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• Do you still limit line length in code?

  - by Noldorin

  This is a matter on which I would like to gauge the opinion of the community: Do you still limit the length of lines of code to a fixed maximum? This was certainly a convention of the past for many languages; one would typically cap the number of characters per line to a value such as 80 (and more recnetly 100 or 120 I believe). As far as I understand, the primary reasons for limiting line length are: Readability - You don't have to scroll over horizontally when you want to see the end of some lines. Printing - Admittedly (at least in my experience), most code that you are working on does not get printed out on paper, but by limiting the number of characters you can insure that formatting doesn't get messed up when printed. Past editors (?) - Not sure about this one, but I suspect that at some point in the distant past of programming, (at least some) text editors may have been based on a fixed-width buffer. I'm sure there are points that I am still missing out, so feel free to add to these... Now, when I tend to observe C or C# code nowadays, I often see a number of different styles, the main ones being: Line length capped to 80, 100, or even 120 characters. As far as I understand, 80 is the traditional length, but the longer ones of 100 and 120 have appeared because of the widespread use of high resolutions and widescreen monitors nowadays. No line length capping at all. This tends to be pretty horrible to read, and I don't see it too often, though it's certainly not too rare either. Inconsistent capping of line length. The length of some lines are limited to a fixed maximum (or even a maximum that changes depending on the file/location in code), while others (possibly comments) are not at all. My personal preference here (at least recently) has been to cap the line length to 100 in the Visual Studio editor. This means that in a decently sized window (on a non-widescreen monitor), the ends of lines are still fully visible. I can however see a few disadvantages in this, especially when you end up writing code that's indented 3 or 4 levels and then having to include a long string literal - though I often take this as a sign to refactor my code! In particular, I am curious what the C and C# coders (or anyone who uses Visual Studio for that matter) think about this point, though I would be interested in hearing anyone's thoughts on the subject. Edit Thanks for the all answers - I appreciate the variety of opinions here, all presenting sound reasons. Consensus does seem to be tipping in the direction of always (or almost always) limit the line length. Interestingly, it seems to be in various coding standards to limit the line length. Judging by some of the answers, both the Python and Google CPP guidelines set the limit at 80 chars. I haven't seen anything similar regarding C# or VB.NET, but I would be curious to see if there are ones anywhere.

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• Help with ListView Databse

  - by Weston Dunn

  I am having issues @ run with this code: App Force Closing.. Sprinter.Java import android.app.ListActivity; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle; import android.widget.ListAdapter; import android.widget.SimpleCursorAdapter; public class Sprinter extends ListActivity { /** Called when the activity is first created. */ final static String MY_DB_NAME = "Sprinter"; final static String MY_DB_TABLE = "Stations"; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); SQLiteDatabase myDB = null; try { myDB = this.openOrCreateDatabase(MY_DB_NAME, MODE_PRIVATE, null); myDB.execSQL("CREATE TABLE IF NOT EXISTS " + MY_DB_TABLE + "_id integer primary key autoincrement, name varchar(100);"); myDB.execSQL("INSERT INTO " + MY_DB_TABLE + " (_id, name)" + " VALUES ('', 'Oceanside Transit Center');"); myDB.execSQL("INSERT INTO " + MY_DB_TABLE + " (_id, name)" + " VALUES ('', 'Coast Highway');"); Cursor mCursor = myDB.rawQuery("SELECT name" + " FROM " + MY_DB_TABLE, null); startManagingCursor(mCursor); ListAdapter adapter = new SimpleCursorAdapter(this, R.layout.list_item, mCursor, new String[] { "name" }, new int[] { R.id.Name }); this.setListAdapter(adapter); this.getListView().setTextFilterEnabled(true); } finally { if (myDB != null) { myDB.close(); } } } } main.xml <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <ListView android:id="@id/android:list" android:layout_width="wrap_content" android:layout_height="wrap_content"> </ListView> <TextView android:id="@id/android:empty" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="No Data" /> </LinearLayout> list_item.xml <?xml version="1.0" encoding="utf-8"?> <LinearLayout android:id="@+id/LinearLayout" android:layout_width="fill_parent" android:layout_height="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android"> <TextView android:id="@+id/Name" android:layout_width="wrap_content" android:layout_height="wrap_content"> </TextView> </LinearLayout>

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• Oracle Coding Standards Feature Implementation

  - by Mike Hofer

  Okay, I have reached a sort of an impasse. In my open source project, a .NET-based Oracle database browser, I've implemented a bunch of refactoring tools. So far, so good. The one feature I was really hoping to implement was a big "Global Reformat" that would make the code (scripts, functions, procedures, packages, views, etc.) standards compliant. (I've always been saddened by the lack of decent SQL refactoring tools, and wanted to do something about it.) Unfortunatey, I am discovering, much to my chagrin, that there doesn't seem to be any one widely-used or even "generally accepted" standard for PL-SQL. That kind of puts a crimp on my implementation plans. My search has been fairly exhaustive. I've found lots of conflicting documents, threads and articles and the opinions are fairly diverse. (Comma placement, of all things, seems to generate quite a bit of debate.) So I'm faced with a couple of options: Add a feature that lets the user customize the standard and then reformat the code according to that standard. —OR— Add a feature that lets the user customize the standard and simply generate a violations list like StyleCop does, leaving the SQL untouched. In my mind, the first option saves the end-users a lot of work, but runs the risk of modifying SQL in potentially unwanted ways. The second option runs the risk of generating lots of warnings and doing no work whatsoever. (It'd just be generally annoying.) In either scenario, I still have no standard to go by. What I'd need to know from you guys is kind of poll-ish, but kind of not. If you were going to use a tool of this nature, what parts of your SQL code would you want it to warn you about or fix? Again, I'm just at a loss due to a lack of a cohesive standard. And given that there isn't anything out there that's officially published by Oracle, I think this is something the community could weigh in on. Also, given the way that voting works on SO, the votes would help to establish the popularity of a given "refactoring." P.S. The engine parses SQL into an expression tree so it can robustly analyze the SQL and reformat it. There should be quite a bit that we can do to correct the format of the SQL. But I am thinking that for the first release of the thing, layout is the primary concern. Though it is worth noting that the thing already has refactorings for converting keywords to upper case, and identifiers to lower case.

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• Experienced developer trying to get outsourcing contract with current client.

