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  • Indexed key vs indexed separate columns, which one is faster ?

    - by Jerry
    In MYSQL, from a pure performance perspective, if I have a table with large amount of data with 10/1 read/write ratio. is it faster in read/write performance to have 4 search criteria in separate columns and all indexed or have them combined in to one single string acting as a key and store in one indexed column ? e.g. say this table with 5 columns, first name, last name, sex, country and file where the first four columns will ALWAYS be given as a part of search parameters in a search or have a table with two columns, key and file. where the value of key can be john-smith-male-australia ?? I don't quite get the pros and cons. the point I try to stress is the fact that all parameters will be given.in a search.

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  • Archiving Database Tables using Java

    - by HonorGod
    My application demands archiving database tables between sybase and db2 and vice-a-versa and within(db2 to db2 and sybase to sybase) using java. I am trying to understand the best strategies around in terms performance, implementation, ease of use and scalability. Here is my current process - source and destination tables with the acceptable parameters (from java) are defined within xml. the application reads the source and destination configurations and execute them sequentially. destination is sometime optional when source is just deleting data from a specific table or when the source is just calling a stored procedure. dataset between source and destination is extremely large (in millions) From top of my head, it looks like I can define dependencies between multiple source and destination combination and have them execute in parallel in multiple treads. But will this improve any performance(i hope it will)? Are there any open-source frameworks for data archiving using java? Any other thoughts on the implements side will be really helpful. Thanks

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  • How have your coding values changed since graduating?

    - by Matt
    We all walked out of school with the stars in our eyes and little experience in "real-world" programming. How have your opinions on programming as a craft changed since you've gained more experience away from academia? I've become more and more about design a la McConnell : wide use of encapsulation, quality code that gives you warm fuzzy feelings when you read it, maintainability over execution performance, etc..., whereas many of my co-workers have followed a different path of fewer middlemen layers getting in the way, code that is right out in the open and easier to locate, even if harder to read, and performance-centric designs. What have you learned about the craft of software design which has changed the way you approach coding since leaving the academic world?

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  • MS Access vs SQL Server and others ? Is it worth taking a db server when less than 2 Gb and only 20

    - by asksuperuser
    After my experiment with MSAccess vs MySQL which shows MS Access hugely overperforming Mysql odbc insert by a factor 1000% before I would do the same experiment with SQL Server I searched for some other's people and found this one: http://blog.nkadesign.com/2009/access-vs-sql-server-some-stats-part-1/ which says "As a side note, in this particular test, Access offers much better raw performance than SQL Server. In more complex scenarios it’s very likely that Access’ performance would degrade more than SQL Server, but it’s nice to see that Access isn’t a sloth." So is worth bother with some db server when data is less than 2 Gb and users are about 20 (knowing that MS Access theorically supports up to 255 concurrent users though practically it's around a dozen concurrent users only). Are there any real world studies that really compare MS Access with other db in these specific use case ? Because professionaly speaking I keep hearing people systematically recommend DB server from people who have never used Access just because they think DB Server can only perform better in every case which I used to think myself I confess.

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  • how to get apache log like debugging in Android logcat

    - by Nav
    I am currently using a webview to load a webpage which contains lots of javascript and having lots of trouble debugging what exactly gets loaded and when in the webview . Then I saw this post where the op seems to be using apache log to monitor webpage load events in his webview. Enhance webView performance (should be the same performance as native Web Browser) Can I get a similar utility plugin or anything so that I can use it with logcat in ddms view. If possible please provide some resource as to how to configure it for android.

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  • Best way to merge two identical ASPNET web sites?

    - by ase69s
    We have two websites which only diference is in the design (Diferent images, styles, layouts..etc) but the web structure of files and cs code is the same so we want to simplify its manteinance... The actual structure would be: DefaultA.aspx DefaultA.aspx.cs DefaultB.aspx DefaultB.aspx.cs LoginA.aspx LoginA.aspx.cs LoginB.aspx LoginB.aspx.cs One idea would be changing the design differencies at runtime depending of the origin website, but we dont like much this because performance, abstraction in designing them and url confusion... Another one is sharing the cs (both aspx inheriting and using the same cs) file but we never have done or seen it done in any website before so we wonder if its a good aproach... What do you think? Any other way better in terms of performance vs development-ease?

