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  • How I shoud use BIT in MS SQL 2005

    - by adopilot
    Regarding to SQL performance. I have Scalar-Valued function for checking some specific condition in base, It returns BIT value True or False, I now do not know how I should fill @BIT parameter If I write. set @bit = convert(bit,1) or set @bit = 1 or set @bit='true' Function will work anyway but I do not know which method is recommended for daily use. Another Question, I have table in my base with around 4 million records, Daily insert is about 4K records in that table. Now I want to add CONSTRAINT on that table whit scalar valued function that I mentioned already Something like this ALTER TABLE fin_stavke ADD CONSTRAINT fin_stavke_knjizenje CHECK ( dbo.fn_ado_chk_fin(id)=convert(bit,1)) Where is filed "id" primary key of table fin_stavke and dbo.fn_ado_chk_fin looks like create FUNCTION fn_ado_chk_fin ( @stavka_id int ) RETURNS bit AS BEGIN declare @bit bit if exists (select * from fin_stavke where id=@stavka_id and doc_id is null and protocol_id is null) begin set @bit=0 end else begin set @bit=1 end return @bit; END GO Will this type and method of cheeking constraint will affect badly performance on my table and SQL at all ? If there is also better way to add control on this table please let me know.

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  • storing/retrieving data for graph with long continuous stretches

    - by james
    i have a large 2-dimensional data set which i would like to graph. the graph is displayed in a browser and the data is retrieved via ajax. long stretches of this graph will be continuous - e.g., for x=0 through x=1000, y=9, then for x=1001 through x=1100, y=80, etc. the approach i'm considering is to send (from the server) and store (in the browser) only the points where the data changes. so for the example above, i would say data[0] = 9, then data[1001] = 80. then given x=999 for example, retrieving data[999] would actually look up data[0]. the problem that arises is finding a dictionary-like data structure which behaves like this. the approach i'm considering is to store the data in a traditional dictionary object, then also maintain a sorted array of key for that object. when given x=999, it would look at the mid-point of this array, determine whether the nearest lower key is left or right of that midpoint, then repeat with the correct subsection, etc.. does anyone have thoughts on this problem/approach?

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  • Dojox Datagrid contains data, but shows up as empty

    - by Vivek
    I'd really appreciate any help on this. There is this Dojox Datagrid that I'm creating programatically and supplying JSON data. As of now, I'm creating this data within JavaScript itself. Please refer to the below code sample. var upgradeStageStructure =[{ cells:[ { field: "stage", name: "Stage", width: "50%", styles: 'text-align: left;' }, { field:"status", name: "Status", width: "50%", styles: 'text-align: left;' } ] }]; var upgradeStageData = [ {id:1, stage: "Preparation", status: "Complete"}, {id:2, stage: "Formatting", status: "Complete"}, {id:3, stage: "OS Installation", status: "Complete"}, {id:4, stage: "OS Post-Installation", status: "In Progress"}, {id:5, stage: "Application Installation", status: "Not Started"}, {id:6, stage: "Application Post-Installation", status: "Not Started"} ]; var stagestore = new dojo.data.ItemFileReadStore({data:{identifier:"id", items: upgradeStageData}}); var upgradeStatusGrid = new dojox.grid.DataGrid({ autoHeight: true, style: "width:400px;padding:0em;margin:0em;", store: stagestore, clientSort: false, rowSelector: '20px', structure: upgradeStageStructure, columnReordering: false, selectable: false, singleClickEdit: false, selectionMode: 'none', loadingMessage: 'Loading Upgrade Stages', noDataMessage:'There is no data', errorMessage: 'Failed to load Upgrade Status' }); dojo.byId('progressIndicator').innerHTML=''; dojo.byId('progressIndicator').appendChild(upgradeStatusGrid.domNode); upgradeStatusGrid.startup(); The problem is that I am not seeing anything within the grid upon display (no headers, no data). But I know for sure that the data in the grid does exist and the grid is properly initialized, because I called alert (grid.domNode.innerHTML);. The resultant HTML that is thrown up does show a table containing header rows and the above data. This link contains an image which illustrates what I'm seeing when I display the page. (Can't post images since my account is new here) As you may notice, there are 6 rows for 6 pieces of data I have created but the grid is a mess. Please help out if you think you know what could be going wrong. Thanks in advance, Viv

