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  • Best practices for Java logging from multiple threads?

    - by Jason S
    I want to have a diagnostic log that is produced by several tasks managing data. These tasks may be in multiple threads. Each task needs to write an element (possibly with subelements) to the log; get in and get out quickly. If this were a single-task situation I'd use XMLStreamWriter as it seems like the best match for simplicity/functionality without having to hold a ballooning XML document in memory. But it's not a single-task situation, and I'm not sure how to best make sure this is "threadsafe", where "threadsafe" in this application means that each log element should be written to the log correctly and serially (one after the other and not interleaved in any way). Any suggestions? I have a vague intuition that the way to go is to use a queue of log elements (with each one able to be produced quickly: my application is busy doing real work that's performance-sensitive), and have a separate thread which handles the log elements and sends them to a file so the logging doesn't interrupt the producers. The logging doesn't necessarily have to be XML, but I do want it to be structured and machine-readable. edit: I put "threadsafe" in quotes. Log4j seems to be the obvious choice (new to me but old to the community), why reinvent the wheel...

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  • Making one table equal to another without a delete *

    - by Joshua Atkins
    Hey, I know this is bit of a strange one but if anyone had any help that would be greatly appreciated. The scenario is that we have a production database at a remote site and a developer database in our local office. Developers make changes directly to the developer db and as part of the deployment process a C# application runs and produces a series of .sql scripts that we can execute on the remote side (essentially delete *, insert) but we are looking for something a bit more elaborate as the downtime from the delete * is unacceptable. This is all reference data that controls menu items, functionality etc of a major website. I have a sproc that essentially returns a diff of two tables. My thinking is that I can insert all the expected data in to a tmp table, execute the diff, and drop anything from the destination table that is not in the source and then upsert everything else. The question is that is there an easy way to do this without using a cursor? To illustrate the sproc returns a recordset structured like this: TableName Col1 Col2 Col3 Dest Src Anything in the recordset with TableName = Dest should be deleted (as it does not exist in src) and anything in Src should be upserted in to dest. I cannot think of a way to do this purely set based but my DB-fu is weak. Any help would be appreciated. Apologies if the explanation is sketchy; let me know if you need anymore details.

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  • Maintaining state and data context between requests in ASP.NET + EF4

    - by Nick
    I have a EF4/ASP.NET web application that is structured to use POCOs and generic repositories, based essentially on this excellent article. The application is relatively sophisticated with one page that involves selection and linking of multiple entities to build up a complex user profile. This requires access to multiple entity types (20 or so) and associated repositories across multiple posts. When a repository is first accessed it uses the existing data context if exists, else it creates a new context. The problem is that if the lifetime of the context is only per-request (as suggested in the article) then you have to deal with multiple contexts and the complexity around detaching and attaching entities from contexts. My solution is to share the context between posts by creating a single View Model that includes all required repositories (initialised to share the same context) plus any associated data and store this model in a Session variable, retrieving from Session on subsequent page requests. Therefore maintaining the same context across all posts until the profile is saved. This works fine BUT I am concerned that I don't actually know exactly what is stored in the model session variable or more importantly the size of the Session variable. So two questions I suppose: firstly should I look for a better solution to handle the shared context across posts issue (any suggestions welcome)? And secondly what is actually stored in the Session when it includes a repository plus context? Any help appreciated!

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  • How can I remove an "ALMOST" Duplicate using LINQ? ( OR SQL? )

    - by Atomiton
    This should be and easy one for the LINQ gurus out there. I'm doing a complex Query using UNIONS and CONTAINSTABLE in my database to return ranked results to my application. I'm getting duplicates in my returned data. This is expected. I'm using CONTAINSTABLE and CONTAINS to get all the results I need. CONTAINSTABLE is ranked by SQL and CONTAINS (which is run only on the Keywords field ) is hard-code-ranked by me. ( Sorry if that doesn't make sense ) Anyway, because the tuples aren't identical ( their rank is different ) a duplicate is returned. I figure the best way to deal with this is use LINQ. I know I'll be using the Distinct() extension method, but do I have to implement the IEqualityComparer interface? I'm a little fuzzy on how to do this. For argument's sake, say my resultset is structured like this class: class Content { ContentID int //KEY Rank int Description String } If I have a List<Content> how would I write the Distinct() method to exclude Rank? Ideally I'd like to keep the Content's highest Rank. SO, if one Content's RAnk is 112 and the other is 76. I'd like to keep the 112 rank. Hopefully I've given enough information.

