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• Memcache key generation strategy

  - by Maxim Veksler

  Given function f1 which receives n String arguments, would be considered better random key generation strategy for memcache for the scenario described below ? Our Memcache client does internal md5sum hashing on the keys it gets public class MemcacheClient { public Object get(String key) { String md5 = Md5sum.md5(key) // Talk to memcached to get the Serialization... return memcached(md5); } } First option public static String f1(String s1, String s2, String s3, String s4) { String key = s1 + s2 + s3 + s4; return get(key); } Second option /** * Calculate hash from Strings * * @param objects vararg list of String's * * @return calculated md5sum hash */ public static String stringHash(Object... strings) { if(strings == null) throw new NullPointerException("D'oh! Can't calculate hash for null"); MD5 md5sum = new MD5(); // if(prevHash != null) // md5sum.Update(prevHash); for(int i = 0; i < strings.length; i++) { if(strings[i] != null) { md5sum.Update("_" + strings[i] + "_"); // Convert to String... } else { // If object is null, allow minimum entropy by hashing it's position md5sum.Update("_" + i + "_"); } } return md5sum.asHex(); } public static String f1(String s1, String s2, String s3, String s4) { String key = stringHash(s1, s2, s3, s4); return get(key); } Note that the possible problem with the second option is that we are doing second md5sum (in the memcache client) on an already md5sum'ed digest result. Thanks for reading, Maxim.

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• Example: Communication between Activity and Service using Messaging