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  • Measuring execution time of selected loops

    - by user95281
    I want to measure the running times of selected loops in a C program so as to see what percentage of the total time for executing the program (on linux) is spent in these loops. I should be able to specify the loops for which the performance should be measured. I have tried out several tools (vtune, hpctoolkit, oprofile) in the last few days and none of them seem to do this. They all find the performance bottlenecks and just show the time for those. Thats because these tools only store the time taken that is above a threshold (~1ms). So if one loop takes lesser time than that then its execution time won't be reported. The basic block counting feature of gprof depends on a feature in older compilers thats not supported now. I could manually write a simple timer using gettimeofday or something like that but for some cases it won't give accurate results. For ex: for (i = 0; i < 1000; ++i) { for (j = 0; j < N; ++j) { //do some work here } } Now here I want to measure the total time spent in the inner loop and I will have to put a call to gettimeofday inside the first loop. So gettimeofday itself will get called a 1000 times which introduces its own overhead and the result will be inaccurate.

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  • Oracle: Insertion on an indexed table, avoiding duplicates. Looking for tips and advice.

    - by Tom
    Hi everyone, Im looking for the best solution (performance wise) to achieve this. I have to insert records into a table, avoiding duplicates. For example, take table A Insert into A ( Select DISTINCT [FIELDS] from B,C,D.. WHERE (JOIN CONDITIONS ON B,C,D..) AND NOT EXISTS ( SELECT * FROM A ATMP WHERE ATMP.SOMEKEY = A.SOMEKEY ) ); I have an index over A.SOMEKEY, just to optimize the NOT EXISTS query, but i realize that inserting on an indexed table will be a performance hit. So I was thinking of duplicating Table A in a Global Temporary Table, where I would keep the index. Then, removing the index from Table A and executing the query, but modified Insert into A ( Select DISTINCT [FIELDS] from B,C,D.. WHERE (JOIN CONDITIONS ON B,C,D..) AND NOT EXISTS ( SELECT * FROM GLOBAL_TEMPORARY_TABLE_A ATMP WHERE ATMP.SOMEKEY = A.SOMEKEY ) ); This would solve the "inserting on an index table", but I would have to update the Global Temporary A with each insertion I make. I'm kind of lost here, Is there a better way to achieve this? Thanks in advance,

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  • rpy2: Converting a data.frame to a numpy array

    - by Mike Dewar
    I have a data.frame in R. It contains a lot of data : gene expression levels from many (125) arrays. I'd like the data in Python, due mostly to my incompetence in R and the fact that this was supposed to be a 30 minute job. I would like the following code to work. To understand this code, know that the variable path contains the full path to my data set which, when loaded, gives me a variable called immgen. Know that immgen is an object (a Bioconductor ExpressionSet object) and that exprs(immgen) returns a data frame with 125 columns (experiments) and tens of thousands of rows (named genes). robjects.r("load('%s')"%path) # loads immgen e = robjects.r['data.frame']("exprs(immgen)") expression_data = np.array(e) This code runs, but expression_data is simply array([[1]]). I'm pretty sure that e doesn't represent the data frame generated by exprs() due to things like: In [40]: e._get_ncol() Out[40]: 1 In [41]: e._get_nrow() Out[41]: 1 But then again who knows? Even if e did represent my data.frame, that it doesn't convert straight to an array would be fair enough - a data frame has more in it than an array (rownames and colnames) and so maybe life shouldn't be this easy. However I still can't work out how to perform the conversion. The documentation is a bit too terse for me, though my limited understanding of the headings in the docs implies that this should be possible. Anyone any thoughts?

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  • Non distinct Unique ID in MySQL database table.

    - by Geoff
    First of, a simplified version: I am wondering if I can create a trigger to activate during INSERT (it's actually LOAD DATA INFILE) and NOT enter records for an RMA already in my table? I have a table that has no records that are unique. Some may be duplicates but there is one field that I can use to know if the data has been entered or not. For instance RMA Op Days --------------------- 213 Repair 0.10 213 Test 0.20 213 Repair 0.10 So I could do an index on the three columns together but as you see it's possible for an RMA to be in a step for the same amount of time twice so it's possible to have duplicate records. This data comes from a report that I cannot edit and this is all it provides. The key is that an RMA's data is only in the report once so if my database already has that RMA in it's records I want to skip the loading of that RMA's records from the report. By all means please let me know if that didn't make sense, I'll Explain as needed. I'm sure it's not uncommon but I couldn't find anything on the net.

