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  • Deleting orphans with JPA

    - by homaxto
    I have a one-to-one relation where I use CascadeType.PERSIST. This has over time build up a huge amount of child records that has not been deleted, to such an extend that it is reflected in the performance. Now I wish to add some code that cleans up the database removing all the child records that are not referenced by a parent. At the moment we are talking 400K+ records, at I need to run the code on all customer installations just to be sure they do not run into the same problem. I think the best solution would be to run a named query (because we support two databases) that deletes the necessary records, and this is where I get into problems, because how should I write it in JPQL? The result I want can be defined like the following sql statement, which unfortunaltely does not run on MySQL. DELETE FROM child c1 WHERE c1.pk NOT IN (SELECT DISTINCT p.pk FROM child c2 JOIN parent p ON p.child = c2.pk);

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  • Database EAV model, record listing as per search

    - by Shyam Sunder Verma
    I am building a dynamic application. I have three tables : ( EAV model style) 1: Items ( ItemId, ItemName) 2: Fields (FieldId, FieldName) 3: Field Values ( ItemID, FieldId, Value) Can you tell me how to write SINGLE query to get starting 20 records from ALL items where FieldId=4 is equal to TRUE. Expected Result : Columns = ItemID | Name | Field1 | Field2 | Field3 Each Row= ItemId | ItemName| Value1 | Value2 | Value3 Important concerns : 1: Number of fields per item are not known 2: I need one to write ONE query. 3: Query will be running on 100K records, so performance is concern. 4: I am using MySQL 5.0, so need solution for MYSQL Should I denormalize the tables if above query is not possible at all ? Any advice ?

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  • Collection wrapping a array is read-only. Possible to make it writeable without casting?

    - by Brian Triplett
    I have a Collection<T> property that wraps a array like T[] array; public Collection<T> Items { get { return new Collection<T>(array); } } When I attempt to assign to the collection via: T variable; Items[i] = variable; I get a NotSupportedException because the colleciton's IsReadOnly property is true. Turns out that this is a design choice by Microsoft. Does anyone know a workaround that does NOT involve enumeration? It could be done if the underlying data is not an array but I enjoy the performance gains because the data is fixed length.

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  • Who is preventing the release of Java 1.7

    - by Shawn
    I recently attended a talk by a Sun engineer Charlie Hunt regarding performance. The talk was interesting enough but one question was regarding release date of 1.7. He said it's delayed as there are parties who are refusing to sign off JSRs they own and thus preventing the 1.7 release. It apparently has something to do with the cost of determining your Sun compliance. I would be interested to know the full story if anyone knows or can point me in the right direction. What triggered my question was the amazing long release notes for 6u18. Thanks

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  • .Net Logger (Write your own vs log4net/enterprise logger/nlog etc.)

    - by Jack
    I work for an IT department with about 50+ developers. It used to be about 100+ developers but was cut because of the recession. When our department was bigger there was an ambitious effort made to set up a special architecture group. One thing this group decided to do was create our own internal logger. They thought it was such a simple task that we could spend recources and do it ourselves. Now we are having issues with performance and difficulty viewing the logs generated and some employees are frustrated that we are spending recources on infrastructure stuff like this instead of focusing on serving our business and using stuff that already exists like log4net or Enterprise Logger. Can you assist me in listing up reasons why you should not create your own .net logger. Also reasons for why you should are welcome to get a fair point of view :)

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  • mmap() for large file I/O?

    - by Boatzart
    I'm creating a utility in C++ to be run on Linux which can convert videos to a proprietary format. The video frames are very large (up to 16 megapixels), and we need to be able to seek directly to exact frame numbers, so our file format uses libz to compress each frame individually, and append the compressed data onto a file. Once all frames are finished being written, a journal which includes meta data for each frame (including their file offsets and sizes) is written to the end of the file. I'm currently using ifstream and ofstream to do the file i/o, but I am looking to optimize as much as possible. I've heard that mmap() can increase performance in a lot of cases, and I'm wondering if mine is one of them. Our files will be in the tens to hundreds of gigabytes, and although writing will always be done sequentially, random access reads should be done in constant time. Any thoughts as to whether I should investigate this further, and if so does anyone have any tips for things to look out for? Thanks!