  - by Lance Lefebure

  I couldn't find any examples of how to send messages between an activity and a service, and spent far too many hours figuring this out. Here is an example project for others to reference. This example allows you to start or stop a service directly, and separately bind/unbind from the service. When the service is running, it increments a number at 10Hz. If the activity is bound to the service, it will display the current value. Data is transferred as an Integer and as a String so you can see how to do that two different ways. There are also buttons in the activity to send messages to the service (changes the increment-by value). Screenshot: AndroidManifest.xml: <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.exampleservice" android:versionCode="1" android:versionName="1.0"> <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".MainActivity" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <service android:name=".MyService"></service> </application> <uses-sdk android:minSdkVersion="8" /> </manifest> res\values\strings.xml: <?xml version="1.0" encoding="utf-8"?> <resources> <string name="app_name">ExampleService</string> <string name="service_started">Example Service started</string> <string name="service_label">Example Service Label</string> </resources> res\layout\main.xml: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <RelativeLayout android:id="@+id/RelativeLayout01" android:layout_width="fill_parent" android:layout_height="wrap_content"> <Button android:id="@+id/btnStart" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Start Service"></Button> <Button android:id="@+id/btnStop" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Stop Service" android:layout_alignParentRight="true"></Button> </RelativeLayout> <RelativeLayout android:id="@+id/RelativeLayout02" android:layout_width="fill_parent" android:layout_height="wrap_content"> <Button android:id="@+id/btnBind" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Bind to Service"></Button> <Button android:id="@+id/btnUnbind" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Unbind from Service" android:layout_alignParentRight="true"></Button> </RelativeLayout> <TextView android:id="@+id/textStatus" android:textSize="24sp" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="Status Goes Here" /> <TextView android:id="@+id/textIntValue" android:textSize="24sp" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="Integer Value Goes Here" /> <TextView android:id="@+id/textStrValue" android:textSize="24sp" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="String Value Goes Here" /> <RelativeLayout android:id="@+id/RelativeLayout03" android:layout_width="fill_parent" android:layout_height="wrap_content"> <Button android:id="@+id/btnUpby1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Increment by 1"></Button> <Button android:id="@+id/btnUpby10" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Increment by 10" android:layout_alignParentRight="true"></Button> </RelativeLayout> </LinearLayout> src\com.exampleservice\MainActivity.java: package com.exampleservice; import android.app.Activity; import android.content.ComponentName; import android.content.Context; import android.content.Intent; import android.content.ServiceConnection; import android.os.Bundle; import android.os.Handler; import android.os.IBinder; import android.os.Message; import android.os.Messenger; import android.os.RemoteException; import android.util.Log; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.TextView; public class MainActivity extends Activity { Button btnStart, btnStop, btnBind, btnUnbind, btnUpby1, btnUpby10; TextView textStatus, textIntValue, textStrValue; Messenger mService = null; boolean mIsBound; final Messenger mMessenger = new Messenger(new IncomingHandler()); class IncomingHandler extends Handler { @Override public void handleMessage(Message msg) { switch (msg.what) { case MyService.MSG_SET_INT_VALUE: textIntValue.setText("Int Message: " + msg.arg1); break; case MyService.MSG_SET_STRING_VALUE: String str1 = msg.getData().getString("str1"); textStrValue.setText("Str Message: " + str1); break; default: super.handleMessage(msg); } } } private ServiceConnection mConnection = new ServiceConnection() { public void onServiceConnected(ComponentName className, IBinder service) { mService = new Messenger(service); textStatus.setText("Attached."); try { Message msg = Message.obtain(null, MyService.MSG_REGISTER_CLIENT); msg.replyTo = mMessenger; mService.send(msg); } catch (RemoteException e) { // In this case the service has crashed before we could even do anything with it } } public void onServiceDisconnected(ComponentName className) { // This is called when the connection with the service has been unexpectedly disconnected - process crashed. mService = null; textStatus.setText("Disconnected."); } }; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); btnStart = (Button)findViewById(R.id.btnStart); btnStop = (Button)findViewById(R.id.btnStop); btnBind = (Button)findViewById(R.id.btnBind); btnUnbind = (Button)findViewById(R.id.btnUnbind); textStatus = (TextView)findViewById(R.id.textStatus); textIntValue = (TextView)findViewById(R.id.textIntValue); textStrValue = (TextView)findViewById(R.id.textStrValue); btnUpby1 = (Button)findViewById(R.id.btnUpby1); btnUpby10 = (Button)findViewById(R.id.btnUpby10); btnStart.setOnClickListener(btnStartListener); btnStop.setOnClickListener(btnStopListener); btnBind.setOnClickListener(btnBindListener); btnUnbind.setOnClickListener(btnUnbindListener); btnUpby1.setOnClickListener(btnUpby1Listener); btnUpby10.setOnClickListener(btnUpby10Listener); restoreMe(savedInstanceState); CheckIfServiceIsRunning(); } @Override protected void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); outState.putString("textStatus", textStatus.getText().toString()); outState.putString("textIntValue", textIntValue.getText().toString()); outState.putString("textStrValue", textStrValue.getText().toString()); } private void restoreMe(Bundle state) { if (state!