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  • Combining aggregate functions in an (ANSI) SQL statement

    - by morpheous
    I have aggregate functions foo(), foobar(), fredstats(), barneystats() I want to create a domain specific query language (DSQL) above my DB, to facilitate using using a domain language to query the DB. The 'language' comprises of boolean expressions (or more specifically SQL like criteria) which I then 'translate' back into pure (ANSI) SQL and send to the underlying Db. The following lines are examples of what the language statements will look like, and hopefully, it will help further clarify the concept: **Example 1** DQL statement: foobar('yellow') between 1 and 3 and fredstats('weight') > 42 Translation: fetch all rows in an underlying table where computed values for aggregate function foobar() is between 1 and 3 AND computed value for AGG FUNC fredstats() is greater than 42 **Example 2** DQL statement: fredstats('weight') < barneystats('weight') AND foo('fighter') in (9,10,11) AND foobar('green') <> 42 Translation: Fetch all rows where the specified criteria matches **Example 3** DQL statement: foobar('green') / foobar('red') <> 42 Translation: Fetch all rows where the specified criteria matches **Example 4** DQL statement: foobar('green') - foobar('red') >= 42 Translation: Fetch all rows where the specified criteria matches Given the following information: The table upon which the queries above are being executed is called 'tbl' table 'tbl' has the following structure (id int, name varchar(32), weight float) The result set returns only the tbl.id, tbl.name and the names of the aggregate functions as columns in the result set - so for example the foobar() AGG FUNC column will be called foobar in the result set. So for example, the first DQL query will return a result set with the following columns: id, name, foobar, fredstats Given the above, my questions then are: What would be the underlying SQL required for Example1 ? What would be the underlying SQL required for Example3 ? Given an algebraic equation comprising of AGGREGATE functions, Is there a way of generalizing the algorithm needed to generate the required ANSI SQL statement(s)? I am using PostgreSQL as the db, but I would prefer to use ANSI SQL wherever possible.

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  • Strangely structured xml code finding last value of a certain type using java

    - by Damien.Bell
    Thus the structure is something like this: OasisReportMessagePayloadRTOReport_ItemReport_Data Under report data it's broken into categories: >>Zone >>Type >>Value >>Interval What I need to do is: Get the value if the type is equal to 'myType' and the interval value is the LARGEST. So an example of the xml might be (under report_data): OasisReport MessagePayload RTO REPORT_ITEM REPORT_DATA <zone>myZone1</zone> -- This should be the same in all reports since I only get them for 1 zone <type>myType</type> --This can change from line to line <value>12345</value>--This changes every interval <Interval>122</Interval> -- This is essentially how many 5 minute intervals have taken place since the beginning of a day, finding the "max" lets me know it's the newest data. Thereby I want to find stuff of "MyType" for the "max" interval and pull the Value (into a string, or a double, if not I can convert from string. Can someone help me with this task? Thanks! Note: I've used Xpath to handle things like this in the past, but it seems outlandish for this... as it's SO complex (since not all the reports live in the same report_item, and not all the types are the same in each report)

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  • Bulk Insert of hundreds of millions of records

    - by Dave Jarvis
    What is the fastest way to insert 237 million records into a table that has rules (for distributing the data across 84 child tables)? First I tried inserts. No go. Then I tried inserts with BEGIN/COMMIT. Not nearly fast enough. Next, I tried COPY FROM, but then noticed the documentation states that the rules are ignored. (And it was having difficulties with the column order and date format -- it said that '1984-07-1' was not a valid integer; true, but a bit unexpected.) Some example data: station_id,taken,amount,category_id,flag 1,'1984-07-1',0,4, 1,'1984-07-2',0,4, 1,'1984-07-3',0,4, 1,'1984-07-4',0,4,T Here is the table structure (with one rule included): CREATE TABLE climate.measurement ( id bigserial NOT NULL, station_id integer NOT NULL, taken date NOT NULL, amount numeric(8,2) NOT NULL, category_id smallint NOT NULL, flag character varying(1) NOT NULL DEFAULT ' '::character varying ) WITH ( OIDS=FALSE ); ALTER TABLE climate.measurement OWNER TO postgres; CREATE OR REPLACE RULE i_measurement_01_001 AS ON INSERT TO climate.measurement WHERE date_part('month'::text, new.taken)::integer = 1 AND new.category_id = 1 DO INSTEAD INSERT INTO climate.measurement_01_001 (id, station_id, taken, amount, category_id, flag) VALUES (new.id, new.station_id, new.taken, new.amount, new.category_id, new.flag); I can generate the data into any format. Am looking for something that won't take four days. I originally had the data in MySQL (still do), but am hoping to get a performance increase by switching to PostgreSQL and am eager to use its PL/R extensions for stats. I was also thinking about using: http://pgbulkload.projects.postgresql.org/ Any help, tips, or guidance would be greatly appreciated. Thank you!