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  • C# and SQL - sub select from a table parameter

    - by Dr.HappyPants
    Below is a code snippet for passing a table as a parameter to a query that can be used in Sql Server 2008. I'm confused though about the "SELECT id.custid FROM @custids id". Why does it use id.custid and @custids id...? private static void datatable_example() { string [] custids = {"ALFKI", "BONAP", "CACTU", "FRANK"}; DataTable custid_list = new DataTable(); custid_list.Columns.Add("custid", typeof(String)); foreach (string custid in custids) { DataRow dr = custid_list.NewRow(); dr["custid"] = custid; custid_list.Rows.Add(dr); } using(SqlConnection cn = setup_connection()) { using(SqlCommand cmd = cn.CreateCommand()) { cmd.CommandText = @"SELECT C.CustomerID, C.CompanyName FROM Northwind.dbo.Customers C WHERE C.CustomerID IN (SELECT id.custid FROM @custids id)"; cmd.CommandType = CommandType.Text; cmd.Parameters.Add("@custids", SqlDbType.Structured); cmd.Parameters["@custids"].Direction = ParameterDirection.Input; cmd.Parameters["@custids"].TypeName = "custid_list_tbltype"; cmd.Parameters["@custids"].Value = custid_list; using (SqlDataAdapter da = new SqlDataAdapter(cmd)) using (DataSet ds = new DataSet()) { da.Fill(ds); PrintDataSet(ds); } } }

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  • Need help in tuning a sql-query

    - by Viper
    Hello, i need some help to boost this SQL-Statement. The execution time is around 125ms. During the runtime of my program this sql (better: equally structured sqls for different tables) will be called 300.000 times. The average row count in the tables lies around 10.000.000 rows and new rows (updates/inserts) will be added with a timestamp each day. Data which are interesting for this particular export-program lies in the last 1-3 days. Maybe this is helpful for an index to create. The data i need is the current valid row for a given id and the forerunner datarow to get the updates (if exists). We use a Oracle 11g database and Dot.Net Framework 3.5 SQL-Statement to boost: select ID_SOMETHING, -- Number(12) ID_CONTRIBUTOR, -- Char(4 Byte) DATE_VALID_FROM, -- DATE DATE_VALID_TO -- DATE from TBL_SOMETHING XID where ID_SOMETHING = :ID_INSTRUMENT and ID_CONTRIBUTOR = :ID_CONTRIBUTOR and DATE_VALID_FROM <= :EXPORT_DATE and DATE_VALID_TO >= :EXPORT_DATE order by DATE_VALID_FROM asc; Here i uploaded the current Explain-Plan for this query. I'm not a database expert so i don't know which index-type would fit best for this requirement. I have seen that there are many different possible index-types which could be applied. Maybe Oracle Optimizer Hints are helpful, too. Does anyone has a good idea for tuning this sql or can point me in a right direction?

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  • Python template engine

    - by jturo
    Hello there, Could it be possible if somebody could help me get started in writing a python template engine? I'm new to python and as I learn the language I've managed to write a little MVC framework running in its own light-weight-WSGI-like server. I've managed to write a script that finds and replaces keys for values: (Obviously this is not how my script is structured or implemented. this is just an example) from string import Template html = '<html>\n' html += ' <head>\n' html += ' <title>This is so Cool : In Controller HTML</title>\n' html += ' </head>\n' html += ' <body>\n' html += ' Home | <a href="/hi">Hi ${name}</a>\n' html += ' </body>\n' html += '<html>' Template(html).safe_substitute(dict(name = 'Arturo')) My next goal is to implement custom statements, modifiers, functions, etc (like 'for' loop) but i don't really know if i should use another module that i don't know about. I thought of regular expressions but i kind feel like that wouldn't be an efficient way of doing it Any help is appreciated, and i'm sure this will be of use to other people too. Thank you