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  • Index Tuning for SSIS tasks

    - by Raj More
    I am loading tables in my warehouse using SSIS. Since my SSIS is slow, it seemed like a great idea to build indexes on the tables. There are no primary keys (and therefore, foreign keys), indexes (clustered or otherwise), constraints, on this warehouse. In other words, it is 100% efficiency free. We are going to put indexes based on usage - by analyzing new queries and current query performance. So, instead of doing it our old fashioned sweat and grunt way of actually reading the SQL statements and execution plans, I thought I'd put the shiny new Database Engine Tuning Advisor to use. I turned SQL logging off in my SSIS package and ran a "Tuning" trace, saved it to a table and analyzed the output in the Tuning Advisor. Most of the lookups are done as: exec sp_executesql N'SELECT [Active], [CompanyID], [CompanyName], [CompanyShortName], [CompanyTypeID], [HierarchyNodeID] FROM [dbo].[Company] WHERE ([CompanyID]=@P1) AND ([StartDateTime] IS NOT NULL AND [EndDateTime] IS NULL)',N'@P1 int',1 exec sp_executesql N'SELECT [Active], [CompanyID], [CompanyName], [CompanyShortName], [CompanyTypeID], [HierarchyNodeID] FROM [dbo].[Company] WHERE ([CompanyID]=@P1) AND ([StartDateTime] IS NOT NULL AND [EndDateTime] IS NULL)',N'@P1 int',2 exec sp_executesql N'SELECT [Active], [CompanyID], [CompanyName], [CompanyShortName], [CompanyTypeID], [HierarchyNodeID] FROM [dbo].[Company] WHERE ([CompanyID]=@P1) AND ([StartDateTime] IS NOT NULL AND [EndDateTime] IS NULL)',N'@P1 int',3 exec sp_executesql N'SELECT [Active], [CompanyID], [CompanyName], [CompanyShortName], [CompanyTypeID], [HierarchyNodeID] FROM [dbo].[Company] WHERE ([CompanyID]=@P1) AND ([StartDateTime] IS NOT NULL AND [EndDateTime] IS NULL)',N'@P1 int',4 and when analyzed, these statements have the reason "Event does not reference any tables". Huh? Does it not see the FROM dbo.Company??!! What is going on here? So, I have multiple questions: How do I get it to capture the actual statement executing in my trace, not what was submitted in a batch? Are there any best practices to follow for tuning performance related to SSIS packages running against SQL Server 2008?

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  • How to find the latest row for each group of data

    - by Jason
    Hi All, I have a tricky problem that I'm trying to find the most effective method to solve. Here's a simplified version of my View structure. Table: Audits AuditID | PublicationID | AuditEndDate | AuditStartDate 1 | 3 | 13/05/2010 | 01/01/2010 2 | 1 | 31/12/2009 | 01/10/2009 3 | 3 | 31/03/2010 | 01/01/2010 4 | 3 | 31/12/2009 | 01/10/2009 5 | 2 | 31/03/2010 | 01/01/2010 6 | 2 | 31/12/2009 | 01/10/2009 7 | 1 | 30/09/2009 | 01/01/2009 There's 3 query's that I need from this. I need to one to get all the data. The next to get only the history data (that is, everything but exclude the latest data item by AuditEndDate) and then the last query is to obtain the latest data item (by AuditEndDate). There's an added layer of complexity that I have a date restriction (This is on a per user/group basis) where certain user groups can only see between certain dates. You'll notice this in the where clause as AuditEndDate<=blah and AuditStartDate=blah Foreach publication, select all the data available. select * from Audits Where auditEndDate<='31/03/10' and AuditStartDate='06/06/2009'; foreach publication, select all the data but Exclude the latest data available (by AuditEndDate) select * from Audits left join (select AuditId as aid, publicationID as pid and max(auditEndDate) as pend from Audit where auditenddate <= '31/03/2009' /* user restrict / group by pid) Ax on Ax.pid=Audit.pubid where pend!=Audits.auditenddate AND auditEndDate<='31/03/10' and AuditStartDate='06/06/2009' / user restrict */ Foreach publication, select only the latest data available (by AuditEndDate) select * from Audits left join (select AuditId as aid, publicationID as pid and max(auditEndDate) as pend from Audit where auditenddate <= '31/03/2009'/* user restrict / group by pid) Ax on Ax.pid=Audit.pubid where pend=Audits.auditenddate AND auditEndDate<='31/03/10' and AuditStartDate='06/06/2009' / user restrict */ So at the moment, query 1 and 3 work fine, but query 2 just returns all the data instead of the restriction. Can anyone help me? Thanks jason

