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• C++ Asymptotic Profiling

  - by Travis

  I have a performance issue where I suspect one standard C library function is taking too long and causing my entire system (suite of processes) to basically "hiccup". Sure enough if I comment out the library function call, the hiccup goes away. This prompted me to investigate what standard methods there are to prove this type of thing? What would be the best practice for testing a function to see if it causes an entire system to hang for a sec (causing other processes to be momentarily starved)? I would at least like to definitively correlate the function being called and the visible freeze. Thanks

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• Call function in query in Entity framework 3.5

  - by Ashwani K

  Hello All: I am trying to run following query in entity framework 3.5 var test = from e in customers where IsValid(e) select e; Here IsValid function takes current customer and validate against some conditions and returns false or true. But when I am trying to run the query it is giving error "LINQ Method cannot be translated into a store expression." Can any body tell me any other approach? One approach I can think of is to write all validation conditions here, but that will make the code difficult to read. Thanks Ashwani

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• why is there extra using where in execution plan of query

  - by user366534

  I see plan of query: EXPLAIN SELECT * FROM `subscribers` WHERE state =4 AND date_added < '2010-12-23 11:47:45' It shows: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE subscribers range state_date_added state_date_added 9 NULL 8 Using where Here is indexes of table: Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment subscribers 0 PRIMARY 1 subscriber_id A 382039 NULL NULL BTREE subscribers 0 email_list_id 1 email_address A 191019 NULL NULL BTREE subscribers 0 email_list_id 2 list_id A 382039 NULL NULL BTREE subscribers 1 FK_list_id 1 list_id A 10 NULL NULL BTREE subscribers 1 state_date_added 1 state A 12 NULL NULL BTREE subscribers 1 state_date_added 2 date_added A 8128 NULL NULL BTREE The last two lines describes index what is supposed for the query. Why is there in extra column using where? Even If I fetch only state and date_added column, it has in extra column: Using where; Using index. I understand why it has using index, but I don't understand Using where here.

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• Avoid IF statement after condition has been met

  - by greye

  I have a division operation inside a cycle that repeats many times. It so happens that in the first few passes through the loop (more or less first 10 loops) the divisor is zero. Once it gains value, a div by zero error is not longer possible. I have an if condition to test the divisor value in order to avoid the div by zero, but I am wondering that there is a performance impact that evaluating this if will have for each run in subsequent loops, especially since I know it's of no use anymore. How should this be coded? in Python?

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• SQL Join query help

  - by lostInTransit

  Hi I have 2 tables A and B with the following columns Table A - id,bId,aName,aVal Table B - id,bName where A.bId is the same as B.id. I want a result set from a query to get A.id, A.aName, B.bName where A.bId=B.id OR A.id, A.aName, "" when A.bId=0. In both cases, only those records should be considered where A.aVal LIKE "aVal" Can someone please help me with the query? I can use left join but how do I get the blank string if bId=0 and B.bName otherwise? Thanks

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• How to keep Hibernate mapping use under control as requirements grow

  - by David Plumpton

  I've worked on a number of Java web apps where persistence is via Hibernate, and we start off with some central class (e.g. an insurance application) without any time being spent considering how to break things up into manageable chunks. Over time as features are added we add more mappings (rates, clients, addresses, etc.) and then amount of time spent saving and loading an insurance object and everything it connects to grows. In particular you get close to a go-live date and performance testing with larger amounts of data in each table is starting to demonstrate that it's all too slow. Obviously there are a number of ways that we could attempt to partition things up, e.g. map only the client classes for the client CRUD screens, etc., which would have been better to get in place earlier rather than trying to work it in at the end of the dev cycle. I'm just wondering if there are recommendations about ways to handle/mitigate this.

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• Query in sql involving joins of two table