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  • Dumping an ADODB recordset to XML, then back to a recordset, then saving to the db

    - by Mark Biek
    I've created an XML file using the .Save() method of an ADODB recordset in the following manner. dim res dim objXML: Set objXML = Server.CreateObject("MSXML2.DOMDocument") 'This returns an ADODB recordset set res = ExecuteReader("SELECT * from some_table) With res Call .Save(objXML, 1) Call .Close() End With Set res = nothing Let's assume that the XML generated above then gets saved to a file. I'm able to read the XML back into a recordset like this: dim res : set res = Server.CreateObject("ADODB.recordset") res.open server.mappath("/admin/tbl_some_table.xml") And I can loop over the records without any problem. However what I really want to do is save all of the data in res to a table in a completely different database. We can assume that some_table already exists in this other database and has the exact same structure as the table I originally queried to make the XML. I started by creating a new recordset and using AddNew to add all of the rows from res to the new recordset dim outRes : set outRes = Server.CreateObject("ADODB.recordset") dim outConn : set outConn = Server.CreateObject("ADODB.Connection") dim testConnStr : testConnStr = "DRIVER={SQL Server};SERVER=dev-windows\sql2000;UID=myuser;PWD=mypass;DATABASE=Testing" outConn.open testConnStr outRes.activeconnection = outConn outRes.cursortype = adOpenDynamic outRes.locktype = adLockOptimistic outRes.source = "product_accessories" outRes.open while not res.eof outRes.addnew for i=0 to res.fields.count-1 outRes(res.fields(i).name) = res(res.fields(i).name) next outRes.movefirst res.movenext wend outRes.updatebatch But this bombs the first time I try to assign the value from res to outRes. Microsoft OLE DB Provider for ODBC Drivers error '80040e21' Multiple-step OLE DB operation generated errors. Check each OLE DB status value, if available. No work was done. Can someone tell me what I'm doing wrong or suggest a better way for me to copy the data loaded from XML to a different database?

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  • Anonymous union definition/declaration in a macro GNU vs VS2008

    - by Alan_m
    I am attempting to alter an IAR specific header file for a lpc2138 so it can compile with Visual Studio 2008 (to enable compatible unit testing). My problem involves converting register definitions to be hardware independent (not at a memory address) The "IAR-safe macro" is: #define __IO_REG32_BIT(NAME, ADDRESS, ATTRIBUTE, BIT_STRUCT) \ volatile __no_init ATTRIBUTE union \ { \ unsigned long NAME; \ BIT_STRUCT NAME ## _bit; \ } @ ADDRESS //declaration //(where __gpio0_bits is a structure that names //each of the 32 bits as P0_0, P0_1, etc) __IO_REG32_BIT(IO0PIN,0xE0028000,__READ_WRITE,__gpio0_bits); //usage IO0PIN = 0x0xAA55AA55; IO0PIN_bit.P0_5 = 0; This is my comparable "hardware independent" code: #define __IO_REG32_BIT(NAME, BIT_STRUCT)\ volatile union \ { \ unsigned long NAME; \ BIT_STRUCT NAME##_bit; \ } NAME; //declaration __IO_REG32_BIT(IO0PIN,__gpio0_bits); //usage IO0PIN.IO0PIN = 0xAA55AA55; IO0PIN.IO0PIN_bit.P0_5 = 1; This compiles and works but quite obviously my "hardware independent" usage does not match the "IAR-safe" usage. How do I alter my macro so I can use IO0PIN the same way I do in IAR? I feel this is a simple anonymous union matter but multiple attempts and variants have proven unsuccessful. Maybe the IAR GNU compiler supports anonymous unions and vs2008 does not. Thank you.

