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  • move data from one table to another, postgresql edition

    - by IggShaman
    Hi All, I'd like to move some data from one table to another (with a possibly different schema). Straightforward solution that comes into mind is - start a transaction with serializable isolation level; INSERT INTO dest_table SELECT data FROM orig_table,other-tables WHERE <condition>; DELETE FROM orig_table USING other-tables WHERE <condition>; COMMIT; Now what if the amount of data is rather big, and the <condition> is expensive to compute? In PostgreSQL, a RULE or a stored procedure can be used to delete data on the fly, evaluating condition only once. Which solution is better? Are there other options?

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  • How can i test my DB speed? (Learning)

    - by acidzombie24
    I have design a database. Theres no columns with indexing, nor any code for optimizing. I am positive i should index certain columns since i search them a lot. My question is HOW do i test if any part of my database will be slow? ATM I am using sqlite and i will be switching to either MS Sql or MySql based on my host provider. Will creating 100,000 records in each table be enough? Or will that always be fast in sqlite and i need to do 1mil? Do i need 10mil before a database will become slow? Also how do i time it? I am using C# so should i use StopWatch or is there a ADO.NET/Sqlite function i should use?

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  • Having to insert a record, then update the same record warrants 1:1 relationship design?

    - by dianovich
    Let's say an Order has many Line items and we're storing the total cost of an order (based on the sum of prices on order lines) in the orders table. -------------- orders -------------- id ref total_cost -------------- -------------- lines -------------- id order_id price -------------- In a simple application, the order and line are created during the same step of the checkout process. So this means INSERT INTO orders .... -- Get ID of inserted order record INSERT into lines VALUES(null, order_id, ...), ... where we get the order ID after creating the order record. The problem I'm having is trying to figure out the best way to store the total cost of an order. I don't want to have to create an order create lines on an order calculate cost on order based on lines then update record created in 1. in orders table This would mean a nullable total_cost field on orders for starters... My solution thus far is to have an order_totals table with a 1:1 relationship to the orders table. But I think it's redundant. Ideally, since everything required to calculate total costs (lines on an order) is in the database, I would work out the value every time I need it, but this is very expensive. What are your thoughts?

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  • Using Remote Web Page to Initialize iPhone App

    - by Chris_K
    My iPhone app relies on a vendor's XML feed to provide data. But that feed is not locked down. The vendor could change the format of the XML at any time, although so far they've promised not to. Since I might want to tell my app to use a different URL for its data source, I'd like to set up a single "Command Central" Web page, on my own server, to direct the app to the correct data source. In other words, each time my app starts, in the background and unseen by the user, it would visit "http://www.myserver.com/iphoneapp_data_sources.xml" to retrieve the URL for retrieving data from my vendor. That way, if my vendor suddenly changes the exact URL or the XML feed that the app needs, I can update that Web page and ensure that all installations of the app are using the correct XML feed. Does anyone have any advice or examples showing this kind of approach? It seems as if this must be a common problem, but so far I haven't found a well-established design pattern that fits it.

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  • Dynamic Custom Fields for Data Model

    - by Jerry Deng
    I am in the process of creating a dynamic database where user will be able to create resource type where he/she can add custom fields (multiple texts, strings, and files) Each resource type will have the ability to display, import, export its data; I've been thinking about it and here are my approaches. I would love to hear what do you guys think. Ideas: just hashing all the custom data in a data field (pro: writing is easier, con: reading back out may be harder); children fields (the model will have multiple fields of strings, fields of text, and fields for file path); fixed number of custom fields in the same table with a key mapping data hash stored in the same row; Non-SQL approach, but then the problem would be generating/changing models on the fly to work with different custom fields;

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  • Caching result of SELECT statement for reuse in multiple queries

    - by Andrew
    I have a reasonably complex query to extract the Id field of the results I am interested in based on parameters entered by the user. After extracting the relevant Ids I am using the resulting set of Ids several times, in separate queries, to extract the actual output record sets I want (by joining to other tables, using aggregate functions, etc). I would like to avoid running the initial query separately for every set of results I want to return. I imagine my situation is a common pattern so I am interested in what the best approach is. The database is in MS SQL Server and I am using .NET 3.5.

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  • Faster code with another compiler

    - by Andrei
    I'm using the standard gcc compiler in math software development with C-language. I don't know that much about compilers or compiler options, and I was just wondering, is it possible to make faster executables using another compiler or choosing better options? The default Makefile sets options -ffast-math and -O3 and I think both of them have some impact in the overall calculation time. My software is using memory quite extensively, so I imagine some options related to memory management might do the trick? Any ideas?

