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  • What is the most efficient way to store a mapping "key -> event stream"?

    - by jkff
    Suppose there are ~10,000's of keys, where each key corresponds to a stream of events. I'd like to support the following operations: push(key, timestamp, event) - pushes event to the event queue for key, marked with the given timestamp. It is guaranteed that event timestamps for a particular key are pushed in sorted or almost sorted order. tail(key, timestamp) - get all events for key since the given timestamp. Usually the timestamp requests for a given key are almost monotonically increasing, almost synchronously with pushes for the same key. This stuff has to be persistent (although it is not absolutely necessary to persist pushes immediately and to keep tails with pushes strictly in sync), so I'm going to use some kind of database. What is the optimal kind of database structure for this task? Would it be better to use a relational database, a key-value storage, or something else?

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  • Python faster way to read fixed length fields form a file into dictionary

    - by Martlark
    I have a file of names and addresses as follows (example line) OSCAR ,CANNONS ,8 ,STIEGLITZ CIRCUIT And I want to read it into a dictionary of name and value. Here self.field_list is a list of the name, length and start point of the fixed fields in the file. What ways are there to speed up this method? (python 2.6) def line_to_dictionary(self, file_line,rec_num): file_line = file_line.lower() # Make it all lowercase return_rec = {} # Return record as a dictionary for (field_start, field_length, field_name) in self.field_list: field_data = file_line[field_start:field_start+field_length] if (self.strip_fields == True): # Strip off white spaces first field_data = field_data.strip() if (field_data != ''): # Only add non-empty fields to dictionary return_rec[field_name] = field_data # Set hidden fields # return_rec['_rec_num_'] = rec_num return_rec['_dataset_name_'] = self.name return return_rec

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  • Complicated SQL query

    - by Yandawl
    Please bare with me this is difficult to explain xD http://img90.imageshack.us/i/croppercapture1.png/ This is based on an undergraduate degree course where a student takes many units (say 4 core units and 1 optional unit per year). tblAwardCoreUnits and tblAwardOptUnits store which units are optional and core for which award, hence the relationship to tblAward and tblStudentCoreUnits and tblStudentOptUnits store the particular instances of those units which a particular student is taking. Secondly, a unit can have multiple events (say a lecture and a unit) and each of those events has sessions in which a student can attend, hence tblEvents, tblSessions and tblAttendances. The query I am trying to produce is to get a list of all level one students, grouped by their award that lists the percentage of attendances in all the units in the current level. I've tried and tried with this and the following is the best I've managed to come up with so far... I'd REALLY appreciate any help you can give with this! SELECT tblStudents.enrolmentNo, tblStudents.forename, tblStudents.surname, tblAwards.title, (SELECT COUNT((tblAttendances.attended + tblAttendances.authorisedAbsence)) AS SumOfAttendances FROM tblAttendances INNER JOIN (tblStudents ON tblStudents.enrolmentNo = tblAttendances.enrolmentNo)) / FROM tblUnits, tblAwards INNER JOIN ((tblStudents INNER JOIN tblStudentOptUnit ON tblStudents.studentID = tblStudentOptUnit.studentID) INNER JOIN tblStudentCoreUnit ON tblStudents.studentID = tblStudentCoreUnit.studentID) ON tblAwards.awardID = tblStudents.awardID WHERE (((tblStudents.level)="1") AND ((tblStudents.status)="enrolled")) GROUP BY tblAwards.title ORDER BY tblStudents.forname;

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  • Is it possible to combine these 3 mySQL queries?

    - by Greenie
    I know the $downloadfile - and I want the $user_id. By trial and error I found that this does what I want. But it's 3 separate queries and 3 while loops. I have a feeling there is a better way. And yes, I only have a very little idea about what I'm doing :) $result = pod_query("SELECT ID FROM wp_posts WHERE guid LIKE '%/$downloadfile'"); while ($row = mysql_fetch_assoc($result)) { $attachment = $row['ID']; } $result = pod_query("SELECT pod_id FROM wp_pods_rel WHERE tbl_row_id = '$attachment'"); while ($row = mysql_fetch_assoc($result)) { $pod_id = $row['pod_id']; } $result = pod_query("SELECT tbl_row_id FROM wp_pods_rel WHERE tbl_row_id = '$pod_id' AND field_id = '28'"); while ($row = mysql_fetch_assoc($result)) { $user_id = $row['pod_id']; }

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  • I could use some help with my SQL command