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  • Multiple calls to data service from SL3?

    - by Chris
    I have an SL3 that makes asynchronous calls to a data service. Basically, there is a treeview that is bound to a collection of objects. The idea is that as a user selects a specific treeviewitem, a call is made to the data service, with a parameter specific to the selected treeviewitem being passed to the corresponding web method in the data service. The data service returns data back to the SL3 client, and the client presents the data to the user. This works well. The problem is that when users start to navigate through the treeview using the arrow keys on their keyboard, they could press the down arrow key, for example, 10 times, and 10 calls will be made to the data service, and then each of the 10 items will be displayed to the user momentarily, until finishing with the data for the most recently selected treeview item. So - onto the question. How can I put in some form of delay, to allow someone to navigate quickly through a treeview, then, once then stop at a certain treeviewitem, a call is made to the data service? Thanks for any suggestions. Chris

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  • Downloading javascript Without Blocking

    - by doug
    The context: My question relates to improving web-page loading performance, and in particular the effect that javascript has on page-loading (resources/elements below the script are blocked from downloading/rendering). This problem is usually avoided/mitigated by placing the scripts at the bottom (eg, just before the tag). The code i am looking at is for web analytics. Placing it at the bottom reduces its accuracy; and because this script has no effect on the page's content, ie, it's not re-writing any part of the page--i want to move it inside the head. Just how to do that without ruining page-loading performance is the crux. From my research, i've found six techniques (w/ support among all or most of the major browsers) for downloading scripts so that they don't block down-page content from loading/rendering: (i) XHR + eval(); (ii) XHR + 'inject'; (iii) download the HTML-wrapped script as in iFrame; (iv) setting the script tag's 'async' flag to 'TRUE' (HTML 5 only); (v) setting the script tag's 'defer' attribute; and (vi) 'Script DOM Element'. It's the last of these i don't understand. The javascript to implement the pattern (vi) is: (function() { var q1 = document.createElement('script'); q1.src = 'http://www.my_site.com/q1.js' document.documentElement.firstChild.appendChild(q1) })(); Seems simple enough: inside this anonymous function, a script element is created, its 'src' element is set to it's location, then the script element is added to the DOM. But while each line is clear, it's still not clear to me how exactly this pattern allows script loading without blocking down-page elements/resources from rendering/loading?

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  • memcache is not storing data accross requests

    - by morpheous
    I am new to using memcache, so I may be doing something wrong. I have written a wrapper class around memcache. The wrapper class has only static methods, so is a quasi singleton. The class looks something like this: class myCache { private static $memcache = null; private static $initialized = false; public static function init() { if (self::$initialized) return; self::$memcache = new Memcache(); if (self::configure()) //connects to daemon { self::store('foo', 'bar'); } else throw ConnectionError('I barfed'); } public static function store($key, $data, $flag=MEMCACHE_COMPRESSED, $timeout=86400) { if (self::$memcache->get($key)!== false) return self::$memcache->replace($key, $data, $flag, $timeout); return self::$memcache->set($key, $data, $flag, $timeout); } public static function fetch($key) { return self::$memcache->get($key); } } //in my index.php file, I use the class like this require_once('myCache.php'); myCache::init(); echo 'Stored value is: '. myCache::fetch('foo'); The problem is that the myCache::init() method is being executed in full everytime a page is requested. I then remembered that static variables do not maintain state accross page requests. So I decided instead, to store the flag that indicates whether the server contains the start up data (for our purposes, the variable 'foo', with value 'bar') in memcache itself. Once the status flag is stored in memcache itself, It solves the problem of the initialisation data being loaded for every page request (which quite frankly, defeats the purpose of memcache). However, having solved that problem, when I come to fetch the data in memcache, it is empty. I dont understand whats going on. Can anyone clarify how I can store my data once and retrieve it accross page requests? BTW, (just to clarify), the get/set is working correctly, and if I allow memcache to load the initialisation data for each page request, (which is silly), then the data is available in memcache.

