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• Rails running multiple delayed_job - lock tables

  - by pepernik

  Hey. I use delayed_job for background processing. I have 8 CPU server, MySQL and I start 7 delayed_job processes RAILS_ENV=production script/delayed_job -n 7 start Q1: I'm wondering is it possible that 2 or more delayed_job processes start processing the same process (the same record-row in the database delayed_jobs). I checked the code of the delayed_job plugin but can not find the lock directive in a way it should be. I think each process should lock the database table before executing an UPDATE on lock_by column. They lock the record simply by updating the locked_by field (UPDATE delayed_jobs SET locked_by...). Is that really enough? No locking needed? Why? I know that UPDATE has higher priority than SELECT but I think this does not have the effect in this case. My understanding of the multy-threaded situation is: Process1: Get waiting job X. [OK] Process2: Get waiting jobs X. [OK] Process1: Update locked_by field. [OK] Process2: Update locked_by field. [OK] Process1: Get waiting job X. [Already processed] Process2: Get waiting jobs X. [Already processed] I think in some cases more jobs can get the same information and can start processing the same process. Q2: Is 7 delayed_jobs a good number for 8CPU server? Why yes/not. Thx 10x!

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• Monotouch threads, GC, WCF

  - by cvista

  Hi This is a question about best practices i guess but it applies directly to my current MT project. I'm using WCF services to communicate with the server. To do this i do the following: services.MethodToCall(params); and the asynch: services.OnMethodToCallCompleted += delegate{ //do stuff and ting }; This can lead to issues if you're not careful in that variables defined within the scope of the asynch callback can sometimes be cleaned up by the gc and this can cause crashes. So - I am making it a practice to declare these outside of the scope of the callback unless I am 100% sure they are not needed. Now - when doing stuff and ting implies changing the ui - i wrap it all in an InvokeOnMainThread call. I guess wrapping everything in this would slow the main thread down and rubbish the point of having multi threads. Even though I'm being careful about all this i am still getting crashes and I have no idea why! I am certain it has something to do with threads, scope and all that. Now - the only thing I can think of outside of updating the UI that may need to happen inside of InvokeOnMainThread is that I have a singleton 'Database' class. This is based on the version 5 code from this thread http://www.yoda.arachsys.com/csharp/singleton.html So now if the service method returns data that needs to be added/updated to the Database class -I also wrap this inside an InvokeOnMainThread call. Still getting random crashes. So... My question is this: I am new to thick client dev - I'm coming from a web dev perspective where we don't need to worry about threads so much :) Aside from what I have mentioned -are there any other things I should be aware of? Is the above stuff correct? Or am i miss-understanding something? Cheers w://

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• How to define a "complicated" ComputedColumn in SQL Server?

  - by Slauma

  SQL Server Beginner question: I'm trying to introduce a computed column in SQL Server (2008). In the table designer of SQL Server Management Studio I can do this, but the designer only offers me one single edit cell to define the expression for this column. Since my computed column will be rather complicated (depending on several database fields and with some case differentiations) I'd like to have a more comfortable and maintainable way to enter the column definition (including line breaks for formatting and so on). I've seen there is an option to define functions in SQL Server (scalar value or table value functions). Is it perhaps better to define such a function and use this function as the column specification? And what kind of function (scalar value, table value)? To make a simplified example: I have two database columns: DateTime1 (smalldatetime, NULL) DateTime2 (smalldatetime, NULL) Now I want to define a computed column "Status" which can have four possible values. In Dummy language: if (DateTime1 IS NULL and DateTime2 IS NULL) set Status = 0 else if (DateTime1 IS NULL and DateTime2 IS NOT NULL) set Status = 1 else if (DateTime1 IS NOT NULL and DateTime2 IS NULL) set Status = 2 else set Status = 3 Ideally I would like to have a function GetStatus() which can access the different column values of the table row which I want to compute the value of "Status" for, and then only define the computed column specification as GetStatus() without parameters. Is that possible at all? Or what is the best way to work with "complicated" computed column definitions? Thank you for tips in advance!

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• .NET - Is there a way to programmatically fill all tables in a strongly-typed dataset?

