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• SQL Server union selects built dynamically from list of words

  - by Adam Tuttle

  I need to count occurrence of a list of words across all records in a given table. If I only had 1 word, I could do this: select count(id) as NumRecs where essay like '%word%' But my list could be hundreds or thousands of words, and I don't want to create hundreds or thousands of sql requests serially; that seems silly. I had a thought that I might be able to create a stored procedure that would accept a comma-delimited list of words, and for each word, it would run the above query, and then union them all together, and return one huge dataset. (Sounds reasonable, right? But I'm not sure where to start with that approach...) Short of some weird thing with union, I might try to do something with a temp table -- inserting a row for each word and record count, and then returning select * from that temp table. If it's possible with a union, how? And does one approach have advantages (performance or otherwise) over the other?

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• Reading files from an embedded ZIP archive

  - by aix

  I have a ZIP archive that's embedded inside a larger file. I know the archive's starting offset within the larger file and its length. Are there any Java libraries that would enable me to directly read the files contained within the archive? I am thinking along the lines of ZipFile.getInputStream(). Unfortunately, ZipFile doesn't work for this use case since its constructors require a standalone ZIP file. For performance reasons, I cannot copy the ZIP achive into a separate file before opening it. edit: Just to be clear, I do have random access to the file.

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• C#: When should I use TryParse?

  - by zxcvbnm

  I understand it doesn't throw an Exception and because of that it might be sightly faster, but also, you're most likely using it to convert input to data you can use, so I don't think it's used so often to make that much of difference in terms of performance. Anyway, the examples I saw are all along the lines of an if/else block with TryParse, the else returning an error message. And to me, that's basically the same thing as using a try/catch block with the catch returning an error message. So, am I missing something? Is there a situation when this is actually useful?

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• Interpreters: How much simplification?

  - by Ray

  In my interpreter, code like the following x=(y+4)*z echo x parses and "optimizes" down to four single operations performed by the interpreter, pretty much assembly-like: add 4 to y multiply <last operation result> with z set x to <last operation result> echo x In modern interpreters (for example: CPython, Ruby, PHP), how simplified are the "opcodes" for which are in end-effect run by the interpreter? Could I achieve better performance when trying to keep the structures and commands for the interpreter more complex and high-level? That would be surely a lot harder, or?

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• Which Android platform and API to target?

  - by Ben Mc

  I'm just about to launch my first Android app, and it runs on the Android 1.1 platform, API Level 2, but is this what I should officially sign and launch the app as? Does it affect performance at all or is it simply for Android to know which devices it works on? The only problem I see is that I can't specify <supports-screens> in the Manifest, which I would like to do, but it appears I'd have to launch at 1.6 at least for this to work. Would I be missing a huge number of phones by launching at 1.6 instead of 1.1? Thank you!

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• What is the preferred way to associate css styles with GWT widgets (using UiBinder)?

  - by smallbec

  From the GWT page (http://code.google.com/webtoolkit/doc/latest/DevGuideUiCss.html#cssfiles), it mentions 2 ways (for modern application): Using a CssResource contained within a ClientBundle. Using an inline element in a UiBinder template. Modern GWT applications typically use a combination of CssResource and UiBinder. So my question is, when should I use a css file and create a CssResource for it, and when should I define styles directly in the ui.xml file using <ui:style>? Are there any performance implication (i.e. resource size to download on the client) with either of these ways?

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• WCF Rest services for use with the repository pattern?

  - by mark smith

  Hi there, I am considering moving my Service Layer and my data layer (repository pattern) to a WCF Rest service. So basically i would have my software installed locally (WPF client) which would call the Service Layer that exists via a Rest Service... The service layer would then call my data layer using a WCF Rest Service also OR maybe just call it via the DLL assembly I was hoping to understand what the performance would be like. Currently I have my datalayer and servicelayer installed locally via DLL Assemblies locally on the pc. Also i presume the WCF REST services won't support method overloading hance the same name but with a different signature?? I would really appreciate any feedback anyone can give. Thanks

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• Entity data field validation and part data submission

