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  • B-trees, databases, sequential inputs, and speed.

    - by IanC
    I know from experience that b-trees have awful performance when data is added to them sequentially (regardless of the direction). However, when data is added randomly, best performance is obtained. This is easy to demonstrate with the likes of an RB-Tree. Sequential writes cause a maximum number of tree balances to be performed. I know very few databases use binary trees, but rather used n-order balanced trees. I logically assume they suffer a similar fate to binary trees when it comes to sequential inputs. This sparked my curiosity. If this is so, then one could deduce that writing sequential IDs (such as in IDENTITY(1,1)) would cause multiple re-balances of the tree to occur. I have seen many posts argue against GUIDs as "these will cause random writes". I never use GUIDs, but it struck me that this "bad" point was in fact a good point. So I decided to test it. Here is my code: SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[T1]( [ID] [int] NOT NULL CONSTRAINT [T1_1] PRIMARY KEY CLUSTERED ([ID] ASC) ) GO CREATE TABLE [dbo].[T2]( [ID] [uniqueidentifier] NOT NULL CONSTRAINT [T2_1] PRIMARY KEY CLUSTERED ([ID] ASC) ) GO declare @i int, @t1 datetime, @t2 datetime, @t3 datetime, @c char(300) set @t1 = GETDATE() set @i = 1 while @i < 2000 begin insert into T2 values (NEWID(), @c) set @i = @i + 1 end set @t2 = GETDATE() WAITFOR delay '0:0:10' set @t3 = GETDATE() set @i = 1 while @i < 2000 begin insert into T1 values (@i, @c) set @i = @i + 1 end select DATEDIFF(ms, @t1, @t2) AS [Int], DATEDIFF(ms, @t3, getdate()) AS [GUID] drop table T1 drop table T2 Note that I am not subtracting any time for the creation of the GUID nor for the considerably extra size of the row. The results on my machine were as follows: Int: 17,340 ms GUID: 6,746 ms This means that in this test, random inserts of 16 bytes was almost 3 times faster than sequential inserts of 4 bytes. Would anyone like to comment on this? Ps. I get that this isn't a question. It's an invite to discussion, and that is relevant to learning optimum programming.

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  • Store an image in a SQL Server CE database

    - by Vaccano
    Does any one know of an example on how to store an image in a SQL Server CE database? What data type should the column be? (I am guessing binary.) I use Linq-To-Datasets. Is it possible using that to put the image into the database and pull it out again later? Thanks for any advice.

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  • How to map a Entity Data Model conceptual model property to a storage model column using the "Serial

    - by codekaizen
    I have a conceptual model in EDM where one of the entities has a property which is essentially a big value object whose properties aren't really useful as columns in the datamodel. I'd like to apply the Serialized LOB pattern to it so that I can fit it into a 192 byte binary column. How do I map this in the EDM v4? Is it even possible at this time? Actually, is it possible in any ORM?

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  • PHP Upload file enhance security

    - by mandril
    Hey.. my question is how to prevent someone upload a virus or some malicious code with the extension you pretend for example i have a pdf file uploader, anyone can upload a binary with pdf camouflage there are lots of programs to do that.

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  • How to tell svn to not manage history for one file

    - by Prabu
    I don't know whether SVN has this feature, How do I tell svn to not maintain the history of changes for a file but it should have only the latest version of the file. Of course this is not the work of a version control, but it will be useful if I want to have some binary files within the repo without versioning.

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  • How can a C/C++ program put itself into background?