  - by Mike Loux

  Hello, all! I have a SQL Server database for which I have created a strongly-typed DataSet (using the DataSet Designer in Visual Studio 2008), so all the adapters and select commands and whatnot were created for me by the wizard. It's a small database with largely static data, so I would like to pull the contents of this DB in its entirety into my application at startup, and then grab individual pieces of data as needed using LINQ. Rather than hard-code each adapter Fill call, I would like to see if there is a way to automate this (possibly via Reflection). So, instead of: Dim _ds As New dsTest dsTestTableAdapters.Table1TableAdapter.Fill(_ds.Table1) dsTestTableAdapters.Table2TableAdapter.Fill(_ds.Table2) <etc etc etc> I would prefer to do something like: Dim _ds As New dsTest For Each tableName As String In _ds.Tables Dim adapter as Object = <routine to grab adapter associated with the table> adapter.Fill(tableName) Next Is that even remotely doable? I have done a fair amount of searching, and I wouldn't think this would be an uncommon request, but I must be either asking the wrong question, or I'm just weird to want to do this. I will admit that I usually prefer to use unbound controls and not go with strongly-typed datasets (I prefer to write SQL directly), but my company wants to go this route, so I'm researching it. I think the idea is that as tables are added, we can just refresh the DataSet using the Designer in Visual Studio and not have to make too many underlying DB code changes. Any help at all would be most appreciated. Thanks in advance!

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• SQL Server Express performance issue

  - by Developer IT

  Hi folks ! I know my questions will sound silly and probably nobody will have perfect answer but since I am in a complete dead-end with the situation it will make me feel better to post it here. So... I have a SQL Server Express database that's 500 Mb. It contains 5 tables and maybe 30 stored procedure. This database is use to store articles and is use for the Developer It web site. Normally the web pages load quickly, let's say 2 ou 3 sec. BUT, sqlserver process uses 100% of the processor for those 2 or 3 sec. I try to find which stored procedure was the problem and I could not find one. It seems like every read into the table dans contains the articles (there are about 155,000 of them and 20 or so gets added every 15 minutes). I added few index but without luck... It is because the table is full text indexed ? Should I have order with the primary key instead of date ? I never had any problems with ordering by dates.... Should I use dynamic SQL ? Should I add the primary key into the url of the articles ? Should I use mutiple indexes for seperate columns or one big index ? I you want more details or code bits, just ask for it. Basicly, every little hint is much apreciated. Thanks.

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• Managing logs/warnings in Python extensions

  - by Dimitri Tcaciuc

  TL;DR version: What do you use for configurable (and preferably captured) logging inside your C++ bits in a Python project? Details follow. Say you have a a few compiled .so modules that may need to do some error checking and warn user of (partially) incorrect data. Currently I'm having a pretty simplistic setup where I'm using logging framework from Python code and log4cxx library from C/C++. log4cxx log level is defined in a file (log4cxx.properties) and is currently fixed and I'm thinking how to make it more flexible. Couple of choices that I see: One way to control it would be to have a module-wide configuration call. # foo/__init__.py import sys from _foo import import bar, baz, configure_log configure_log(sys.stdout, WARNING) # tests/test_foo.py def test_foo(): # Maybe a custom context to change the logfile for # the module and restore it at the end. with CaptureLog(foo) as log: assert foo.bar() == 5 assert log.read() == "124.24 - foo - INFO - Bar returning 5" Have every compiled function that does logging accept optional log parameters. # foo.c int bar(PyObject* x, PyObject* logfile, PyObject* loglevel) { LoggerPtr logger = default_logger("foo"); if (logfile != Py_None) logger = file_logger(logfile, loglevel); ... } # tests/test_foo.py def test_foo(): with TemporaryFile() as logfile: assert foo.bar(logfile=logfile, loglevel=DEBUG) == 5 assert logfile.read() == "124.24 - foo - INFO - Bar returning 5" Some other way? Second one seems to be somewhat cleaner, but it requires function signature alteration (or using kwargs and parsing them). First one is.. probably somewhat awkward but sets up entire module in one go and removes logic from each individual function. What are your thoughts on this? I'm all ears to alternative solutions as well. Thanks,