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  • Pros and Cons of using SqlCommand Prepare in C#?

    - by MadBoy
    When i was reading books to learn C# (might be some old Visual Studio 2005 books) I've encountered advice to always use SqlCommand.Prepare everytime I execute SQL call (whether its' a SELECT/UPDATE or INSERT on SQL SERVER 2005/2008) and I pass parameters to it. But is it really so? Should it be done every time? Or just sometimes? Does it matter whether it's one parameter being passed or five or twenty? What boost should it give if any? Would it be noticeable at all (I've been using SqlCommand.Prepare here and skipped it there and never had any problems or noticeable differences). For the sake of the question this is my usual code that I use, but this is more of a general question. public static decimal pobierzBenchmarkKolejny(string varPortfelID, DateTime data, decimal varBenchmarkPoprzedni, decimal varStopaOdniesienia) { const string preparedCommand = @"SELECT [dbo].[ufn_BenchmarkKolejny](@varPortfelID, @data, @varBenchmarkPoprzedni, @varStopaOdniesienia) AS 'Benchmark'"; using (var varConnection = Locale.sqlConnectOneTime(Locale.sqlDataConnectionDetailsDZP)) //if (varConnection != null) { using (var sqlQuery = new SqlCommand(preparedCommand, varConnection)) { sqlQuery.Prepare(); sqlQuery.Parameters.AddWithValue("@varPortfelID", varPortfelID); sqlQuery.Parameters.AddWithValue("@varStopaOdniesienia", varStopaOdniesienia); sqlQuery.Parameters.AddWithValue("@data", data); sqlQuery.Parameters.AddWithValue("@varBenchmarkPoprzedni", varBenchmarkPoprzedni); using (var sqlQueryResult = sqlQuery.ExecuteReader()) if (sqlQueryResult != null) { while (sqlQueryResult.Read()) { //sqlQueryResult["Benchmark"]; } } } }

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  • Getting zeros between data while reading a binary file in C

    - by indiajoe
    I have a binary data which I am reading into an array of long integers using a C programme. hexdump of the binary data shows, that after first few data points , it starts again at a location 20000 hexa adresses away. hexdump output is as shown below. 0000000 0000 0000 0000 0000 0000 0000 0000 0000 * 0020000 0000 0000 0053 0000 0064 0000 006b 0000 0020010 0066 0000 0068 0000 0066 0000 005d 0000 0020020 0087 0000 0059 0000 0062 0000 0066 0000 ........ and so on... But when I read it into an array 'data' of long integers. by the typical fread command fread(data,sizeof(*data),filelength/sizeof(*data),fd); It is filling up with all zeros in my data array till it reaches the 20000 location. After that it reads in data correctly. Why is it reading regions where my file is not there? Or how will I make it read only my file, not anything inbetween which are not in file? I know it looks like a trivial problem, but I cannot figure it out even after googling one night.. Can anyone suggest me where I am doing it wrong? Other Info : I am working on a gnu/linux machine. (slax-atma distro to be specific) My C compiler is gcc.