=null) { textStatus.setText(state.getString("textStatus")); textIntValue.setText(state.getString("textIntValue")); textStrValue.setText(state.getString("textStrValue")); } } private void CheckIfServiceIsRunning() { //If the service is running when the activity starts, we want to automatically bind to it. if (MyService.isRunning()) { doBindService(); } } private OnClickListener btnStartListener = new OnClickListener() { public void onClick(View v){ startService(new Intent(MainActivity.this, MyService.class)); } }; private OnClickListener btnStopListener = new OnClickListener() { public void onClick(View v){ doUnbindService(); stopService(new Intent(MainActivity.this, MyService.class)); } }; private OnClickListener btnBindListener = new OnClickListener() { public void onClick(View v){ doBindService(); } }; private OnClickListener btnUnbindListener = new OnClickListener() { public void onClick(View v){ doUnbindService(); } }; private OnClickListener btnUpby1Listener = new OnClickListener() { public void onClick(View v){ sendMessageToService(1); } }; private OnClickListener btnUpby10Listener = new OnClickListener() { public void onClick(View v){ sendMessageToService(10); } }; private void sendMessageToService(int intvaluetosend) { if (mIsBound) { if (mService != null) { try { Message msg = Message.obtain(null, MyService.MSG_SET_INT_VALUE, intvaluetosend, 0); msg.replyTo = mMessenger; mService.send(msg); } catch (RemoteException e) { } } } } void doBindService() { bindService(new Intent(this, MyService.class), mConnection, Context.BIND_AUTO_CREATE); mIsBound = true; textStatus.setText("Binding."); } void doUnbindService() { if (mIsBound) { // If we have received the service, and hence registered with it, then now is the time to unregister. if (mService != null) { try { Message msg = Message.obtain(null, MyService.MSG_UNREGISTER_CLIENT); msg.replyTo = mMessenger; mService.send(msg); } catch (RemoteException e) { // There is nothing special we need to do if the service has crashed. } } // Detach our existing connection. unbindService(mConnection); mIsBound = false; textStatus.setText("Unbinding."); } } @Override protected void onDestroy() { super.onDestroy(); try { doUnbindService(); } catch (Throwable t) { Log.e("MainActivity", "Failed to unbind from the service", t); } } } src\com.exampleservice\MyService.java: package com.exampleservice; import java.util.ArrayList; import java.util.Timer; import java.util.TimerTask; import android.app.Notification; import android.app.NotificationManager; import android.app.PendingIntent; import android.app.Service; import android.content.Intent; import android.os.Bundle; import android.os.Handler; import android.os.IBinder; import android.os.Message; import android.os.Messenger; import android.os.RemoteException; import android.util.Log; public class MyService extends Service { private NotificationManager nm; private Timer timer = new Timer(); private int counter = 0, incrementby = 1; private static boolean isRunning = false; ArrayList<Messenger> mClients = new ArrayList<Messenger>(); // Keeps track of all current registered clients. int mValue = 0; // Holds last value set by a client. static final int MSG_REGISTER_CLIENT = 1; static final int MSG_UNREGISTER_CLIENT = 2; static final int MSG_SET_INT_VALUE = 3; static final int MSG_SET_STRING_VALUE = 4; final Messenger mMessenger = new Messenger(new IncomingHandler()); // Target we publish for clients to send messages to IncomingHandler. @Override public IBinder onBind(Intent intent) { return mMessenger.getBinder(); } class IncomingHandler extends Handler { // Handler of incoming messages from clients. @Override public void handleMessage(Message msg) { switch (msg.what) { case MSG_REGISTER_CLIENT: mClients.add(msg.replyTo); break; case MSG_UNREGISTER_CLIENT: mClients.remove(msg.replyTo); break; case MSG_SET_INT_VALUE: incrementby = msg.arg1; break; default: super.handleMessage(msg); } } } private void sendMessageToUI(int intvaluetosend) { for (int i=mClients.size()-1; i>=0; i--) { try { // Send data as an Integer mClients.get(i).send(Message.obtain(null, MSG_SET_INT_VALUE, intvaluetosend, 0)); //Send data as a String Bundle b = new Bundle(); b.putString("str1", "ab" + intvaluetosend + "cd"); Message msg = Message.obtain(null, MSG_SET_STRING_VALUE); msg.setData(b); mClients.get(i).send(msg); } catch (RemoteException e) { // The client is dead. Remove it from the list; we are going through the list from back to front so this is safe to do inside the loop. mClients.remove(i); } } } @Override public void onCreate() { super.onCreate(); Log.i("MyService", "Service Started."); showNotification(); timer.scheduleAtFixedRate(new TimerTask(){ public void run() {onTimerTick();}}, 0, 100L); isRunning = true; } private void showNotification() { nm = (NotificationManager)getSystemService(NOTIFICATION_SERVICE); // In this sample, we'll use the same text for the ticker and the expanded notification CharSequence text = getText(R.string.service_started); // Set the icon, scrolling text and timestamp Notification notification = new Notification(R.drawable.icon, text, System.currentTimeMillis()); // The PendingIntent to launch our activity if the user selects this notification PendingIntent contentIntent = PendingIntent.getActivity(this, 0, new Intent(this, MainActivity.class), 0); // Set the info for the views that show in the notification panel. notification.setLatestEventInfo(this, getText(R.string.service_label), text, contentIntent); // Send the notification. // We use a layout id because it is a unique number. We use it later to cancel. nm.notify(R.string.service_started, notification); } @Override public int onStartCommand(Intent intent, int flags, int startId) { Log.i("MyService", "Received start id " + startId + ": " + intent); return START_STICKY; // run until explicitly stopped. } public static boolean isRunning() { return isRunning; } private void onTimerTick() { Log.i("TimerTick", "Timer doing work." + counter); try { counter += incrementby; sendMessageToUI(counter); } catch (Throwable t) { //you should always ultimately catch all exceptions in timer tasks. Log.e("TimerTick", "Timer Tick Failed.", t); } } @Override public void onDestroy() { super.onDestroy(); if (timer != null) {timer.cancel();} counter=0; nm.cancel(R.string.service_started); // Cancel the persistent notification. Log.i("MyService", "Service Stopped."); isRunning = false; } }