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  • database schema eligible for delta synchronization

    - by WilliamLou
    it's a question for discussion only. Right now, I need to re-design a mysql database table. Basically, this table contains all the contract records I synchronized from another database. The contract record can be modified, deleted or users can add new contract records via GUI interface. At this stage, the table structure is exactly the same as the Contract info (column: serial number, expiry date etc.). In that case, I can only synchronize the whole table (delete all old records, replace with new ones). If I want to delta(only synchronize with modified, new, deleted records) synchronize the table, how should I change the database schema? here is the method I come up with, but I need your suggestions because I think it's a common scenario in database applications. 1)introduce a sequence number concept/column: for each sequence, mark the new added records, modified records, deleted records with this sequence number. By recording the last synchronized sequence number, only pass those records with higher sequence number; 2) because deleted contracts can be added back, and the original table has primary key constraints, should I create another table for those deleted records? or add a flag column to indicate if this contract has been deleted? I hope I explain my question clearly. Anyway, if you know any articles or your own suggestions about this, please let me know. Thanks!

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  • How can I reuse .NET resources in multiple executables?

    - by Brandon
    I have an existing application that I'm supposed to take and create a "mini" version of. Both are localized apps and we would like to reuse the resources in the main application as is. So, here's the basic structure of my apps: MainApplication.csproj /Properties/Resources.resx /MainUserControl.xaml (uses strings in Properties/Resources.resx) /MainUserControl.xaml.cs MiniApplication.csproj link to MainApplication/Properties/Resources.resx link to MainApplication/MainUserControl.xaml link to MainApplication/MainUserControl.xaml.cs MiniApplication.xaml (tries to use MainUserControl from MainApplication link) So, in summary, I've added the needed resources and user control from the main application as links in the mini application. However, when I run the mini application, I get the following exception. I'm guessing it's having trouble with the different namespaces, but how do I fix? Could not find any resources appropriate for the specified culture or the neutral culture. Make sure \"MainApplication.Properties.Resources.resources\" was correctly embedded or linked into assembly \"MiniApplication\" at compile time, or that all the satellite assemblies required are loadable and fully signed. FYI, I know I could put the user control in a user control library but the problem is that the mini application needs to have a small footprint. So, we only want to include what we need.

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  • How can I work around WinXP using ports 1025-5000 as ephemeral?

    - by Chris Dolan
    If you create a TCP client socket with port 0 instead of a non-zero port, then the operating system chooses any free ephemeral port for you. Most OSes choose ephemeral ports from the IANA dynamic port range of 49152-65535. However in Windows Server 2003 and earlier (including XP) Microsoft used ports 1025-5000 as the ephemeral range, according to their bind() documentation. I run multiple Java services on the same hardware. On rare occasions, this range collides with well-known ports that I use for other services (e.g. port 4160 for Jini discovery). While rare, this has caused real problems. Is there any easy way to tell Windows or Java to use a different port range for client sockets? Microsoft's docs indicate that I can change the high end of that range via the MaxUserPort TcpIP registry setting, but I see no way to change the low end. Update: I've made some progress on this. It looks like Microsoft has a concept of reserved ports that are exceptions to the ephemeral port range. There's a registry setting that lets you change this permanently and apparently there must be an API to do the same thing because there's a data structure that holds high/low values for reserved port ranges, but I can't find the actual function call anywhere... The registry solution may work, but now I'm fixated on this API.