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• Password hashing, salt and storage of hashed values

  - by Jonathan Leffler

  Suppose you were at liberty to decide how hashed passwords were to be stored in a DBMS. Are there obvious weaknesses in a scheme like this one? To create the hash value stored in the DBMS, take: A value that is unique to the DBMS server instance as part of the salt, And the username as a second part of the salt, And create the concatenation of the salt with the actual password, And hash the whole string using the SHA-256 algorithm, And store the result in the DBMS. This would mean that anyone wanting to come up with a collision should have to do the work separately for each user name and each DBMS server instance separately. I'd plan to keep the actual hash mechanism somewhat flexible to allow for the use of the new NIST standard hash algorithm (SHA-3) that is still being worked on. The 'value that is unique to the DBMS server instance' need not be secret - though it wouldn't be divulged casually. The intention is to ensure that if someone uses the same password in different DBMS server instances, the recorded hashes would be different. Likewise, the user name would not be secret - just the password proper. Would there be any advantage to having the password first and the user name and 'unique value' second, or any other permutation of the three sources of data? Or what about interleaving the strings? Do I need to add (and record) a random salt value (per password) as well as the information above? (Advantage: the user can re-use a password and still, probably, get a different hash recorded in the database. Disadvantage: the salt has to be recorded. I suspect the advantage considerably outweighs the disadvantage.) There are quite a lot of related SO questions - this list is unlikely to be comprehensive: Encrypting/Hashing plain text passwords in database Secure hash and salt for PHP passwords The necessity of hiding the salt for a hash Clients-side MD5 hash with time salt Simple password encryption Salt generation and Open Source software I think that the answers to these questions support my algorithm (though if you simply use a random salt, then the 'unique value per server' and username components are less important).

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• Where should I put contextual data related to an Object that is not really a property of the object?

  - by RenderIn

  I have a Car class. It has three properties: id, color and model. In a particular query I want to return all the cars and their properties, and I also want to return a true/false field called "searcherKnowsOwner" which is a field I calculate in my database query based on whether or not the individual conducting the search knows the owner. I have a database function that takes the ID of the searcher and the ID of the car and returns a boolean. My car class looks like this (pseudocode): class Car{ int id; Color color; Model model; } I have a screen where I want to display all the cars, but I also want to display a flag next to each car if the person viewing the page knows the owner of that car. Should I add a field to the Car class, a boolean searcherKnowsOwner? It's not a property of the car, but is actually a property of the user conducting the search. But this seems like the most efficient place to put this information.

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• 'Bank Switching' Sprites on old NES applications

  - by Jeffrey Kern

  I'm currently writing in C# what could basically be called my own interpretation of the NES hardware for an old-school looking game that I'm developing. I've fired up FCE and have been observing how the NES displayed and rendered graphics. In a nutshell, the NES could hold two bitmaps worth of graphical information, each with the dimensions of 128x128. These are called the PPU tables. One was for BG tiles and the other was for sprites. The data had to be in this memory for it to be drawn on-screen. Now, if a game had more graphical data then these two banks, it could write portions of this new information to these banks -overwriting what was there - at the end of each frame, and use it from the next frame onward. So, in old games how did the programmers 'bank switch'? I mean, within the level design, how did they know which graphic set to load? I've noticed that Mega Man 2 bankswitches when the screen programatically scrolls from one portion of the stage to the next. But how did they store this information in the level - what sprites to copy over into the PPU tables, and where to write them at? Another example would be hitting pause in MM2. BG tiles get over-written during pause, and then get restored when the player unpauses. How did they remember which tiles they replaced and how to restore them? If I was lazy, I could just make one huge static bitmap and just grab values that way. But I'm forcing myself to limit these values to create a more authentic experience. I've read the amazing guide on how M.C. Kids was made, and I'm trying to be barebones about how I program this game. It still just boggles my mind how these programmers accomplisehd what they did with what they had. EDIT: The only solution I can think of would be to hold separate tables that state what tiles should be in the PPU at what time, but I think that would be a huge memory resource that the NES wouldn't be able to handle.