  - by Mike

  I work for a major bank as a contract software developer. I've been there a few months, and without exception this place has the worst software practices I've ever seen. The software my team makes has no formal testing, terrible code (not reusable, hard to read, etc), minimal documentation, no defined development process and an absolutely sickening amount of waste due to bureaucratic overhead. Part of my contract is to maintain a group of thousands of very poorly written batch jobs. When one of the jobs fails (read: crashes), it's a developers job to look at the source, figure out what's wrong, fix it, and check it in. There is no quality assurance process or auditing of the results whatsoever. Once the developer says "it works" a manager signs off and it goes into production. What's disturbing is that these jobs essentially grab market data and put it into a third-party risk management system, which provides the bank with critical intelligence. I've discovered the disturbing truth that this has been happening since the 90s and nobody really has evidence the system is getting the correct data! Without going into details, an issue arose on Friday that was so horrible I actually stormed out of the place. I was ready to quit, but I decided to just get out to calm my nerves and possibly go back Monday. I've been reflecting today on how to handle this. I have realized that, in probably less than 6 months, I could (with 2 other developers) remake a large component of this system. The new system would provide them with, as primary benefits, a maintainable codebase less prone to error and a solid QA framework. To do it properly I would have to be outside the bank, the internal bureaucracy is just too much. And moreover, I think a bank is fundamentally not a place that can make good software. This is my plan. Write a report explaining in depth all the problems with their current system Explain why their software practices fail and generate a tremendous amount of error and waste. Use this as the basis for claiming the project must be developed externally. Write a high level development plan, including what resources I will require Hand 1,2,3 to my manager, hopefully he passes it up the chain. Worst case he fires me, but this isn't so bad. Convinced Executive decides to award my company a contract for the new system I have 8 years experience as a software contractor and have delivered my share of successful software products, but all working in-house for small/medium sized companies. When I read this over, I think I have a dynamite plan. But since this is the first time doing something this bold so I have my doubts. My question is, is this a good idea? If you think not, please spare no detail.

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• Search for multiple values in an xml column

  - by Yuriy Gettya

  Environment: SQL Server 2012. Primary and secondary (value) index is built on xml column. Say I have a table Message with xml column WordIndex. I also have a table Word which has WordId and WordText. Xml for Message.WordIndex has the following schema: <xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.com"> <xs:element name="wi"> <xs:complexType> <xs:sequence> <xs:element maxOccurs="unbounded" name="w"> <xs:complexType> <xs:sequence> <xs:element maxOccurs="unbounded" name="p" type="xs:unsignedByte" /> </xs:sequence> <xs:attribute name="wid" type="xs:unsignedByte" use="required" /> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element> </xs:schema> and some data to go with it: <wi xmlns="http://www.example.com"> <w wid="1"> <p>28</p> <p>72</p> <p>125</p> </w> <w wid="4"> <p>89</p> </w> <w wid="5"> <p>11</p> </w> </wi> I need to search for multiple values in my xml column WordIndex either using OR or AND. What I'm doing is fairly rudimentary, since I'm a n00b in XQuery (taken from debug output, hence real values): with xmlnamespaces(default 'http://www.example.com') select m.Subject, m.MessageId, m.WordIndex.query(' let $dummy := 0 return <word_list> { for $w in /wi/w where $w/@wid=64 return <word wid="64" pos="{data($w/p)}"/> } { for $w in /wi/w where $w/@wid=70 return <word wid="70" pos="{data($w/p)}"/> } { for $w in /wi/w where $w/@wid=63 return <word wid="63" pos="{data($w/p)}"/> } </word_list> ') as WordPosition from Message as m -- more joins go here ... where -- more conditions go here ... and m.WordIndex.exist('/wi/w[@wid=64]') = 1 and m.WordIndex.exist('/wi/w[@wid=70]') = 1 and m.WordIndex.exist('/wi/w[@wid=63]') = 1 How can this be optimized?

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• Entering and retrieving data from SQLite for an android List View

  - by Infiniti Fizz

  Hi all, I started learning android development a few weeks ago and have gone through the developer.android.com tutorials etc. But now I have a problem. I'm trying to create an app which tracks the usage of each installed app. Therefore I'm pulling the names of all installed apps using the PackageManager and then trying to put them into an SQLite database table. I am using the Notepad Tutorial SQLite implementation but I'm running into some problems that I have tried for days to solve. I have 2 classes, the DBHelper class and the actual ListActivity class. For some reason the app force closes when I try and run my fillDatabase() function which gets all the app names from the PackageManager and tries to put them into the database: private void fillDatabase() { PackageManager manager = this.getPackageManager(); List<ApplicationInfo> appList = manager.getInstalledApplications(0); for(int i = 0; i < appList.size(); i++) { mDbHelper.addApp(manager.getApplicationLabel(appList.get(i)).toString(), 0); } } addApp() is a function defined in my AppsDbHelper class and looks as follows: public long createApp(String name, int usage) { ContentValues initialValues = new ContentValues(); initialValues.put(KEY_NAME, name); initialValues.put(KEY_USAGE, usage); return mDb.insert(DATABASE_TABLE, null, initialValues); } The database create is defined as follows: private static final String DATABASE_CREATE = "create table notes (_id integer primary key autoincrement, " + "title text not null, usage integer not null);"; I have commented out all statements that follow fillDatabase(); in the onCreate() method of the ListActivity and so know that it is definetely the problem but I don't know why. I am taking the appName and putting it into the KEY_NAME field of the row and putting 0 into the KEY_USAGE field of the row (because initially, my app will default the usage of each app to 0 (not used yet)). If my addApp() function doesn't take the usage and just puts KEY_NAME into the ContentValues and into the database, it seems to work fine, but I want a column for usage. Any ideas why it is not working? Have I overlooked something? Thanks for your time, InfinitiFizz

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• How does MySQL's ORDER BY RAND() work?

  - by Eugene

  Hi, I've been doing some research and testing on how to do fast random selection in MySQL. In the process I've faced some unexpected results and now I am not fully sure I know how ORDER BY RAND() really works. I always thought that when you do ORDER BY RAND() on the table, MySQL adds a new column to the table which is filled with random values, then it sorts data by that column and then e.g. you take the above value which got there randomly. I've done lots of googling and testing and finally found that the query Jay offers in his blog is indeed the fastest solution: SELECT * FROM Table T JOIN (SELECT CEIL(MAX(ID)*RAND()) AS ID FROM Table) AS x ON T.ID >= x.ID LIMIT 1; While common ORDER BY RAND() takes 30-40 seconds on my test table, his query does the work in 0.1 seconds. He explains how this functions in the blog so I'll just skip this and finally move to the odd thing. My table is a common table with a PRIMARY KEY id and other non-indexed stuff like username, age, etc. Here's the thing I am struggling to explain SELECT * FROM table ORDER BY RAND() LIMIT 1; /*30-40 seconds*/ SELECT id FROM table ORDER BY RAND() LIMIT 1; /*0.25 seconds*/ SELECT id, username FROM table ORDER BY RAND() LIMIT 1; /*90 seconds*/ I was sort of expecting to see approximately the same time for all three queries since I am always sorting on a single column. But for some reason this didn't happen. Please let me know if you any ideas about this. I have a project where I need to do fast ORDER BY RAND() and personally I would prefer to use SELECT id FROM table ORDER BY RAND() LIMIT 1; SELECT * FROM table WHERE id=ID_FROM_PREVIOUS_QUERY LIMIT 1; which, yes, is slower than Jay's method, however it is smaller and easier to understand. My queries are rather big ones with several JOINs and with WHERE clause and while Jay's method still works, the query grows really big and complex because I need to use all the JOINs and WHERE in the JOINed (called x in his query) sub request. Thanks for your time!

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• Is this scenario in compliance with GPLv3?