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  • Perl launched from Java takes forever

    - by Wade Williams
    I know this is an absolute shot in the dark, but we're absolutely perplexed. A perl (5.8.6) script run by Java (1.5) is taking more than an hour to complete. The same script, when run manually from the command line takes 12 minutes to complete. This is on a Linux host. Logging is the same in both cases and the script is run with the same parameters in both cases. The script does some complex stuff like Oracle DB access, some scp's, etc, but again, it does the exact same actions in both cases. We're stumped. Has anyone ever run into a similar situation? If not and if you were faced with the same situation, how would you consider debugging it?

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  • Problem mapping data located in a NSMutableArray

    - by Graeme
    I have an NSMutableArray which contains some addresses which I need to map using Apple's MapKit SDK which I can't seem to get to load. The NSLog keeps telling me that the data source is (null) and a 0x0 error displays when I attempt to print out the array. Any ideas? The data is parsed and stored from another class, perhaps I'm not linking it across properly? The data is originally gathered from an RSS feed, bought into the app with an IMporter class, and then displayed in a table view. I want to be able to connect into that data with my mapping class, but am struggling to do so.

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  • Understanding linear linked list

    - by ArtWorkAD
    Hi, I have some problems understanding the linear linked list data structure. This is how I define a list element: class Node{ Object data; Node link; public Node(Object pData, Node pLink){ this.data = pData; this.link = pLink; } } To keep it simple we say that a list are linked nodes so we do not need to define a class list (recursion principle). My problem is that I am really confused in understanding how nodes are connected, more precisely the sequence of the nodes when we connect them. Node n1 = new Node(new Integer(2), null); Node n2 = new Node(new Integer(1), n1); What is link? Is it the previous or the next element? Any other suggestions to help me understanding this data structure?

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  • Java program runs smoothly in Netbeans but slowly in Eclipse and as an executed jar. WTF?

    - by comp sci balla
    A java program that does frequent swing/awt painting animation (but nothing more advanced than g.fillOval(...)) runs at a consistent 60fps in Netbeans, and at about 6fps when ran in Eclipse or executed as a jar file from a unix terminal. The program was developed in Netbeans and is run-of-the-mill desktop application (not webstart or japplet or ...). This is occurring in Ubuntu 10 with java 1.6. How is this possible? The universe no longer makes sense to me.

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  • Problem with Refreshing data in ExpandableListView

    - by -providerivan.longin1
    Hi! My problem is when I want to refresh data in ExpandableListView while being in that current activity. I create adapter and when I want to add new data to list I call again constructor of that adapter(it is my private variable) with all new data....and then I call onContentChanged() method to redraw my list. But what happens is that I cant expand my list any more...like it is blocked or something and logcat isn't saying anything... This is the code that i call after setting new data in arraylists and maps: mAdapter = new MyExpandableListAdapter( this, groupData, R.layout.contact_list_parent, new String[] { NAME ,NUM_PHOTOS},//NUM_PHOTOS new int[] { R.id.rowText1, R.id.rowText2, R.id.photoAlbumImg }, childData, R.layout.contact_list_child, new String[] { NAME,NUM_PHOTOS}, //NUM_PHOTOS new int[] { R.id.rowText1, R.id.rowText2, R.id.photoAlbumImg } ); this.onContentChanged(); If anyone knows answer to this question please help me:) Thanks.

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  • Installing VMware Worstation/Player 8.0.4 on Ubuntu 12.10 fails to load with Unable to start services

    - by user106986
    I have been attempting to install this application for a few weeks without any success. I have installed and uninstalled the application and pathes with no change. I have even tried to load a VM in Virtualbox and install the application there to a base install of Ubuntu 12.10 and it still did not install. I have downloaded the patch and modified it to reflect the version of VMware Worstation and Player I am installing. I still receive the same error I saw in the first attempt to install the software. Which leads me to think that I am missing something. The error is: Unable to start services. See log file /tmp/vmware-root/modconfig-7674.log for details. I have the output of the log file if that will help. According to the dialogue box Virtual Network Device and VMware Blocking Filesystem fail to either load or execute. Any help would be greatly appreciated.

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  • C++, using one byte to store two variables

    - by 2di
    Hi All I am working on representation of the chess board, and I am planning to store it in 32 bytes array, where each byte will be used to store two pieces. (That way only 4 bits are needed per piece) Doing it in that way, results in a overhead for accessing particular index of the board. Do you think that, this code can be optimised or completely different method of accessing indexes can be used? c++ char getPosition(unsigned char* c, int index){ //moving pointer c+=(index>>1); //odd number if (index & 1){ //taking right part return *c & 0xF; }else { //taking left part return *c>>4; } } void setValue(unsigned char* board, char value, int index){ //moving pointer board+=(index>>1); //odd number if (index & 1){ //replace right part //save left value only 4 bits *board = (*board & 0xF0) + value; }else { //replacing left part *board = (*board & 0xF) + (value<<4); } } int main() { char* c = (char*)malloc(32); for (int i = 0; i < 64 ; i++){ setValue((unsigned char*)c, i % 8,i); } for (int i = 0; i < 64 ; i++){ cout<<(int)getPosition((unsigned char*)c, i)<<" "; if (((i+1) % 8 == 0) && (i > 0)){ cout<<endl; } } return 0; } I am equally interested in your opinions regarding chess representations, and optimisation of the method above, as a stand alone problem. Thanks a lot