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• The instruction at "0x7c910a19" referenced memory at "oxffffffff". The memory could not be "read"

  - by ClareBear

  Hello guys/girls The instruction at "0x7c910a19" referenced memory at "oxffffffff". The memory could not be "read" I have a small issue, I receive the error above before the .vbs terminates. I don't know why this error is thrown. Below is the process of the .vbs file: Call ImportTransactions() Call UpdateTransactions() Function ImportTransactions() Dim objConnection, objCommand, objRecordset, strOracle Dim strSQL, objRecordsetInsert Set objConnection = CreateObject("ADODB.Connection") objConnection.Open "DSN=*****;UID=*****;PWD==*****;" Set objCommand = CreateObject("ADODB.Command") Set objRecordset = CreateObject("ADODB.Recordset") strOracle = "SELECT query here from Oracle database" objCommand.CommandText = strOracle objCommand.CommandType = 1 objCommand.CommandTimeout = 0 Set objCommand.ActiveConnection = objConnection objRecordset.cursorType = 0 objRecordset.cursorlocation = 3 objRecordset.Open objCommand, , 1, 3 If objRecordset.EOF = False Then Do Until objRecordset.EOF = True strSQL = "INSERT query here into SQL database" strSQL = Query(strSQL) Call RunSQL(strSQL, objRecordsetInsert, False, conTimeOut, conServer, conDatabase, conUsername, conPassword) objRecordset.MoveNext Loop End If objRecordset.Close() Set objRecordset = Nothing Set objRecordsetInsert = Nothing End Function Function UpdateTransactions() Dim strSQLUpdateVAT, strSQLUpdateCodes Dim objRecordsetVAT, objRecordsetUpdateCodes strSQLUpdateVAT = "UPDATE query here SET [value:costing output] = ([value:costing output] * -1)" Call RunSQL(strSQLUpdateVAT, objRecordsetVAT, False, conTimeOut, conServer, conDatabase, conUsername, conPassword) strSQLUpdateCodes = "UPDATE query here SET [value:costing output] = ([value:costing output] * -1) different WHERE clause" Call RunSQL(strSQLUpdateCodes, objRecordsetUpdateCodes, False, conTimeOut, conServer, conDatabase, conUsername, conPassword) Set objRecordsetVAT = Nothing Set objRecordsetUpdateCodes = Nothing End Function UDPATE: If I exit the function after I open the connection (see below) it still causes the same error. Function ImportTransactions() Dim objConnection, objCommand, objRecordset, strOracle Dim strSQL, objRecordsetInsert Set objConnection = CreateObject("ADODB.Connection") objConnection.Open "DSN=*****;UID=*****;PWD==*****;" Set objCommand = CreateObject("ADODB.Command") Set objRecordset = CreateObject("ADODB.Recordset") Exit Function End Function It does both the import and update and seems to throw this error after. Thanks in advance for any help, Clare

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• Family Tree :- myheritage.com

  - by Nitesh Panchal

  Hello, The other day i just accidently visited the site myheritage.com. I was just wondering, how they must have created one? Can anybody tell me what can be their database design? and if possible, algorithm that we can use to generate such a tree? Generating simple binary tree is very easy using recursion. But if you have a look at the site(if you have time please make account on it and add few nodes to feel) when we add son to a father, it's mother is automatically added(if you don't add explicitly). Mother's family tree is also generated side by side and many such fancy things are happening. In a simple binary tree we have a root node and then many nodes below it. Thus we cannot show wife and husband in the tree and then show a line from wife and husband to child. In spare time, can anybody discuss what can be it's database design and the recursive algorithm that we can follow to generate it? I hope i am not asking too much from you :).

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• Access 2007 DAO VBA Error 3381 causes objects in calling methods to "break".