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  • Do MySQL Locked Tables affect related Views?

    - by CogitoErgoSum
    So after reading http://stackoverflow.com/questions/1415602/performance-in-pdo-php-mysql-transaction-versus-direct-execution in regards to performance issues I was thinking about I did some research on locking tables in MySQL. On http://dev.mysql.com/doc/refman/5.0/en/table-locking.html Table locking enables many sessions to read from a table at the same time, but if a session wants to write to a table, it must first get exclusive access. During the update, all other sessions that want to access this particular table must wait until the update is done. This part struck me particularly becuase most of our queries will be updates rather than inserts. I was wondering if one created a table called foo on which all updates/inserts were carried out and then a view called foo_view (A copy of foo, or perhaps foo and a linkage of several other tables plus foo) on which all selects occured, would this locking issue still occur? That is, would SELECT quries on foo_view still have to wait for an update to finish on foo?

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  • When accessing ResultSets in JDBC, is there an elegant way to distinguish between nulls and actual z

    - by Uri
    When using JDBC and accessing primitive types via a result set, is there a more elegant way to deal with the null/0 than the following: int myInt = rs.getInt(columnNumber) if(rs.wasNull())? { // Treat as null } else { // Treat as 0 } I personally cringe whenever I see this sort of code. I fail to see why ResultSet was not defined to return the boxed integer types (except, perhaps, performance) or at least provide both. Bonus points if anyone can convince me that the current API design is great :) My solution was to write a wrapper that returns an Integer (I care more about elegance of client code than performance), but I'm wondering if I'm missing a better way to do this.

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  • Adding more OR searches with CONTAINS Brings Query to Crawl

    - by scolja
    I have a simple query that relies on two full-text indexed tables, but it runs extremely slow when I have the CONTAINS combined with any additional OR search. As seen in the execution plan, the two full text searches crush the performance. If I query with just 1 of the CONTAINS, or neither, the query is sub-second, but the moment you add OR into the mix the query becomes ill-fated. The two tables are nothing special, they're not overly wide (42 cols in one, 21 in the other; maybe 10 cols are FT indexed in each) or even contain very many records (36k recs in the biggest of the two). I was able to solve the performance by splitting the two CONTAINS searches into their own SELECT queries and then UNION the three together. Is this UNION workaround my only hope? Thanks. SELECT a.CollectionID FROM collections a INNER JOIN determinations b ON a.CollectionID = b.CollectionID WHERE a.CollrTeam_Text LIKE '%fa%' OR CONTAINS(a.*, '"*fa*"') OR CONTAINS(b.*, '"*fa*"') Execution Plan (guess I need more reputation before I can post the image):

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  • How to change size of STL container in C++

    - by Jaime Pardos
    I have a piece of performance critical code written with pointers and dynamic memory. I would like to rewrite it with STL containers, but I'm a bit concerned with performance. Is there a way to increase the size of a container without initializing the data? For example, instead of doing ptr = new BYTE[x]; I want to do something like vec.insert(vec.begin(), x, 0); However this initializes every byte to 0. Isn't there a way to just make the vector grow? I know about reserve() but it just allocates memory, it doesn't change the size of the vector, and doesn't allows me to access it until I have inserted valid data. Thank you everyone.

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  • Using Lambda Statements for Event Handlers

    - by lush
    I currently have a page which is declared as follows: public partial class MyPage : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { //snip MyButton.Click += (o, i) => { //snip } } } I've only recently moved to .NET 3.5 from 1.1, so I'm used to writing event handlers outside of the Page_Load. My question is; are there any performance drawbacks or pitfalls I should watch out for when using the lambda method for this? I prefer it, as it's certainly more concise, but I do not want to sacrifice performance to use it. Thanks.

