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  • Why is numpy c extension slow?

    - by Bitwise
    I am working on large numpy arrays, and some native numpy operations are too slow for my needs (for example simple operations such as "bitwise" A&B). I started looking into writing C extensions to try and improve performance. As a test case, I tried the example given here, implementing a simple trace calculation. I was able to get it to work, but was surprised by the performance: for a (1000,1000) numpy array, numpy.trace() was about 1000 times faster than the C extension! This happens whether I run it once or many times. Is this expected? Is the C extension overhead that bad? Any ideas how to speed things up?

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  • MEF Why is ComposePart an extension method?

    - by ILovePaperTowels
    CompositionContainer.ComposePart is an extension method. why is that? Looking into the System.Componentmodel.Composition assembly, it looks like it's because it is ONLY meant to work with the attributed programming model while the .Compose() method is able to take in exports as long as it is a composablepart. ComposePart is even hosted in the 'AttributedModelServices' class which makes me think I'm correct. Am I correct on this? If not, why is it an extension method and not a method in the container class?

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  • How do I make a firefox extension execute script on page open/load? [migrated]

    - by Will Mc
    Thanks in advance! I am creating my first extension (A firefox extension). See below for full description of final product. I need help starting off. I have looked and studied the HelloWorld.xpi example found on Mozilla's site so I am happy to edit that to learn. In the example, when you click a menu item it runs script to display an alert message. My question is, how would I edit this extension to run the script on page load? I am guessing I need to insert some code in the browserOverlay as it loads on page load so, here is the browserOverlay.xpi from the example I am editing to learn: <?xml version="1.0"?> <?xml-stylesheet type="text/css" href="chrome://global/skin/" ?> <?xml-stylesheet type="text/css" href="chrome://xulschoolhello/skin/browserOverlay.css" ?> <!DOCTYPE overlay SYSTEM "chrome://xulschoolhello/locale/browserOverlay.dtd"> <overlay id="xulschoolhello-browser-overlay" xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <script type="application/x-javascript" src="chrome://xulschoolhello/content/browserOverlay.js" /> <stringbundleset id="stringbundleset"> <stringbundle id="xulschoolhello-string-bundle" src="chrome://xulschoolhello/locale/browserOverlay.properties" /> </stringbundleset> <menubar id="main-menubar"> <menu id="xulschoolhello-hello-menu" label="&xulschoolhello.hello.label;" accesskey="&xulschoolhello.helloMenu.accesskey;" insertafter="helpMenu"> <menupopup> <menuitem id="xulschoolhello-hello-menu-item" label="&xulschoolhello.hello.label;" accesskey="&xulschoolhello.helloItem.accesskey;" oncommand="XULSchoolChrome.BrowserOverlay.sayHello(event);" /> </menupopup> </menu> </menubar> <vbox id="appmenuSecondaryPane"> <menu id="xulschoolhello-hello-menu-2" label="&xulschoolhello.hello.label;" accesskey="&xulschoolhello.helloMenu.accesskey;" insertafter="appmenu_addons"> <menupopup> <menuitem id="xulschoolhello-hello-menu-item-2" label="&xulschoolhello.hello.label;" accesskey="&xulschoolhello.helloItem.accesskey;" oncommand="XULSchoolChrome.BrowserOverlay.sayHello(event);" /> </menupopup> </menu> </vbox> </overlay> I hope you can help me. I need to know what code I should use and where I should put it... Here is the gist of my overall extension - I am creating a click to call extension. This extension will search any new page for a phone number whether just refreshed, new page, new tab etc... Each phone number when clicked will open a new tab and direct user to a custom URL. Thanks again!

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  • SQLiteQueryBuilder.buildQuery not using selectArgs?