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  • RIA Services for transmitting non DB object-graph

    - by Mike Gates
    I have been getting into RIA services because I thought it would simplify dealing with the services layer of web applications I wish to build. I see lots of examples out there showing how to create DomainService classes which expose and consume entities that have some kind of relational database backing, and therefore have foreign-key relationships. However, I would like to know how to expose and consume normal object graphs...objects that contain references to eachother but don't have foreign keys. For example, say I want a service operation called "GetFolderInformation(string pathToFolder)". I want this to return a custom object called "FolderInformation" structured with: - string Name - IEnumerable<FileInformation> Files I cannot get this to work because it seems that RIA wants to deal with entities that have foreign key relationships. Why? Why can't the serializer just see my object references and recreate that in the proxy on the other side? Data exists behind service layers that doesn't necessarily have foreign key relationships...like folder/file for example. EDIT: I realized I hadn't asked my question! My question is, is there a way to do what I am trying to do?

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  • Formatting the parent and child nodes of a Treeview that is populated by a XML file

    - by Marina
    Hello Everyone, I'm very new to xml so I hope I'm not asking any silly question here. I'm currently working on populating a treeview from an XML file that is not hierarchically structured. In the xml file that I was given the child and parent nodes are defined within the attributes of the item element. How would I be able to utilize the attributes in order for the treeview to populate in the right hierarchical order. (Example Mary Jane should be a child node of Peter Smith). At present all names are under one another. root <item parent_id="0" id="1"><content><name>Peter Smith</name></content></item> <item parent_id="1" id="2"><content><name>Mary Jane</name></content></item> <item parent_id="1" id="7"><content><name>Lucy Lu</name></content></item> <item parent_id="2" id="3"><content><name>Informatics Team</name></content></item> <item parent_id="3" id="4"><content><name>Sandy Chu</name></content></item> <item parent_id="4" id="5"><content><name>John Smith</name></content></item> <item parent_id="5" id="6"><content><name>Jane Smith</name></content></item> /root Thank you for all of your help, Marina

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  • What's the best way to read a UDT from a database with Java?

    - by Lukas Eder
    I thought I knew everything about UDTs and JDBC until someone on SO pointed out some details of the Javadoc of java.sql.SQLInput and java.sql.SQLData JavaDoc to me. The essence of that hint was (from SQLInput): An input stream that contains a stream of values representing an instance of an SQL structured type or an SQL distinct type. This interface, used only for custom mapping, is used by the driver behind the scenes, and a programmer never directly invokes SQLInput methods. This is quite the opposite of what I am used to do (which is also used and stable in productive systems, when used with the Oracle JDBC driver): Implement SQLData and provide this implementation in a custom mapping to ResultSet.getObject(int index, Map mapping) The JDBC driver will then call-back on my custom type using the SQLData.readSQL(SQLInput stream, String typeName) method. I implement this method and read each field from the SQLInput stream. In the end, getObject() will return a correctly initialised instance of my SQLData implementation holding all data from the UDT. To me, this seems like the perfect way to implement such a custom mapping. Good reasons for going this way: I can use the standard API, instead of using vendor-specific classes such as oracle.sql.STRUCT, etc. I can generate source code from my UDTs, with appropriate getters/setters and other properties My questions: What do you think about my approach, implementing SQLData? Is it viable, even if the Javadoc states otherwise? What other ways of reading UDT's in Java do you know of? E.g. what does Spring do? what does Hibernate do? What does JPA do? What do you do? Addendum: UDT support and integration with stored procedures is one of the major features of jOOQ. jOOQ aims at hiding the more complex "JDBC facts" from client code, without hiding the underlying database architecture. If you have similar questions like the above, jOOQ might provide an answer to you.