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  • Serialize Object

    - by Mark Pearl
    Hi.. I am new to serialization and I cannot for the life of me figure out how to fix this exception I am getting... I have an object that has the following structure [XmlRoot("MaxCut2")] public class MaxCut2File : IFile { public MaxCut2File() { MyJob = new Job(); Job.Reference = "MyRef"; } [XmlElement("JobDetails", typeof(Job))] public IJob MyJob { get; set; } } An inteferface... public interface IJob { string Reference { get; set; } } And an class [Serializable()] public class Job : IJob { [XmlElement("Reference")] public string Reference { get; set; } } When I try to serialize an instance of the MaxCut2File object I get an error {"Cannot serialize member 'MaxCut2File.MaxCut2File.MyJob' of type 'MaxCut2BL.Interfaces.IJob', see inner exception for more details."} "There was an error reflecting type 'MaxCut2File.MaxCut2File'." However if I change my property MyJob from the IJob type to the Job type it works fine... Any ideas?

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  • Grouping a list of of entities which has a sublist in c#

    - by mikei
    I have a set of Entities which basically has this structure. {Stats Name="<Product name> (en)" TotalResources="10" ..} {DayStats Date="2009-12-10" TotalResources="5"} {DayStats Date="2009-12-11" TotalResources="5"} {Stats} {Stats Name="<Product name> (us)" TotalResources="10" ..} {DayStats Date="2009-12-10" TotalResources="5"} {DayStats Date="2009-12-11" TotalResources="5"} {Stats} ... What I wan't to extract from this set is a new set entities (or entity in the example above) where the first level has been grouped by the (ignoring the country label) where all/some of the properties has been summmed together, including the the sublist of {DayStas} on a per day basis. So the result set of the example would look something like this: {Stats Name="<Product name>" TotalResources="20" ..} {DayStats Date="2009-12-10" TotalResources="10"} {DayStats Date="2009-12-11" TotalResources="10"} {Stats} ... So my question is: Is it possible to do this in a more elegant way in LINQ rather than the vanilla "loop-trhough-each-entity-and-compare"-way? And I wan't the set to contain the same type of entities as the original set ({Stats}, {DayStats}), your answer doesn't need to include code for that, I can probably work that out by myself. Just letting you know incase you need to take that into account. (I'm sorry if this question has been discussed before, I tried searching to no avail. I guess my searching skills are fuubar ;)) Merry christmas =)

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  • How to distribute an offline cube for excel

    - by Mike M
    I have the following scenario. A cube created in SSAS 2008. I can connected to this cube via Excel. I can create an offline cube file. I can connect to this offline cube file. Now, say I want to email this excel file along with the cube file so that another user can view it. I run into the problem that the connection path the offline cube is hard coded into the excel file. Its the same problem this person had. http://stackoverflow.com/questions/1253950/opening-offline-cube-from-another-machine Their solution was to just make sure the other user saved the cube in the same directory structure. I don't love that solution. I also came across this idea: http://www.pcreview.co.uk/forums/thread-948974.php I tried that, it errored out, but I am not an Excel VBA programmer and really have no idea if I even put the code in the right place. So anyway, anyone out there have any ideas about who to do this? If the VBA solution is the best, could someone give me some tips on where to actually put that code?

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  • XML file creation Using XDocument in C#

    - by Pramodh
    i've a list (List< string) "sampleList" which contains Data1 Data2 Data3... How to create an XML file using XDocument by iterating the items in the list in c sharp. The file structure is like <file> <name filename="sample"/> <date modified =" "/> <info> <data value="Data1"/> <data value="Data2"/> <data value="Data3"/> </info> </file> Now i'm Using XmlDocument to do this Example List<string> lst; XmlDocument XD = new XmlDocument(); XmlElement root = XD.CreateElement("file"); XmlElement nm = XD.CreateElement("name"); nm.SetAttribute("filename", "Sample"); root.AppendChild(nm); XmlElement date = XD.CreateElement("date"); date.SetAttribute("modified", DateTime.Now.ToString()); root.AppendChild(date); XmlElement info = XD.CreateElement("info"); for (int i = 0; i < lst.Count; i++) { XmlElement da = XD.CreateElement("data"); da.SetAttribute("value",lst[i]); info.AppendChild(da); } root.AppendChild(info); XD.AppendChild(root); XD.Save("Sample.xml"); please help me to do this

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  • ConcurrentLinkedQueue$Node remains in heap after remove()