    - by user297468
    Alright, I'm trying to query a sqlite database. I was trying to be good and use the query method of SQLiteDatabase and pass in the values in the selectArgs parameter to ensure everything got properly escaped, but it wouldn't work. I never got any rows returned (no errors, either). I started getting curious about the SQL that this generated so I did some more poking around and found SQLiteQueryBuilder (and apparently Stack Overflow doesn't handle links with parentheses in them well, so I can't link to the anchor for the buildQuery method), which I assume uses the same logic to generate the SQL statement. I did this: SQLiteQueryBuilder builder = new SQLiteQueryBuilder(); builder.setTables(BarcodeDb.Barcodes.TABLE_NAME); String sql = builder.buildQuery(new String[] { BarcodeDb.Barcodes.ID, BarcodeDb.Barcodes.TIMESTAMP, BarcodeDb.Barcodes.TYPE, BarcodeDb.Barcodes.VALUE }, "? = '?' AND ? = '?'", new String[] { BarcodeDb.Barcodes.VALUE, barcode.getValue(), BarcodeDb.Barcodes.TYPE, barcode.getType()}, null, null, null, null); Log.d(tag, "Query is: " + sql); The SQL that gets logged at this point is: SELECT _id, timestamp, type, value FROM barcodes WHERE (? = '?' AND ? = '?') However, here's what the documentation for SQLiteQueryBuilder.buildQuery says about the selectAgs parameter: You may include ?s in selection, which will be replaced by the values from selectionArgs, in order that they appear in the selection. ...but it isn't working. Any ideas?

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  • Adding visible "Markers" to represent Geopoints to a MapView using ItemizedOverlay in Android

    - by LordSnoutimus
    Hello, I am building an application which stores GPS locations in a SQLite database and then outputs the data onto a MapView using an Overlay by drawing a red line between the points. I want to be able to show graphical markers (images) for each of these points as well as the red line. My code is as follows: public class MyOverlay extends ItemizedOverlay { // private Projection projection; private Paint linePaint; private Vector points; public MyOverlay(Drawable defaultMarker) { super(defaultMarker); points = new Vector<GeoPoint>(); //set colour, stroke width etc. linePaint = new Paint(); linePaint.setARGB(255, 255, 0, 0); linePaint.setStrokeWidth(3); linePaint.setDither(true); linePaint.setStyle(Style.FILL); linePaint.setAntiAlias(true); linePaint.setStrokeJoin(Paint.Join.ROUND); linePaint.setStrokeCap(Paint.Cap.ROUND); } public void addPoint(GeoPoint point) { populate(); points.addElement(point); } //public void setProjection(Projection projection) { // this.projection = projection; // } public void draw(Canvas canvas, MapView view, boolean shadow) { populate(); int size = points.size(); Point lastPoint = new Point(); if(size == 0) return; view.getProjection().toPixels(points.get(0), lastPoint); Point point = new Point(); for(int i = 1; i<size; i++){ view.getProjection().toPixels(points.get(i), point); canvas.drawLine(lastPoint.x, lastPoint.y, point.x, point.y, linePaint); lastPoint = point; } } @Override protected OverlayItem createItem(int arg0) { // TODO Auto-generated method stub return null; } @Override public int size() { // TODO Auto-generated method stub return 0; } } What would be the easiest way to implement adding markers for each GeoPoint? Thanks

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  • The Date type and the Android database

    - by cdonner
    I understand that SQLite stores dates as long integers. When I read rows into a cursor using the standard method (i.e. using the query() method that reads data into a cursor), the result is a date string that includes the time. If I want a different format, I have to parse the string back into a date - possible, but a bit backwards. By using a ViewBinder (as suggested in this question), I can pretty much do anything I want, but the date is already a string at the time the method executes. The accepted answer to the above question also suggests that storing dates as longs would help avoid this problem. I don't want to do that, just in case I want to interpret my data with something else than this application. Maybe I want to expose it via a provider. Is there a way to handle this in the database adapter instead, i.e. controlling the date format that the cursor contains, so that I don't have to change the schema, and don't have to parse the default output back into a Date type?

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  • process csv in scala

    - by portoalet
    I am using scala 2.7.7, and wanted to parse CSV file and store the data in SQLite database. I ended up using OpenCSV java library to parse the CSV file, and using sqlitejdbc library. Using these java libraries makes my scala code looks almost identical to that of Java code (sans semicolon and with val/var) As I am dealing with java objects, I can't use scala list, map, etc, unless I do scala2java conversion or upgrade to scala 2.8 Is there a way I can simplify my code further using scala bits that I don't know? val filename = "file.csv"; val reader = new CSVReader(new FileReader(filename)) var aLine = new Array[String](10) var lastSymbol = "" while( (aLine = reader.readNext()) != null ) { if( aLine != null ) { val symbol = aLine(0) if( !symbol.equals(lastSymbol)) { try { val rs = stat.executeQuery("select name from sqlite_master where name='" + symbol + "';" ) if( !rs.next() ) { stat.executeUpdate("drop table if exists '" + symbol + "';") stat.executeUpdate("create table '" + symbol + "' (symbol,data,open,high,low,close,vol);") } } catch { case sqle : java.sql.SQLException => println(sqle) } lastSymbol = symbol } val prep = conn.prepareStatement("insert into '" + symbol + "' values (?,?,?,?,?,?,?);") prep.setString(1, aLine(0)) //symbol prep.setString(2, aLine(1)) //date prep.setString(3, aLine(2)) //open prep.setString(4, aLine(3)) //high prep.setString(5, aLine(4)) //low prep.setString(6, aLine(5)) //close prep.setString(7, aLine(6)) //vol prep.addBatch() prep.executeBatch() } } conn.close()