  - by MT

  ---AFTER FURTHER INVESTIGATION--- "tblABC" in the below example must be a linked table (to another Access database). If "tblABC" is in the same database as the code then the problem does not occur. Hi, We have recently upgraded to Office 2007. We have a method in which we have an open recordset (DAO). We then call another sub (UpdatingSub below) that executes SQL. This method has its own error handler. If error 3381 is encountered then the recordset in the calling method becomes "unset" and we get error 3420 'Object invalid or no longer set'. Other errors in UpdatingSub do not cause the same problem. This code works fine in Access 2003. Private Sub Whatonearth() Dim rs As dao.Recordset set rs = CurrentDb.OpenRecordset("tblLinkedABC") Debug.Print rs.RecordCount UpdatingSub "ALTER TABLE tblTest DROP Column ColumnNotThere" 'Error 3240 occurs on the below line even though err 3381 is trapped in the calling procedure 'This appears to be because error 3381 is encountered when calling UpdatingSub above Debug.Print rs.RecordCount End Sub Private Sub WhatonearthThatWorks() Dim rs As dao.Recordset set rs = CurrentDb.OpenRecordset("tblLinkedABC") Debug.Print rs.RecordCount 'Change the update to generate a different error UpdatingSub "NONSENSE SQL STATEMENT" 'Error is trapped in UpdatingSub. Next line works fine. Debug.Print rs.RecordCount End Sub Private Sub UpdatingSub(strSQL As String) On Error GoTo ErrHandler: CurrentDb.Execute strSQL ErrHandler: 'LogError' End Sub Any thoughts? We are running Office Access 2007 (12.0.6211.1000) SP1 MSO (12.0.6425.1000). Perhaps see if SP2 can be distributed? Sorry about formatting - not sure how to fix that.

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• Dataset bind to Gridview within WCF REST retrieval method and Linq to Sql

  - by user643794

  I used a WCF REST template to build a WCF service library to create PUT and GET calls. PUT method works fine sending my blob to a database. On the GET, I want to be able to access the web service directly and display the results from a stored procedure as a dataset and bind this to a gridview. The stored procedure is a simple select statement, returning three of the four columns from the table. I have the following: [WebGet(UriTemplate = "/?name={name}", ResponseFormat = WebMessageFormat.Xml)] public List<Object> GetCollection(string name) { try { db.OpenDbConnection(); // Call to SQL stored procedure return db.GetCustFromName(name); } catch (Exception e) { Log.Error("Stored Proc execution failed. ", e); } finally { db.CloseDbConnection(); } return null; } I also added Linq to SQL class to include my database table and stored procedures access. I also created the Default.aspx file in addition to the other required files. protected void Page_Load(object sender, EventArgs e) { ServiceDataContext objectContext = new ServiceDataContext(); var source = objectContext.GetCustFromName("Tiger"); Menu1.DataSource = source; Menu1.DataBind(); } But this gives me The entity type '' does not belong to any registered model. Where should the data binding be done? What should be the return type for GetCollection()? I am stuck with this. Please provide help on how to do this.

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• MsSql Server high Resource Waits and Head Blocker

  - by MartinHN

  Hi I have a MS SQL Server 2008 Standard installation running a database for a webshop. The current size of the database is 2.5 GB. Running on Windows 2008 Standard. Dual Intel Xeon X5355 @ 2.00 GHz. 4 GB RAM. When I open the Activity Monitor, I see that I have a Wait Time (ms/sec) of 5000 in the "Other" category. In the Processes list, all connections from the webshop, the Head Blocker value is 1. I see every day that when I try to access the website, it can take 20-30 secs before it even starts to "work". I know that it is not network latency. (I have a 301 redirect from the same server that is executed instantly). When the first request has been served, it seems as if it's not a sleep anymore and every subsequent request is served instantly with the speed of light. The problem was worse two weeks ago, until I changed every query to include WITH (NOLOCK). But I still experience the problem, and the Wait times in the Activity Monitor is about the same. The largest table (Images) has 32764 rows (448576 KB). Some tables exceed 300000 rows, thought they're much smaller in size than the Images table. I have the default clustered index for every primary key column, only. Any ideas?