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  • logging in scala

    - by IttayD
    In Java, the standard idiom for logging is to create a static variable for a logger object and use that in the various methods. In Scala, it looks like the idiom is to create a Logging trait with a logger member and mixin the trait in concrete classes. This means that each time an object is created it calls the logging framework to get a logger and also the object is bigger due to the additional reference. Is there an alternative that allows the ease of use of "with Logging" while still using a per-class logger instance? EDIT: My question is not about how one can write a logging framework in Scala, but rather how to use an existing one (log4j) without incurring an overhead of performance (getting a reference for each instance) or code complexity. Also, yes, I want to use log4j, simply because I'll use 3rd party libraries written in Java that are likely to use log4j.

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  • Alternative databases to use when putting IIS Logs into a database using LogParser

    - by Robin Day
    We have run some scripts that use LogParser to dump our IIS logs into a SQL Server database. We can then query this to get simple stats on hits, usage etc. It's also good when linking it to error log databases and performance counter database to compare usage with errors, etc. Having implemented this for just one system and for the last 2-3 weeks we already have a 5GB database with around 10 million records. This is making any queries to this database quite slow and will no doubt cause storage issues if we continue to log as we are. Can anyone suggest any alternative databases that we could use for this data that would be more efficient for such logs? I'd be particularly interested in any experience of Google's BigTable or Amazon's SimbleDB. Are either of these suitable for reporting queries? COUNTs, GROUP BYs, PIVOTs?

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  • Best practice for Python Assert

    - by meade
    Is there a performance or code maintenance issue with using assert as part of the standard code instead of using it just for debugging purposes? Is assert x >= 0, 'x is less then zero' and better or worse then if x < 0: raise Exception, 'x is less then zero' Also, is there anyway to set a business rule like if x < 0 raise error that is always checked with out the try, except, finally so, if at anytime throughout the code x is < 0 an error is raised, like if you set assert x < 0 at the start of a function, anywhere within the function where x becomes less then 0 an exception is raised?

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  • Optimize C# Code Fragment

    - by Eric J.
    I'm profiling some C# code. The method below is one of the most expensive ones. For the purpose of this question, assume that micro-optimization is the right thing to do. Is there an approach to improve performance of this method? Changing the input parameter to p to ulong[] would create a macro inefficiency. static ulong Fetch64(byte[] p, int ofs = 0) { unchecked { ulong result = p[0 + ofs] + ((ulong)p[1 + ofs] << 8) + ((ulong)p[2 + ofs] << 16) + ((ulong)p[3 + ofs] << 24) + ((ulong)p[4 + ofs] << 32) + ((ulong)p[5 + ofs] << 40) + ((ulong)p[6 + ofs] << 48) + ((ulong)p[7 + ofs] << 56); return result; } }

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  • Using SQL Server for WSS 3.0 instead of Windows Internal database

    - by val
    Hi Folks, There are actually two related questions: is it possible or advisable to use a full blown stand-alone SQL server for SharePoint Services WSS3.0 instead of the supplied windows internal database it comes with? The client I am working for is asking to utilize their existent SQL server for all WSS content databases to possibly minimize admin effort and improve performance. As well, would you advise to install WSS on one physical server and the content database on another server? Any gain in performace? Practicality? ect. The default is WSS and all of its databases are installed on the same single server. We don't really need a farm setup of MOSS, because the WSS capabilities are enough for our needs. Thanks, Val

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  • Python urllib3 and how to handle cookie support?

