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  • Rails log shows unexpected data as to the time spent on a DB stuff

    - by Arhimed
    I'm running on WinXP + Ruby 1.8.6 + Rails 2.3.5 (frozen to the project) in development environment. Looking at development.log I observe inconsistent data as to the time spent on a database stuff. Example #1 (good): Processing PagesController#index (for 127.0.0.1 at 2010-05-11 12:15:54) [GET] Parameters: {"action"=>"index", "controller"=>"pages"} City Columns (563.0ms) SHOW FIELDS FROM `cities` City Load (15.0ms) SELECT * FROM `cities` WHERE (`cities`.`short_name` = 'NY') LIMIT 1 Redirected to http://xyz:3000/sightings Completed in 953ms (DB: 578) | 302 Found [http://xyz/] Example #2 (unexpected): Processing PagesController#index (for 127.0.0.1 at 2010-05-11 12:15:36) [GET] Parameters: {"action"=>"index", "controller"=>"pages"} City Columns (0.0ms) SHOW FIELDS FROM `cities` City Load (0.0ms) SELECT * FROM `cities` WHERE (`cities`.`short_name` = 'NY') LIMIT 1 Redirected to http://xyz:3000/sightings Completed in 47ms (DB: 32) | 302 Found [http://xyz/] Example #2 shows 32ms were spent on DB while there were just 2 sql querries and both of zero time spent. Example #3 (unexpected): Processing PagesController#index (for 127.0.0.1 at 2010-05-11 11:21:24) [GET] Parameters: {"action"=>"index", "controller"=>"pages"} City Columns (63.0ms) SHOW FIELDS FROM `cities` City Load (62.0ms) SELECT * FROM `cities` WHERE (`cities`.`short_name` = 'NY') LIMIT 1 Redirected to http://xyz:3000/sightings Completed in 1187ms (DB: 297) | 302 Found [http://xyz/] Example #3 shows 297ms while there were querries of 63ms and 62ms (125ms in total). Can't understand it. Could someone explain? Thanks in advance.

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  • Is there a module that implements an efficient array type in Erlang?

    - by dsmith
    I have been looking for an array type with the following characteristics in Erlang. append(vector(), term()) O(1) nth(Idx, vector()) O(1) set(Idx, vector(), term()) O(1) insert(Idx, vector(), term()) O(N) remove(Idx, vector()) O(N) I normally use a tuple for this purpose, but the performance characteristics are not what I would want for large N. My testing shows the following performance characteristics... erlang:append_element/2 O(N). erlang:setelement/3 O(N). I have started on a module based on the clojure.lang.PersistentVector implementation, but if it's already been done I won't reinvent the wheel.

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  • What is the impact of a CMS on page load time versus a static site?

    - by PleaseStand
    I am creating a 20-page site that will go on shared hosting. Each page will be about 20 KB (including HTML, CSS, and images common to all pages). To avoid manually adding navigation elements to each page, I am considering using a CMS. However, I am concerned that on a busy server, using a CMS would make the site load more slowly. In a shared hosting environment where PHP is run as a CGI binary, how much does a CMS (WordPress, Drupal, etc.) generally affect page load time, compared to both "plain HTML" static sites and those using PHP as merely a templating language?

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  • how to optimize an oracle query that has to_char in where clause for date

    - by panorama12
    I have a table that contains about 49403459 records. I want to query the table on a date range. say 04/10/2010 to 04/10/2010. However, the dates are stored in the table as format 10-APR-10 10.15.06.000000 AM (time stamp). As a result. When I do: SELECT bunch,of,stuff,create_date FROM myTable WHERE TO_CHAR (create_date,'MM/DD/YYYY)' >= '04/10/2010' AND TO_CHAR (create_date, 'MM/DD/YYYY' <= '04/10/2010' I get 529 rows but in 255.59 seconds! which is because I guess I am doing to_char on EACH record. However, When I do SELECT bunch,of,stuff,create_date FROM myTable WHERE create_date >= to_date('04/10/2010','MM/DD/YYYY') AND create_date <= to_date('04/10/2010','MM/DD/YYYY') then I get 0 results in 0.14 seconds. How can I make this query fast and still get valid (529) results?? At this point I can not change indexes. Right now I think index is created on create_date column