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• jQuery dynamically created table rows not responding to events

  - by mithunmo

  I have a table with one row in my HTML file. Now in jQuery I append lot of rows based on the data in the database. But the anchor tag which is created dynamically doesn't respond to events. How do I make this anchor tag respond to events? jQuery part //Appending rows from the Database $('<tr> <td> </td> <td id="log'+i+'"><a href="viewlog.php" target="_blank">log</a></td></tr> ').appendTo('#container'); Event part in jQuery Now when I write a line of code like this it does not respond. $('#container a ').click(function() { alert("Coming here "); }); //HTML <html> <table id="container"> <tr> <td> Name </td> <td> Link </td> </tr> </table> </html>

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• Good practice to create extension methods that apply to System.Object?

  - by Christian

  Hello, I'm wondering whether I should create extension methods that apply on the object level or whether they should be located at a lower point in the class hierarchy. What I mean is something along the lines of: public static string SafeToString(this Object o) { if (o == null || o is System.DBNull) return ""; else { if (o is string) return (string)o; else return ""; } } public static int SafeToInt(this Object o) { if (o == null || o is System.DBNull) return 0; else { if (o.IsNumeric()) return Convert.ToInt32(o); else return 0; } } //same for double.. etc I wrote those methods since I have to deal a lot with database data (From the OleDbDataReader) that can be null (shouldn't, though) since the underlying database is unfortunately very liberal with columns that may be null. And to make my life a little easier, I came up with those extension methods. What I'd like to know is whether this is good style, acceptable style or bad style. I kinda have my worries about it since it kinda "pollutes" the Object-class. Thank you in advance & Best Regards :) Christian P.S. I didn't tag it as "subjective" intentionally.

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• DB2 Driver Connection Hanging in Glassfish Connection Pool

  - by Ant

  We have an intermittent issue around the DB2 used from a Glassfish connection pool. What happens is this: Under situations where the database (DB2 on ZOS) is under stress, our application (which is a multi-threaded application using connections to DB2 via a Glassfish connection pool) stops doing anything. The following are observed: 1) Looking at the server using JConsole, we can see a thread waiting indefinitely in the DB2 driver's getConnection() method. We can also see that it has gained a lock on a Vector within the driver. Several other threads are also calling the getConnection() method in the driver, and are hanging waiting for the lock on the Vector to be released. 2) Looking at the database itself, we can see that there are connections from the Glassfish server open and waiting to be used. It seems that there is some sort of mismatch between the connection pool on Glassfish and the connections actually open to DB2. Has anyone come across this issue before? Or something similar? If you need any more information that I haven't provided, then please let me know!

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• Ditching Django's models for Ajax/Web Services

  - by Igor Ganapolsky

  Recently I came across a problem at work that made me rethink Django's models. The app I am developing resides on a Linux server. Its a simple model/view/controller app that involves user interaction and updating data in the database. The problem is that this data resides in a MS SQL database on a Windows machine. So in order to use Django's models, I would have to leverage an ODBC driver on linux, and the use a python add-on like pyodbc. Well, let me tell you, setting up a reliable and functional ODBC connection on linux is no easy feat! So much so, that I spent several hours maneuvering this on my CentOS with no luck, and was left with frustration and lots of dumb system errors. In the meantime I have a deadline to meet, and suddenly the very agile and rapid Django application is a roadblock rather than a pleasure to work with. Someone on my team suggested writing this app in .NET. But there are a few problems with that: it won't be deployable on a linux machine, and I won't be able to work on it since I don't know ASP.net. Then a much better suggestion was made: keep the app in django, but instead of using models, do straight up ajax/web services calls in the template. And then it dawned on me - what a great idea. Django's models seem like a nuissance and hindrance in this case, and I can just have someone else write .Net services on their side, that I can call from my template. As a result my app will be leaner and more compact. So, I was wondering if you guys ever came across a similar dillema and what you decided to do about it.

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• Rotate MapView in Android

  - by Matthew B.