    - by bigredbob
    So I'm looking into urllib3 because it has connection pooling and is thread safe (so performance is better, especially for crawling), but the documentation is... minimal to say the least. urllib2 has build_opener so something like: #!/usr/bin/python import cookielib, urllib2 cj = cookielib.CookieJar() opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj)) r = opener.open("http://example.com/") But urllib3 has no build_opener method, so the only way I have figured out so far is to manually put it in the header: #!/usr/bin/python import urllib3 http_pool = urllib3.connection_from_url("http://example.com") myheaders = {'Cookie':'some cookie data'} r = http_pool.get_url("http://example.org/", headers=myheaders) But I am hoping there is a better way and that one of you can tell me what it is. Also can someone tag this with "urllib3" please.

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  • Checking whether an object exists in StructureMap container

    - by Kevin Pang
    I'm using StructureMap to handle the creation of NHibernate's ISessionFactory and ISession. I've scoped ISessionFactory as a singleton so that it's only created once for my web app and I've scoped ISession as a hybrid so that it will only be opened once per web request. I want to make sure that at the end of each web request, I properly dispose of ISession if it was created for that web request. I figured I could put some code in my Application_EndRequest routine to first check if an ISession was created, and if so, call ISession.Dispose. My current workaround is to just open up an ISession on Application_BeginRequest then dispose of it on Application_EndRequest, but that seems somewhat wasteful in that static file requests for images and css files and whatnot will create an ISession without ever using it. I know that the overall performance hit is negligable since ISessions are very lightweight, but it's getting annoying seeing all those ISessions being created inside NHProf.

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  • How can I calculate data for a boxplot (quartiles, median) in a Rails app on Heroku? (Heroku uses Po

    - by hadees
    I'm trying to calculate the data needed to generate a box plot which means I need to figure out the 1st and 3rd Quartiles along with the median. I have found some solutions for doing it in Postgresql however they seem to depend on either PL/Python or PL/R which it seems like Heroku does not have either enabled for their postgresql databases. In fact I ran "select lanname from pg_language;" and only got back "internal". I also found some code to do it in pure ruby but that seems somewhat inefficient to me. I'm rather new to Box Plots, Postgresql, and Ruby on Rails so I'm open to suggestions on how I should handle this. There is a possibility to have a lot of data which is why I'm concerned with performance however if the solution ends up being too complex I may just do it in ruby and if my application gets big enough to warrant it get my own Postgresql I can host somewhere else. *note: since I was only able to post one link, cause I'm new, I decided to share a pastie with some relevant information

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  • What messaging technologies in windows-ce for gauranteed msg delivery?

    - by Aidanapword
    All, We are building a windows-ce (6.0R3) based device that requires guaranteed and audit-ready message delivery (including store & forward) up to and down from the cloud. I have been looking for choices beyond: MSMQ a proprietary solution (what our prototype device is using) AMQP (research on using this in our context is now starting) ... are there any others? We will be transporting sensitive data (who isn't?!?!) over a public network, and large scale options are required. Anything running on an embedded device will be performance sensitive too. Thanks! Aidanapword

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  • Finding the Formula for a Curve

    - by Mystagogue
    Is there a program that will take "response curve" values from me, and provide a formula that approximates the response curve? It would be cool if such a program would take a numeric "percent correct" (perhaps with a standard deviation) so that it returns simplified formulas when laxity is permissable, and more precise (viz. complex) formulas when the curve needs to be approximated closely. My interest is to play with the response curve values and "laxity" factor, until such a tool spits out a curve-fit formula simple enough that I know it will be high performance during machine computations.

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  • checking if records exists in DB, in single step or 2 steps?

    - by Sinan
    Suppose you want to get a record from database which returns a large data and requires multiple joins. So my question would be is it better to use a single query to check if data exists and get the result if it exists. Or do a more simple query to check if data exists then id record exists, query once again to get the result knowing that it exists. Example: 3 tables a, b and ab(junction table) select * from from a, b, ab where condition and condition and condition and condition etc... or select id from a, b ab where condition then if exists do the query above. So I don't know if there is any reason to do the second. Any ideas how this affects DB performance or does it matter at all?

