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  • How do you create a transaction that spans multiple statements in Python with MySQLdb?

    - by Fast Fish
    I know that with an InnoDB table, transactions are autocommit, however I understand that to mean for a single statement? For example, I want to check if a user exists in a table, and then if it doesn't, create it. However there lies a race condition. I believe using a transaction prior to doing the select, will ensure that the table remains untouched until the subsequent insert, and the transaction is committed. How can you do this with MySQLdb and Python?

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  • How to add new object to an IList mapped as a one-to-many with NHibernate?

    - by Jørn Schou-Rode
    My model contains a class Section which has an ordered list of Statics that are part of this section. Leaving all the other properties out, the implementation of the model looks like this: public class Section { public virtual int Id { get; private set; } public virtual IList<Static> Statics { get; private set; } } public class Static { public virtual int Id { get; private set; } } In the database, the relationship is implemented as a one-to-many, where the table Static has a foreign key pointing to Section and an integer column Position to store its index position in the list it is part of. The mapping is done in Fluent NHibernate like this: public SectionMap() { Id(x => x.Id); HasMany(x => x.Statics).Cascade.All().LazyLoad() .AsList(x => x.WithColumn("Position")); } public StaticMap() { Id(x => x.Id); References(x => x.Section); } Now I am able to load existing Statics, and I am also able to update the details of those. However, I cannot seem to find a way to add new Statics to a Section, and have this change persisted to the database. I have tried several combinations of: mySection.Statics.Add(myStatic) session.Update(mySection) session.Save(myStatic) but the closest I have gotten (using the first two statements), is to an SQL exception reading: "Cannot insert the value NULL into column 'Position'". Clearly an INSERT is attempted here, but NHibernate does not seem to automatically append the index position to the SQL statement. What am I doing wrong? Am I missing something in my mappings? Do I need to expose the Position column as a property and assign a value to it myself? EDIT: Apparently everything works as expected, if I remove the NOT NULL constraint on the Static.Position column in the database. I guess NHibernate makes the insert and immediatly after updates the row with a Position value. While this is an anwers to the question, I am not sure if it is the best one. I would prefer the Position column to be not nullable, so I still hope there is some way to make NHibernate provide a value for that column directly in the INSERT statement. Thus, the question is still open. Any other solutions?

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  • Do i need to dispose of MySqlCommand?

    - by acidzombie24
    I find it incredibly annoying to write a using statement on every one of my queries (which require its own command or write parameters.clear()) which sometimes require declaring variables outside of the using block. Its so incredibly annoying and looks much dirtier compared to the version without disposing the object. Do i need to dispose of it? what happens if i dont? I do know its good practice to dispose of an object when it has that interface.

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  • In Python, can I single line a for loop over iterator with an IF filter?

    - by Tal Weiss
    Silly question: I have a simple for loop followed by a simple if statement: for airport in airports: if airport.is_important: and I was wondering if I can write this as a single line somehow. So, yes, I can do this: for airport in (airport for airport in airports if airport.is_important): but it reads so silly and redundant ("for airport in airport for airport in airports..."). Is there a better way?

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  • LINQ causing my obfuscator to break

    - by JL
    I have the following LINQ that is causing my obfuscator to break. .Where(f => f.FileName == fileName).OrderByDescending(f => f.Position).FirstOrDefault(); Is there another way I could reword this LINQ statement to test against my obfuscator? I've reported the bug, but it could take 1-2 months to fix, so I need to try recode this LINQ in the meantime.

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  • SQL simple selection of rows according to their time

    - by iracema78280
    Hello, I have a table with measures and the time this measures have been taken in the following form: MM/DD/YYYY HH:MI:SS AM. I have measures over many days starting at the same time every day.The datas are minute by minute so basically the seconds are always = 0. I want to select only the measures for the first 5 minutes of each day. I would have used the where statement but the condition would only be on the minutes and note the date is there a way to do this? Thanks

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  • How do I empty Drupal Cache (without Devel)

    - by alexanderpas
    Okay... Seems i can't find it with google... so here you go SO ;) How do i empty the drupal caches: without the Devel module without running some PHP Statement in a new node etc. without going into the database itself Effectively, how do you instruct a luser to clear his caches

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  • Java Regular Expression. Check if String contains ONLY Letters

    - by user69514
    How do I check if a String contains only letters in java? I want to write an if statement that will return false if there is a white space, a number, a symbol or anything else other than a-z A-Z. My string must contain ONLY letters. I thought I could do it this way, but I'm doing it wrong: if( ereg("[a-zA-Z]+", $myString)) return true; else return false;

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  • Get query from java.sql.PreparedStatement

    - by llm
    In my code I am using java.sql.PreparedStatement. I then execute the setString() method to populate the wildcards of the prepared statement. Is there a way for me to retrieve (and print out) the final query before the executeQuery() method is called and the query is executed? I Just want this for debugging purposes. Thanks.