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  • How to benchmark on multi-core processors

    - by Pascal Cuoq
    I am looking for ways to perform micro-benchmarks on multi-core processors. Context: At about the same time desktop processors introduced out-of-order execution that made performance hard to predict, they, perhaps not coincidentally, also introduced special instructions to get very precise timings. Example of these instructions are rdtsc on x86 and rftb on PowerPC. These instructions gave timings that were more precise than could ever be allowed by a system call, allowed programmers to micro-benchmark their hearts out, for better or for worse. On a yet more modern processor with several cores, some of which sleep some of the time, the counters are not synchronized between cores. We are told that rdtsc is no longer safe to use for benchmarking, but I must have been dozing off when we were explained the alternative solutions. Question: Some systems may save and restore the performance counter and provide an API call to read the proper sum. If you know what this call is for any operating system, please let us know in an answer. Some systems may allow to turn off cores, leaving only one running. I know Mac OS X Leopard does when the right Preference Pane is installed from the Developers Tools. Do you think that this make rdtsc safe to use again? More context: Please assume I know what I am doing when trying to do a micro-benchmark. If you are of the opinion that if an optimization's gains cannot be measured by timing the whole application, it's not worth optimizing, I agree with you, but I cannot time the whole application until the alternative data structure is finished, which will take a long time. In fact, if the micro-benchmark were not promising, I could decide to give up on the implementation now; I need figures to provide in a publication whose deadline I have no control over.

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  • Converting to a column oriented array in Java

    - by halfwarp
    Although I have Java in the title, this could be for any OO language. I'd like to know a few new ideas to improve the performance of something I'm trying to do. I have a method that is constantly receiving an Object[] array. I need to split the Objects in this array through multiple arrays (List or something), so that I have an independent list for each column of all arrays the method receives. Example: List<List<Object>> column-oriented = new ArrayList<ArrayList<Object>>(); public void newObject(Object[] obj) { for(int i = 0; i < obj.length; i++) { column-oriented.get(i).add(obj[i]); } } Note: For simplicity I've omitted the initialization of objects and stuff. The code I've shown above is slow of course. I've already tried a few other things, but would like to hear some new ideas. How would you do this knowing it's very performance sensitive?

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  • Parsing multiple files at a time in Perl

    - by sfactor
    I have a large data set (around 90GB) to work with. There are data files (tab delimited) for each hour of each day and I need to perform operations in the entire data set. For example, get the share of OSes which are given in one of the columns. I tried merging all the files into one huge file and performing the simple count operation but it was simply too huge for the server memory. So, I guess I need to perform the operation each file at a time and then add up in the end. I am new to perl and am especially naive about the performance issues. How do I do such operations in a case like this. As an example two columns of the file are. ID OS 1 Windows 2 Linux 3 Windows 4 Windows Lets do something simple, counting the share of the OSes in the data set. So, each .txt file has millions of these lines and there are many such files. What would be the most efficient way to operate on the entire files.

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  • AJAX Post Not Sending Data?

    - by Jascha
    I can't for the life of me figure out why this is happening. This is kind of a repost, so forgive me, but I have new data. I am running a javascript log out function called logOut() that has make a jQuery ajax call to a php script... function logOut(){ var data = new Object; data.log_out = true; $.ajax({ type: 'POST', url: 'http://www.mydomain.com/functions.php', data: data, success: function() { alert('done'); } }); } the php function it calls is here: if(isset($_POST['log_out'])){ $query = "INSERT INTO `token_manager` (`ip_address`) VALUES('logOutSuccess')"; $connection->runQuery($query); // <-- my own database class... // omitted code that clears session etc... die(); } Now, 18 hours out of the day this works, but for some reason, every once in a while, the POST data will not trigger my query. (this will last about an hour or so). I figured out the post data is not being set by adding this at the end of my script... $query = "INSERT INTO `token_manager` (`ip_address`) VALUES('POST FAIL')"; $connection->runQuery($query); So, now I know for certain my log out function is being skipped because in my database is the following data: if it were NOT being skipped, my data would show up like this: I know it is being skipped for two reasons, one the die() at the end of my first function, and two, if it were a success a "logOutSuccess" would be registered in the table. Any thoughts? One friend says it's a janky hosting company (hostgator.com). I personally like them because they are cheap and I'm a fan of cpanel. But, if that's the case??? Thanks in advance. -J

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  • Cross-domain data access in JavaScript