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  • Clustered index on frequently changing reference table of one or more foreign keys

    - by Ian
    My specific concern is related to the performance of a clustered index on a reference table that has many rapid inserts and deletes. Table 1 "Collection" collection_pk int (among other fields) Table 2 "Item" item_pk int (among other fields) Reference Table "Collection_Items" collection_pk int, item_pk int (combined primary key) Because the primary key is composed of both pks, a clustered index is created and the data physically ordered in the table according to the combined keys. I have many users creating and deleting collections and adding and removing items to those collections very frequently affecting the "Collection_Items" table, and its clustered index. QUESTION PART: Since the "Collection_Items" table is so dynamic, wouldn't there be a big performance hit on constantly resorting the table rows because of the clustered index ? If yes, what should I do to minimize this ?

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  • Video chat application : Which technology to choose ?

    - by WarDoGG
    I have to undertake a project which is to make a video chat application. The video has to be streamed from one location and can be viewed by multiple people spread out over the globe. Performance is really an issue and a delay of more than 2-3 seconds is unacceptable. From what i gather, this can be done in Flex and also in JAVA. Any performance issues and caveats with a particular approach ? I would really like the pros to comment on this and guide me through. Will be very very helpful. Are there any open source libraries available for video recording in flash / JAVA which i can integrate into my app and customize according to my needs ?

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  • Controlling access to large files in Apache

    - by obeattie
    Hi there, I am looking to control access to some large files (we're talking many GB here) by the use of signed URLs. The files are currently restricted by LDAP Basic authentication (mod_auth_ldap), but I need to change this to verify the signature (passed as a query parameter in the URL). Basically, I just need to run a script to verify the signature, and allow the request to proceed as if authentication had succeeded. My initial thought to this was just to use a simple CGI script, but as the files are so large I'm concerned about performance. So, really, this question is (probably) more like "are there any performance implications of streaming large files from a CGI script via Apache?"… and if so, "is there a better way of doing this (short of writing a dedicated authentication module)?" If this makes any sense, help would be much appreciated :) P.S. I wasn't sure exactly what to search for for this (10 minutes of Googling were fruitless), so I may very well be duplicating someone else's post.

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  • Javascript large number array compression

    - by gatapia
    Hi All, I've got a javascript application that sends a large amount of numerical data down the wire. This data is then stored in a database. I am having size issues (too much bandwidth, database getting too big). I am now ready to sacrifice some performance for compression. I was thinking of implementing a base 62 number.toString(62) and parseInt(compressed, 62). This would certainly reduce the size of the data but before I go ahead and do this I thought I would put it to the folks here as I know there must be some outside the box solution I have not considered. The basic specs are: - Compress large number arrays into strings for JSONP transfer (So I think UTF is out) - Be relatively fast, look I'm not expecting same performance as I have now but I also don't want gzip compression either. Any ideas would be greatly appreciated. Thanks Guido Tapia

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  • Benchmark of Java Try/Catch Block

    - by hectorg87
    I know that going into a catch block has some significance cost when executing a program, however, I was wondering if entering a try{} block also had any impact so I started looking for an answer in google with many opinions, but no benchmarking at all. Some answers I found were: Java try/catch performance, is it recommended to keep what is inside the try clause to a minimum? Try Catch Performance Java Java try catch blocks However they didn't answer my question with facts, so I decided to try it for myself. Here's what I did. I have a csv file with this format: host;ip;number;date;status;email;uid;name;lastname;promo_code; where everything after status is optional and will not even have the corresponding ; , so when parsing a validation has to be done to see if the value is there, here's where the try/catch issue came to my mind. The current code that in inherited in my company does this: StringTokenizer st=new StringTokenizer(line,";"); String host = st.nextToken(); String ip = st.nextToken(); String number = st.nextToken(); String date = st.nextToken(); String status = st.nextToken(); String email = ""; try{ email = st.nextToken(); }catch(NoSuchElementException e){ email = ""; } and it repeats what it's done for email with uid, name, lastname and promo_code. and I changed everything to: if(st.hasMoreTokens()){ email = st.nextToken(); } and in fact it performs faster. When parsing a file that doesn't have the optional columns. Here are the average times: --- Trying:122 milliseconds --- Checking:33 milliseconds however, here's what confused me and the reason I'm asking: When running the example with values for the optional columns in all 8000 lines of the CSV, the if() version still performs better than the try/catch version, so my question is Does really the try block does not have any performance impact on my code? The average times for this example are: --- Trying:105 milliseconds --- Checking:43 milliseconds Can somebody explain what's going on here? Thanks a lot