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  • C# to unmanaged dll data structures interop

    - by Shane Powell
    I have a unmanaged DLL that exposes a function that takes a pointer to a data structure. I have C# code that creates the data structure and calls the dll function without any problem. At the point of the function call to the dll the pointer is correct. My problem is that the DLL keeps the pointer to the structure and uses the data structure pointer at a later point in time. When the DLL comes to use the pointer it has become invalid (I assume the .net runtime has moved the memory somewhere else). What are the possible solutions to this problem? The possible solutions I can think of are: Fix the memory location of the data structure somehow? I don't know how you would do this in C# or even if you can. Allocate memory manually so that I have control over it e.g. using Marshal.AllocHGlobal Change the DLL function contract to copy the structure data (this is what I'm currently doing as a short term change, but I don't want to change the dll at all if I can help it as it's not my code to begin with). Are there any other better solutions?

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  • Effective Data Validation

    - by John Conde
    What's an effective way to handle data validation, say, from a form submission? Originally I had a bunch of if statements that checked each value and collected invalid values in an array for later retrieval (and listing). // Store errors here $errors = array(); // Hypothetical check if a string is alphanumeric if (!preg_match('/^[a-z\d]+$/i', $fieldvalue)) { $errors[$fieldname] = 'Please only use letters and numbers for your street address'; } // etc... What I did next was create a class that handles various data validation scenarios and store the results in an internal array. After data validation was complete I would check to see if any errors occurred and handle accordingly: class Validation { private $errorList = array(); public function isAlphaNumeric($string, $field, $msg = '') { if (!preg_match('/^[a-z\d]+$/i', $string)) { $this->errorList[$field] = $msg; } } // more methods here public function creditCard($cardNumber, $field, $msg = '') { // Validate credit card number } // more methods here public function hasErrors() { return count($this->errorList); } } /* Client code */ $validate = new Validation(); $validate->isAlphaNumeric($fieldvalue1, $fieldname1, 'Please only use letters and numbers for your street address'); $validate->creditCard($fieldvalue2, $fieldname2, 'Please enter a valid credit card number'); if ($validate->hasErrors()) { // Handle as appropriate } Naturally it didn't take long before this class became bloated with the virtually unlimited types of data to be validated. What I'm doing now is using decorators to separate the different types of data into their own classes and call them only when needed leaving generic validations (i.e. isAlphaNumeric()) in the base class: class Validation { private $errorList = array(); public function isAlphaNumeric($string, $field, $msg = '') { if (!preg_match('/^[a-z\d]+$/i', $string)) { $this->errorList[$field] = $msg; } } // more generic methods here public function setError($field, $msg = '') { $this->errorList[$field] = $msg; } public function hasErrors() { return count($this->errorList); } } class ValidationCreditCard { protected $validate; public function __construct(Validation $validate) { $this->validate = $validate; } public function creditCard($cardNumber, $field, $msg = '') { // Do validation // ... // if there is an error $this->validate->setError($field, $msg); } // more methods here } /* Client code */ $validate = new Validation(); $validate->isAlphaNumeric($fieldvalue, $fieldname, 'Please only use letters and numbers for your street address'); $validateCC = new ValidationCreditCard($validate); $validateCC->creditCard($fieldvalue2, $fieldname2, 'Please enter a valid credit card number'); if ($validate->hasErrors()) { // Handle as appropriate } Am I on the right track? Or did I just complicate data validation more then I needed to?