  I am writing an Android app where one of the features is that the map will rotate according to the compass (i.e. if the phone is pointing east, the map will be oriented so that the east side of the map is on top). Previous answers that I have found suggested over writing the onDraw() method in mapView, however, the api changed the method to final so it cannot be overwritten. As a result I have tried to overwrite the dispatchDraw() method like so: Note: -compass is a boolean that if true, rotate the view -bearing is a float variable that has the degrees that the view should rotate protected void dispatchDraw(Canvas canvas) { canvas.save(); if (compass) { final float w = this.getWidth(); final float h = this.getHeight(); final float scaleFactor = (float)(Math.sqrt(h * h + w * w) / Math.min(w, h)); final float centerX = w / 2.0f; final float centerY = h / 2.0f; canvas.rotate(bearing, centerX, centerY); canvas.scale(scaleFactor, scaleFactor, centerX, centerY); } super.dispatchDraw(canvas); canvas.restore(); }

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• Move rotating image along Canvas

  - by fatnic

  Hi. I've managed to make an image rotate on my canvas. And I've managed to make an image move along the canvas. My problem now is making it do both. I have got it working but I seems a bit like a hack. I've posted a demo online Here's the code. var cnv = document.getElementById("drawing"); var c = cnv.getContext('2d'); var image = new Image(); image.src = 'images/spaceship.png'; var imgWidth = image.width; var imgHeight = image.height; var i=0; function animate() { c.clearRect(0,0,640,480); c.save(); c.translate(-(imgWidth/2)+i,200); c.rotate(i * Math.PI/180); c.translate(-(imgWidth/2),-(imgHeight/2)); c.drawImage(image, 0, 0); c.restore(); (i==640+imgWidth) ? i=0: i+=2; }; setInterval(animate, 1); I think my problem is I'm not understanding the translate() method properly. Is this the correct way to do it or am I competely way off?

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• Is there a way to use Linq projections with extension methods

  - by Acoustic

  I'm trying to use AutoMapper and a repository pattern along with a fluent interface, and running into difficulty with the Linq projection. For what it's worth, this code works fine when simply using in-memory objects. When using a database provider, however, it breaks when constructing the query graph. I've tried both SubSonic and Linq to SQL with the same result. Thanks for your ideas. Here's an extension method used in all scenarios - It's the source of the problem since everything works fine without using extension methods public static IQueryable<MyUser> ByName(this IQueryable<MyUser> users, string firstName) { return from u in users where u.FirstName == firstName select u; } Here's the in-memory code that works fine var userlist = new List<User> {new User{FirstName = "Test", LastName = "User"}}; Mapper.CreateMap<User, MyUser>(); var result = (from u in userlist select Mapper.Map<User, MyUser>(u)) .AsQueryable() .ByName("Test"); foreach (var x in result) { Console.WriteLine(x.FirstName); } Here's the same thing using a SubSonic (or Linq to SQL or whatever) that fails. This is what I'd like to make work somehow with extension methods... Mapper.CreateMap<User, MyUser>(); var result = from u in new DataClasses1DataContext().Users select Mapper.Map<User, MyUser>(u); var final = result.ByName("Test"); foreach(var x in final) // Fails here when the query graph built. { Console.WriteLine(x.FirstName); } The goal here is to avoid having to manually map the generated "User" object to the "MyUser" domain object- in other words, I'm trying to find a way to use AutoMapper so I don't have this kind of mapping code everywhere a database read operation is needed: var result = from u in new DataClasses1DataContext().Users select new MyUser // Can this be avoided with AutoMapper AND extension methods? { FirstName = v.FirstName, LastName = v.LastName };

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• Implementing eval and load functions inside a scripting engine with Flex and Bison.

  - by Simone Margaritelli

  Hy guys, i'm developing a scripting engine with flex and bison and now i'm implementing the eval and load functions for this language. Just to give you an example, the syntax is like : import std.*; load( "some_script.hy" ); eval( "foo = 123;" ); println( foo ); So, in my lexer i've implemented the function : void hyb_parse_string( const char *str ){ extern int yyparse(void); YY_BUFFER_STATE prev, next; /* * Save current buffer. */ prev = YY_CURRENT_BUFFER; /* * yy_scan_string will call yy_switch_to_buffer. */ next = yy_scan_string( str ); /* * Do actual parsing (yyparse calls yylex). */ yyparse(); /* * Restore previous buffer. */ yy_switch_to_buffer(prev); } But it does not seem to work. Well, it does but when the string (loaded from a file or directly evaluated) is finished, i get a sigsegv : Program received signal SIGSEGV, Segmentation fault. 0xb7f2b801 in yylex () at src/lexer.cpp:1658 1658 if ( YY_CURRENT_BUFFER_LVALUE->yy_buffer_status == YY_BUFFER_NEW ) As you may notice, the sigsegv is generated by the flex/bison code, not mine ... any hints, or at least any example on how to implement those kind of functions? PS: I've succesfully implemented the include directive, but i need eval and load to work not at parsing time but execution time (kind of PHP's include/require directives).