    - by SuperSpy
    I've got a database table called 'mesg' with the following structure: receiver_id | sender_id | message | timestamp | read Example: 2 *(«me)* | 6 *(«nice girl)* | 'I like you, more than ghoti' | yearsago | 1 *(«seen it)* 2 *(«me)* | 6 *(«nice girl)* | 'I like you, more than fish' | now | 1 *(«seen it)* 6 *(«nice girl)* | 2 *(«me)* | 'Hey, wanna go fish?' | yearsago+1sec | 0 *(«she hasn't seen it)* It's quite a tricky thing that I want to achieve. I want to get: the most recent message(=ORDER BY time DESC) + 'contact name' + time for each 'conversation'. Contact name = uname WHERE uid = 'contact ID' (the username is in another table) Contact ID = if(sessionID*(«me)*=sender_id){receiver_id}else{sender_id} Conversation is me = receiver OR me = sender For example: From: **Bas Kreuntjes** *(« The message from bas is the most recent)* Hey $py, How are you doing... From: **Sophie Naarden** *(« Second recent)* Well hello, would you like to buy my spam? ... *(«I'll work on that later >p)* To: **Melanie van Deijk** *(« My message to Melanie is 3th)* And? Did you kiss him? ... That is a rough output. QUESTION: Could someone please help me setup a good SQL command. This will be the while loup <?php $sql = "????"; $result = mysql_query($sql); while($fetch = mysql_fetch_assoc($result)){ ?> <div class="message-block"> <h1><?php echo($fetch['uname']); ?></h1> <p><?php echo($fetch['message']); ?></p> <p><?php echo($fetch['time']); ?></p> </div> <?php } ?> I hope my explanation is good enough, if not, please tell me. Please don't mind my English, and the Dutch names (I am Dutch myself) Feel free to correct my English UPDATE1: Best I've got until now: But I do not want more than one conversation to show up... u=user table m=message table SELECT u.uname, m.message, m.receiver_uid, m.sender_uid, m.time FROM m, u WHERE (m.receiver_uid = '$myID' AND u.uid = m.sender_uid) OR (m.sender_uid = '$myID' AND u.uid = m.receiver_uid) ORDER BY time DESC;

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  • iPhone Image Resources, ICO vs PNG, app bundle filesize

    - by Jasarien
    My application has a collection of around 1940 icons that are used throughout. They're currently in ICO and new images provided to me come in ICO format too. I have noticed that they contain a 16x16 and 32x32 representation of each icon in one file. Each file is roughly 4KB in filesize (as reported by finder, but ls reports that they vary from being ~1000 bytes to 5000 bytes) A very small number of these icons only contain the 32x32 representation, and as a result are only around 700 bytes in size. Currently I am bundling these icons with my application and they are inflating the size of the app a bit more than I would like. Altogether, the images total just about 25.5MB. Xcode must do some kind of compression because the resulting app bundle is about 12.4MB. Compressing this further into a ZIP (as it would be when submitted to the App Store), results in a final file of 5.8MB. I'm aware that the maximum limit for over the air App Store downloads has been raised to 20MB since the introduction of the iPad (I'm not sure if that extends to iPhone apps as well as iPad apps though, if not the limit would be 10MB). My worry is that new icons are going to be added (sometimes up to 10 icons per week), and will continue to inflate the app bundle over time. What is the best way to distribute these icons with my app? Things I've tried and not had much success with: Converting the icons from ICO to PNG: I tried this in the hopes that the pngcrush utility would help out with the filesize. But it appears that it doesn't make much of a difference between a normal PNG and a crushed png (I believe it just optimises the image for display on the iPhone's GPU rather than compress it's size). Also in going from ICO to PNG actually increased the size of the icon file... Zipping the images, and then uncompressing them on first run. While this did reduce the overall image sizes, I found that the effort needed to unzip them, copy them to the documents folder and ensure that duplication doesn't happen on upgrades was too much hassle to be worth the benefit. Also, on original and 3G iPhones unzipping and copying around 25MB of images takes too long and creates a bad experience... Things I've considered but not yet tried: Instead of distributing the icons within the app bundle, host them online, and download each icon on demand (it depends on the user's data as to which icons will actually be displayed and when). Issues with this is that bandwidth costs money, and image downloads will be bandwidth intensive. However, my app currently has a small userbase of around 5,500 users (of which I estimate around 1500 to be active based on Flurry stats), and I have a huge unused bandwidth allowance with my current hosting package. So I'm open to thoughts on how to solve this tricky issue.

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  • How to Check for record existence and do Insert in MYSQL ?

    - by karthik
    How to Check for record existence and do Insert or Update in MYSQL ? I have a script, which has set of Insert statements for multiple tables. Now when i try to execute the Insert statement, i want to do the following.. Check for the record existence and then do Insert or Update. If the Record is not exist do Insert. If the Record is already do not do anything. How to accomplish this ? Note : The script with Insert Statements are generated programmaticaly using SP

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  • How can one fetch partial objects in NHibernate?