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  • List filtering: list comprehension vs. lambda + filter

    - by Agos
    I happened to find myself having a basic filtering need: I have a list and I have to filter it by an attribute of the items. My code looked like this: list = [i for i in list if i.attribute == value] But then i thought, wouldn't it be better to write it like this? filter(lambda x: x.attribute == value, list) It's more readable, and if needed for performance the lambda could be taken out to gain something. Question is: are there any caveats in using the second way? Any performance difference? Am I missing the Pythonic Way™ entirely and should do it in yet another way (such as using itemgetter instead of the lambda)? Thanks in advance

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  • What is the best solution to replace a new memory allocator in an existing code?

    - by O. Askari
    During the last few days I've gained some information about memory allocators other than the standard malloc(). There are some implementations that seem to be much better than malloc() for applications with many threads. For example it seems that tcmalloc and ptmalloc have better performance. I have a C++ application that uses both malloc and new operators in many places. I thought replacing them with something like ptmalloc may improve its performance. But I wonder how does the new operator act when used in C++ application that runs on Linux? Does it use the standard behavior of malloc or something else? What is the best way to replace the new memory allocator with the old one in the code? Is there any way to override the behavior or new and malloc or do I need to replace all the calls to them one by one?

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  • Checking exception before using GETITEMBYID()

    - by ps123
    Hello, I am getting item by getiembyid...but I want to check before using it that whether item exist or not...I don't want to use query as main purpose of using Getitembyid is performance.....any idea how to achieve this... itemid = Response.QueryString["loc"]; SPList mylist = myweb.GetList(SPUrlUtility.CombineUrl(myweb.ServerRelativeUrl, "/Lists/Location")); //now id itemid does not exist it throws exception...so i want to check before using following statement that itemid exist...I know i can check throw SPQuery but as i said above because of performance issue only i m using itemid.... SPListItem myitem = mylist.GetItemById(Convert.ToInt32(itemid)); Any idea how to achieve this?

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  • Marvell C++ compiler (for Windows CE) for building Qt

    - by vnm
    Hello, I was able to build Qt 4.5 for Windows CE (ARM4VI) using MS VisualC++ compiler. Now, I am trying to compile Qt 4.5 for Windows CE 5.0 using Marvel C++ compiler v 2.2 (former Intel C++ compiler for XScale architecture) for achieving some performance benefit. It seems, that this compiler not officially supported for building Qt by trolltech (no appropriate mkspec in mkspec's folder of Qt folder). So, my questions: Is it worth to trying build Qt by this compiler for achieving performance enhancement ? Is there any way for building Qt using Marvell C++ compiler (by creating my own mkspec or something like that)?

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  • which is better, creating a view or a new table?

    - by Carson
    I have some demanding mysql queries that are needed to grap same datasets from several mysql tables. I am thinking of creating a table or view to gather all demanding columns from other tables, so as to increase performance. If I create that table, I may need to do extra insert / update / delete operation each time other tables updated. if I create view, I am worrying if the performance can be greatly improved. Because data from other tables are changing very frequently. Most likely, the view may need to be created first everytime before selecting it. Any ideas? e.g. how to cache? other extra measures I can do?

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  • mysql twitter/facebook like status feed

    - by barjonah
    Hi, I have two tables. One named status like this... user_id | status --------+----------- 1 | random status from user 1 2 | random status from user 2 3 | random message from user 3 4 | staus from user 4 1 | second status for user1 etc... and another named users_following like this... user_id | is_following --------+----------- 1 | 2 1 | 3 2 | 1 3 | 2 meaning that user 1 is following both users 2 and 3 etc... So, let's say I chose user 1. What is the best query (performance wise) to show the status updates of users that user 1 is following, in this case users 2 and 3 currently I have something like SELECT * from status WHERE user_id IN(SELECT is_following FROM users_following WHERE user_id='1') LIMIT 0,5 but I don't think this is good for performance if a user was following thousands+ of users

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