  - by Sean Kinsey

  For arguments sake, say that we create a web application , that depends on a GPLv3 licensed component, lets say Ext JS. Based on Section 0 of the license, the common notion is that the entire web application (the client side javascript) falls under the definition of a covered work: A “covered work” means either the unmodified Program or a work based on the Program. and that it will therefor have to be distributed under the same license Ok, so here comes the fun part: This is a short 'program' that is based on Ext JS var myPanel = new Ext.Panel(); The question that arises is: Have I now violated the GPL by not including the source of Ext JS and its license? Ok, so lets take another example <!doctype html> <html> <head> <title>my title</title> <script type="text/javascript" src="http://extjs.cachefly.net/ext-3.2.1/ext-all.js"> </script> <link rel="stylesheet" type="text/css" href="http://extjs.cachefly.net/ext-3.2.1/resources/css/ext-all.css" /> <script type="text/javascript"> var myPanel = new Ext.Panel(); </script> </head> <body> </body> </html> Have I now violated the terms of the GPL? The code conveyed by me to you is in a non-functional state - it will have to be combined with the actual source of Ext JS, which you(your browser) will have to retrieve, from a source made public by someone else to be usable. Now, if the answer to the above is no, how does me conveying this code in visible form differ from the 'invisible' form conveyed by my web server? As a side note, a very similar thing is done in Linux with many projects that depends on less permissive licenses - the user has to retrieve these on its own and make these available for the primary lib/executable. How is this not the same if the user is informed on beforehand that he (the browser) will have to retrieve the needed resources from a different source? Just to make it clear, I'm pro FLOSS, and I have also published a number of projects licensed under more permissive licenses. The reason I'm asking this is that I still haven't found anyone offering a definitive answer to this.

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• WCF Troubleshooting from ASP.NET Client -- Help!

  - by Kobojunkie

  I am trying to call a method in my service that is as below, from an ASP.NET application. public bool ValidateUser(string username, string password) { try { // String CurrentLoggedInWindowsUserName = WindowsIdentity.GetCurrent().Name; // //primary identity of the call // String CurrentServiceSecurityContextPrimaryIdentityName = // ServiceSecurityContext.Current.PrimaryIdentity.Name; // } catch (Exception ex) { FaultExceptionFactory fct = new FaultExceptionFactory(); throw new FaultException<CustomFaultException>(fct.CreateFaultException(ex)); } return false; } The Config for the client end of my service is as below <binding name="WSHttpBinding_IMembershipService" closeTimeout="00:01:00" openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00" bypassProxyOnLocal="false" transactionFlow="false" hostNameComparisonMode="StrongWildcard" maxBufferPoolSize="524288" maxReceivedMessageSize="65536" messageEncoding="Text" textEncoding="utf-8" useDefaultWebProxy="false" allowCookies="false"> <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384" maxBytesPerRead="4096" maxNameTableCharCount="16384" /> <reliableSession ordered="true" inactivityTimeout="00:10:00" enabled="false" /> <security mode="Message"> <transport clientCredentialType="Windows" proxyCredentialType="None" realm="" /> <message clientCredentialType="Windows" negotiateServiceCredential="true" algorithmSuite="Default" establishSecurityContext="true" /> </security> </binding> Problem I keep having is when I call it; I get the following exception message. Server Error in '/' Application. The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it is in the Faulted state. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.ServiceModel.CommunicationObjectFaultedException: The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it is in the Faulted state. Stack Trace: [CommunicationObjectFaultedException: The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it is in the Faulted state.] System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg) +7596735 System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type) +275 System.ServiceModel.ICommunicationObject.Close(TimeSpan timeout) +0 System.ServiceModel.ClientBase`1.System.ServiceModel.ICommunicationObject. Close(TimeSpan timeout) +142 System.ServiceModel.ClientBase`1.Close() +38 System.ServiceModel.ClientBase`1.System.IDisposable.Dispose() +4 Controls.Membership.accountLogin.ValidateUserCredentials(String UserName, String Password) in C:\ Petition.WebClient\Controls\ Membership\accountLogin.ascx.cs:49 Controls.Membership.accountLogin.Login1_Authenticate(Object sender, AuthenticateEventArgs e) in C:\ WebClient\ Controls\Membership \accountLogin.ascx.cs:55 I am not entirely sure why I keep getting this. Just in case, here is how I call my service from the client private bool ValidateUserCredentials(string UserName, string Password) { bool boolReturnValue = false; using(Members.MembershipServiceClient client = new Controls.Members.MembershipServiceClient()) { try { boolReturnValue = client.ValidateUser(UserName, Password); } catch (FaultException<CustomFaultException> ex) { throw ex; } } return boolReturnValue; } Anyone have any idea what I need to do in this case?

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• SaaS Architecture Question from Newbie

  - by user226767

  I have developed a number of departmental client-server applications, and am now ready to begin working on moving one of these applications to a SaaS model. I have done some basic web development, but I'm a newbie when it comes to SaaS architectures. One of the first questions that comes to mind as I try to design the architecture is the question of single vs. multi tenancy. The pros and cons of each vary significantly depending on the type of application and scale required, so I'd like to describe my application and scale needs below, and hope others can comment on how I should get started with the architecture. The client-server application currently consists of a Firebird database and a Windows application. The database contains about 20 tables containing a few thousand records in 4 primary tables, and a few hundred records in various lookup and related tables. Although the number of records is small, the size can get large, as the database can contain large BLOBS. Each customer sets up their own database and has a handful of users within the organization connected to it. When I update the db schema, a new windows application is released, and it checks the db schema and then applies the updates as needed. For the SaaS application, I am designing for 100's (not 1000's or millions) of new customers per year. My first thought was to go with a multi tenancy model to make updates easy (shut down apply the updates to one database, and then start up). On the other hand, a single tenancy model would provide a means to roll updates out to a group of customers at a time, and spread the risk of data corruption - i.e. if something goes wrong with a database, it will impact one customer instead of all customers. With this idea, I was thinking of having a single web front-end which would connect to a single customer database upon login. Thus, when a new customer creates an account, a new database would be created (each customer would have their own db with multiple users as needed for the customer). In this model, a db update would require either a process to go through each db to apply schema changes, or a trigger upon logging in to initiate a schema update similar to the client-server model currently in use. Can anyone point me to information for similar applications which have been ported from client-server to SaaS? Or provide any pointers to consider? Basically I'm looking for architecture examples of taking a departmental application and making it available as a self service website for multiple customers. Thanks for any suggestions, resources, etc.

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• How do you make a Custom Data Generator for SQL XML DataType.