    - by mark
    Dear ladies and sirs. I have an object O with 2 fields - A and B. How can I fetch O from the database so that only the field A is fetched? Of course, my real application has objects with many more fields, but two fields are enough to understand the principal. I am using NHibernate 2.1. Thanks.

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  • How do I echo out something different when reached last row?

    - by Josh Brown
    I am wanting to not echo out the comma at the end of the echo after the last row. How can I do that? Here is my code: <?php header("Content-type: application/json"); echo '{"points":['; mysql_connect("localhost", "user", "password"); mysql_select_db("database"); $q = "SELECT venues.id, venues.lat, venues.lon, heat_indexes.temperature FROM venues, heat_indexes WHERE venues.id = heat_indexes.venue_id"; $res = mysql_query($q) or die(mysql_error()); while ($point = mysql_fetch_assoc($res)) { echo $point['lat'] . "," . $point['lon'] . "," . $point['temperature'] . ","; } mysql_free_result($res); echo ']}'; ?>

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  • ASP .NET page runs slow in production

    - by Brandi
    I have created an ASP .NET page that works flawlessly and quickly from Visual Studio. It does a very large database read from a database on our network to load a gridview inside of an update panel. It displays progress in an Ajax modalpopupextender. Of course I don't expect it to be instant what with the large db reads, but it takes on the order of seconds, not on the order of minutes. This is all working great until I put it up on the server - it is very, VERY slow when I access it via the internet - takes several minutes to load the database information into the gridview. I'm baffled why it would not perform the exact same as it had from Visual Studio. (It is in release mode and I have taken off the debug flag) I have since been trying things like eliminating unneeded update panels and throwing out the ajax tool. Nothing has made it any faster on production. It is not the database as far as I know, since it has been consistently fast from my computer (from visual studio) and consistently slow from the server. I am wondering, where do I look next? Has anyone else had this problem before? Could this be caused by update panels or Ajax modalpopupextenders in different parts of the application? Why would the live behaviour differ so much from the localhost behaviour? Both the server with the ASP .NET page and the server with the database are servers on our network. I'm using Visual Studio 2008. Thank you in advance for any insight or advice.

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  • Ideas Related to Subset Sum with 2,3 and more integers

    - by rolandbishop
    I've been struggling with this problem just like everyone else and I'm quite sure there has been more than enough posts to explain this problem. However in terms of understanding it fully, I wanted to share my thoughts and get more efficient solutions from all the great people in here related to Subset Sum problem. I've searched it over the Internet and there is actually a lot sources but I'm really willing to re-implement an algorithm or finding my own in order to understand fully. The key thing I'm struggling with is the efficiency considering the set size will be large. (I do not have a limit, just conceptually large). The two phases I'm trying to implement ideas on is finding two numbers that are equal to given integer T, finding three numbers and eventually K numbers. Some ideas I've though; For the two integer part I'm thing basically sorting the array O(nlogn) and for each element in the array searching for its negative value. (i.e if the array element is 3 searching for -3). Maybe a hash table inclusion could be better, providing a O(1) indexing the element? For the three or more integers I've found an amazing blog post;http://www.skorks.com/2011/02/algorithms-a-dropbox-challenge-and-dynamic-programming/. However even the author itself states that it is not applicable for large numbers. So I was for 2 and 3 and more integers what ideas could be applied for the subset problem. I'm struggling with setting up a dynamic programming method that will be efficient for the large inputs as well.

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  • Bynary string search on one field.

    - by CrazyJoe
    I have 300 boolean fields in one table, and im trying to do somithing like that: One string field: 10000010000100100100100100010001 Ha a simple way to do a simple search os this field like: select * from table where field xor "10000010000100100100000000010001" :) Help!!

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  • How to shift pixels of a pixmap efficient in Qt4

    - by stanleyxu2005
    Hello, I have implemented a marquee text widget using Qt4. I painted the text content onto a pixmap first. And then paint a portion of this pixmap onto a paint device by calling painter.drawTiledPixmap(offsetX, offsetY, myPixmap) My Imagination is that, Qt will fill the whole marquee text rectangle with the content from myPixmap. Is there a ever faster way, to shift all existing content to left by 1px and than fill the newly exposed 1px wide and N-px high area with the content from myPixmap?

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  • Is opening too many datacontexts bad?