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  • Loading a CSV file using jQuery GET returns the header but no data

    - by Cees Meijer
    When reading a CSV file from a server using the jQuery 'GET' function I do not get any data. When I look at the code using FireBug I can see the GET request is sent and the return value is '200 OK'. Also I see that the header is returned correctly so the request is definitely made, and data is returned. This is also what I see in Wireshark. Here I see the complete contents of the CSV file is returned as a standard HTTP response. But the actual data is not there in my script. Firebug shows an empty response and the 'success' function is never called. What could be wrong ? <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>New Web Project</title> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <script src="jquery.js" type="text/javascript" charset="utf-8"></script> <script type="text/javascript"> var csvData; $(document).ready(function() { $("#btnGET").click(function() { csvData = $.ajax({ type: "GET", url: "http://www.mywebsite.com/data/sample_file.csv", dataType: "text/csv", success: function () { alert("done!"+ csvData.getAllResponseHeaders()) } }); }); }) </script> </head> <body> <h1>New Web Project Page</h1> <button id="btnGET">GET Data</button> </body> </html>

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  • Fill data gaps - UNION, PARTITION BY, or JOIN?

    - by Dave Jarvis
    Problem There are data gaps that need to be filled. Would like to avoid UNION or PARTITION BY if possible. Query Statement The select statement reads as follows: SELECT count( r.incident_id ) AS incident_tally, r.severity_cd, r.incident_typ_cd FROM report_vw r GROUP BY r.severity_cd, r.incident_typ_cd ORDER BY r.severity_cd, r.incident_typ_cd Data Sources The severity codes and incident type codes are from: severity_vw incident_type_vw The columns are: incident_tally severity_cd incident_typ_cd Actual Result Data 36 0 ENVIRONMENT 1 1 DISASTER 27 1 ENVIRONMENT 4 2 SAFETY 1 3 SAFETY Required Result Data 36 0 ENVIRONMENT 0 0 DISASTER 0 0 SAFETY 27 1 ENVIRONMENT 0 1 DISASTER 0 1 SAFETY 0 2 ENVIRONMENT 0 2 DISASTER 4 2 SAFETY 0 3 ENVIRONMENT 0 3 DISASTER 1 3 SAFETY Question How would you use UNION, PARTITION BY, or LEFT JOIN to fill in the zero counts?

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  • What limits scaling in this simple OpenMP program?

    - by Douglas B. Staple
    I'm trying to understand limits to parallelization on a 48-core system (4xAMD Opteron 6348, 2.8 Ghz, 12 cores per CPU). I wrote this tiny OpenMP code to test the speedup in what I thought would be the best possible situation (the task is embarrassingly parallel): // Compile with: gcc scaling.c -std=c99 -fopenmp -O3 #include <stdio.h> #include <stdint.h> int main(){ const uint64_t umin=1; const uint64_t umax=10000000000LL; double sum=0.; #pragma omp parallel for reduction(+:sum) for(uint64_t u=umin; u<umax; u++) sum+=1./u/u; printf("%e\n", sum); } I was surprised to find that the scaling is highly nonlinear. It takes about 2.9s for the code to run with 48 threads, 3.1s with 36 threads, 3.7s with 24 threads, 4.9s with 12 threads, and 57s for the code to run with 1 thread. Unfortunately I have to say that there is one process running on the computer using 100% of one core, so that might be affecting it. It's not my process, so I can't end it to test the difference, but somehow I doubt that's making the difference between a 19~20x speedup and the ideal 48x speedup. To make sure it wasn't an OpenMP issue, I ran two copies of the program at the same time with 24 threads each (one with umin=1, umax=5000000000, and the other with umin=5000000000, umax=10000000000). In that case both copies of the program finish after 2.9s, so it's exactly the same as running 48 threads with a single instance of the program. What's preventing linear scaling with this simple program?

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  • getting data from dynamic schema

    - by coure2011
    I am using mongoose/nodejs to get data as json from mongodb. For using mongoose I need to define schema first like this var mongoose = require('mongoose'); var Schema = mongoose.Schema; var GPSDataSchema = new Schema({ createdAt: { type: Date, default: Date.now } ,speed: {type: String, trim: true} ,battery: { type: String, trim: true } }); var GPSData = mongoose.model('GPSData', GPSDataSchema); mongoose.connect('mongodb://localhost/gpsdatabase'); var db = mongoose.connection; db.on('open', function() { console.log('DB Started'); }); then in code I can get data from db like GPSData.find({"createdAt" : { $gte : dateStr, $lte: nextDate }}, function(err, data) { res.writeHead(200, { "Content-Type": "application/json", "Access-Control-Allow-Origin": "*" }); var body = JSON.stringify(data); res.end(body); }); How to define scheme for a complex data like this, you can see that subSection can go to any deeper level. [ { 'title': 'Some Title', 'subSection': [{ 'title': 'Inner1', 'subSection': [ {'titile': 'test', 'url': 'ab/cd'} ] }] }, .. ]

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  • What is a good approach to preloading data?