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  • T-SQL query and group by reporting help

    - by Dayton Brown
    So I have some data that looks like this. `USERID1 USERID2` 1 10 2 20 2 30 3 40 3 50 1 10 2 20 2 30 3 50 I want a query that produces the following `USERID1 COUNT` 2 2 3 2 It's a group by query that shows me the count of unique USERID2 for each USERID1 that has more than 1 USERID2 associated with it. God I hope you aren't as confused as I am by that last statement.

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  • Cleaning up a SQL SP with Regex

    - by Douglas Osborne
    1) If I am running a find and replace in SQL 2005 - what would be the regular expression to find tab and space sequences ( or space and tab sequences ) and replace them with just tab? 2) If I have a line which begins with a space - is there a regular expression to convert that leading space to a tab? 3) What would be the regular expression to remove all of the spaces before a CR/LF in a SQL statement? TIA for the help - I know this will be trivial to most of you, Doug

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  • Should mutex.WaitOne() inside or before the try/finally block.

    - by chillitom
    Hi Guys, I was wondering which of the following was the suggested pattern when using Mutex (or Semaphores or ReadWriteLockSlims etc.). Should the initial lock happen inside or outside of the try statement? Is it unimportant? _mutex.WaitOne() try { // critical code } finally { _mutex.ReleaseMutex(); } or try { _mutex.WaitOne() // critical code } finally { _mutex.ReleaseMutex(); }

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  • Dispose a Web Service Proxy class?

    - by Matt
    When you create and use a Web Service proxy class in the ASP.Net framework, the class ultimately inherits from Component, which implements IDisposable. I have never seen one example online where people dispose of a web proxy class, but was wondering if it really needs to be done. When I call only one method, I normally wrap it in a using statement, but if I have a need to call it several times throughout the page, I might end up using the same instance, and just wondered what the ramifications are of not disposing it.

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  • SQLite3 Integer Max Value

    - by peterwkc
    Hello to all, what is the maximum value of data type INTEGER in sqlite3 ? How do you store ip address in database ? What is attached ? How to create table which belongs to a specific database using sql ddl? What is this error about ? error while the list of system catalogue : no such table: temp.sqlite_master Unable to execute statement Does sqlite3 text data type supoports unicode? Thanks.

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  • C# equivalent to VB.NET Catch ... When

    - by fung
    In VB.NET I often Catch ... When ... Try ' Some code' Catch e As ArgumentNullException When e.ParamName.ToUpper() = "SAMPLES" ' Handle the error' End Try Is there a C# equivalent to Catch ... When? I don't want to resort to using an if statement inside a catch if possible.

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  • Example for creating a configuration

    - by Steven
    hi, i am facing some difficulties in creating a session. Can anyone provide me an example or link where a configuration is created by using an external file by giving url,like Configuration config = new Configuration.configure(url); the cinfig file is in another hibernate project. is there anything that i should add to classpath or store the config file. My app is just getting hanged there at that statement.Help

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  • Problem with writing a file to excel with spreadsheet

    - by winter sun
    I am trying to write excel file by using ruby 1.9 spreadsheet version 0.6.4.1 on windows. Everything is going ok, until I get to the book.write statement when I write book.write "c:/spreadsheet/excel-file.xls I keep getting the following error No such file or directory - c:/spreadsheet/excel-file.xls Can anyone tell me what I should change in this path name?

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  • Three level heirarchal data-linq

    - by user326010
    Hi I have three level heirarchal data. using the statement below i managed to display two level data. I need to extend it to one more level. Current heirachy is Modules--Documents I need to extend it as Packages--Modules--Documents var data = (from m in DataContext.SysModules join d in DataContext.SysDocuments on m.ModuleID equals d.ModuleID into tempDocs from SysDocument in tempDocs.DefaultIfEmpty() group SysDocument by m).ToList(); Regards Tassadaque

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  • Python combinations no repeat by constraint

    - by user2758113
    I have a tuple of tuples (Name, val 1, val 2, Class) tuple = (("Jackson",10,12,"A"), ("Ryan",10,20,"A"), ("Michael",10,12,"B"), ("Andrew",10,20,"B"), ("McKensie",10,12,"C"), ("Alex",10,20,"D")) I need to return all combinations using itertools combinations that do not repeat classes. How can I return combinations that dont repeat classes. For example, the first returned statement would be: tuple0, tuple2, tuple4, tuple5 and so on.

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