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  • Searching a list of tuples in python

    - by Niclas Nilsson
    I'm having a database (sqlite) of members of an organisation (less then 200 people). Now I'm trying to write an wx app that will search the database and return some contact information in a wx.grid. The app will have 2 TextCtrls, one for the first name and one for the last name. What I want to do here is make it possible to only write one or a few letters in the textctrls and that will start to return result. So, if I search "John Smith" I write "Jo" in the first TextCtrl and that will return every single John (or any one else having a name starting with those letters). It will not have an "search"-button, instead it will start searching whenever I press a key. One way to solve this would be to search the database with like " SELECT * FROM contactlistview WHERE forname LIKE 'Jo%' " But that seems like a bad idea (very database heavy to do that for every keystroke?). Instead i thought of use fetchall() on a query like this " SELECT * FROM contactlistview " and then, for every keystroke, search the list of tuples that the query have returned. And that is my problem: Searching a list is not that difficult but how can I search a list of tuples with wildcards?

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  • SQLiteDataAdapter Update method returning 0 C#

    - by Lirik
    I loaded 83 rows from my CSV file, but when I try to update the SQLite database I get 0 rows... I can't figure out what I'm doing wrong. The program outputs: Num rows loaded is 83 Num rows updated is 0 The source code is: public void InsertData(String csvFileName, String tableName) { String dir = Path.GetDirectoryName(csvFileName); String name = Path.GetFileName(csvFileName); using (OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + dir + @";Extended Properties=""Text;HDR=Yes;FMT=Delimited\""")) { conn.Open(); using (OleDbDataAdapter adapter = new OleDbDataAdapter("SELECT * FROM " + name, conn)) { QuoteDataSet ds = new QuoteDataSet(); adapter.Fill(ds, tableName); Console.WriteLine("Num rows loaded is " + ds.Tags.Rows.Count); InsertData(ds, tableName); } } } public void InsertData(QuoteDataSet data, String tableName) { using (SQLiteConnection conn = new SQLiteConnection(_connectionString)) { using (SQLiteDataAdapter sqliteAdapter = new SQLiteDataAdapter("SELECT * FROM " + tableName, conn)) { using (new SQLiteCommandBuilder(sqliteAdapter)) { conn.Open(); Console.WriteLine("Num rows updated is " + sqliteAdapter.Update(data, tableName)); } } } } Any hints on why it's not updating the correct number of rows?

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  • How do I pass a callback function to sqlite3_exec on iOS 5.1?

    - by John Doh
    I am new to both xcode/iOS/Objective-C and sqlite. I am trying to teach myself the basics - and I would like to use the sqlite3 wrapper "sqlite3_exec" for a select query. For some reason, I can't find a simple example anywhere of someone doing this. Basically, the method has a parameter (the third one) for a callback function: int sqlite3_exec( sqlite3*, /* An open database */ const char *sql, /* SQL to be evaluated */ int (*callback)(void*,int,char**,char**), /* Callback function */ void *, /* 1st argument to callback */ char **errmsg /* Error msg written here */ ); That's fine. I'm no stranger to callbacks. However, I just can't seem to get the syntax down right. I took over one of the view controllers in my iPad (iOS 5.1) xcode (4.3) project, and made the changes shown below: #import "SecondViewController.h" #import "sqlite3.h" #import "AppState.h" @interface SecondViewController () @end @implementation SecondViewController - (int)myCallback:(void *)a_parm argc:(int)argc argv:(char **)argv column:(char **)column { return 0; } - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. //grab questionnaire names char *sql = "select * from QST2Main order by [Name]"; char *err = nil; sqlite3 *db = [[AppState sharedManager] getgCn]; sqlite3_exec(db, sql, myCallback, nil, &err); } Essentially, I want to run a query when this view first loads, to store some data for later use. But, XCode doesn't like the "myCallback" usage at the bottom there. It says: Undeclared Use of Identifier 'myCallback.' That method is declared in the header file, and I've even tried making it static. Nothing seems to make this error go away. I know I must be doing something fundamentally wrong here, but for the life of me I can't figure out what - I can't even find other code samples in this area that could help me figure out what I'm missing. Many thanks!