    - by Bob Horn
    Are there best practices out there for loading data into a database, to be used with a new installation of an application? For example, for application foo to run, it needs some basic data before it can even be started. I've used a couple options in the past: TSQL for every row that needs to be preloaded: IF NOT EXISTS (SELECT * FROM Master.Site WHERE Name = @SiteName) INSERT INTO [Master].[Site] ([EnterpriseID], [Name], [LastModifiedTime], [LastModifiedUser]) VALUES (@EnterpriseId, @SiteName, GETDATE(), @LastModifiedUser) Another option is a spreadsheet. Each tab represents a table, and data is entered into the spreadsheet as we realize we need it. Then, a program can read this spreadsheet and populate the DB. There are complicating factors, including the relationships between tables. So, it's not as simple as loading tables by themselves. For example, if we create Security.Member rows, then we want to add those members to Security.Role, we need a way of maintaining that relationship. Another factor is that not all databases will be missing this data. Some locations will already have most of the data, and others (that may be new locations around the world), will start from scratch. Any ideas are appreciated.

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  • SQL query: how to translate IN() into a JOIN?

    - by tangens
    I have a lot of SQL queries like this: SELECT o.Id, o.attrib1, o.attrib2 FROM table1 o WHERE o.Id IN ( SELECT DISTINCT Id FROM table1, table2, table3 WHERE ... ) These queries have to run on different database engines (MySql, Oracle, DB2, MS-Sql, Hypersonic), so I can only use common SQL syntax. Here I read, that with MySql the IN statement isn't optimized and it's really slow, so I want to switch this into a JOIN. I tried: SELECT o.Id, o.attrib1, o.attrib2 FROM table1 o, table2, table3 WHERE ... But this does not take into account the DISTINCT keyword. Question: How do I get rid of the duplicate rows using the JOIN approach?

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  • Decent profiler for Windows?

    - by olliej
    Does windows have any decent sampling (eg. non-instrumenting) profilers available? Preferably something akin to Shark on MacOS, although i am willing to accept that i am going to have to pay for such a profiler on windows. I've tried the profiler in VS Team Suite and was not overly impressed, and was wondering if there were any other good ones. [Edit: Erk, i forgot to say this is for C/C++, rather than .NET -- sorry for any confusion]

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  • XSLT 1.0: restrict entries in a nodeset

    - by Mike
    Hi, Being relatively new to XSLT I have what I hope is a simple question. I have some flat XML files, which can be pretty big (eg. 7MB) that I need to make 'more hierarchical'. For example, the flat XML might look like this: <D0011> .... .... and it should end up looking like this: <D0011> .... .... I have a working XSLT for this, and it essentially gets a nodeset of all the b elements and then uses the 'following-sibling' axis to get a nodeset of the nodes following the current b node (ie. following-sibling::*[position() =$nodePos]). Then recursion is used to add the siblings into the result tree until another b element is found (I have parameterised it of course, to make it more generic). I also have a solution that just sends the position in the XML of the next b node and selects the nodes after that one after the other (using recursion) via a *[position() = $nodePos] selection. The problem is that the time to execute the transformation increases unacceptably with the size of the XML file. Looking into it with XML Spy it seems that it is the 'following-sibling' and 'position()=' that take the time in the two respective methods. What I really need is a way of restricting the number of nodes in the above selections, so fewer comparisons are performed: every time the position is tested, every node in the nodeset is tested to see if its position is the right one. Is there a way to do that ? Any other suggestions ? Thanks, Mike

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  • backing up user data

    - by shani
    in my app the user saves data in archive using core data and sqllite. 1. is there a way letting him the option to back up his data and restoring it in the future? 2. does the user info is backed up with the iphone regular back up? thanks shani

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  • How to clear APC cache entries?