  - by pradeeptp

  I have an entity class that has 10 fields. I am using MS Validation Application block to mark all fields as mandatory (IsRequired). I am implementing a securiy feature in which during updation of the data, not all the fields in the entity class will have data. For example a few users can only view 5 fileds while others all 10 fields during updation on GUI I have the following options 1) Bring all the data for all the fields from the DB table and hide the ones not accessible to the users in GUI. I am concerned about the performance because everytime GUI will pull unncessary data. 2) Bring the data (e.g. only 5 fields) that are permissible for access/view by the user on GUI. During submit, validation block will throw exception because all fields are marked as IsRequired and only data for 5 fields are sent back to the server. I want to know if there are any other good approaches to solve problems like this. I am using .NET 3.5 Thanks.

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• Site images don't refresh after setting expired headers on .htaccess

  - by Miguel Hernandez

  I have a site that uses a CSS sprite for all the images. I set the .htaccess file to set the expired headers to a future time as they recommend to improve site performance. However, when I updated the sprite image none of my browsers on two different computers seem to fetch the new image. I deleted the .htaccess serveral times but no luck. I am sure this must be easy as pie to fix but right now I am out of options. Here is the code inside my .htaccess file: # CONFIGURE media caching # Header unset ETag FileETag None <FilesMatch "(?i)^.*\.(ico|flv|jpg|jpeg|png|gif|js|css)$"> Header unset Last-Modified Header set Expires "Fri, 21 Dec 2012 00:00:00 GMT" Header set Cache-Control "public, no-transform" </FilesMatch> <IfModule mod_deflate.c> <FilesMatch "\.(js|css)$"> SetOutputFilter DEFLATE </FilesMatch> </IfModule> Thanks!

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• assistance with classifying tests

  - by amateur

  I have a .net c# library that I have created that I am currently creating some unit tests for. I am at present writing unit tests for a cache provider class that I have created. Being new to writing unit tests I have 2 questions These being: My cache provider class is the abstraction layer to my distributed cache - AppFabric. So to test aspects of my cache provider class such as adding to appfabric cache, removing from cache etc involves communicating with appfabric. Therefore the tests to test for such, are they still categorised as unit tests or integration tests? The above methods I am testing due to interacting with appfabric, I would like to time such methods. If they take longer than a specified benchmark, the tests have failed. Again I ask the question, can this performance benchmark test be classifed as a unit test? The way I have my tests set up I want to include all unit tests together, integration tests together etc, therefore I ask these questions that I would appreciate input on.

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• How to reliably measure available memory in Linux?

  - by Alex B

  Linux /proc/meminfo shows a number of memory usage statistics. MemTotal: 4040732 kB MemFree: 23160 kB Buffers: 163340 kB Cached: 3707080 kB SwapCached: 0 kB Active: 1129324 kB Inactive: 2762912 kB There is quite a bit of overlap between them. For example, as far as I understand, there can be active page cache (belongs to "cached" and "active") and inactive page cache ("inactive" + "cached"). What I want to do is to measure "free" memory, but in a way that it includes used pages that are likely to be dropped without a significant impact on overall system's performance. At first, I was inclined to use "free" + "inactive", but Linux's "free" utility uses "free" + "cached" in its "buffer-adjusted" display, so I am curious what a better approach is. When the kernel runs out of memory, what is the priority of pages to drop and what is the more appropriate metric to measure available memory?

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• Which data structure for List of objects + datagrid wiev

  - by Martin

  Hi, I have to develop a code which will store a list of objects, as example below 101, value 11, value 12, value 13 ...etc 102, value 21, value 22, value 23 ...etc 103, value 31, value 32, value 33 ...etc 104, value 41, value 42, value 43 ...etc Now, the difficulty is, that first column is an identifier, and whole table should always be sorted by it. Easy access to each element is required. Additionally, list should be easily updated, and extended by adding element at the end as well as in front and still keep being sorted by first column. Finally, I would like to be able to display values of the above in datagridview. What is most important is a performance of the implementation, as rows will be updated many times per second, and datagridview should be able to display all changes immediately. I was thinking about creating class for the values, and then a Dictionary but encountered a problem with displaying values in gridview. What would be the most optimal way of implementing the code? Thanks in advance Martin

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• data between pages: $_SESSION vs. $_GET ?