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  • puzzled with java if else performance

    - by user1906966
    I am doing an investigation on a method's performance and finally identified the overhead was caused by the "else" portion of the if else statement. I have written a small program to illustrate the performance difference even when the else portion of the code never gets executed: public class TestIfPerf { public static void main( String[] args ) { boolean condition = true; long time = 0L; int value = 0; // warm up test for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } // benchmark if condition only time = System.nanoTime(); for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } } time = System.nanoTime() - time; System.out.println( "1) performance " + time ); time = System.nanoTime(); // benchmark if else condition for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } time = System.nanoTime() - time; System.out.println( "2) performance " + time ); } } and run the test program with java -classpath . -Dmx=800m -Dms=800m TestIfPerf. I performed this on both Mac and Linux Java with 1.6 latest build. Consistently the first benchmark, without the else is much faster than the second benchmark with the else section even though the code is structured such that the else portion is never executed because of the condition. I understand that to some, the difference might not be significant but the relative performance difference is large. I wonder if anyone has any insight to this (or maybe there is something I did incorrectly). Linux benchmark (in nano) performance 1215488 performance 2629531 Mac benchmark (in nano) performance 1667000 performance 4208000

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  • Dependency Injection for objects that require parameters

    - by Andrew
    All of our reports are created from object graphs that are translated from our domain objects. To enable this, we have a Translator class for each report, and have been using Dependency Injection for passing in dependencies. This worked great, and would yield nice classes structured like this: public class CheckTranslator : ICheckTranslator { public CheckTranslator (IEmployeeService empSvc , IPaycheckService paySvc) { _empSvc = empSvc; _paySvc = paySvc; } public Check CreateCheck() { //do the translation... } } However, in some cases the mapping has many different grouping options. As a result, the c-tor would turn into a mix of class dependencies and parameters. public class CheckTranslator : ICheckTranslator { public CheckTranslator (IEmployeeService empSvc , IPaycheckService paySvc , bool doTranslateStubData , bool doAttachLogo) { _empSvc = empSvc; _paySvc = paySvc; _doTranslateStubData = doTranslateStubData; _doAttachLogo = doAttachLogo; } public Check CreateCheck() { //do the translation... } } Now, we can still test it, but it no longer really works with an IoC container, at least in a clean fashion. Plus, we can no longer call the CreateCheck twice if the settings are different for each check. While I recognize it's a problem, I don't necessarily see the right solution. It seems kind of strange to create a Factory for each class ... or is this the best way?

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  • JDBC/OSGi and how to dynamically load drivers without explicitly stating dependencies in the bundle?

    - by Chris
    Hi, This is a biggie. I have a well-structured yet monolithic code base that has a primitive modular architecture (all modules implement interfaces yet share the same classpath). I realize the folly of this approach and the problems it represents when I go to deploy on application servers that may have different conflicting versions of my library. I'm dependent on around 30 jars right now and am mid-way though bnding them up. Now some of my modules are easy to declare the versioned dependencies of, such as my networking components. They statically reference classes within the JRE and other BNDded libraries but my JDBC related components instantiate via Class.forName(...) and can use one of any number of drivers. I am breaking everything up into OSGi bundles by service area. My core classes/interfaces. Reporting related components. Database access related components (via JDBC). etc.... I wish for my code to be able to still be used without OSGi via single jar file with all my dependencies and without OSGi at all (via JARJAR) and also to be modular via the OSGi meta-data and granular bundles with dependency information. How do I configure my bundle and my code so that it can dynamically utilize any driver on the classpath and/or within the OSGi container environment (Felix/Equinox/etc.)? Is there a run-time method to detect if I am running in an OSGi container that is compatible across containers (Felix/Equinox/etc.) ? Do I need to use a different class loading mechanism if I am in a OSGi container? Am I required to import OSGi classes into my project to be able to load an at-bundle-time-unknown JDBC driver via my database module? I also have a second method of obtaining a driver (via JNDI, which is only really applicable when running in an app server), do I need to change my JNDI access code for OSGi-aware app servers?

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  • How would I structure the loop to go through inputs?