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  • [Repost-ish] Impossibly slow queries, Tables indexed, How can I speed it up?

    - by colorfulgrayscale
    Hi guys, I posted a little earlier on here at http://stackoverflow.com/questions/2656837/query-results-taking-too-long-on-200k-database-speed-up-tips asking about slow executing SQL queries. I was told to index the columns; I did. and its still slow (slow as in, i never see the results, both mysql and sqlite freeze up on query). Help would be greatly appreciated. Here is the SQL SELECT equipment.`unitID` AS `equipment_unitID`, equipment.`fleetCode` AS `equipment_fleetCode`, equipment.type AS equipment_type, equipment.tiremap AS equipment_tiremap, tiremap.`TireID` AS `tiremap_TireID`, tiremap.`WorkMap` AS `tiremap_WorkMap`, tiremap.`Position` AS `tiremap_Position`, tiremap.`DepthMap` AS `tiremap_DepthMap`, tiremap.timestamp AS tiremap_timestamp, workreference.`aMap` AS `workreference_aMap`, workreference.`bMap` AS `workreference_bMap`, tirework.`RO` AS `tirework_RO`, tirework.location AS tirework_location, tirework.mileage AS tirework_mileage, tirework.`mechanicCode` AS `tirework_mechanicCode`, tirework.`partNumber` AS `tirework_partNumber`, tirework.`historyID` AS `tirework_historyID`, tirework.workmap AS tirework_workmap, tirework.timestamp AS tirework_timestamp FROM equipment, tiremap, workreference, tirework WHERE equipment.tiremap = tiremap.`TireID` AND tiremap.`WorkMap` = workreference.`aMap` AND workreference.`bMap` = tirework.workmap LIMIT 5 and here is the EXPLAIN for it id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE equipment ALL tiremap 14079 1 SIMPLE tiremap ref PRIMARY,WorkMap,TireID,WorkMap_2 PRIMARY 52 tire.equipment.tiremap 3 1 SIMPLE workreference ref aMap,bMap aMap 52 tire.tiremap.WorkMap 1 1 SIMPLE tirework eq_ref NewIndex1 NewIndex1 52 tire.workreference.bMap 1

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  • Warning: passing Argument 1 of "sqlite3_bind_text" from incompatible pointer type" What should I do

    - by Amarpreet
    Hi All, i am pretty new in iphone development. I have created one function to insert data into database. The code compiles successfully. But when comes to statement sqlite3_bind_text(sqlStatement, 1, [s UTF8String], -1, SQLITE_TRANSIENT); it does not do anything but hangs AND in warning it says "passing Argument 1 of "sqlite3_bind_text" from incompatible pointer type"" for all statements in Red colour The same code i am using to fetch the data from database and its working on other viewController. Below in the code. Its pretty straightforward. Please help guys. -(void) SaveData: (NSString *)FirstName: (NSString *)LastName: (NSString *)State: (NSString *)Street: (NSString *)PostCode { databaseName = @"Zen.sqlite"; NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDire ctory, NSUserDomainMask,YES); NSString *documentsDir=[documentPaths objectAtIndex:0]; databasePath=[documentsDir stringByAppendingPathComponent:databaseName]; sqlite3 *database; if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) { const char *sqlStatement = "insert into customers (FirstName, LastName, State, Street, PostCode) values(?, ?, ?, ?, ?)"; sqlite3_stmt *compiledStatement; sqlite3_prepare_v2(database, sqlStatement, -1, &compiledStatement, NULL); sqlite3_bind_text(sqlStatement, 1, [FirstName UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_text(sqlStatement,2,[LastName UTF8String],-1,SQLITE_TRANSIENT); sqlite3_bind_text(sqlStatement,3,[State UTF8String],-1,SQLITE_TRANSIENT); sqlite3_bind_text(sqlStatement,4,[Street UTF8String],-1,SQLITE_TRANSIENT); sqlite3_bind_text(sqlStatement,5,[PostCode UTF8String],-1,SQLITE_TRANSIENT); sqlite3_step(sqlStatement); sqlite3_finalize(compiledStatement); } sqlite3_close(database); }

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  • Will pool the connection help threading in sqlite (and how)?