  - by Haroldo

  Ok, firstly this is not about forms this is about consistent layout as a user explores a site. let me explain: If we imagine a (non-ajax) digital camera online store, say someone was on the DSLR section and specified to view the cameras in Gallery mode and order by price. They then click onto the Compact camera's page. It would be in the users interests if the 'views' they selected we're carried over to this new page. Now, i'd say use a session - am i wrong? are there performance issues i should be aware of for a few small session vars ( ie view=1 , orderby=price) ?

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• Element point map for html5 canvas element, need algorithm

  - by Artiom Chilaru

  I'm currently working on a pure html 5 canvas implementation of the "flying tag cloud sphere", which many of you have undoubtedly seen as a flash object in some pages. The tags are drawn fine, and the performance is satisfactory, but there's one thing in the canvas element that's kind of breaking this idea: you can't identify the objects that you've drawn on a canvas, as it's just a simple flat "image".. What I have to do in this case is catch the click event, and try to "guess" which element was clicked. So I have to have some kind of matrix, which stores a link to a tag object for each pixel on the canvas, AND I have to update this matrix on every redraw. Now this sounds incredibly inefficient, and before I even start trying to implement this, I want to ask the community - is there some "well known" algorithm that would help me in this case? Or maybe I'm just missing something, and the answer is right behind the corner? :)

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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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• Hibernate criteria with projection not performing query for @OneToMany mapping

  - by Josh

  I have a domain object, Expense, that has a field called initialFields. It's annotated as so: @OneToMany(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }, orphanRemoval = true) @JoinTable(blah blah) private final List<Field> initialFields; Now I'm trying to use Projections in order to only pull certain fields for performance reasons, but when doing so the initialFields field is always null. It's the only OneToMany field and the only field I am trying to retrieve with the projection that is behaving this way. If I use a regular HQL query initialFields is populated appropriately, but of course I can't limit the fields. Anyone ever seen anything like this?

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• foreign key constraints on primary key columns - issues ?

  - by zzzeek

  What are the pros/cons from a performance/indexing/data management perspective of creating a one-to-one relationship between tables using the primary key on the child as foreign key, versus a pure surrogate primary key on the child? The first approach seems to reduce redundancy and nicely constrains the one-to-one implicitly, while the second approach seems to be favored by DBAs, even though it creates a second index: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key references parent(id), data varchar(50) ) pure surrogate key: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key, parent_id integer unique references parent(id), data varchar(50) ) the platforms of interest here are Postgresql, Microsoft SQL Server.

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• P/Invoke or C++/CLI for wrapping a C library

  - by Ian G

  Have a moderate size (40-odd function) C API that needs to be called from a C# project. The functions logically break up to form a few classes that will be API presented to the rest of the project. Are there any objective reasons to prefer P/Invoke or C++/CLI for the interoperability underneath that API, in terms of robustness, maintainability, deployment, ...? The issues I could think of that might be, but aren't problematic are: C++/CLI will require an separate assembly, the P/Invoke classes can be in the main assembly. (We've already got multiple assemblies and there'll be the C dlls anyway so not a major issue). Performance doesn't seem differ noticeable between the two methods. Issues that I'm not sure about are: My feeling is C++/CLI will be easier to debug if there's inter-op problem, is this true? Language familiarity enough people know C# and C++ but knowledge of details of C++/CLI are rarer here. Anything else?

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• UNIX-style RegExp Replace running extremely slowly under windows. Help?

  - by John Sullivan

  I'm trying to run a unix regEXP on every log file in a 1.12 GB directory, then replace the matched pattern with ''. Test run on a 4 meg file is took about 10 minutes, but worked. Obviously something is murdering performance by several orders of magnitude. Find: ^(?!.*155[0-2][0-9]{4}\s.*).*$ -- NOTE: match any line NOT starting 152[0-2]NNNN where in is a number 0-9. Replace with: ''. Is there some justifiable reason for my regExp to take this long to replace matching text, or is the program I am using (this is windows / a program called "grepWin") most likely poorly optimized? Thanks.