    - by dmanexe
    I am attempting to make a loop that will go through an array structured like this: $input[n][checked] $input[n][input] The 2nd input acts as a price multiplier, but doesn't have to exist (field can be blank). I don't think a foreach loop is right because I don't think it handles the inputs from the form in the correct dimensional array order to keep the information together. I have inputs on a form that look like this: <input type="checkbox" name="measure[<?php echo $item->id; ?>][checked]" value="<?php echo $item->id; ?>"> <input class="item_mult" type="text" name="measure[<?php echo $item->id; ?>][input]" /> I am attempting to make the loop go through and act as a multiplier on the input relative to its sibling field. (i.e. input[1][input] would be an integer that I want to retrieve later, grouped with input[1][checked]) <? $field = $this->input->post('measure',true); $totals = array(); foreach($field as $value): if ($value['input'] == TRUE) { $query = $this->db->get_where('items', array('id' => $value['input']))->row(); $totals[] = $query->price; ?> <p><?=$query->name?> - <?=money_format('%(#10n', $query->price)?></p> <?php } else { } endforeach; ?> And finally, the last code to array_sum and print the grand total: <? $grand_total = array_sum($totals); ?> <p><?=money_format('%(#10n', $grand_total)?></p> Eventually, I will need to store these records in a database, so I am sending complete item IDs through, etc.

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  • How large a role does subjectiveness play in programming?

    - by Bob
    I often read about the importance of readability and maintainability. Or, I read very strong opinions about which syntax features are bad or good. Or discussions about the values of certain paradigms, like OOP. Aside from that, this same question floats about in my mind whenever I read debates on SO or Meta about subjective questions. Or read questions about best practices and sometimes find myself or others disagreeing. What role does subjectiveness play within the programming realm? Sometimes I think it plays a large role. Software developers are engineers in a way, but also people. A large part of programming is dealing with code that's human readable. This is very different from Math or Physics or other disciplines with very exact and structured rules. Here the exact structure and rules are largely up in the air, changeable on a whim, and hence the amount of languages in existence. And one person may find one language very readable, and another person may find their own language the most comforting. The same with practices. One person may not like certain accepted practices. I myself find splitting classes into different files very unreadable, for instance. But, I can't say rules haven't helped in general. Certain practices have and do make life easier. And new languages have given rise to syntax and structure that make life easier. There's certainly been a progression towards code that is easier to read and maintain even given a largely diverse group of people. So maybe these things aren't as subjective as I thought. It reminds me, in a way, of UI design. Certainly it's subjective, but then there's an entire discipline involved in crafting good UI and it tends to work. Is there something non-subjective about the ideas behind maintainability, readability, and other best practices? Is there something tangible to grasp when one develops a new language or thinks of new practices?

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  • Linked List Sorting with Strings In C

    - by user308583
    I have a struct, with a Name and a single Node called nextName It's a Singly Linked list, and my task is to create the list, based on alphabetical order of the strings. So iff i enter Joe Zolt and Arthur i should get my list structured as Joe Than Joe Zolt Than Arthur Joe Zolt I'm having trouble implementing the correct Algorithm, which would put the pointers in the right order. This is What I have as of Now. Temp would be the name the user just entered and is trying to put into the list, namebox is just a copy of my root, being the whole list if(temp != NULL) { struct node* namebox = root; while (namebox!=NULL && (strcmp((namebox)->name,temp->name) <= 0)) { namebox = namebox->nextName; printf("here"); } temp->nextName = namebox; namebox = temp; root = namebox; This Works right now, if i enter names like CCC BBB than AAA I Get Back AAA BBB CCC when i print But if i put AAA BBB CCC , When i print i only get CCC, it cuts the previous off.

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  • SEO: Where do I start?