    - by action8
    I have a multithreaded app writing and reading a ConcurrentLinkedQueue, which is conceptually used to back entries in a list/table. I originally used a ConcurrentHashMap for this, which worked well. A new requirement required tracking the order entries came in, so they could be removed in oldest first order, depending on some conditions. ConcurrentLinkedQueue appeared to be a good choice, and functionally it works well. A configurable amount of entries are held in memory, and when a new entry is offered when the limit is reached, the queue is searched in oldest-first order for one that can be removed. Certain entries are not to be removed by the system and wait for client interaction. What appears to be happening is I have an entry at the front of the queue that occurred, say 100K entries ago. The queue appears to have the limited number of configured entries (size() == 100), but when profiling, I found that there were ~100K ConcurrentLinkedQueue$Node objects in memory. This appears to be by design, just glancing at the source for ConcurrentLinkedQueue, a remove merely removes the reference to the object being stored but leaves the linked list in place for iteration. Finally my question: Is there a "better" lazy way to handle a collection of this nature? I love the speed of the ConcurrentLinkedQueue, I just cant afford the unbounded leak that appears to be possible in this case. If not, it seems like I'd have to create a second structure to track order and may have the same issues, plus a synchronization concern.

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  • JSF 2.0 Dynamic Views

    - by Robe Eleckers
    Hello, I'm working on a web project which uses JSF 2.0, PrimeFaces and PrettyFaces as main frameworks / libraries. The pages have the following (common) structure: Header, Content, Footer. Header: The Header always contains the same menu. This menu is a custom component, which generates a recursive html <ul><li> list containing <a href="url"> html links, this is all rendered with a custom renderer. The link looks like 'domain.com/website/datatable.xhtml?ref=2'. Where the ref=2 used to load the correct content from the database. I use prettyfaces to store this request value in a backingbean. Question 1: Is it ok to render the <a href> links myself, or should I better add an HTMLCommandLink from my UIComponent and render that in the encodeBegin/End? Question 2: I think passing variables like this is not really the JSF 2.0 style, how to do this in a better way? Content: The content contains dynamic data. It can be a (primefaces) datatable, build with dynamic data from the database. It can also be a text page, also loaded from the database. Or a series of graphs. You got the point, it's dynamic. The content is based on the link pressed in the header menu. If the content is of type datatable, then I put the ref=2 variable to a DataTableBean (via prettyfaces), which then loads the correct datatable from the database. If the content is of type chart, I'll put it on the ChartBean. Question 3: Is this a normal setup? Ideally I would like to update my content via Ajax. I hope it's clear :)

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  • How to set up single array or dictionary for use in multiple datasources?

    - by Roman
    I have multiple TableViewDatasources that need to display list of objects form same pool depending of certain property. E.g. object.flag1 is set- it will show up in TableView1 object.flag2 is set- it will show up in TableView2 The obvious way would be to have separate arrays for each TableView, But same object may appear in different arrays. Also I need to update objects very often or access all objects through same array. How do I setup a single dictionary or array to have all objects in one structure? To put it in another way: When table view or selection changes, application need to redraw TableViews with the new data. Application have to access the pool of objects and search through them using iterator and accessing each object and its properties. I think that this is an expensive operation and want to avoid that. Perhaps maybe by making a global pool of objects a dictionary and exposing objects properties as dictionary fields. So instead of iterating global pool of objects I could access global pool Dicitonary in a manner of database by selecting objects that has fields that match particular criteria. Anyone know any example of doing that?