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  • HttpWebRequest POST and retrieve data from php script after login

    - by KenaGT
    Hello guys i am newbie to this stuff so i'll try to explain my problem.I am building application that retrieve data after login to php script that looks like this: https://zamger.etf.unsa.ba/getrssid.php (see the page source for php scirpt definition) and definition(source) here: Korisnicko ime (UID): Šifra: After i login it shows me data that i must collect like this: RSSID: 1321B312 (this is only data that it shows and nothing else) I must do this with httpwebrequest but don't know how i tried to do it with POST(data) but it always give me the defnition of php script as response.But i need response to be like "RSSID: 1321B312" not as script definition mentioned above...please heeelp ASAP....

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  • High CPU - What to do.

    - by Udi Kantzuker
    I have a high CPU problem with MYSQL using "top" ( linux ) shows cpu peaks of 90%. I was trying to find the source of the problem, turned on general log and slow query log, The slow query log did not find anything. The Db contains a few small tables and one large table that contains almost 100k rows, Database Engine is MyIsam. strange thing i have noticed that on the large table, select, insert are very fast but update takes 0.2 - 0.5 secs. already used optimize and repair and no improvement. the table is being updated frequently, could this be the source of the high CPU% ? What can i do to improve this?

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  • Quickest way to compare a buch of array or list of values.

    - by zapping
    Can you please let me know on the quickest and efficient way to compare a large set of values. Its like there are a list of parent codes(string) and each code has a series of child values(string). The child lists have to be compared with each other and find out duplicates and count how many times they repeat. code1(code1_value1, code1_value2, code3_value3, ..., code1_valueN); code2(code2_value1, code1_value2, code2_value3, ..., code2_valueN); code3(code2_value1, code3_value2, code3_value3, ..., code3_valueN); . . . codeN(codeN_value1, codeN_value2, codeN_value3, ..., codeN_valueN); The lists are huge say like there are 100 parent codes and each has about 250 values in them. There will not be duplicates within a code list. Doing it in java and the solution i could figure out is. Store the values of first set of code in as codeMap.put(codeValue, duplicateCount). The count initialized to 0. Then compare the rest of the values with this. If its in the map then increment the count otherwise append it to the map. The downfall of this is to get the duplicates. Another iteration needs to be performed on a very large list. An alternative is to maintain another hashmap for duplicates like duplicateCodeMap.put(codeValue, duplicateCount) and change the initial hashmap to codeMap.put(codeValue, codeValue). Speed is what is requirement. Hope one of you can help me with it.

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  • How to pass some data to JQuery AJAX in CAKEPHP

    - by kwokwai
    Hi all, I am learning how to use JQuery to help check data availability. To start with it, I wrote a few lines of codes using cakePHP. I have written a function in a Controller for checking data input, and the URL is like this: http://www.mywebsite.com/controllers/action/avariable I was trying to pass the value in a Input TextBox field using the JQuery Ajax to the URL above,but I don't know why it is not working in passing a variable to the Controller's action. Could you help me out please? <Script language="javascript"> //<!-- $(document).ready(function(){ $(document).change(function() { var usr = $("#data\\[User\\]\\[name\\]").val(); if(usr.length >= 3){ $("#username").append('<span><img align="absmiddle" src="loader.gif" />Checking</span>'); $.ajax({ type: "POST", url: "http://www.mywebsite.com/controllers/action/", data: usr, success: function(msg){ if(msg == 'OK') { $("#username").append('<span><img align="absmiddle" src="accepted.png"/></span>'); } else { $("#username").append('<span>'+msg+'</span>'); } } }); } else { $("#username").append('<span>The username should have at least 3 characters.</span>'); } }); }); //--> </Script> <form name="adduser" id="adduser" method="post" action="/controllers/action2"> <table border=0 width="100%"> <tr> <td>Username</td> <td> <div id="username"> <input type=text name="data[User][name]" id="data[User][name]"> </div> </td> </tr> <tr> <td> <input type="submit" value="Send"> </td> </tr> </table> </form>

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  • mysql: inserting data and autoincrement

    - by every_answer_gets_a_point
    i am converting from access to mysql i have a table in access where one of the columns is an autonumber when i transfer the data into the mysql database (where i also have a column that is auto_increment), should i be transfering the auto_increment data into the auto_increment column, or will it auto_increment itself? how do i ensure that if i do not transfer the autoincrement data from access, that it auto_increments properly?

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