    - by vit
    We have an ASP.Net application hosted on our network and exposed to a specific client. This client wants to be able to import data from their own server into our application. The data is retrieved with an HTTP request and is CSV formatted. The problem is that they do not want to expose their server to our network and are requesting the import to be done on the client side (all clients are from the same network as their server). So, what needs to be done is: They request an import page from our server The client script on the page issues a request to their server to get CSV formatted data The data is sent back to our application This is not a challenge when both servers are on the same domain: a simple hidden iframe or something similar will do the trick, but here what I'm getting is a cross-domain "access denied" error. They also refuse to change the data format to return JSON or XML formatted data. What I tried and learned so far is: Hidden iframe -- "access denied" XMLHttpRequest -- behaviour depends on the browser security settings: may work, may work while nagging a user with security warnings, or may not work at all Dynamic script tags -- would have worked if they could have returned data in JSON format IE client data binding -- the same "access denied" error Is there anything else I can try before giving up and saying that it will not be possible without exposing their server to our application, changing their data format or changing their browser security settings? (DNS trick is not an option, by the way).

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  • Exporting de-aggregated data

    - by Ben
    I'm currently working on a data export feature for a survey application. We are using SQL2k8. We store data in a normalized format: QuestionId, RespondentId, Answer. We have a couple other tables that define what the question text is for the QuestionId and demographics for the RespondentId... Currently I'm using some dynamic SQL to generate a pivot that joins the question table to the answer table and creates an export, its working... The problem is that it seems slow and we don't have that much data (less than 50k respondents). Right now I'm thinking "why am I 'paying' to de-aggregate the data for each query? Why don't I cache that?" The data being exported is based on dynamic criteria. It could be "give me respondents that completed on x date (or range)" or "people that like blue", etc. Because of that, I think I have to cache at the respondent level, find out what respondents are being exported and then select their combined cached de-aggregated data. To me the quick and dirty fix is a totally flat table, RespondentId, Question1, Question2, etc. The problem is, we have multiple clients and that doesn't scale AND I don't want to have to maintain the flattened table as the survey changes. So I'm thinking about putting an XML column on the respondent table and caching the results of a SELECT * FROM Data FOR XML AUTO WHERE RespondentId = x. With that in place, I would then be able to get my export with filtering and XML calls into the XML column. What are you doing to export aggregated data in a flattened format (CSV, Excel, etc)? Does this approach seem ok? I worry about the cost of XML functions on larger result sets (think SELECT RespondentId, XmlCol.value('//data/question_1', 'nvarchar(50)') AS [Why is there air?], XmlCol.RinseAndRepeat)... Is there a better technology/approach for this? Thanks!

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  • How to deal with a flaw in System.Data.DataTableExtensions.CopyToDataTable()

    - by andy
    Hey guys, so I've come across something which is perhaps a flaw in the Extension method .CopyToDataTable. This method is used by Importing (in VB.NET) System.Data.DataTableExtensions and then calling the method against an IEnumerable. You would do this if you want to filter a Datatable using LINQ, and then restore the DataTable at the end. i.e: Imports System.Data.DataRowExtensions Imports System.Data.DataTableExtensions Public Class SomeClass Private Shared Function GetData() As DataTable Dim Data As DataTable Data = LegacyADO.NETDBCall Data = Data.AsEnumerable.Where(Function(dr) dr.Field(Of Integer)("SomeField") = 5).CopyToDataTable() Return Data End Function End Class In the example above, the "WHERE" filtering might return no results. If this happens CopyToDataTable throws an exception because there are no DataRows. Why? The correct behavior should be to return a DataTable with Rows.Count = 0. Can anyone think of a clean workaround to this, in such a way that whoever calls CopyToDataTable doesn't have to be aware of this issue? System.Data.DataTableExtensions is a Static Class so I can't override the behavior....any ideas? Have I missed something? cheers UPDATE: I have submitted this as an issue to Connect. I would still like some suggestions, but if you agree with me, you could vote up the issue at Connect via the link above cheers

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  • The Current State Of Serving a PHP 5.x App on the Apache, LightTPD & Nginx Web Servers?