  - by Satish

  I have two tables reports and holidays. reports: (username varchar(30),activity varchar(30),hours int(3),report_date date) holidays: (holiday_name varchar(30), holiday_date date) select * from reports gives +----------+-----------+---------+------------+ | username | activity | hours | date | +----------+-----------+---------+------------+ | prasoon | testing | 3 | 2009-01-01 | | prasoon | coding | 4 | 2009-01-03 | | prasoon | coding | 4 | 2009-01-06 | | prasoon | coding | 4 | 2009-01-10 | +----------+-----------+---------+------------+ select * from holidays gives +--------------+---------------+ | holiday_name | holiday_date | +--------------+---------------+ | Diwali | 2009-01-02 | | Holi | 2009-01-05 | +--------------+---------------+ Is there any way by which I can output the following? +-------------+-----------+---------+-------------------+ | date | activity | hours | holiday_name | +-------------+-----------+---------+-------------------+ | 2009-01-01 | testing | 3 | | | 2009-01-02 | | | Diwali | | 2009-01-03 | coding | 4 | | | 2009-01-04 | Absent | Absent | | | 2009-01-05 | | | Holi | | 2009-01-06 | coding | 4 | | | 2009-01-07 | Absent | Absent | | | 2009-01-08 | Absent | Absent | | | 2009-01-09 | Absent | Absent | | | 2009-01-10 | coding | 4 | | +-------------+-----------+---------+-------------------+ In other words I want to fill the activity and hours columns with "Absent" on the dates which are neither in table reports nor in table holidays. How can I write a specific query for it. The query should give the output between two specific dates.

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• Wordpress Database SQL query help needed

  - by i-CONICA

  Hi, I've written a PHP script to access the latest item from the wordpress database, which it does. But I need to use it twice, once for the latest item from a specific category, and another from a differerent category... But right now I cannot figure out how to put the query together. The post has a post_parent, which in another table, called wp_term_relationships, is referred to as object_id, and has a term_taxonomy_id, which then relates to a different table, called wp_terms where the term_taxonomy_id is now term_id and then you have the category slug name available to select... I really cannot understand how this query would work though. I've made a really crap mock up of it, to try to "visually" explain what i'm trying to do... SELECT * FROM wp_posts WHERE post_status = 'publish' AND (SELECT term_taxonomy_id FROM wp_term_relationships WHERE object_id = post_parent) AND (SELECT slug FROM wp_terms WHERE term_id = term_taxonomy_id) ORDER BY ID DESC LIMIT 1 Really would appreciate some help... Thanks.

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• Query for model by key

  - by Jason Hall

  What I'm trying to do is query the datastore for a model where the key is not the key of an object I already have. Here's some code: class User(db.Model): partner = db.SelfReferenceProperty() def text_message(self, msg): user = User.get_or_insert(msg.sender) if not user.partner: # user doesn't have a partner, find them one # BUG: this line returns 'user' himself... :( other = db.Query(User).filter('partner =', None).get() if other: # connect users else: # no one to connect to! The idea is to find another User who doesn't have a partner, that isn't the User we already know. I've tried filter('key !=, user.key()), filter('__key__ !=, user.key()) and a couple others, and nothing returns another User who doesn't have a partner. filter('foo !=, user.key()) also returns nothing, for the record.

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• Regular Expression for $_GET query strings

  - by sandelius

  Hi there! I'm trying to find a regular expression for $_GET query strings. I have an array like this: private $_regexp = array( ':id' => '[0-9]+', ':year' => '[12][0-9]{3}', ':month' => '0[1-9]|1[012]', ':day' => '0[1-9]|[12][0-9]|3[01]', ':slug' => '[a-zA-Z0-9-]+', ':query' => '...' ); and I loop throw them to see if I have a matching wildcard like this: if ( array_key_exists($matches[0], $this->_regexp) ) { return '^('.$this->_regexp[$matches[0]].')$'; } All other regexp go throw but I've tried a whole lot of different regexp to find: ?anything=anything can't figure it out, googled like h..l but can't find anything. I've tried, for example something like this: (\?)(.*)(=)(.*) but without result... Any regexp gurus here? / Tobias

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• Why does php show error for my SQL query

  - by ZincX

  UPDATE: My mistake - I made a typo. Nevermind this question. I'm using php to update a mysql database. The resultant query I'm using when i print it out on my webpage before executing is as follows: INSERT INTO perch2_content_items (itemOrder, regionID, pageID, itemRev, itemID, itemJSON, itemSearch ) SELECT MAX(itemOrder)+1, 105, 81, 11, 118, 'json', 'search' FROM perch2_content_items WHERE regionID=105 When I copy and paste this query directly into the phpmyadmin SQL interface, it works fine. The table gets updated. However, when I try to execute it using my php code as follows, it throws an error. $insertToPerch = "INSERT INTO perch2_content_items (itemOrder, regionID, pageID, itemRev, itemID, itemJSON, itemSearch ) SELECT MAX(itemOrder)+1, $regionID, $pageID, $regionRev, $newItemID, 'json', 'search' FROM perch2_content_items WHERE regionID=$regionID"; mysql_query(insertToPerch) or die(mysql_error()); The error I'm getting is: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'insertToPerch' at line 1 Can anybody help me figure out why it is failing.