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  • Creating self-referential tables with polymorphism in SQLALchemy

    - by Jace
    I'm trying to create a db structure in which I have many types of content entities, of which one, a Comment, can be attached to any other. Consider the following: from datetime import datetime from sqlalchemy import create_engine from sqlalchemy import Column, ForeignKey from sqlalchemy import Unicode, Integer, DateTime from sqlalchemy.orm import relation, backref from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Entity(Base): __tablename__ = 'entities' id = Column(Integer, primary_key=True) created_at = Column(DateTime, default=datetime.utcnow, nullable=False) edited_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False) type = Column(Unicode(20), nullable=False) __mapper_args__ = {'polymorphic_on': type} # <...insert some models based on Entity...> class Comment(Entity): __tablename__ = 'comments' __mapper_args__ = {'polymorphic_identity': u'comment'} id = Column(None, ForeignKey('entities.id'), primary_key=True) _idref = relation(Entity, foreign_keys=id, primaryjoin=id == Entity.id) attached_to_id = Column(Integer, ForeignKey('entities.id'), nullable=False) #attached_to = relation(Entity, remote_side=[Entity.id]) attached_to = relation(Entity, foreign_keys=attached_to_id, primaryjoin=attached_to_id == Entity.id, backref=backref('comments', cascade="all, delete-orphan")) text = Column(Unicode(255), nullable=False) engine = create_engine('sqlite://', echo=True) Base.metadata.bind = engine Base.metadata.create_all(engine) This seems about right, except SQLAlchemy doesn't like having two foreign keys pointing to the same parent. It says ArgumentError: Can't determine join between 'entities' and 'comments'; tables have more than one foreign key constraint relationship between them. Please specify the 'onclause' of this join explicitly. How do I specify onclause?

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  • Force Download Files Broken Headers wrong?

    - by Sinan
    if($_POST['mode']=="save") { $root = $_SERVER['DOCUMENT_ROOT']; $path = "/mcboeking/"; $path = $root.$path; $file_path = $_POST['path']; $file = $path.$file_path; if(!file_exists($file)) { die('file not found'); } else { header("Cache-Control: public"); header("Content-Description: File Transfer"); header('Content-Type: application/force-download'); header("Content-Disposition: attachment; filename=\"".basename($file)."\";" ); header("Content-Length: ".filesize($file)); readfile($file);}} As soon as i download the file and open it i get an error message. When i try to open a .doc i get the message : file structure is invalid. And when i try to open a jpg : This file can not be opened. It may be corrupt or a file format that Preview does not recognize. But when i download PDF files, they open without any problem. Can someone help me? P.s. i tried different headers including : header('Content-Type: application/octet-stream');

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  • Django error - no module named

    - by Shreyas
    Here is my relevant directory structure (Windows 7, Python 2.7, virtualenv) -userProf - - manage.py - -UserProfile - sampleapp_db - urls.py - views.py - wsgi.py - __init__.py - -libs - - __init__.py - -allauth - - app_settings.py - - models.py - - tests.py - - urls.py - - utils.py - - - -account - - - admin.py - - - context_processors.py - - - models.py - - - urls.py - - - __init__.py - -socialaccount - - - admin.py - - - context_processors.py - - - models.py - - - urls.py - - - views.py - - - __init__.py - - - - -templates - -account - - - base.html - - - email.html -settings - base_settings.py - dev.py - __init__.py - -static -css I get the following error when I try to run this dango app Error: No module named account I have read other posts on SO that refer to the syspath being the issue or that the appname matches the project name Django Shell No module named settings ...as a result of this, I added the following statements in the base_settings.py file import sys base = os.path.abspath(os.path.dirname(os.path.dirname(__file__))) base_parent = os.path.dirname(base) sys.path.append(base) sys.path.append(base_parent) sys.path.append(os.path.join(base,'libs')) sys.path.append(os.path.join(base,'libs','allauth','account')) I verified that the sys.path is correct by putting a break in PyCharm and evaluating sys.path Should I be putting this in manage.py? Some other SO postings referred to not being able to import the module but I can launch the python console and import UserProfile.libs.allauth.account without any exceptions being thrown! My base_setings.py has the following relevant section INSTALLED_APPS = ( 'UserProfile.libs.allauth.account', )

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  • asyncronous call doesn't return json