    - by mamcx
    I currently use a singleton to acces my database (see related question) but now when try to add some background processing everything fall apart. I read the sqlite docs and found that sqlite could work thread-safe, but each thread must have their own db connection. I try using egodatabase that promise a sqlite wrapper with thread safety but is very buggy, so I return to my old FMDB library I start to see how use it in multi-thread way. Because I have all code with the idea of singleton, change everything will be expensive (and a lot of open/close connections could become slow), so I wonder if, as the sqlite docs hint, build a pooling for each connection will help. If is the case, how make it? How know wich connection get from the pool (because 2 threads can't share the connection)? I wonder if somebody already use sqlite in multu-threading with NSOperation or similar stuff, my searching only return "yeah, its possible" but let the details to my imagination...

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  • sql query - how to apply limit within group by

    - by Raj
    hey guys assuming i have a table named t1 with following fields: ROWID, CID, PID, Score, SortKey it has the following data: 1, C1, P1, 10, 1 2, C1, P2, 20, 2 3, C1, P3, 30, 3 4, C2, P4, 20, 3 5, C2, P5, 30, 2 6, C3, P6, 10, 1 7, C3, P7, 20, 2 what query do i write so that it applies group by on CID, but instead of returning me 1 single result per group, it returns me a max of 2 results per group. also where condition is score = 20 and i want the results ordered by CID and SortKey. If I had to run my query on above data, i would expect the following result: RESULTS FOR C1 - note: ROWID 1 is not considered as its score < 20 C1, P2, 20, 2 C1, P3, 30, 3 RESULTS FOR C2 - note: ROWID 5 appears before ROWID 4 as ROWID 5 has lesser value SortKey C2, P5, 30, 2 C2, P4, 20, 3 RESULTS FOR C3 - note: ROWID 6 does not appear as its score is less than 20 so only 1 record returned here C3, P7, 20, 2 IN SHORT, I WANT A LIMIT WITHIN A GROUP BY. I want the simplest solution and want to avoid temp tables. sub queries are fine. also note i am using sqlite for this

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  • SQLiteDataAdapter Update method returning 0

    - by Lirik
    I loaded 83 rows from my CSV file, but when I try to update the SQLite database I get 0 rows... I can't figure out what I'm doing wrong. The program outputs: Num rows loaded is 83 Num rows updated is 0 The source code is: public void InsertData(String csvFileName, String tableName) { String dir = Path.GetDirectoryName(csvFileName); String name = Path.GetFileName(csvFileName); using (OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + dir + @";Extended Properties=""Text;HDR=Yes;FMT=Delimited""")) { conn.Open(); using (OleDbDataAdapter adapter = new OleDbDataAdapter("SELECT * FROM " + name, conn)) { QuoteDataSet ds = new QuoteDataSet(); adapter.Fill(ds, tableName); Console.WriteLine("Num rows loaded is " + ds.Tags.Rows.Count); InsertData(ds, tableName); } } } public void InsertData(QuoteDataSet data, String tableName) { using (SQLiteConnection conn = new SQLiteConnection(_connectionString)) { using (SQLiteDataAdapter sqliteAdapter = new SQLiteDataAdapter("SELECT * FROM " + tableName, conn)) { using (new SQLiteCommandBuilder(sqliteAdapter)) { conn.Open(); Console.WriteLine("Num rows updated is " + sqliteAdapter.Update(data, tableName)); } } } } Any hints on why it's not updating the correct number of rows?

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  • SQL Query: How to determine "Seen during N hour" if given two DateTime time stamps?