  - by Keith Sirmons

  Howdy, I am using Visual Studio 2010 and am playing around with the Database Projects. I am creating a DataGenerationPlan to insert data into a simple table, in which one of the column datatypes is XML. Out of the box, the generation plan uses the Regular Expression generator and generates something like this : HGcSv9wa7yM44T9x5oFT4pmBkEmv62lJ7OyAmCnL6yqXC2X.......... I am looking at creating a custom data Generator for this data type and have followed this site for the basics: http://msdn.microsoft.com/en-us/library/aa833244.aspx This example works if I am creating a string datatype and using it for a nvarchar datatype. What do I need to change to hook this Generator to the XML Datatype? Below are my code files. The string property works for nvarchar. The XElement property does not work for the xml datatype, and the RecordXMLDataGenerator is not listed as an option in the Generator column for the generation plan. CustomDataGenerators: using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Data.Schema.Tools.DataGenerator; using Microsoft.Data.Schema.Extensibility; using Microsoft.Data.Schema; using Microsoft.Data.Schema.Sql; using System.Xml.Linq; namespace CustomDataGenerators { [DatabaseSchemaProviderCompatibility(typeof(SqlDatabaseSchemaProvider))] public class RecordXMLDataGenerator : Generator { private XElement _RecordData; [Output(Description = "Generates string of XML Data for the Record.", Name = "RecordDataString")] public string RecordDataString { get { return _RecordData.ToString(SaveOptions.None); } } [Output(Description = "Generates XML Data for the Record.", Name = "RecordData")] public XElement RecordData { get { return _RecordData; } } protected override void OnGenerateNextValues() { base.OnGenerateNextValues(); XElement element = new XElement("Root", new XElement("Children1", 1), new XElement("Children6", 6) ); _RecordData = element; } } } XML Extensions File: <?xml version="1.0" encoding="utf-8" ?> <extensions assembly="" version="1" xmlns="urn:Microsoft.Data.Schema.Extensions" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:Microsoft.Data.Schema.Extensions Microsoft.Data.Schema.Extensions.xsd"> <extension type="CustomDataGenerators.RecordXMLDataGenerator" assembly="CustomDataGenerators, Version=1.0.0.0, Culture=neutral, PublicKeyToken=xxxxxxxxxxxx" enabled="true"/> </extensions> Table.sql: CREATE TABLE [dbo].[Record] ( id int IDENTITY (1,1) NOT NULL, recordData xml NULL, userId int NULL, test nvarchar(max) NULL, rowver rowversion NULL, CONSTRAINT pk_RecordID PRIMARY KEY (id) )

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• How to designing a generic databse whos layout may change over time?

  - by mawg

  Here's a tricky one - how do I programatically create and interrogate a database who's contents I can't really foresee? I am implementing a generic input form system. The user can create PHP forms with a WYSIWYG layout and use them for any purpose he wishes. He can also query the input. So, we have three stages: a form is designed and generated. This is a one-off procedure, although the form can be edited later. This designs the database. someone or several people make use of the form - say for daily sales reports, stock keeping, payroll, etc. Their input to the forms is written to the database. others, maybe management, can query the database and generate reports. Since these forms are generic, I can't predict the database structure - other than to say that it will reflect HTML form fields and consist of a the data input from collection of edit boxes, memos, radio buttons and the like. Questions and remarks: A) how can I best structure the database, in terms of tables and columns? What about primary keys? My first thought was to use the control name to identify each column, then I realized that the user can edit the form and rename, so that maybe "name" becomes "employee" or "wages" becomes ":salary". I am leaning towards a unique number for each. B) how best to key the rows? I was thinking of a timestamp to allow me to query and a column for the row Id from A) C) I have to handle column rename/insert/delete. Foe deletion, I am unsure whether to delete the data from the database. Even if the user is not inputting it from the form any more he may wish to query what was previously entered. Or there may be some legal requirements to retain the data. Any gotchas in column rename/insert/delete? D) For the querying, I can have my PHP interrogate the database to get column names and generate a form with a list where each entry has a database column name, a checkbox to say if it should be used in the query and, based on column type, some selection criteria. That ought to be enough to build searches like "position = 'senior salesman' and salary 50k". E) I probably have to generate some fancy charts - graphs, histograms, pie charts, etc for query results of numerical data over time. I need to find some good FOSS PHP for this. F) What else have I forgotten? This all seems very tricky to me, but I am database n00b - maybe it is simple to you gurus?

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• Complex Entity Framework linked-graphs issue: how to limit change set / break the graph?

  - by Hightechrider

  I have an EDMX containing Sentences, and Words, say and a Sentence contains three Words, say. Appropriate FK relationships exist between the tables. I create some words: Word word1 = new Word(); Word word2 = ... I build a Sentence: Sentence x = new Sentence (word1, word2, word3); I build another Sentence: Sentence y = new Sentence (word1, word4, word5); I try to save x to the database, but EF builds a change set that includes everything, including y, word4 and word5 that aren't ready to save to the database. When SaveChanges() happens it throws an exception: Unable to determine the principal end of the ... relationship. Multiple added entities may have the same primary key. I think it does this because Word has an EntityCollection<Sentence> on it from the FK relationship between the two tables, and thus Sentence y is inextricably linked to Sentence x through word1. So I remove the Navigation Property Sentences from Word and try again. It still tries to put the entire graph into the change set. What suggestions do the Entity Framework experts have for ways to break this connection. Essentially what I want is a one-way mapping from Sentence to Word; I don't want an EntityCollection<Sentence> on Word and I don't want the object graph to get intertwined like this. Code sample: This puts two sentences into the database because Verb1 links them and EF explores the entire graph of existing objects and added objects when you do Add/SaveChanges. Word subject1 = new Word(){ Text = "Subject1"}; Word subject2 = new Word(){ Text = "Subject2"}; Word verb1 = new Word(){ Text = "Verb11"}; Word object1 = new Word(){ Text = "Object1"}; Word object2 = new Word(){ Text = "Object2"}; Sentence s1 = new Sentence(){Subject = subject1, Verb=verb1, Object=object1}; Sentence s2 = new Sentence(){Subject=subject2, Verb=verb1, Object=object2}; context.AddToSentences(s1); context.SaveChanges(); foreach (var s in context.Sentences) { Console.WriteLine(s.Subject + " " + s.Verb + " " + s.Object); }

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• How do I add a column that displays the number of distinct rows to this query?