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  • git: having 2 push/pull repos in sync (or 1 push/pull and 1 pull in sync)

    - by xavjuan
    Hello, We work on multiple geographically seperate sites. Today I have our git clones all live on one site A. Then users from site B have to ssh over to do a git clone or to push in changes. These are bare repos where the update is through pushes. Ideally, for git clone/push performance, I'd like to limit having to go over ssh. I'd like to have a copy of git repo X live on site A and site B... and have some syncing mechanism between them. OR to have X live on both sites, but only allow pushing to A (and have that setup correctly at clone time on B) I'm worried about the case where someone on site A pushes changes to the repo at site A at the same time that someone on site B pushes a truely conflicting change to the repo at site B. Is there some 'sync'ing solution built into git for distributed open repos like this? Or a way to have a clone from X set the origin/parent to the X from the other site? thanks, -John

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  • GWT : Type of Container

    - by moorsu
    I see that there are two ways of transferring objects from server to client Use the same domain object (Contact.java) as used in the service layer. (I do not use hibernate) Use the HashMap to send the domain object field values in the form of Map with the help of BeanUtilsBean class. For multiple objects, use the List. Similary, use the Map to submit form values from client to server Is there any performance advantage for option 1 over 2?. Is there a way to hide the classname/package name that is sent to the browser if we use option 1?. thanks!.

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  • Replication - syncronizing most of the data some of the time

    - by uncle brad
    I have some data that isn't properly "partitioned" (for lack of a better word). All inserts, processing and reporting happen on the same table. The bulk of the processing happens not long after the insert and not long after that it becomes immutable (we're talking days). I could do all inserts and processing on a new table that I replicate to the old table. When I detect that the data has become immutable I would delete the data from the new table, but I would edit the delete replication stored procedure so that the delete did not replicate. How bad an idea is this? It seems attractive at the moment (I haven't slept on it yet) because it might mitigate a performance problem with only very small changes to the application. It also seems like it might be a good way to shoot myself in the foot.

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  • What is the best possible technology for pulling huge data from 4 remote servers

    - by Habib Ullah Bahar
    Hello, For one of our project, we need to pull huge real time stock data from 4 remote servers across two countries. The trivial process here, check the sources for a regular interval and save the update to database. But as these are real time stock data of more than 1000 companies, I have to pull every second, which isn't good in case of memory, bandwidth I think. Please give me suggestion on which technology/platform [We are flexible here. PHP, Python, Java, PERL - anyone of them will be OK for us] we should choose, it can be achieved easily and with better performance.

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  • Silverlight/Web Service Serializing Interface for use Client Side