    - by efess
    Hello all. I'm writing a statistics application based off a SQLite database. There is a table which records when users Login and Logout (SessionStart, SessionEnd DateTimes). What i'm looking for is a query that can show what hours user have been logged in, in sort of a line graph way- so between the hours of 12:00 and 1:00AM there were 60 users logged in (at any point), between the hours of 1:00 and 2:00AM there were 54 users logged in, etc... And I want to be able to run a SUM of this, which is why I can't bring the records into .NET and iterate through them that way. I've come up with a rather primative approach, a subquery for each hour of the day, however this approach has proved to be slow and slow. I need to be able to calculate this for a couple hundred thousand records in a split second.. SELECT case when (strftime('%s',datetime(date(sessionstart), '+0 hours')) > strftime('%s',sessionstart) AND strftime('%s',datetime(date(sessionstart), '+0 hours')) < strftime('%s',sessionend)) OR (strftime('%s',datetime(date(sessionstart), '+1 hours')) > strftime('%s',sessionstart) AND strftime('%s',datetime(date(sessionstart), '+1 hours')) < strftime('%s',sessionend)) OR (strftime('%s',datetime(date(sessionstart), '+0 hours')) < strftime('%s',sessionstart) AND strftime('%s',datetime(date(sessionstart), '+1 hours')) > strftime('%s',sessionend)) then 1 else 0 end as hour_zero, ... hour_one, ... hour_two, ........ hour_twentythree FROM UserSession I'm wondering what better way to determine if two DateTimes have been seen durring a particular hour (best case scenario, how many times it has crossed an hour if it was logged in multiple days, but not necessary)? The only other idea I had is have a "hour" table specific to this, and just tally up the hours the user has been seen at runtime, but I feel like this is more of a hack than the previous SQL. Any help would be greatly appreciated!

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  • Core Data, Bindings, value transformers : crash when saving

    - by Gael
    Hi, I am trying to store a PNG image in a core data store backed by an sqlite database. Since I intend to use this database on an iPhone I can't store NSImage objects directly. I wanted to use bindings and an NSValueTransformer subclass to handle the transcoding from the NSImage (obtained by an Image well on my GUI) to an NSData containing the PNG binary representation of the image. I wrote the following code for the ValueTransformer : + (Class)transformedValueClass { return [NSImage class]; } + (BOOL)allowsReverseTransformation { return YES; } - (id)transformedValue:(id)value { if (value == nil) return nil; return [[[NSImage alloc] initWithData:value] autorelease]; } - (id)reverseTransformedValue:(id)value { if (value == nil) return nil; if(![value isKindOfClass:[NSImage class]]) { NSLog(@"Type mismatch. Expecting NSImage"); } NSBitmapImageRep *bits = [[value representations] objectAtIndex: 0]; NSData *data = [bits representationUsingType:NSPNGFileType properties:nil]; return data; } The model has a transformable property configured with this NSValueTransformer. In Interface Builder a table column and an image well are both bound to this property and both have the proper value transformer name (an image dropped in the image well shows up in the table column). The transformer is registered and called every time an image is added or a row is reloaded (checked with NSLog() calls). The problem arises when I am trying to save the managed objects. The console output shows the error message : [NSImage length]: unrecognized selector sent to instance 0x1004933a0 It seems like core data is using the value transformer to obtain the NSImage back from the NSData and then tries to save the NSImage instead of the NSData. There are probably workarounds such as the one presented in this post but I would really like to understand why my approach is flawn. Thanks in advance for your ideas and explanations.

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  • SQL: Join multiple tables and get a grouped sum

    - by Scienceprodigy
    I have a database with 3 tables that have related data. One table has transactions, and the other two relate to transaction categories. Basically it's financial data, so each transaction has a category (i.e. "gasoline" for a gas purchase transaction). A short version of my Transactions table looks like this- Transactions Table: ________________________________ | ID | Type | Amount | Category | --------------------------------- I also have two more tables relating a category to a categories parent. So basically, every Category entry in the Transactions Table belongs to a parent category (i.e. "gasoline" would belong to say "Automotive Expenses"). For categories, and their parent, I have two tables - Category Children: ____________________________________________ | ID | Parent Category ID | Child Category | -------------------------------------------- Category Parent: ________________________ | ID | Parent Category | ------------------------ What I'm trying to do is query the database and have it return a total spending by parent category. To get "spending" the Type of transactions must be "Debit". I tried the following statement: SELECT category_parents.parent_category, SUM(amount) AS totals FROM (transactions INNER JOIN category_children ON transactions.category = 'category_children.child_category') INNER JOIN category_parents ON category_children.parent_category_id = category_parents._id WHERE trans_type = 'Debit' GROUP BY parent_category ORDER BY totals DESC but it gives me the following exception: 12-31 13:51:21.515: ERROR/Exception on query(4403): android.database.sqlite.SQLiteException: no such column: category_children.parent_category_id: , while compiling: SELECT category_parents.parent_category, SUM(amount) AS totals FROM (transactions INNER JOIN category_children ON transactions.category='category_children.child_category') INNER JOIN category_parents ON category_children.parent_category_id=category_parents._id where trans_type='Debit' group by parent_category order by totals desc Any help is appreciated. (EXTRA CREDIT: I also need to make another statement to do spending by child category, given the parent category)