    - by James
    Hi, I am primarily a software developer however I tend to delve in some web development from time to time. I have recently been asked to have a look at a friends website as they are wanting to improve their position in search engine results i.e. google/yahoo etc. I am aware there is no guarentee that their position will change, however, I do know there are techniques/ways to make your website more visible to search engine spiders and to consequently improve your position in the rankings i.e. performing SEO. Before I started looking at the SEO of the site I did the following prerequsite checks: Ran the website through the W3C Markup Validator and the W3C CSS Validator services. Looked through the markup code manually (check for meta tags etc) Performed a thorough cross browser compatibility test. From those checks, the following was evident: No SEO has been performed on the site before. The website has been developed using a visual editing tool such as dreamweaver (as it failed the validation services miserably and tables where being used everywhere!) The site is fairly cross browser compatibile (only some slight issues with IE8 which are easily resolved). How the site navigation is, isn't very search engine friendly (e.g. index.php?page=home) I can see right away a major improvement for SEO (or I at least think) would be to change the way the website is structured i.e. change from using dynamic pages such as "index.php?page=home" and actually having pages called "home.html". Other area's would be to add meta tags to identify keywords, and then sprinkling these keywords over the pages. As I am a rookie in this department, could anyone give me some advice on how I could perform thorough SEO on this website? Thanks in advance.

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  • iPhone: Creating a hierarchy-based table navigation.

    - by Jack Griffiths
    Hi there, I've tried to ask this before, but nothing got answered. Basically, I would like someone to explain to me how to create a table, which when a cell is tapped, pushes the user to the next view for that cell. I have this so far: Click here to view what I have. I would further like to, say when CSS is tapped, it goes to a new view which has another table in it. This table would then take the user to a detail view, which is scrollable and you can switch pages through it. I would appreciate longer, more structured tutorials on how to do each and every bit to get it to work. Here's my array in my implementation file: - (void)viewDidLoad { arryClientSide = [[NSArray alloc] initWithObjects:@"CSS", @"HTML", @"JavaScript", @"XML", nil]; arryServerSide = [[NSArray alloc] initWithObjects:@"Apache", @"PHP", @"SQL", nil]; self.title = @"Select a Language"; [super viewDidLoad]; } and my .h: @interface RootViewController : UITableViewController <UITableViewDelegate, UITableViewDataSource> { IBOutlet UITableView *tblSimpleTable; NSArray *arryClientSide; NSArray *arryServerSide; } My current code crashes the script, and this error is returned in the console: Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[UITableViewController loadView] loaded the "NextView" nib but didn't get a UITableView.' If that error is the source of why it's not pushing, then an explanation of how to remedy that would also be appreciated Many thanks, Jack

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  • Slow retrieval of data in SQLITE takes a long using ContentProvider

    - by Arlyn
    I have an application in Android (running 4.0.3) that stores a lot of data in Table A. Table A resides in SQLite Database. I am using a ContentProvider as an abstraction layer above the database. Lots of data here means almost 80,000 records per month. Table A is structured like this: String SQL_CREATE_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_A + " ( " + COLUMN_ID + " INTEGER PRIMARY KEY NOT NULL" + "," + COLUMN_GROUPNO + " INTEGER NOT NULL DEFAULT(0)" + "," + COLUMN_TIMESTAMP + " DATETIME UNIQUE NOT NULL" + "," + COLUMN_TAG + " TEXT" + "," + COLUMN_VALUE + " REAL NOT NULL" + "," + COLUMN_DEVICEID + " TEXT NOT NULL" + "," + COLUMN_NEW + " NUMERIC NOT NULL DEFAULT(1)" + " )"; Here is the index statement: String SQL_CREATE_INDEX_TIMESTAMP = "CREATE INDEX IF NOT EXISTS " + TABLE_A + "_" + COLUMN_TIMESTAMP + " ON " + TABLE_A + " (" + COLUMN_TIMESTAMP + ") "; I have defined the columns as well as the table name as String Constants. I am already experiencing significant slow down when retrieving this data from Table A. The problem is that when I retrieve data from this table, I first put it in an ArrayList and then I display it. Obviously, this is possibly the wrong way of doing things. I am trying to find a better way to approach this problem using a ContentProvider. But this is not the problem that bothers me. The problem is for some reason, it takes a lot longer to retrieve data from other tables which have only upto 12 records maximum. I see this delay increase as the number of records in Table A increase. This does not make any sense. I can understand the delay if I retrieve data from Table A, but why the delay in retrieving data from other tables. To clarify, I do not experience this delay if Table A is empty or has less than 3000 records. What could be the problem?