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• What is the differnce between "LINQ to Entities", "LINQ to SQL" and "LINQ to Dataset".

  - by Marcel

  Hi all, I'm working for quite a while now with LINQ. However, it remained still a bit of a mystery what are the real differences between the mentioned flavours of LINQ. The successful answer will contain a short differentiation between them. What is the main goal if it, what is the benefit, and is there a performance impact... P.S. I know that there are a lot of information sources out there, but I look for a kind of a "cheat sheet" which instructs a newbie where to head to for a specific goal.

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• Self-Configuring Classes W/ Command Line Args: Pattern or Anti-Pattern?

  - by dsimcha

  I've got a program where a lot of classes have really complicated configuration requirements. I've adopted the pattern of decentralizing the configuration and allowing each class to take and parse the command line/configuration file arguments in its c'tor and do whatever it needs with them. (These are very coarse-grained classes that are only instantiated a few times, so there is absolutely no performance issue here.) This avoids having to do shotgun surgery to plumb new options I add through all the levels they need to be passed through. It also avoids having to specify each configuration option in multiple places (where it's parsed and where it's used). What are some advantages/disadvantages of this style of programming? It seems to reduce separation of concerns in that every class is now doing configuration stuff, and to make programs less self-documenting because what parameters a class takes becomes less explicit. OTOH, it seems to increase encapsulation in that it makes each class more self-contained because no other part of the program needs to know exactly what configuration parameters a class might need.

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• For what purpose does java have a float primitive type?

  - by Roman

  I heard plenty times different claims about float type in java. The most popular issues typicaly regard to converting float value to double and vice versa. I read (rather long time ago and not sure that it's actual now with new JVM) that float gives much worse performance then double. And it's also not recommended to use float in scientific applications which should have certain accuracy. I also remember that when I worked with AWT and Swing I had some problems with using float or double (like using Point2D.Float or Point2D.Double). So, I see only 2 advantages of float over double: it needs only 4 bytes while double needs 8 bytes JMM garantees that assignment operation is atomic with float variables while it's not atomic with double's. Are there any other cases where float is better then double? Do you use float's in your applications? It seems to me that the only valuable reason java has float is backward compatibility.

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• Reading ResultSet from multiple threads

  - by superdario

  Hello, In the database, I have a definition table that is read from the application once upon starting. This definition table rarely changes, so it makes sense to read it once and restart the application every time it changes. However, after the table is read (put into a ResultSet), it will be read by multiple handlers running in their own threads. How do you suggest to accomplish this? My idea was to populate a CachedRowSet, and then create a copy of this set (through the createCopy() method) for each handler every time a new request comes. Do you think this is wise? Does this offer a good performance? Thanks.

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• Rails/mysql SUM distinct records - optimization

  - by pepernik

  Hey. How would you optimize this SQL SELECT SUM(tmp.cost) FROM ( SELECT DISTINCT clients.id as client, countries.credits_cost AS cost FROM countries INNER JOIN clients ON clients.country_id = countries.id INNER JOIN clients_groups ON clients_groups.client_id=clients.id WHERE clients_groups.group_id IN (1,2,3,4,5,6,7,8,9) GROUP BY clients.id ) AS tmp; I'm using this example as part of my Ruby on Rails project. Note that my nested SQL (tmp) can have more then 10 milion records. You can split that in more SQLs if the performance is better. Should I add any indexes to make it quicker (i have it on IDs)?

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• Decoupling into DAL and BLL - my concerns.

  - by novice_man

  Hi, In many posts concerning this topic I come across very simple examples that do not answer my question. Let's say a have a document table and user table. In DAL written in ADO.NET i have a method to retries all documents for some criteria. Now I the UI I have a case where I need to show this list along with the names of the creator. Up to know I have it done with one method in DAL containig JOIN statement. However eveytime I have such a complex method i have to do custom mapping to some object that doesn't mark 1:1 to DB. Should it be put into another layer ? If so then I will have to resing from join query for iteration through results and querying each document author. . . which doen't make sense... (performance) what is the best approach for such scenarios ?

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