    - by ryudice
    I've been checking my application with linq 2 sql profiler, and I noticed that it opens a lot of datacontexts, most of them are opened by the linq datasource I used, since my repositories use only the instance stored in Request.Items, is it bad to open too many datacontext? and how can I make my linqdatasource to use the datacontext that I store in Request.Items for the duration of the request? thanks for any help!

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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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  • Massive speed diff in upgrade to Java 7

    - by Brett Rigby
    We use Java within our build process, as it is used to resolve/publish our dependencies via Ivy. No problem, nor have we had with it for 2 years, until we've tried to upgrade Java 6 Update 26 to Version 7 Update 7, whereas a build on a local developer PC (WinXP) now takes 2 hours to complete, instead of 10 minutes!! Nothing else has changed on the PC, making it the absolute target for our concerns. Does anyone know of any reason as to why version 7 of Java would make such a speed difference like this?

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  • Checking for reciprocal relationships in mysql. A trivial one table problem.

    - by calumbrodie
    I have a mysql table that stores relationships. Items can be related to another item in one direction, or both items can be related to each other. I want to return all items related to my primary item - but I also want to check to see if the related item has a 'reverse relationship' to the current item and show this as a boolean |--------------|---------------| | SKU | related_SKU | |--------------|---------------| | 0001 | 0099 | | 0002 | 0099 | | 0099 | 0001 | |--------------|---------------| If I want to get all relationships for SKU=0001 SELECT related_SKU from relationships where SKU='0001' returns |--------------| | related_SKU | |--------------| | 0099 | |--------------| but what I want is |--------------|---------------| | related_SKU | reciprocal | |--------------|---------------| | 0099 | 1 | |--------------|---------------| or SELECT related_SKU from relationships where SKU='0002' |--------------|---------------| | related_SKU | reciprocal | |--------------|---------------| | 0099 | 0 | |--------------|---------------| What's the best way to do this?

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  • Which database I can used and relationship in it ??

    - by mimo-hamad
    My projece make me confused which I didn't find clear things that make me understand the required database and the relationships in it So, would a super one help me to solve it ?!! ;D this is required: 1) Model the data stored in the database (Identify the entities, roles, relationships, constraints, etc.) 2) Write the Oracle commands to create the database, find appropriate data, and populate the database 3) Write five different queries on your database, using the SELECT/FROM/WHERE construct provided in SQL. Your five queries should illustrate several different aspects of database querying, such as: a. Queries over more than one relation (by listing more than one relation in the FROM clause) b. Queries involving aggregate functions, such as SUM, COUNT, and AVG c. Queries involving complicated selects and joins d. Queries involving GROUP BY, HAVING or other similar functions. e. Queries that require the use of the DISTINCT keyword. And this the condition that we need to determine it to solve the required Q's above : 5) It is desired to develop an Internet membership club to buy products at special prices online. To join, new members must be referred by another existing member of the club. The system will keep the following information for each member: The member ID, referring member, birth date, member name, address, phone, mobile, credit card type, number and expiration date. The items are always shipped to the member's address noted in the membership application. The shipping fees will differ for each order.For each item to be requested, the member will select an item from a long list of possible items. For each item in the database, we store an item ID, an item name, description, and list price. The list price will be different from the actual sale price. The available quantity and the back-ordered quantity (the back-ordered quantity is the quantity on-order by the club from its suppliers) is also noted

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  • Calculate the retrieved rows in database Visual C#

    - by Tanya Lertwichaiworawit
    I am new in Visual C# and would want to know how to calculate the retrieved data from a database. Using the above GUI, when "Calculate" is click, the program will display the number of students in textBox1, and the average GPA of all students in textBox2. Here is my database table "Students": I was able to display the number of students but I'm still confused to how I can calculate the average GPA Here's my code: private void button1_Click(object sender, EventArgs e) { string connection = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Database1.accdb"; OleDbConnection connect = new OleDbConnection(connection); string sql = "SELECT * FROM Students"; connect.Open(); OleDbCommand command = new OleDbCommand(sql, connect); DataSet data = new DataSet(); OleDbDataAdapter adapter = new OleDbDataAdapter(command); adapter.Fill(data, "Students"); textBox1.Text = data.Tables["Students"].Rows.Count.ToString(); double gpa; for (int i = 0; i < data.Tables["Students"].Rows.Count; i++) { gpa = Convert.ToDouble(data.Tables["Students"].Rows[i][2]); } connect.Close(); }

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  • Friendfeed schemaless data in MYSQL

    - by John Stewart
    I read an article around schema-less database which sounds cool. (http://bret.appspot.com/entry/how-friendfeed-uses-mysql) But what isn't clear to me is how do they run search queries on this data? Since the data is in JSON format how do we look for it?

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