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  • Need help finding a good curriculum/methodology for self-teaching to program from scratch

    - by BrotherGA2
    My friend and I have both dedicated ourselves to learning the essentials of programming by June of this year from nearly no programming experience. I have done some research and have come to the conclusion that using the Python language will be the best for us, but I am open to suggestions with good reasoning behind them. My motives for learning programming are: Potential Career Path to be able to create programs that can: solve problems; entertain, i.e. useful applications and games. Online college lectures + book (which I am willing to purchase) sounds like a good combination, but I do not know which would be most suitable for me. tl;dr: What I would like to find from the excellent people here is the following: a good, potentially best, programming course and/or book that is well structured and uses good pedagogy so that a person dedicated to learn programming may do so by following its curriculum (or use it to develop a curriculum) over the course of a few months. Thanks! (I apologize if this type of question is not considered proper etiquette, but I haven't found a consensus on this, and would like some guidance beyond the research I've already done)

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  • Why doesn't 'Q' unify in this PROLOG program

    - by inspectorG4dget
    Hello SO, I am writing a PROLOG program in which the variable of interest (Q) refuses to unify. I have gotten around this with a hacky solution (include a write statement). But there has to be a way to make this unify, but for the love of me, I am not able to figure it out. I'd really appreciate any help. Thanks in advance. Here is my code (I have annotated wherever I have excluded code for brevity) :- use_module(library(bounds)). :- use_module(library(lists)). solve([17],Q,_,_,_):- write(Q). %this is the hacky workaround solve(L,Q,1,3,2) :- jump(L,Q,N,1,3,2,R), solve(N,R,S,D,M), member([S|[D|[M|[]]]],[[1, 3, 2], [1, 9, 4], [2, 10, 5] this list contains 76 items - all of which are lists of length 3. I have omitted them here for the sake of brevity]). % there are about 75 other definitions for solve, all of which are structured exactly the same. The only difference is that the numbers in the input parameters will be different in each definition jump(L,Q,N,S,D,M,R):- member(S,L), not(member(D,L)), member(M,L), delete(L,S,X), delete(X,M,Y), append(Y,[D],N), append(Q,[[S,D]],R). cross_sol(Q) :- solve([5,9,10,11,17,24],[],S,D,M), member([S,D,M], [ I have edited out this list here for the sake of brevity. It is the same list found in the definition of solve ]). For some reason, Q does not unify. Please help!

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  • How can I visualise a "broken" hierarchical dataset?

    I have a reasonably large datatable structured something like this: StaffNo Grade Direct Boss2 Boss3 Boss4 Boss5 Boss6 ------- ----- ----- ----- ----- ----- ----- ----- 10001 1 10002 10002 10057 10094 10043 10099 10002 2 10057 NULL 10057 10094 10043 10099 10003 1 10004 10004 10057 10094 10043 10099 10004 2 10057 NULL 10057 10094 10043 10099 10057 3 10094 NULL NULL 10094 10043 10099 etc.... i.e. a unique id , their level (grade) in the hierarchy, a record of their bosses ID and the IDs of the supervisors above. (The 2,3,4, etc refers to the boss at that particular grade). The system relies on a strict hierarchy - if you are my boss (/parent) then your boss must be my grandparent. Unfortunately this rule is not enforced within the data model and the data ultimately comes from other systems which don't even know about the rule, let alone observe it. So you and I may share the same boss, but our bosses boss won't be the same. note: I cannot change the data model I cannot fix the data at source. So (for the moment) I have to fix the data once it's in place. Once a fortnight someone will do something which breaks the model and I'll need to modify the procs slightly to resolve. Not ideal, but I'm stuck with this for the next six months. Anyway, specific queries are easy to produce but I find it hard to keep track of the bigger picutre. The application which sits on this runs without complaint regardless but navigating around the system becoming extraordinarily confusing. So my question is: Can anyone recommend a tool (or technique) for generating some kind of "broken tree" diagram in this sort of circumstances? I don't want something that will fix things for me, or attempt statistical analysis but at least something that will give a visual indication of how broken it is at any one time. Note : At the moment this is in a SQL Server database but I'm open to ideas utilising C#, Perl or Python.