    - by Rebecca
    I am running wamp on an xp box. I am fairly new to web programming, this is for a student project, and have run out of avenues to try to solve this problem. Problem We have client side JavaScript code that uses GDownloadUrl- from the Google api- to wrap xmlHttpRequest calls to a php server side program that is accessing our database. In my callback program, the result of this call is always " ". However, if I use an alert to display the http:// call, with the arguments, and cut and paste that into my browser, the json I expected is displayed. I zipped my dir containing all the files, and tried it out on another team member's computer, and they were able to get the json in the callback function. Note this is exactly the same code and structure I was using, he just unzipped and ran. So now I'm thinking this is something about Firefox or Wamp? Would this be a config problem? I'm running wamp server 2.0, and Firefox 3.5.8. I have no problems with syncronous php, or reading in files asyncronously. Any help would be greatly appreciated. Rebecca

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  • How to import a class from default package

    - by mykhaylo
    Hi, I am using Eclipse 3.5 and I have created a project with some package structure along with the default package. I have one class in default package - Calculations.java and I want to make the use of that class in any of the package (for instance in com.company.calc). When I try to make the use of the class which is default package, its giving me compile error. Its not able to recognise the class in default package. Where is a problem? Calculations.java - source code public class Calculations{ native public int Calculate(int contextId); native public double GetProgress(int contextId); static { System.loadLibrary("Calc"); } } I can put my class in any other package. This class has some native method which is implemented in Delphi . If I put that class in any of the folder,I will have to make the change that DLL which I want to avoid(really - I can not). Thats why I put my class in the default package.

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  • howto distinguish composition and self-typing use-cases

    - by ayvango
    Scala has two instruments for expressing object composition: original self-type concept and well known trivial composition. I'm curios what situations I should use which in. There are obvious differences in their applicability. Self-type requires you to use traits. Object composition allows you to change extensions on run-time with var declaration. Leaving technical details behind I can figure two indicators to help with classification of use cases. If some object used as combinator for a complex structure such as tree or just have several similar typed parts (1 car to 4 wheels relation) than it should use composition. There is extreme opposite use case. Lets assume one trait become too big to clearly observe it and it got split. It is quite natural that you should use self-types for this case. That rules are not absolute. You may do extra work to convert code between this techniques. e.g. you may replace 4 wheels composition with self-typing over Product4. You may use Cake[T <: MyType] {part : MyType} instead of Cake { this : MyType => } for cake pattern dependencies. But both cases seem counterintuitive and give you extra work. There are plenty of boundary use cases although. One-to-one relations is very hard to decide with. Is there any simple rule to decide what kind of technique is preferable? self-type makes you classes abstract, composition makes your code verbose. self-type gives your problems with blending namespaces and also gives you extra typing for free (you got not just a cocktail of two elements but gasoline-motor oil cocktail known as a petrol bomb). How can I choose between them? What hints are there? Update: Let us discuss the following example: Adapter pattern. What benefits it has with both selt-typing and composition approaches?

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  • Delete specific files after installation using visual studio setup project

    - by Vadiklk
    I have this problem. I want to build an installer for my c# solution, that will be placed in a folder with other installation folders and files that are needed to be copied to the installed folder. So that is easy, I just copy them to the folder I create using the folder structure I want. Now, I want also to install another program and run a .exe file I've created to unzip some files for me. For that I need to copy 2 .exe files and 2 dlls (for the exes) to the folder to which I am installing and create 2 custom actions that will use them. That I've managed to do. After that I want to delete those 4 extra files, as the user does not need them and shouldn't even be aware they are there. How to do so? I couldn't find a way in the built in setup project preferences + I do not know how to make a custom installer class. A bonus question, is how to make the other installer (one of the .exe files is just a plain installer) install quietly to any path? I do not want the user to see an installer pop out of my program installer. Thanks!

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  • updating system's time using .Net