  - by Fake Code Monkey Rashid

  Hello good people! I don't know how to ask my question clearly so I'll just show you the money. To start with, here's a sample table: CREATE TABLE sandbox ( id integer NOT NULL, callsign text NOT NULL, this text NOT NULL, that text NOT NULL, "timestamp" timestamp with time zone DEFAULT now() NOT NULL ); CREATE SEQUENCE sandbox_id_seq START WITH 1 INCREMENT BY 1 NO MINVALUE NO MAXVALUE CACHE 1; ALTER SEQUENCE sandbox_id_seq OWNED BY sandbox.id; SELECT pg_catalog.setval('sandbox_id_seq', 14, true); ALTER TABLE sandbox ALTER COLUMN id SET DEFAULT nextval('sandbox_id_seq'::regclass); INSERT INTO sandbox VALUES (1, 'alpha', 'foo', 'qux', '2010-12-29 16:51:09.897579+00'); INSERT INTO sandbox VALUES (2, 'alpha', 'foo', 'qux', '2010-12-29 16:51:36.108867+00'); INSERT INTO sandbox VALUES (3, 'bravo', 'bar', 'quxx', '2010-12-29 16:52:36.370507+00'); INSERT INTO sandbox VALUES (4, 'bravo', 'foo', 'quxx', '2010-12-29 16:52:47.584663+00'); INSERT INTO sandbox VALUES (5, 'charlie', 'foo', 'corge', '2010-12-29 16:53:00.742356+00'); INSERT INTO sandbox VALUES (6, 'delta', 'foo', 'qux', '2010-12-29 16:53:10.884721+00'); INSERT INTO sandbox VALUES (7, 'alpha', 'foo', 'corge', '2010-12-29 16:53:21.242904+00'); INSERT INTO sandbox VALUES (8, 'alpha', 'bar', 'corge', '2010-12-29 16:54:33.318907+00'); INSERT INTO sandbox VALUES (9, 'alpha', 'baz', 'quxx', '2010-12-29 16:54:38.727095+00'); INSERT INTO sandbox VALUES (10, 'alpha', 'bar', 'qux', '2010-12-29 16:54:46.237294+00'); INSERT INTO sandbox VALUES (11, 'alpha', 'baz', 'qux', '2010-12-29 16:54:53.891606+00'); INSERT INTO sandbox VALUES (12, 'alpha', 'baz', 'corge', '2010-12-29 16:55:39.596076+00'); INSERT INTO sandbox VALUES (13, 'alpha', 'baz', 'corge', '2010-12-29 16:55:44.834019+00'); INSERT INTO sandbox VALUES (14, 'alpha', 'foo', 'qux', '2010-12-29 16:55:52.848792+00'); ALTER TABLE ONLY sandbox ADD CONSTRAINT sandbox_pkey PRIMARY KEY (id); Here's the current SQL query I have: SELECT * FROM ( SELECT DISTINCT ON (this, that) id, this, that, timestamp FROM sandbox WHERE callsign = 'alpha' AND CAST(timestamp AS date) = '2010-12-29' ) playground ORDER BY timestamp DESC This is the result it gives me: id this that timestamp ----------------------------------------------------- 14 foo qux 2010-12-29 16:55:52.848792+00 13 baz corge 2010-12-29 16:55:44.834019+00 11 baz qux 2010-12-29 16:54:53.891606+00 10 bar qux 2010-12-29 16:54:46.237294+00 9 baz quxx 2010-12-29 16:54:38.727095+00 8 bar corge 2010-12-29 16:54:33.318907+00 7 foo corge 2010-12-29 16:53:21.242904+00 This is what I want to see: id this that timestamp count ------------------------------------------------------------- 14 foo qux 2010-12-29 16:55:52.848792+00 3 13 baz corge 2010-12-29 16:55:44.834019+00 2 11 baz qux 2010-12-29 16:54:53.891606+00 1 10 bar qux 2010-12-29 16:54:46.237294+00 1 9 baz quxx 2010-12-29 16:54:38.727095+00 1 8 bar corge 2010-12-29 16:54:33.318907+00 1 7 foo corge 2010-12-29 16:53:21.242904+00 1 EDIT: I'm using PostgreSQL 9.0.* (if that helps any).

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• Exception opening TAdoDataset: Arguments are of the wrong type, are out of acceptable range, or are

  - by Dave Falkner

  I've been trying to debug the following problem for several weeks now - this method is called from several places within the same datamodule, but this exception (from the subject line of this post) only occurs when integers for a certain purpose (pickup orders vs. orders that we ship through a carrier) are used - and don't ask me how the application can tell the difference between one integer's purpose and another! Furthermore, I cannot duplicate this issue on my machine - the error occurs on a warehouse machine but not my own development machine, even when working with the same production database. I have suspected an MDAC version conflict between the two machines, but have run a version checker and confirmed that both machines are running 2.8, and additionally have confirmed this by logging the TAdoDataset's .Version property at runtime. function TdmESShip.SecondaryID(const PrimaryID : Integer ): String; begin try with qESPackage2 do begin if Active then Close; LogMessage('-----------------------------------'); LogMessage('Version: ' + FConnection.Version); LogMessage('DB Info: ' + FConnection.Properties['Initial Catalog'].Value + ' ' + FConnection.Properties['Data Source'].Value); LogMessage('Setting the parameter.'); Parameters.ParamByName('ParameterName').Value := PrimaryID; LogMessage('Done setting the parameter.'); Open; Ninety-nine times out of 100 this logging code logs a successful operation as follows: Version: 2.8 DB Info: (database name and instance) Setting the parameter. Done setting the parameter. Opened the dataset. But then whenever a "pickup" order is processed, this exception gets thrown whenever the dataset is opened: Version: 2.8 DB Info: (database name and instance) Setting the parameter. Done setting the parameter. GetESPackageID() threw an exception. Type: EOleException, Message: Arguments are of the wrong type, are out of acceptable range, or are in conflict with one another Error: Arguments are of the wrong type, are out of acceptable range, or are in conflict with one another for packageID 10813711 I've tried eliminating the parameter and have built the commandtext for this dataset programmatically, suspecting that some part of the TParameter's configuration might be out of whack, but the same error occurs under the same circumstances. I've tried every combination of TParameter properties that I can think of - this is the millionth TParameter I've created for my millionth dataset, and I've never encountered this error. I've even created a second dataset from scratch and removed all references to the original dataset in case some property of the original dataset in the .dfm might be corrupted, but the same error occurs under the same circumstances. The commandtext for this dataset is a simple select ValueA from TableName where ValueB = @ParameterB I'm about ready to do something extreme, such as writing a web service to look these values up - it feels right now as though I could destroy my machine, rebuild it, rewrite this entire application from scratch, and the application would still know to throw an exception whenever I try to look up a secondary value from a primary value, but only for pickup orders, and only from the one machine in the warehouse, but I'm probably missing something simple. So, any help anyone could provide would be greatly appreciated.

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• SQL Server 2005 - query with case statement

  - by user329266

  Trying to put a single query together to be used eventually in a SQL Server 2005 report. I need to: Pull in all distinct records for values in the "eventid" column for a time frame - this seems to work. For each eventid referenced above, I need to search for all instances of the same eventid to see if there is another record with TaskName like 'review1%'. Again, this seems to work. This is where things get complicated: For each record where TaskName is like review1, I need to see if another record exists with the same eventid and where TaskName='End'. Utimately, I need a count of how many records have TaskName like 'review1%', and then how many have TaskName like 'review1%' AND TaskName='End'. I would think this could be accomplished by setting a new value for each record, and for the eventid, if a record exists with TaskName='End', set to 1, and if not, set to 0. The query below seems to accomplish item #1 above: SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000'))) AS T WHERE seq = 1 order by eventid And the query below seems to accomplish #2: SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000')) and TaskName like 'Review1%') AS T WHERE seq = 1 order by eventid This will bring back the eventid's that also have a TaskName='End': SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000')) and TaskName like 'Review1%') AS T WHERE seq = 1 and eventid in (Select eventid from eventrecords where TaskName = 'End') order by eventid So I've tried the following to TRY to accomplish #3: SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000')) and TaskName like 'Review1%') AS T WHERE seq = 1 and case when (eventid in (Select eventid from eventrecords where TaskName = 'End') then 1 else 0) as bit end order by eventid When I try to run this, I get: "Incorrect syntax near the keyword 'then'." Not sure what I'm doing wrong. Haven't seen any examples anywhere quite like this. I should mention that eventrecords has a primary key, but it doesn't seem to help anything when I include it, and I am not permitted to change the table. (ugh) I've received one suggestion to use a cursor and temporary table, but am not sure how badley that would bog down performance when the report is running. Thanks in advance.