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• displaying values from join query array

  - by THOmas

  I have used a join query for retrieving value from two tables one is blogquestion and userdetails I wrote this query $this->questions = Doctrine_Query::create() ->select('b.question_id,b.user_id,b.question_title,b.question_tags,b.created_at,u.id,u.name') ->from('BlogQuestion b') ->leftJoin('b.UserDetails u') ->execute(); In the template iam displaying the result using a foreach <?php foreach($questions as $quest):?> echo $quest->getQuestionTitle() echo $quest->getQuestionTags() echo $quest->getName() <?php endforeach?> title is getting from the blogquestion table and name is in usredetails table iam getting the eerror Unknown record property / related component "name" on "BlogQuestion"

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• Will PHP Die In Web Page Development World?

  - by Morgan Cheng

  I know that PHP is still the most popular web programming language in the world. This question just want to bring some of my concerns about PHP. PHP is naturally bound to C10K problem. Since PHP (generally run in Apache) cannot be event-driven or asynchronous, each HTTP request will occupy at least one thread or process. This makes it resistant to be more scalable. Currently, a lot of web sites (like Facebook) with high performance and scalability still depends on PHP in their front end servers. I suppose it is due to legacy reason. Is it possible that PHP will be replaced by language more suitable for C10K?

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• Under what circumstances does Groovy use AbstractConcurrentMap?

  - by Electrons_Ahoy

  (Specifically, org.codehaus.groovy.util.AbstractConcurrentMap) While doing some profiling of our application thats mixed Java/Groovy, I'm seeing a lot of references to the AbstractConcurrentMap class, none of which are explicit in the code base. Does groovy use this class when maps are instantiated in the groovy dynamic def myMap = [:] style? Are there rules somewhere about when groovy chooses to use this as opposed to, say, java.util.HashMap? And does anyone have any performance information comparing the two? My rough "eyeball check" says that AbstractConcurrentMap seems to be much slower - anyone know if I'm right?

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• C sharp: read last "n" lines of log file

  - by frictionlesspulley

  need a snippet of code which would read out last "n lines" of a log file. I came up with the following code from the net.I am kinda new to C sharp. Since the log file might be quite large, I want to avoid overhead of reading the entire file.Can someone suggest any performance enhancement. I do not really want to read each character and change position. var reader = new StreamReader(filePath, Encoding.ASCII); reader.BaseStream.Seek(0, SeekOrigin.End); var count = 0; while (count <= tailCount) { if (reader.BaseStream.Position <= 0) break; reader.BaseStream.Position--; int c = reader.Read(); if (reader.BaseStream.Position <= 0) break; reader.BaseStream.Position--; if (c == '\n') { ++count; } } var str = reader.ReadToEnd();

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• Access Validation Rule Violations on Append Query

  - by Jacques Tardie

  I'm recieving the following error on trying to run an append query in access. Microsoft Office Access set .... and it didnt't add... 779280 records(s) due to validation rule violations. If I choose to run the query anyways, nothing actually happens. To give some context, I'm simply trying to copy a populated field, consisting of values similar to "16-2009-02, 34-2010-02, et cetera" to another currently unpopulated field. The fields themselves have no set validation rules, and both have the standard text field options. I'm hoping to be able to simply remove those hyphens, and fix the issue. But I guess that's what I'm not sure about, are those hyphens actually a problem? Running SP3 w/ Access 2003. Thanks in advance!

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• dataset using where condition from another query

  - by refer

  here's my code. I have a dataset that has its values and then i run an independent query which uses the same tables as dataset. now when i run the dataset, i want it to get a where condition on the query result. here's the code - sql = "SELECT ID, name FROM books WITH(NOLOCK) WHERE id =" & Session("ID") ds = FillDataset(sql) Sql1 = "SELECT n.id as id,a.name as title FROM books n WITH(NOLOCK)" & _ "LEFT JOIN new_books a WITH(NOLOCK) ON a.id = n.book_id " rd = ExecuteReader(SqlCnn, SqlStr) Now after this i make an htmltable and all the cells are loaded with the data from datareader(rd). but 1 dropdown is loaded from the dataset. i want that dropdown to have the selectedvalue which is the value from the datareader(rd). how can i do that?