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  • Testing subpackage modules in Python 3

    - by Mitchell Model
    I have been experimenting with various uses of hierarchies like this and the differences between absolute and relative imports, and can't figure out how to do routine things with the package, subpackages, and modules without simply putting everything on sys.path. I have a two-level package hierarchy: MyApp __init__.py Application __init__.py Module1 Module2 ... Domain __init__.py Module1 Module2 ... UI __init__.py Module1 Module2 ... I want to be able to do the following: Run test code in a Module's "if main" when the module imports from other modules in the same directory. Have one or more test code modules in each subpackage that runs unit tests on the modules in the subpackage. Have a set of unit tests that reside in someplace reasonable, but outside the subpackages, either in a sibling package, at the top-level package, or outside the top-level package (though all these might end up doing is running the tests in each subpackage) "Enter" the structure from any of the three subpackage levels, e.g. run code that just uses Domain modules, run code that just uses Application modules, but Application uses code from both Application and Domain modules, and run code from GUI uses code from both GUI and Application; for instance, Application test code would import Application modules but not Domain modules. After developing the bulk of the code without subpackages, continue developing and testing after organizing the modules into this hierarchy. I know how to use relative imports so that external code that puts MyApp on its sys.path can import MyApp, import any subpackages it wants, and import things from their modules, while the modules in each subpackage can import other modules from the same subpackage or from sibling packages. However, the development needs listed above seem incompatible with subpackage structuring -- in other words, I can't have it both ways: a well-structured multi-level package hierarchy used from the outside and also used from within, in particular for testing but also because modules from one design level (in particular the UI) should not import modules from a design level below the next one down. Sorry for the long essay, but I think it fairly represents the struggles a lot of people have been having adopting to the new relative import mechanisms.

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  • Why do mozilla and webkit prepend -moz- and -webkit- to CSS3 rules?

    - by egarcia
    CSS3 rules bring lots of interesting features. Take border-radius, for example. The standard says that if you write this rule: div.rounded-corners { border-radius: 5px; } I should get a 5px border radius. But neither mozilla nor webkit implement this. However, they implement the same thing, with the same parameters, with a different name (-moz-border-radius and -webkit-border-radius, respectively). In order to satisfy as many browsers as possible, you end up with this: div.rounded-corners { border-radius: 5px; -moz-border-radius: 5px; -webkit-border-radius: 5px; } I can see two obvious disadvantages: Copy-paste code. This has obvious risks that I will not discuss here. The W3C CSS validator will not validate these rules. At the same time, I don't see any obvious advantages. I believe that the people behind mozilla and webkit are more intelligent than myself. There must be some good reasons to have things structured this way. It's just that I can't see them. So, I must ask you people: why is this?

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  • How do I use this indirect relationship?

    - by tyjkenn
    I'm working on incorporating a reputation system into my site, similar to SO. Here is how it is structured: User hasMany Project User hasMany Answer Project hasMany Rating Answer hasMany Rating Rating belongsTo Project where Rating.parent_type = Project Rating belongsTo Answer where Rating.parent_type = Answer Rating's value field will be a number between 1 and 5. The user should gain +10 for every 5-star review, +5 for every 4-star review, and +1 for every 3-star review. The way I currently have it set up is this: a recalcRep($id) action in the UsersController (along with other actions in other controllers, when necessary) calls the calcRep($id) method inside the User model, which is supposed to calculate the reputation of a user with an id of $id. public function calcRep($id) { $rep = 0; $data = $this->Rating->find('all'); //does not work, because it is not directly associated foreach($data as $rating) { if(($rating['Rating']['parent_type'] == 'Project' && $rating['Project']['user_id']==$id) or ($rating['Rating']['parent_type'] == 'Answer' && $rating['Answer']['user_id']==$id)) { if($rating['Rating']['value']==5) { $rep += 10; } else if($rating['Rating']['value']==4) { $rep += 5; } else if($rating['Rating']['value']==3) { $rep += 2; } } } $data['User']['reputation'] = $rep; $this->save($data); } I may be approaching this in completely the wrong way, but I can't figure out how to find all the ratings that belong to any of the children of a specific user.

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