    - by user62958
    I am trying to update my system time using the following: [StructLayout(LayoutKind.Sequential)] private struct SYSTEMTIME { public ushort wYear; public ushort wMonth; public ushort wDayOfWeek; public ushort wDay; public ushort wHour; public ushort wMinute; public ushort wSecond; public ushort wMilliseconds; } [DllImport("kernel32.dll", EntryPoint = "GetSystemTime", SetLastError = true)] private extern static void Win32GetSystemTime(ref SYSTEMTIME lpSystemTime); [DllImport("kernel32.dll", EntryPoint = "SetSystemTime", SetLastError = true)] private extern static bool Win32SetSystemTime(ref SYSTEMTIME lpSystemTime); public void SetTime() { TimeSystem correctTime = new TimeSystem(); DateTime sysTime = correctTime.GetSystemTime(); // Call the native GetSystemTime method // with the defined structure. SYSTEMTIME systime = new SYSTEMTIME(); Win32GetSystemTime(ref systime); // Set the system clock ahead one hour. systime.wYear = (ushort)sysTime.Year; systime.wMonth = (ushort)sysTime.Month; systime.wDayOfWeek = (ushort)sysTime.DayOfWeek; systime.wDay = (ushort)sysTime.Day; systime.wHour = (ushort)sysTime.Hour; systime.wMinute = (ushort)sysTime.Minute; systime.wSecond = (ushort)sysTime.Second; systime.wMilliseconds = (ushort)sysTime.Millisecond; Win32SetSystemTime(ref systime); } When I debug everything looks good and all the values are correct but when it calles the Win32SetSystemTime(ref systime) th actual time of system(display time) doesn't change and stays the same. The strange part is that when I call the Win32GetSystemTime(ref systime) it gives me the new updated time. Can someone give me some help on this?

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  • Suggestions of the easiest algorithms for some Graph operations

    - by Nazgulled
    Hi, The deadline for this project is closing in very quickly and I don't have much time to deal with what it's left. So, instead of looking for the best (and probably more complicated/time consuming) algorithms, I'm looking for the easiest algorithms to implement a few operations on a Graph structure. The operations I'll need to do is as follows: List all users in the graph network given a distance X List all users in the graph network given a distance X and the type of relation Calculate the shortest path between 2 users on the graph network given a type of relation Calculate the maximum distance between 2 users on the graph network Calculate the most distant connected users on the graph network A few notes about my Graph implementation: The edge node has 2 properties, one is of type char and another int. They represent the type of relation and weight, respectively. The Graph is implemented with linked lists, for both the vertices and edges. I mean, each vertex points to the next one and each vertex also points to the head of a different linked list, the edges for that specific vertex. What I know about what I need to do: I don't know if this is the easiest as I said above, but for the shortest path between 2 users, I believe the Dijkstra algorithm is what people seem to recommend pretty often so I think I'm going with that. I've been searching and searching and I'm finding it hard to implement this algorithm, does anyone know of any tutorial or something easy to understand so I can implement this algorithm myself? If possible, with C source code examples, it would help a lot. I see many examples with math notations but that just confuses me even more. Do you think it would help if I "converted" the graph to an adjacency matrix to represent the links weight and relation type? Would it be easier to perform the algorithm on that instead of the linked lists? I could easily implement a function to do that conversion when needed. I'm saying this because I got the feeling it would be easier after reading a couple of pages about the subject, but I could be wrong. I don't have any ideas about the other 4 operations, suggestions?

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  • Attachment_fu file saving problem

    - by Anand
    Attachment_fu plugin is kind of old, but I have to modify an old app and I can't use another plugin like paperclip etc. So here's the code without further ado Submissions table structure --------------------------- | content_type | varchar(255) | YES | | NULL | filename | varchar(255) | YES | | NULL app/models/submission.rb ------------------------ has_attachment :storage => :file_system, :path_prefix => 'public/submissions', :max_size => 2.megabytes, :content_type => ['application/pdf', 'application/msword', 'text/plain'] app/models/user.rb ------------------ has_one :submission, :dependent => :destroy app/views/user/some_action.html.erb ----------------------------------- <% form_for :user, :url => { :action => "some_action" }, :html => {:multipart => true} do |f| %> .... <%= file_field_tag "submission[uploaded_data]" %> <%end%> app/controllers/user_controller.rb ---------------------------------- @user = User.find_user(session[:user_id]) @submission = @user.submission if request.post? @submission.uploaded_data = params[:submission][:uploaded_data] end When the form is submitted, the database fields "content_type" and "filename" get updated and display the correct values, but the file does not appear in public/submissions/ directory. I have checked the permissions on the submissions directory. What am I missing? Many Thanks

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