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• Linq Query - Average Time (DateTime data types)

  - by Jade

  I have a database that has the following records in a DateTime field: 2012-04-13 08:31:00.000 2012-04-12 07:53:00.000 2012-04-11 07:59:00.000 2012-04-10 08:16:00.000 2012-04-09 15:11:00.000 2012-04-08 08:28:00.000 2012-04-06 08:26:00.000 I want to run a linq to sql query to get the average time from the records above. I tried the following: (From o In MYDATA Select o.SleepTo).Average() Since "SleepTo" is a datetime field I get an error on Average(). If I was trying to get the average of say an integer, the above linq query works. What do I need to do to get it to work for datetimes?

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• PHP Apostrophe and query string.

  - by cmaduro

  I want to supply a SQL statement from the query string, but all my efforts result in escaped single quotes and slashes.

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• Query a column and a calculation of columns at the same time PostgreSQL

  - by pablo

  Hi I have two tables, Products and BundleProducts that have o2o relation with BaseProducts. A BundleProduct is a collection of Products using a m2m realtion to the Products table. Products has a price column and the price of a BundleProduct is calculated as the sum of the prices of its Products. BaseProducts have columns like name and description so I can query it to get both Products and BundleProducts. Is it possible to query and sort by price both for the price column of the Products and calculated price of the BundleProducts? Thanks

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• need for tcp fine-tuning on heavily used proxy server

  - by Vijay Gharge

  Hi all, I am using squid like Internet proxy server on RHEL 4 update 6 & 8 with quite heavy load i.e. 8k established connections during peak hour. Without depending much on application provider's expertise I want to achieve maximum o/p from linux. W.r.t. that I have certain questions as following: How to find out if there is scope for further tcp fine-tuning (without exhausting available resources) as the benchmark values given by vendor looks poor! Is there any parameter value that is available from OS / network stack that will show me the results. If at all there is scope, how shall I identify & configure OS tcp stack parameters i.e. using sysctl or any specific parameter Post tuning how shall I clearly measure performance enhancement / degradation ?

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• Problem with sqlite query when using the wrapper

  - by user285096

  - (IBAction)EnterButtonPressed:(id)sender { Sqlite *sqlite = [[Sqlite alloc] init]; NSArray *paths =NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSString *writableDBPath = [documentsDirectory stringByAppendingPathComponent:@"test.sqlite"]; if (![sqlite open:writableDBPath]) return; NSArray *query = [sqlite executeQuery:@"SELECT AccessCode FROM UserAccess"]; NSLog(@"%@",query); I am getting the output as : { ( AccessCode=abcd; ) } Where as in I want it as : abcd I am using the wrapper from : http://th30z.netsons.org/2008/11/objective-c-sqlite-wrapper/ Please help .

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• Retrieving Spotlight query used to open document in application

  - by vicvicvic

  If you search for something that opens Preview.app (e.g. a PDF file) in Spotlight, the application not only opens the file but actually copies the Spotlight query into the application's search field (for deeper search). iPhoto and Mail.app also do this. This is a really nice feature. Unfortunately, Apple does not document how it's implemented. Opening a document from Spotlight appears to simply send application:openFile to the application delegate. Is it possible to retrieve the user's Spotlight query somehow? Or is this a hardcoded feature of Spotlight?

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• Excel Spreadsheet - Best way to perform an Oracle Query on a cell

  - by Jamie

  Hi there, I have an Excel Spreadsheeet. There is a cell containing a concatenated name and surname (don't ask why), for example: Cell A2 BLOGGSJOE On this cell, I would like to run the following SQL and output it to cell A3, A4 and A5 SELECT i.id, i.forename, i.surname FROM individual i WHERE UPPER(REPLACE('" & A2 & "', ' ', '')) = UPPER(REPLACE(i.surname|| i.forename, ' ', '')) AND NVL(i.ind_efface, 'N') = 'N' Any idea how I could perform an oracle query on each cell and return the result? I have enabled an oracle datasource connection in Excel, just not sure what to do now. Is this a stupid approach, and can you recommend a better more proficient way? Thanks muchly! I lack the necessary experience in this type of thing! :-) EDIT: I am aware that I could just write a simple ruby/php/python/whatever script to loop through the excel spreadsheet (or csv file), and then perform the query etc. but i thought there might be a quick way in excel itself.

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• How do I make a sql query where fields are the result of a different query?

  - by CRP

  I have two tables, the first is like this: f1 | f2 | f3 | f4 ----------------- data.... the second contains info about the fields of the first: field | info ------------ f1 a f2 b f3 a etc. I would like to query the first table selecting the fields with a query on the second. So, for example, I might want to get data for fields where info is equal to "a", thus I would do "select f1, f3 from first_table". How do I do this programmatically? I was thinking about something along the lines of select (select fields from second_table where info='a') from first_table Thanks Chris

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