    - by Larry Gritz
    What's the best way for a running C or C++ program that's been launched from the command line to put itself into the background, equivalent to if the user had launched from the unix shell with '&' at the end of the command? (But the user didn't.) It's a GUI app and doesn't need any shell I/O, so there's no reason to tie up the shell after launch. But I want a shell command launch to be auto-backgrounded without the '&' (or on Windows). Ideally, I want a solution that would work on any of Linux, OS X, and Windows. (Or separate solutions that I can select with #ifdef.) It's ok to assume that this should be done right at the beginning of execution, as opposed to somewhere in the middle. One solution is to have the main program be a script that launches the real binary, carefully putting it into the background. But it seems unsatisfying to need these coupled shell/binary pairs. Another solution is to immediately launch another executed version (with 'system' or CreateProcess), with the same command line arguments, but putting the child in the background and then having the parent exit. But this seems clunky compared to the process putting itself into background. Edited after a few answers: Yes, a fork() (or system(), or CreateProcess on Windows) is one way to sort of do this, that I hinted at in my original question. But all of these solutions make a SECOND process that is backgrounded, and then terminate the original process. I was wondering if there was a way to put the EXISTING process into the background. One difference is that if the app was launched from a script that recorded its process id (perhaps for later killing or other purpose), the newly forked or created process will have a different id and so will not be controllable by any launching script, if you see what I'm getting at. Edit #2: fork() isn't a good solution for OS X, where the man page for 'fork' says that it's unsafe if certain frameworks or libraries are being used. I tried it, and my app complains loudly at runtime: "The process has forked and you cannot use this CoreFoundation functionality safely. You MUST exec()." I was intrigued by daemon(), but when I tried it on OS X, it gave the same error message, so I assume that it's just a fancy wrapper for fork() and has the same restrictions. Excuse the OS X centrism, it just happens to be the system in front of me at the moment. But I am indeed looking for a solution to all three platforms.

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  • Settings File as Dictionary with Serialization

    - by AKRamkumar
    This is a three part question. One: Would using a Dictionary<String,Object> be a good way of saving data where it would be Dictionary<Key,Value> as the basis? Two: What would be a better way without using app.settings or xml? Three: How would you serialize this(Or the better solution) into a binary format that is compact and serializes quickly?

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  • Compare odt files in svn

    - by Llistes Sugra
    I use svn to store the revisions of my specification files, written with oowrite (OpenOffice.org). I cannot find the way to compare different revisions of my odt files. It complains their are binary. Is there any tool or plugin to compare odt files stores in svn repository?

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  • Python's cPickle deserialization from PHP?

    - by Ciantic
    Hi! I have to deserialize a dictionary in PHP that was serialized using cPickle in Python. In this specific case I probably could just regexp the wanted information, but is there a better way? Any extensions for PHP that would allow me to deserialize more natively the whole dictionary? Apparently it is serialized in Python like this: import cPickle as pickle data = { 'user_id' : 5 } pickled = pickle.dumps(data) print pickled Contents of such serialization cannot be pasted easily to here, because it contains binary data.

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  • Can I use reflection to find the bin/[Configuration] folder in ASP.NET instead of the asp temporary

    - by vfilby
    I have an ASP.NET website and I want to find the /bin/[Configuration] folder to use an external tool. When I use reflection to get calling assemblies location it returns something similar to: C:\Windows\Microsoft.NET\Framework\...\Temporary ASP.NET Files\a1388a5e\...\my.dll Since each dll has its own directory under the temp ASP.NET Files this fails for me. How can I get the location of the binary, not asp.net's temporary cache?

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  • can i use hadoop cloudera without root access?

    - by in_the_cloud
    a bit of a binary question (okay, not excatly) - but was wondering if one is able to configure cloudera / hadoop to run at the nodes without root shell access to the node computers (although i can setup ssh passwordless login)? appears from their instructions that root access is needed, at yet i found a hadoop wiki which suggest root access might not be needed ? http://wiki.apache.org/nutch/NutchHadoopTutorial

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  • GDB disas question about address values

    - by user324994
    I'm working with a binary file that I disas'd in gdb. Right now I'm just examining the return value of a function. 0x08048604 <playGame+78>: ret Is the address shown the address where ret is stored in the function? Or is it just the address of the instruction to return the ret value?

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  • How do Hex editors display data so quickly?

    - by user146780
    I'v created a Notepad-like application and if I load a 1MB file into the textbox, it takes about 1 minute. The Visual Studio Binary editor displays lines, Hex, and ascii versions in a fraction of a second. How do they get the data into the textbox so quickly? Thanks

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  • ASP.NET MVC image upload store location (db vs filesystem)

    - by adrin
    I am writing web application using ASP.NET MVC + NHibernate + Postres stack. I wonder if images uploaded should be stored in database as binary blobs or on filesystem (and reference only in db). One advantage of db storage I can think of is easy backup/recovery of all data without reverting to filesystem copy tools. On the other hand I suspect that filesystem access may be faster (but is it especially when dealing with many concurrent requests?) What are your suggestions?

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