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  • How do I join three tables with SQLalchemy and keeping all of the columns in one of the tables?

    - by jimka
    So, I have three tables: The class defenitions: engine = create_engine('sqlite://test.db', echo=False) SQLSession = sessionmaker(bind=engine) Base = declarative_base() class Channel(Base): __tablename__ = 'channel' id = Column(Integer, primary_key = True) title = Column(String) description = Column(String) link = Column(String) pubDate = Column(DateTime) class User(Base): __tablename__ = 'user' id = Column(Integer, primary_key = True) username = Column(String) password = Column(String) sessionId = Column(String) class Subscription(Base): __tablename__ = 'subscription' userId = Column(Integer, ForeignKey('user.id'), primary_key=True) channelId = Column(Integer, ForeignKey('channel.id'), primary_key=True) And the SQL commands that are executed to create them: CREATE TABLE subscription ( "userId" INTEGER NOT NULL, "channelId" INTEGER NOT NULL, PRIMARY KEY ("userId", "channelId"), FOREIGN KEY("userId") REFERENCES user (id), FOREIGN KEY("channelId") REFERENCES channel (id) ); CREATE TABLE user ( id INTEGER NOT NULL, username VARCHAR, password VARCHAR, "sessionId" VARCHAR, PRIMARY KEY (id) ); CREATE TABLE channel ( id INTEGER NOT NULL, title VARCHAR, description VARCHAR, link VARCHAR, "pubDate" TIMESTAMP, PRIMARY KEY (id) ); NOTE: I know user.username should be unique, need to fix that, and I'm not sure why SQLalchemy creates some row names with the double-quotes. And I'm trying to come up with a way to retrieve all of the channels, as well as an indication on what channels one particular user (identified by user.sessionId together with user.id) has a subscription on. For example, say we have four channels: channel1, channel2, channel3, channel4; a user: user1; who has a subscription on channel1 and channel4. The query for user1 would return something like: channel.id | channel.title | subscribed --------------------------------------- 1 channel1 True 2 channel2 False 3 channel3 False 4 channel4 True This is a best-case result, but since I have absolutely no clue as how to accomplish the subscribed column, I've been instead trying to get the particular users id in the rows where the user has a subscription and where a subscription is missing, just leave it blank. The database engine that I'm using together with SQLalchemy atm. is sqlite3 I've been scratching my head over this for two days now, I've no problem joining together all three by way of the subscription table but then all of the channels where the user does not have a subscription gets omitted. I hope I've managed to describe my problem sufficiently, thanks in advance.

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  • recommended format to save time with MJD + BCD format in database

    - by pierr
    Hi, There is a time represented in MJD and BCD format with 5 bytes .I am wondering what is the recommended format to save this date-time in the sqlite database so that user can search against it ? My first attempt is to save it just as it is, that is a 5 bytes string. The user will use the same format to search and the result will be converted to unix time by the user with following code. However, later, I was suggested to save the time in the integer - the UTC time, for example. But I can not find a standard way to do the conversion. I feel this is a common issue and would like to hear your comments. time_t sidate_to_unixtime(unsigned char sidate[]) { int k = 0; struct tm tm; double mjd; /* check for the undefined value */ if ((sidate[0] == 0xff) && (sidate[1] == 0xff) && (sidate[2] == 0xff) && (sidate[3] == 0xff) && (sidate[4] == 0xff)) { return -1; } memset(&tm, 0, sizeof(tm)); mjd = (sidate[0] << 8) | sidate[1]; tm.tm_year = (int) ((mjd - 15078.2) / 365.25); tm.tm_mon = (int) (((mjd - 14956.1) - (int) (tm.tm_year * 365.25)) / 30.6001); tm.tm_mday = (int) mjd - 14956 - (int) (tm.tm_year * 365.25) - (int) (tm.tm_mon * 30.6001); if ((tm.tm_mon == 14) || (tm.tm_mon == 15)) k = 1; tm.tm_year += k; tm.tm_mon = tm.tm_mon - 2 - k * 12; tm.tm_sec = bcd_to_integer(sidate[4]); tm.tm_min = bcd_to_integer(sidate[3]); tm.tm_hour = bcd_to_integer(sidate[2]); return mktime(&tm); }

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  • Qt 101: Why can't I use this class?

