting the service ISpecification'1[ZImplementation, AssemblyInfo...] was found" Does Windsor support resolving generic implementations down to base classes if no more specific implementation is registered?

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  • Volatile or synchronized for primitive type?

    - by DKSRathore
    In java, assignment is atomic if the size of the variable is less that or equal to 32 bits but is not if more than 32 bits. What(volatile/synchronized) would be more efficient to use in case of double or long assignment. like, volatile double x = y; synchronized is not applicable with primitive argument. How do i use synchronized in this case. Of course I don't want to lock my class. so this should not be used.

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  • Sending most correct mimetype

    - by Roland Franssen
    Hi all, I have a list of extension to mimetype in a INI file. However some extensions have multiple mimetypes, for example; midi[] = "application/x-midi" midi[] = "audio/midi" midi[] = "audio/x-mid" midi[] = "audio/x-midi" midi[] = "music/crescendo" midi[] = "x-music/x-midi" 6 (possible) mimetypes for 1 extension. Whats common practice to determine the correct mimetype? (e.g. i need to set a HTTP content-type header). I know its not ideal; determining mimetypes based on extension.. but i need consistent (cross-server) results (e.g. fileinfo extension in PHP is making terrible guesses*). * Some fileinfo results for example; js - text/plain css - text/c-h

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  • Data Execution Prevention in Windows Live Messenger

    - by Andrija
    I keep getting "Data Execution Prevention" error in Windows Live Messenger. I have noticed that this is happening usually when I leave computer to get coffee, and screensaver comes up, WLM breaks. Is there any way to prevent this error from happening? I see I can turn off this "Data Execution Prevention", but is that safe, since I know that WLM is under heavy attacks from spammers/hackers? Thanks

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  • how do I update the date type column?

    - by Muhammad Hammad
    update answers a1 set a1.FilingDate=( select date_sub( a2.FilingDate ,Interval 1000 Year) as FilingDate from answers a2 where Year(a2.FilingDate)>=3000 ) where Year(a1.FilingDate)>=3000 but it gives me the following error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'update answers a1 set a1.FilingDate=( select date_sub(a2.FilingDate,Interval 10' at line 1 Can anyone tell me about the issue and its solution?

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  • Abstract Factory Using Generics: Is Explicitly Converting a Specified Type to Generic a Bad Practice

    - by Merritt
    The question's title says it all. I like how it fits into the rest of my code, but does it smell? public interface IFoo<T> { T Bar { get; set; } } public class StringFoo : IFoo<string> { public string Bar { get; set; } } public static class FooFactory { public static IFoo<T> CreateFoo<T>() { if (typeof(T) == typeof(string)) { return new StringFoo() as IFoo<T>; } throw new NotImplementedException(); } } UPDATE: this is sort of a duplicate of Is the StaticFactory in codecampserver a well known pattern?

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