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• MySql: Query multiple identical dynamic tables.

  - by JYelton

  I have a database with 500+ tables, each with identical structure, that contain historical data from sensors. I am trying to come up with a query that will locate, for example, all instances where sensor n exceeds x. The problem is that the tables are dynamic, the query must be able to dynamically obtain the list of tables. I can query information_schema.tables to get a list of the tables, like so: SELECT table_name FROM information_schema.tables WHERE table_schema = 'database_name'; I can use this to create a loop in the program and then query the database repeatedly, however it seems like there should be a way to have MySql do the multiple table search. I have not been able to make a stored procedure that works, but the examples I can find are generally for searching for a string in any column. I want to specifically find data in a specific column that exists in all tables. I admit I do not understand how to properly use stored procedures nor if they are the appropriate solution to this problem. An example query inside the loop would be: SELECT device_name, sensor_value FROM device_table WHERE sensor_value > 10; Trying the following does not work: SELECT device_name, sensor_value FROM ( SELECT table_name FROM information_schema.tables WHERE table_schema = 'database_name' ) WHERE sensor_value > 10; It results in an error: "Every derived table must have its own alias." The goal is to have a list of all devices that have had a given sensor value occur anywhere in their log (table). Ultimately, should I just loop in my program once I've obtained a list of tables, or is there a query structure that would be more efficient?

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• Doctrine Default Primary Key Problem (Again)

  - by 01010011

  Hi, Should I change all of my uniquely-named MySQL database primary keys to 'id' to avoid getting errors related to Doctrine's default primary key set in the plugin 'doctrine_pi.php'? To further elaborate, I am getting the following reoccurring error, this time after trying to login to my login page: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'u.book_id' in 'field list'' in... I suspect the problem resides at a MySQL table used for my login, of which has a primary key called id Marc B originally solved an identical problem for me in this post http://stackoverflow.com/questions/2702229/doctrine-codeigniter-mysql-crud-errors when I had the same problem with a different table within the same database. Following his suggestion, I changed the default primary key located at system/application/plugins/doctrine_pi.php from 'id' to 'book_id': <?php // system/application/plugins/doctrine_pi.php ... // set the default primary key to be named 'id', integer, 4 bytes Doctrine_Manager::getInstance()->setAttribute( Doctrine::ATTR_DEFAULT_IDENTIFIER_OPTIONS, array('name' => 'book_id', 'type' => 'integer', 'length' => 4)); and that solved my previous problem. However, my login page stopped working. So what is the safe thing to do? Change all of my primary keys to 'id' (will that solve the problem without causing some other problem I am not aware of). Or should I add some lines of code in doctrine_pi.php?

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• IIS Restrict Access to Directory for table of users

  - by Dave

  I am trying to restrict access to files in a directory and it's sub directories based user rights. My user rights are stored in an MS SQL database in a custom format, however it is easy to query the list of users with rights to this directory. I need to know how to apply this to a web config on the server to authenticate against a query of a database table to determine if the username is authenticated and allowed to view the file. Of course if they are not they should be blocked / given a 404. I am using IIS and ASP.Net MVC3 with a form based security as opposed to the built in roles and responsibilities that was custom made for us and that works great. There are over 10k users tied to this non-Active Directory authentication so I am not planning to change my authentication type so please don't go there. It is not my decision on the choice of platform, or I would have gone with a LAMP server and been done with this. Edit 11-13-2012 @ 8:57a: In the web config can you put the result of an SQL query?

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