    - by Airjoe
    I have experience with C++ but I've never really used Qt before. I'm trying to connect to a SQLite database, so I found a tutorial here and am going with that. In the QtCreator IDE, I went to Add New -- C++ Class and in the header file pasted in the header the header from that link and in the .cpp file I pasted the source. My main.cpp looks like this: #include <QtGui/QApplication> #include "mainwindow.h" #include "databasemanager.h" #include <qlabel.h> int main(int argc, char *argv[]) { QApplication a(argc, argv); MainWindow w; w.show(); DatabaseManager db(); QLabel hello("nothing..."); if(db.openDB()){ hello.setText("Win!"); } else{ hello.setText("Lame!"); } hello.resize(100, 30); hello.show(); return a.exec(); } And I'm getting this error: main.cpp:13: error: request for member 'openDB' in 'db', which is of non-class type 'DatabaseManager()' Can anyone point me in the right direction? I know "copypaste" code isn't good, I just wanted to see if I could get DB connectivity working and I figured something like this would be simple... thanks for the help.

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  • Question regarding ideal database implementation for iPhone app

    - by Jeff
    So I have a question about the ideal setup for an app I am getting ready to build. The app is basically going to be a memorization tool and I already have an sqlite database full of content that I will be using for the app. The user will navigate through the contents of the database(using the uipickerview), and select something for memorization. If that row or cell of data is selected, it is put into a pool or a uitableview that is dedicated to showing which items you have in your "need to memorize" pool. When you go to that tableview, you can select the row, and the actual data would be populated. All information in the tableview would be deletable, in the event that they don't want it there anymore... Thats it. I know that with database interfacing, there are a few different options out there, in this particular setup, is core data the easiest approach? Is there any other way that would be better? I am just kind of looking for a point in the right direction, any help is greatly appreciated!!

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  • handle large Parcelable ArrayList in Android

    - by Gal Ben-Haim
    I'm developing an Android app that is a client to a JSON webservice API. I have classes of resource objects (some are nested) and I pass results from an IntentService that access the webserive using the Parcelable interface for all the resource classes. the webservice returns arrays or results that can be potentially large (because of the nesting, for example, a post object also contains comments array, each comment also contains a user object). currently I'm either inserting the results into a SQlite database or displaying them in a ListView. (my relevant methods are accepting ArrayList<resourceClass> as arguments). (some data need to be persistent stored and some should not). since I don't know what size of lists I can handle this way without reaching the memory limits, is this a good practice ? is it a better idea to save the parsed JSON to a local file immediately and pass the file path to the ResultReceiver, then either insert to database from that file or display the data ? is there a better way to handle this ? btw - I'm parsing the JSON as a stream with Gson's Reader so there shouldn't be memory issues at that stage.

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  • Select statement with multiple 'where' fields using same value without duplicating text

    - by kdbdallas
    I will start by saying that I don't think what I want can be done, but that said, I am hoping I am wrong and someone knows more than me. So here is your chance... Prove you are smarter than me :) I want to do a search against a SQLite table looking for any records that "are similar" without having to write out the query in long hand. To clarify this is how I know I can write the query: select * from Articles where title like '%Bla%' or category like '%Bla%' or post like '%Bla%' This works and is not a huge deal if you are only checking against a couple of columns, but if you need to check against a bunch then your query can get really long and nasty looking really fast, not to mention the chance for typos. (ie: 'Bla%' instead of '%Bla%') What I am wondering is if there is a short hand way to do this? *This next code does not work the way I want, but just shows kind of what I am looking for select * from Articles where title or category or post like '%Bla%' Anyone know if there is a way to specify that multiple 'where' columns should use the same search value without listing that same search value for every column? Thanks in advance!

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