    - by Steve Brouillard
    I have a Silverlight solution that references a third-party web service. This web service generates XML, which is then processed into objects for use in Silverlight binding. At one point we the processing of XML to objects was done client-side, but we ran into performance issues and decided to move this processing to the proxies in the hosting web project to improve performance (which it did). This is obviously a gross over-simplification, but should work. My basic project structure looks like this. Solution Solution.Web - Holds the web page that hosts Silverlight as well as proxies that access web services and processes as required and obviously the references to those web services). Solution.Infrastructure - Holds references to the proxy web services in the .Web project, all genned code from serialized objects from those proxies and code around those objects that need to be client-side. Solution.Book - The particular project that uses the objects in question after processed down into Infrastructure. I've defined the following Interface and Class in the Web project. They represent the type of objects that the XML from the original third-party gets transformed into and since this is the only project in the Silverlight app that is actually server-side, that was the place to define and use them. //Doesn't get much simpler than this. public interface INavigable { string Description { get; set; } } //Very simple class too public class IndexEntry : INavigable { public List<IndexCM> CMItems { get; set; } public string CPTCode { get; set; } public string DefinitionOfAbbreviations { get; set; } public string Description { get; set; } public string EtiologyCode { get; set; } public bool HighScore { get; set; } public IndexToTabularCommandArguments IndexToTabularCommandArgument { get; set; } public bool IsExpanded { get; set; } public string ManifestationCode { get; set; } public string MorphologyCode { get; set; } public List<TextItem> NonEssentialModifiersAndQualifyingText { get; set; } public string OtherItalics { get; set; } public IndexEntry Parent { get; set; } public int Score { get; set; } public string SeeAlsoReference { get; set; } public string SeeReference { get; set; } public List<IndexEntry> SubEntries { get; set; } public int Words { get; set; } } Again; both of these items are defined in the Web project. Notice that IndexEntry implments INavigable. When the code for IndexEntry is auto-genned in the Infrastructure project, the definition of the class does not include the implmentation of INavigable. After discovering this, I thought "no problem, I'll create another partial class file reiterating the implmentation". Unfortunately (I'm guessing because it isn't being serialized), that interface isn't recognized in the Infrastructure project, so I can't simply do that. Here's where it gets really weird. The BOOK project CAN see the INavigable interface. In fact I use it in Book, though Book has no reference to the Web Service in the Web project where the thing is define, though Infrastructure does. Just as a test, I linked to the INavigable source file from indside the Infrastructure project. That allowed me to reference it in that project and compile, but causes havoc in the Book project, because now there's a conflick between the one define in Infrastructure and the one defined in the Web project's web service. This is behavior I would expect. So, to try and sum up a bit. Web project has a web service that process data from a third-party service and has a class and interface defined in it. The class implements the interface. The Infrastructure project references the web service in the Web Project and the Book project references the Infrastructure project. The implmentation of the interface in the class does NOT serialize down, so the auto-genned code in INfrastructure does not show this relationship, breaking code further down-stream. The Book project, whihc is further down-stream CAN see the interface as defined in the Web Project, even though its only reference is through the Infrastructure project; whihc CAN'T see it. Am I simple missing something easy here? Can I apply an attribute to either the Interface definition or to the its implmentation in the class to ensure its visibility downstream? Anything else I can do here? I know this is a bit convoluted and anyone still with me here, thanks for your patience and any advice you might have. Cheers, Steve

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  • How to diganose an unlogged Error 500 on Apache?

    - by samuel morhaim
    We are running a very simple Symfony script, that randomly returns an Error 500. The system administrator says he can't find any trace of an Error 500 on the error logs, however using Curl or Firebug, it is obvious that an Error 500 is being returned. The script simply parses a POST request submitted to an URL on our server. We already checked for performance, memory etc but nothing seems to be the problem. How is this possible? We already enabled all debugging, logging, on Apache, PHP, etc and nothing.

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  • How can I dynamically inject code to event handlers in Delphi?

    - by mjustin
    For debugging / performance tests I would like to dynamically add logging code to all event handlers of components of a given type. For example, for all Dataset components located ona TDatamodule, I would like to add some code for the BeforeOpen and the AfterOpen event to store the start and end time and send a line to a logger with the elapsed time in the AfterOpen event. I would prefer to do this dynamically (no component subclassing), so that I can add this to all existing datamodules and forms with minimal effort only when needed. Iterating all components and filtering by their type is easy, but for the components which already have event handlers assigned, I need a way to store the existing event handlers, and assign a new modified event handler which first does the logging and then will invoke the original code which was already present. Is there a design pattern which can be applied, or even some example code which shows how to implement this in Delphi?

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  • SELECT INTO or Stored Procedure?

    - by Kerry
    Would this be better as a stored procedure or leave it as is? INSERT INTO `user_permissions` ( `user_id`, `object_id`, `type`, `view`, `add`, `edit`, `delete`, `admin`, `updated_by_user_id` ) SELECT `user_id`, $object_id, '$type', 1, 1, 1, 1, 1, $user_id FROM `user_permissions` WHERE `object_id` = $object_id_2 AND `type` = '$type_2' AND `admin` = 1 You can think of this with different objects, lets say you have groups and subgroups. If someone creates a subgroup, it is making everyone who had access to the parent group now also have access to the subgroup. I've never made a stored procedure before, but this looks like it might be time. This call be probably be called very often. Should I be creating a procedure or will the performance be insignificant?

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