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• Reading a file with a supplied name in C++

  - by Cosmina

  I must read a file with a given name (it's caled "hamlet.txt"). The class used to read the file is defined like this #ifndef READWORDS_H #define READWORDS_H /** * ReadWords class. Provides mechanisms to read a text file, and return * capitalized words from that file. */ using namespace std; #include <string> #include <fstream> class ReadWords { public: /** * Constructor. Opens the file with the default name "text.txt". * Program exits with an error message if the file does not exist. */ ReadWords(); /** * Constructor. Opens the file with the given filename. * Program exits with an error message if the file does not exist. * @param filename - a C string naming the file to read. */ ReadWords(char *filename); My definition of the members of the classis this: #include<string> #include<fstream> #include<iostream> #include "ReadWords.h" using namespace std; ReadWords::ReadWords() { wordfile.open("text.txt"); if( !wordfile ) { cout<<"Errors while opening the file!"<<endl; } } ReadWords::ReadWords(char *filename) { wordfile.open(filename); if ( !wordfile ) { cout<<"Errors while opening the file!"<<endl; } wordfile>>nextword; } And the main to test it. using namespace std; #include #include #include "ReadWords.h" int main() { char name[30]; cout<<"Please input a name for the file that you wish to open"; cin>>name; ReadWords x( name[] ); } When I complie it gives me the error: main.cpp:14: error: expected primary-expression before ']' token I know it's got something to do with the function ReadWords( char *filename), but I do not know what. Any help please?

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• Do you know why introducing jquery ui autocomplete for my dropdown boxes is also changing my listbox

  - by oo

  I am trying to change my comboboxes to use autocomplete so i leverage the code listed here (which worked perfectly for my dropdowns) The issue is that i also on the same page have a listbox with the following code: <%= Html.ListBox("Cars", Model.BodyParts.Select( x => new SelectListItem { Text = x.Name, Value = x.Id, Selected = Model.CarsSelected.Any(y => y.Id == x.Id) } ))%> and it appears that the jquery ui code is changing this to a autocomplete dropdown as well (as opposed to keeping it as a multi select list box) any idea how to prevent this from happening? i literally am just using the exact code on this page <script type="text/javascript"> (function($) { $.widget("ui.combobox", { _create: function() { var self = this; var select = this.element.hide(); var input = $("<input>") .insertAfter(select) .autocomplete({ source: function(request, response) { var matcher = new RegExp(request.term, "i"); response(select.children("option").map(function() { var text = $(this).text(); if (!request.term || matcher.test(text)) return { id: $(this).val(), label: text.replace(new RegExp("(?![^&;]+;)(?!<[^<>]*)(" + request.term.replace(/([\^\$\(\)\[\]\{\}\*\.\+\?\|\\])/gi, "\\$1") + ")(?![^<>]*>)(?![^&;]+;)", "gi"), "<strong>$1</strong>"), value: text }; })); }, delay: 0, select: function(e, ui) { if (!ui.item) { // remove invalid value, as it didn't match anything $(this).val(""); return false; } $(this).focus(); select.val(ui.item.id); self._trigger("selected", null, { item: select.find("[value='" + ui.item.id + "']") }); }, minLength: 0 }) .addClass("ui-widget ui-widget-content ui-corner-left"); $("<button>&nbsp;</button>") .insertAfter(input) .button({ icons: { primary: "ui-icon-triangle-1-s" }, text: false }).removeClass("ui-corner-all") .addClass("ui-corner-right ui-button-icon") .position({ my: "left center", at: "right center", of: input, offset: "-1 0" }).css("top", "") .click(function() { // close if already visible if (input.autocomplete("widget").is(":visible")) { input.autocomplete("close"); return; } // pass empty string as value to search for, displaying all results input.autocomplete("search", ""); input.focus(); }); } }); })(jQuery); $(function() { $("select").combobox(); }); </script>

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• Is there a way to split a widescreen monitor in to two or more virtual monitors?

  - by Mike Thompson

  Like most developers I have grown to love dual monitors. I won't go into all the reasons for their goodness; just take it as a given. However, they are not perfect. You can never seem to line them up "just right". You always end up with the monitors at slight funny angles. And of course the bezel always gets in the way. And this is with identical monitors. The problem is much worse with different monitors -- VMWare's multi monitor feature won't even work with monitors of differnt resolutions. When you use multiple monnitors, one of them becomes your primary monitor of focus. Your focus may flip from one monitor to the other, but at any point in time you are usually focusing on only one monitor. There are exceptions to this (WinDiff, Excel), but this is generally the case. I suggest that having a single large monitor with all the benefits of multiple smaller monitors would be a better solution. Wide screen monitors are fantastic, but it is hard to use all the space efficiently. If you are writing code you are generally working on the left-hand side of the window. If you maximize an editor on a wide-screen monitor the right-hand side of the window will be a sea of white. Programs like WinSplit Revolution will help to organise your windows, but this is really just addressing the symptom, not the problem. Even with WinSplit Revolution, when you maximise a window it will take up the whole screen. You can't lock a window into a specific section of the screen. This is where virtual monitors comes in. What would be really nice is a video driver that sits on top of the existing driver, but allows a single monitor to be virtualised into multiple monitors. Control Panel would see your single physical monitor as two or more virtual monitors. The software could even support a virtual bezel to emphasise what is happening, or you could opt for seamless mode. Programs like WinSplit Revolution and UltraMon would still work. This virtual video driver would allow you to slice & dice your physical monitor into as many virtual monitors as you want. Does anybody know if such software exists? If not, are there any budding Windows display driver guru's out there willing to take up the challenge? I am not after the myriad of virtual desktop/window manager programs that are available. I get frustrated with these programs. They seem good at first but they usually have some strange behaviour and don't work well with other programs (such as WinSplit Revolution). I want the real thing!

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• bundler/capistrano is not installing gems with correct ruby version

  - by Douglas

  I'm trying to deploy my first app on a server with Capistrano, and I'm a bit lost with managing gemsets and ruby version. These are my (server and workstation) versions : Rails 3.2.8 RVM 1.16.17 Gem 1.8.24 Bundler 1.2.1 pg gem 0.14.1 My gemset are : Gemsets for ruby-1.9.3-p194 (found in /usr/local/rvm/gems/ruby-1.9.3-p194) (default) global = rail3dev20120606 I set the default gemset with : rvm use 1.9.3-p194@rail3dev20120606 --default --passenger When I run a : cap bundle:install The task end with success, but when I do a : gem list There are many missing gems though they are present in my Gemfile. When I go to check my gems in /var/www/opf/shared/bundle/ruby/ I find a folder called 1.9.1 and in /var/www/opf/shared/bundle/ruby/1.9.1/gems/ I can fond all of my needed gems (specified in Gemfile). I'm sure there is a problem with ruby version, but how do I solve this ? At the moment, if I do any rake command, I got a ruby crash [Bug] Segmentation fault, as it try to access the db and using postgresql_adapter. I think as many gems are missing there must have some gem dependencies not verified, and maybe a gem is using an incompatible ruby version 1.9.1 though it expect a 1.9.3. I think the issue is around managing ruby versions and gems. I'm certainly doing some mix with gemset and my capistrano deployement. I'm missing experience and info. Could anybody advise me how to handle this on the server ? What are the best practices ? How am I suppose to update my ruby version ? with Capistrano deploy.rb ? manually ? with/without rvm ? I saw a new version of ruby 1.9.3-p327 has just released. Should I use gemset or not ? What about the :rvm_ruby_string in my deploy.rb. Is it correctly spelled or should I remove the p194 part ? Should I Remove the :rvm_ruby_string ? Keep it ? Use a .rvmrc file ??? I'm really lost and some kind help would be welcome. This is my config/deploy.rb in any case : require 'bundler/capistrano' require File.join(File.dirname(__FILE__), 'deploy') + '/capistrano_database' set :rvm_type, :system set :rvm_ruby_string, 'ruby-1.9.3-p194@rail3dev20120606' require 'rvm/capistrano' set :application, 'opf' set :deploy_to, '/var/www/opf' set :rails_env, 'production' set :user, 'the_user' set :use_sudo, false set :group_writable, false set :scm, :git set :repository, '[email protected]:user/opf.git' set :branch, 'master' default_run_options[:pty] = true set :deploy_via, :remote_cache server '192.168.5.200', :web, :app, :db, :primary => true # If you are using Passenger mod_rails uncomment this: namespace :deploy do task :start do ; end task :stop do ; end task :restart, :roles => :app, :except => { :no_release => true } do run "#{try_sudo} touch #{File.join(current_path,'tmp','restart.txt')}" end end Thanks for any help