    - by lo_fye
    I need to clear all APC cache entries when I deploy a new version of the site. APC.php has a button for clearing all opcode caches, but I don't see buttons for clearing all User Entries, or all System Entries, or all Per-Directory Entries. Is it possible to clear all cache entries via the command-line, or some other way?

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  • Preferred data-format for user-data in java applications?

    - by Frederik Wordenskjold
    I'm currently developing a desktop application in java, which stores user data such as bookmarks for ftp-servers. When deciding how to save these informations, I ended up using xml, simply because I like the way xpath works. I was thinking about json too, which seems more lightweight. What is your preferred way to store data in java desktop applications (in general) and why? What about java-persistence, does that have any advantages worth noting? And how much does the size of user data matter? Its not always possible to store data in a database (or preferable), and in my experience xml does not scale well. Let me know what you think!

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  • How to find the worst performing queries in MS SQL Server 2008?

    - by Thomas Bratt
    How to find the worst performing queries in MS SQL Server 2008? I found the following example but it does not seem to work: SELECT TOP 5 obj.name, max_logical_reads, max_elapsed_time FROM sys.dm_exec_query_stats a CROSS APPLY sys.dm_exec_sql_text(sql_handle) hnd INNER JOIN sys.sysobjects obj on hnd.objectid = obj.id ORDER BY max_logical_reads DESC Taken from: http://www.sqlservercurry.com/2010/03/top-5-costly-stored-procedures-in-sql.html

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  • Time complexity O() of isPalindrome()

    - by Aran
    I have this method, isPalindrome(), and I am trying to find the time complexity of it, and also rewrite the code more efficiently. boolean isPalindrome(String s) { boolean bP = true; for(int i=0; i<s.length(); i++) { if(s.charAt(i) != s.charAt(s.length()-i-1)) { bP = false; } } return bP; } Now I know this code checks the string's characters to see whether it is the same as the one before it and if it is then it doesn't change bP. And I think I know that the operations are s.length(), s.charAt(i) and s.charAt(s.length()-i-!)). Making the time-complexity O(N + 3), I think? This correct, if not what is it and how is that figured out. Also to make this more efficient, would it be good to store the character in temporary strings?

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  • Scalable way of doing self join with many to many table

    - by johnathan
    I have a table structure like the following: user id name profile_stat id name profile_stat_value id name user_profile user_id profile_stat_id profile_stat_value_id My question is: How do I evaluate a query where I want to find all users with profile_stat_id and profile_stat_value_id for many stats? I've tried doing an inner self join, but that quickly gets crazy when searching for many stats. I've also tried doing a count on the actual user_profile table, and that's much better, but still slow. Is there some magic I'm missing? I have about 10 million rows in the user_profile table and want the query to take no longer than a few seconds. Is that possible?

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  • Why does Go compile quickly?

    - by Evan Kroske
    I've Googled and poked around the Go website, but I can't seem to find an explanation for Go's extraordinary build times. Are they products of the language features (or lack thereof), a highly optimized compiler, or something else? I'm not trying to promote Go; I'm just curious.

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  • NLB and Web Deploy

    - by asgerhallas
    I have two webservers in a cluster serving a web application. Using MS Web Deploy to push a new version of the application to one server, and then again to synchronize the files to the other server in the cluster. It seems to be the most ordinary thing to do. But wouldn't there be a problemm, when one server is deployed with the new version, and the other is not yet finished. Will it not cause troubles, when a page loaded with the new version makes a webservice request and the balancer sends the request to the server with the old version? What's the best way to avoid this? I thought about scripting a drainstop of the server, that we deploy to, and make sure only one server is running at a time. But I can't find anyone else, who seems to have written about such a solution. And guess that it doesn't scale very well too. Another solution could be to shut down all servers when updating. But that doesn't seems very clever. Any suggestions?

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