    - by Gregory Kornblum
    Being stuck in a MS stack architecture/development position for the last year and a half has prevented me from staying on top of the world of open source stack based web servers recent evolution more than I would have liked to. However I am now building an open source stack based application/system architecture and sadly I do not have the time to give each of the above mentioned web servers a thorough test of my own to decide. So I figured I'd get input from the best development community site and more specifically the people who make it so. This is a site that is a resource for information regarding a specific domain and target audience with features to help users not only find the information but to also interact with one another in various ways for various reasons. I chose the open source stack for the wealth of resources it has along with much better offers than the MS stack (i.e. WordPress vs BlogEngine.NET). I feel Java is more in the middle of these stacks in this regard although I am not ruling out the possibility of using it in certain areas unrelated to the actual web app itself such as background processes. I have already come to the conclusion of using PHP (using CodeIgniter framework & APC), MySQL (InnoDB) and Memcached on CentOS. I am definitely serving static content on Nginx. However the 3 servers mentioned have no consensus on which is best for dynamic content in regards to performance. It seems LightTPD still has the leak issue which rules it out if it does, Nginx seems it is still not mature enough for this aspect and of course Apache tries to be everything for everybody. I am still going to compile the one chosen with as many performance tweaks as possible such as static linking and the likes. I believe I can get Apache to match the other 2 in regards to serving dynamic content through this process and not having it serve anything static. However during my research it seems the others are still worth considering. So with all things considered I would love to hear what everyone here has to say on the matter. Thanks!

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  • What's the best way to store Logon User information for Web Application?

    - by Morgan Cheng
    I was once in a project of web application developed on ASP.NET. For each logon user, there is an object (let's call it UserSessionObject here) created and stored in RAM. For each HTTP request of given user, matching UserSessoinObject instance is used to visit user state information and connection to database. So, this UserSessionObject is pretty important. This design brings several problems found later: 1) Since this UserSessionObject is cached in ASP.NET memory space, we have to config load balancer to be sticky connection. That is, HTTP request in single session would always be sent to one web server behind. This limit scalability and maintainability. 2) This UserSessionObject is accessed in every HTTP request. To keep the consistency, there is a exclusive lock for the UserSessionObject. Only one HTTP request can be processed at any given time because it must to obtain the lock first. The performance and response time is affected. Now, I'm wondering whether there is better design to handle such logon user case. It seems Sharing-Nothing-Architecture helps. That means long user info is retrieved from database each time. I'm afraid that would hurt performance. Is there any design pattern for long user web app? Thanks.

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  • Managing StringBuilder Resources

    - by Jim Fell
    My C# (.NET 2.0) application has a StringBuilder variable with a capacity of 2.5MB. Obviously, I do not want to copy such a large buffer to a larger buffer space every time it fills. By that point, there is so much data in the buffer anyways, removing the older data is a viable option. Can anyone see any obvious problems with how I'm doing this (i.e. am I introducing more performance problems than I'm solving), or does it look okay? tText_c = new StringBuilder(2500000, 2500000); private void AppendToText(string text) { if (tText_c.Length * 100 / tText_c.Capacity > 95) { tText_c.Remove(0, tText_c.Length / 2); } tText_c.Append(text); } EDIT: Additional information: In this application new data is received very rapidly (on the order of milliseconds) through a serial connection. I don't want to populate the multiline textbox with this new information so frequently because that kills the performance of the application, so I'm saving it to a StringBuilder. Every so often, the application copies the contents of the StringBuilder to the textbox and wipes out the StringBuilder contents.

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  • IPad SQLite Push and Pull Data from external MS SQL Server DB

    - by MattyD
    This carries on from my previous post (http://stackoverflow.com/questions/4182664/ipad-app-pull-and-push-relational-data). My plan is that when the ipad application starts I am going to pull data (config data i.e. Departments, Types etc etc relational data that is used across the system) from a webhosted MS SQL Server DB via a webservice and populate it into an SQL Lite DB on the IPad. Then when I load a listing I will pull the data over the line again via a webservice and populate it into the SQL Lite db on the ipad (than just run select commands to populate the listing). My questions are: 1. What is the most efficient way to transfer data across the line via the web? Everyone seems to do it a different way. My idea is that I will have a webService for each type of data pull (e.g. RetrieveContactListing) that will query the db and than convert that data into "something" to send across the line. My question really is what is the "something" that it should be converting into? 2. Everyone talks about odata services. Is this suited for applications where complex read and writes are needed? Ive created a simple iphone app before that talked to an sql server db (i just sent my own structured xml across the line) but now with this app the data calls are going to be a lot larger so efficiency is key.

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