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• Cross-thread operation not valid: Control accessed from a thread other than the thread it was create

  - by SilverHorse

  I have a scenario. (Windows Forms, C#, .NET) There is a main form which hosts some user control. The user control does some heavy data operation, such that if I directly call the Usercontrol_Load method the UI become nonresponsive for the duration for load method execution. To overcome this I load data on different thread (trying to change existing code as little as I can) I used a background worker thread which will be loading the data and when done will notify the application that it has done its work. Now came a real problem. All the UI (main form and its child usercontrols) was created on the primary main thread. In the LOAD method of the usercontrol I'm fetching data based on the values of some control (like textbox) on userControl. The pseudocode would look like this: //CODE 1 UserContrl1_LOadDataMethod() { if(textbox1.text=="MyName") <<======this gives exception { //Load data corresponding to "MyName". //Populate a globale variable List<string> which will be binded to grid at some later stage. } } The Exception it gave was Cross-thread operation not valid: Control accessed from a thread other than the thread it was created on. To know more about this I did some googling and a suggestion came up like using the following code //CODE 2 UserContrl1_LOadDataMethod() { if(InvokeRequired) // Line #1 { this.Invoke(new MethodInvoker(UserContrl1_LOadDataMethod)); return; } if(textbox1.text=="MyName") //<<======Now it wont give exception** { //Load data correspondin to "MyName" //Populate a globale variable List<string> which will be binded to grid at some later stage } } BUT BUT BUT... it seems I'm back to square one. The Application again become nonresponsive. It seems to be due to the execution of line #1 if condition. The loading task is again done by the parent thread and not the third that I spawned. I don't know whether I perceived this right or wrong. I'm new to threading. How do I resolve this and also what is the effect of execution of Line#1 if block? The situation is this: I want to load data into a global variable based on the value of a control. I don't want to change the value of a control from the child thread. I'm not going to do it ever from a child thread. So only accessing the value so that the corresponding data can be fetched from the database.

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• Are there programs that iteratively write new programs?

  - by chris

  For about a year I have been thinking about writing a program that writes programs. This would primarily be a playful exercise that might teach me some new concepts. My inspiration came from negentropy and the ability for order to emerge from chaos and new chaos to arise out of order in infinite succession. To be more specific, the program would start by writing a short random string. If the string compiles the programs will log it for later comparison. If the string does not compile the program will try to rewrite it until it does compile. As more strings (mini 'useless' programs) are logged they can be parsed for similarities and used to generate a grammar. This grammar can then be drawn on to write more strings that have a higher probability of compilation than purely random strings. This is obviously more than a little silly, but I thought it would be fun to try and grow a program like this. And as a byproduct I get a bunch of unique programs that I can visualize and call art. I'll probably write this in Ruby due to its simple syntax and dynamic compilation and then I will visualize in processing using ruby-processing. What I would like to know is: Is there a name for this type of programming? What currently exists in this field? Who are the primary contributors? BONUS! - In what ways can I procedurally assign value to output programs beyond compiles(y/n)? I may want to extend the functionality of this program to generate a program based on parameters, but I want the program to define those parameters through running the programs that compile and assigning meaning to the programs output. This question is probably more involved than reasonable for a bonus, but if you can think of a simple way to get something like this done in less than 23 lines or one hyperlink, please toss it into your response. I know that this is not quite meta-programming and from the little I know of AI and generative algorithms they are usually more goal oriented than what I am thinking. What would be optimal is a program that continually rewrites and improves itself so I don't have to ^_^

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• Closure Tables - Is this enough data to display a tree view?

  - by James Pitt

  Here is the table I have created by testing the closure table method. | id | parentId | childId | hops | | | | | 270 | 6 | 6 | 0 | 271 | 7 | 7 | 0 | 272 | 8 | 8 | 0 | 273 | 9 | 9 | 0 | 276 | 10 | 10 | 0 | 281 | 9 | 10 | 1 | 282 | 7 | 9 | 1 | 283 | 7 | 10 | 2 | 285 | 7 | 8 | 1 | 286 | 6 | 7 | 1 | 287 | 6 | 9 | 2 | 288 | 6 | 10 | 3 | 289 | 6 | 8 | 2 | 293 | 6 | 9 | 1 | 294 | 6 | 10 | 2 I am trying to create a simple tree of this using PHP. There does not seem to be enough data to create the table. For example, when I look purely at parentId = 6: -Part 6 -Part 7 - ? - ? -Part 9 - ? - ? We know that parts 8 and 10 exists below Part 7 or 9, but not which. We know that part 10 exists at both 3 and 4 nodes deep but where? If I look at other data in the table it is possible to tell it should be: - Part 6 - Part 7 - Part 9 - Part 10 - Part 9 - Part 10 I thought one of the benefits of closure tables was there was no need for recursive queries? Could you help explain what I am doing wrong? EDIT: For clarification, this is a mapping table. There is another table called "parts" which has a column called part_id that correlates to both the parentId and childId columns in the "closure" table. The "id" column in the table above (closure) is just for the purposes of maintaining a primary key. It is not really necessary. The methods I have used to create this closure table is described in the following article: http://dirtsimple.org/2010/11/simplest-way-to-do-tree-based-queries.html EDIT2: It can have two and three hops. I will explain easier by assigning names to the items. Part 6 = Bicycle Part 7 = Gears Part 8 = Chain Part 9 = Bolt Part 10 = Nut Nut is part of Bolt. The Bolt and Nut combo exists directly within Bicycle and within Gears which is part of Bicycle. In relation to what method to use I have looked at Adjacency, Edges, Enum Paths, Closures, DAGS(networks) and the Nested Set Model. I am still trying to work out what is what, but this is an extremely complex component database where there are multiple parents and any modification to a sub-tree must propogate through the other trees. More importantly there will be insertions, deletions and tree views that I wish to avoid recursion during general use, even at the cost of database space and query time during entry.

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• Is READ UNCOMMITTED / NOLOCK safe in this situation?

  - by Ben Challenor

  I know that snapshot isolation would fix this problem, but I'm wondering if NOLOCK is safe in this specific case so that I can avoid the overhead. I have a table that looks something like this: drop table Data create table Data ( Id BIGINT NOT NULL, Date BIGINT NOT NULL, Value BIGINT, constraint Cx primary key (Date, Id) ) create nonclustered index Ix on Data (Id, Date) There are no updates to the table, ever. Deletes can occur but they should never contend with the SELECT because they affect the other, older end of the table. Inserts are regular and page splits to the (Id, Date) index are extremely common. I have a deadlock situation between a standard INSERT and a SELECT that looks like this: select top 1 Date, Value from Data where Id = @p0 order by Date desc because the INSERT acquires a lock on Cx (Date, Id; Value) and then Ix (Id, Date), but the SELECT acquires a lock on Ix (Id, Date) and then Cx (Date, Id; Value). This is because the SELECT first seeks on Ix and then joins to a seek on Cx. Swapping the clustered and non-clustered index would break this cycle, but it is not an acceptable solution because it would introduce cycles with other (more complex) SELECTs. If I add NOLOCK to the SELECT, can it go wrong in this case? Can it return: More than one row, even though I asked for TOP 1? No rows, even though one exists and has been committed? Worst of all, a row that doesn't satisfy the WHERE clause? I've done a lot of reading about this online, but the only reproductions of over- or under-count anomalies I've seen (one, two) involve a scan. This involves only seeks. Jeff Atwood has a post about using NOLOCK that generated a good discussion. I was particularly interested in a comment by Rick Townsend: Secondly, if you read dirty data, the risk you run is of reading the entirely wrong row. For example, if your select reads an index to find your row, then the update changes the location of the rows (e.g.: due to a page split or an update to the clustered index), when your select goes to read the actual data row, it's either no longer there, or a different row altogether! Is this possible with inserts only, and no updates? If so, then I guess even my seeks on an insert-only table could be dangerous. Update: I'm trying to figure out how snapshot isolation works. It seems to be row-based, where transactions read the table (with no shared lock!), find the row they are interested in, and then see if they need to get an old version of the row from the version store in tempdb. But in my case, no row will have more than one version, so the version store seems rather pointless. And if the row was found with no shared lock, how is it different to just using NOLOCK?

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• JPA Entity Manager resource handling

  - by chiragshahkapadia

  Every time I call JPA method its creating entity and binding query. My persistence properties are: <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect"/> <property name="hibernate.cache.provider_class" value="net.sf.ehcache.hibernate.SingletonEhCacheProvider"/> <property name="hibernate.cache.use_second_level_cache" value="true"/> <property name="hibernate.cache.use_query_cache" value="true"/> And I am creating entity manager the way shown below: emf = Persistence.createEntityManagerFactory("pu"); em = emf.createEntityManager(); em = Persistence.createEntityManagerFactory("pu").createEntityManager(); Is there any nice way to manage entity manager resource instead create new every time or any property can set in persistence. Remember it's JPA. See below binding log every time : 15:35:15,527 INFO [AnnotationBinder] Binding entity from annotated class: * 15:35:15,527 INFO [QueryBinder] Binding Named query: * = * 15:35:15,527 INFO [QueryBinder] Binding Named query: * = * 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [EntityBinder] Bind entity com.* on table * 15:35:15,542 INFO [HibernateSearchEventListenerRegister] Unable to find org.hibernate.search.event.FullTextIndexEventListener on the classpath. Hibernate Search is not enabled. 15:35:15,542 INFO [NamingHelper] JNDI InitialContext properties:{} 15:35:15,542 INFO [DatasourceConnectionProvider] Using datasource: 15:35:15,542 INFO [SettingsFactory] RDBMS: and Real Application Testing options 15:35:15,542 INFO [SettingsFactory] JDBC driver: Oracle JDBC driver, version: 9.2.0.1.0 15:35:15,542 INFO [Dialect] Using dialect: org.hibernate.dialect.Oracle10gDialect 15:35:15,542 INFO [TransactionFactoryFactory] Transaction strategy: org.hibernate.transaction.JDBCTransactionFactory 15:35:15,542 INFO [TransactionManagerLookupFactory] No TransactionManagerLookup configured (in JTA environment, use of read-write or transactional second-level cache is not recomm ended) 15:35:15,542 INFO [SettingsFactory] Automatic flush during beforeCompletion(): disabled 15:35:15,542 INFO [SettingsFactory] Automatic session close at end of transaction: disabled 15:35:15,542 INFO [SettingsFactory] JDBC batch size: 15 15:35:15,542 INFO [SettingsFactory] JDBC batch updates for versioned data: disabled 15:35:15,542 INFO [SettingsFactory] Scrollable result sets: enabled 15:35:15,542 INFO [SettingsFactory] JDBC3 getGeneratedKeys(): disabled 15:35:15,542 INFO [SettingsFactory] Connection release mode: auto 15:35:15,542 INFO [SettingsFactory] Default batch fetch size: 1 15:35:15,542 INFO [SettingsFactory] Generate SQL with comments: disabled 15:35:15,542 INFO [SettingsFactory] Order SQL updates by primary key: disabled 15:35:15,542 INFO [SettingsFactory] Order SQL inserts for batching: disabled 15:35:15,542 INFO [SettingsFactory] Query translator: org.hibernate.hql.ast.ASTQueryTranslatorFactory 15:35:15,542 INFO [ASTQueryTranslatorFactory] Using ASTQueryTranslatorFactory 15:35:15,542 INFO [SettingsFactory] Query language substitutions: {} 15:35:15,542 INFO [SettingsFactory] JPA-QL strict compliance: enabled 15:35:15,542 INFO [SettingsFactory] Second-level cache: enabled 15:35:15,542 INFO [SettingsFactory] Query cache: enabled 15:35:15,542 INFO [SettingsFactory] Cache region factory : org.hibernate.cache.impl.bridge.RegionFactoryCacheProviderBridge 15:35:15,542 INFO [RegionFactoryCacheProviderBridge] Cache provider: net.sf.ehcache.hibernate.SingletonEhCacheProvider 15:35:15,542 INFO [SettingsFactory] Optimize cache for minimal puts: disabled 15:35:15,542 INFO [SettingsFactory] Structured second-level cache entries: disabled 15:35:15,542 INFO [SettingsFactory] Query cache factory: org.hibernate.cache.StandardQueryCacheFactory 15:35:15,542 INFO [SettingsFactory] Statistics: disabled 15:35:15,542 INFO [SettingsFactory] Deleted entity synthetic identifier rollback: disabled 15:35:15,542 INFO [SettingsFactory] Default entity-mode: pojo 15:35:15,542 INFO [SettingsFactory] Named query checking : enabled 15:35:15,542 INFO [SessionFactoryImpl] building session factory 15:35:15,542 INFO [SessionFactoryObjectFactory] Not binding factory to JNDI, no JNDI name configured 15:35:15,542 INFO [UpdateTimestampsCache] starting update timestamps cache at region: org.hibernate.cache.UpdateTimestampsCache 15:35:15,542 INFO [StandardQueryCache] starting query cache at region: org.hibernate.cache.StandardQueryCache

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