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• Reverse ?? operator

  - by HeavyWave

  Is it possible to do something like this in C#? logger != null ? logger.Log(message) : ; // do nothing if null or logger !?? logger.Log(message); // do only if not null

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• Adjust SQL query to DB2

  - by Guy Roth

  Part of a complex query that our app is running contains the lines: ...(inner query) SELECT ... NULL as column_A, NULL as column_B, ... FROM ... This syntax of creating columns with null values is not allowed in DB2 altough it is totally OK in MSSQL and Oracle DBs. Technically I can change it to: '' as column_A, '' as column_B, But this doesn't have exactly the same meaning and can damage our calculation results. How can I create columns with null values in DB2 using other syntax??

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• Working with Hibernate Queries

  - by jschoen

  I am new to hibernate queries, and trying to get a grasp on how everything works. I am using Hibernate 3 with Netbeans 6.5. I have a basic project set up and have been playing around with how to do everything. I started with essentially a search query. Where the user can enter values into one or more fields. The table would be Person with the columns first_name, middle_name, last_name for the sake of the example. The first way I found was to have a method that took firstName, middleName, and lastName as parameters: Session session = HibernateUtil.getSessionFactory().getCurrentSession(); Transaction tx = session.beginTransaction(); String query = "from Person where (first_name = :firstName or :firstName is null) "+ "and (middle_name = :middleName or :middleName is null) " "and (last_name = :lastname or :lastName is null)"; Query q = session.createQuery(query); q.setString("firstName", firstName); q.setString("middleName", middleName); q.setString("lastName", lastName); List<Person> results = (List<Person>) q.list(); This did not sit well with me, since it seemed like I should not have to write that much, and well, that I was doing it wrong. So I kept digging and found another way: Session session = HibernateUtil.getSessionFactory().getCurrentSession(); Transaction tx = session.beginTransaction(); Criteria crit = session.createCriteria(Person.class); if (firstName != null) { crit.add(Expression.ge("firstName", firstName); } if (middleName != null) { crit.add(Expression.ge("middleName", middleName); } if (lastName != null) { crit.add(Expression.ge("lastName", lastName); } List<Person> results = (List<Person>) crit.list(); So what I am trying to figure out is which way is the preferred way for this type of query? Criteria or Query? Why? I am guessing that Criteria is the preferred way and you should only use Query when you need to write it by hand for performance type reasons. Am I close?

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• Impact of ordering of correlated subqueries within a projection

  - by Michael Petito

  I'm noticing something a bit unexpected with how SQL Server (SQL Server 2008 in this case) treats correlated subqueries within a select statement. My assumption was that a query plan should not be affected by the mere order in which subqueries (or columns, for that matter) are written within the projection clause of the select statement. However, this does not appear to be the case. Consider the following two queries, which are identical except for the ordering of the subqueries within the CTE: --query 1: subquery for Color is second WITH vw AS ( SELECT p.[ID], (SELECT TOP(1) [FirstName] FROM [Preference] WHERE p.ID = ID AND [FirstName] IS NOT NULL ORDER BY [LastModified] DESC) [FirstName], (SELECT TOP(1) [Color] FROM [Preference] WHERE p.ID = ID AND [Color] IS NOT NULL ORDER BY [LastModified] DESC) [Color] FROM Person p ) SELECT ID, Color, FirstName FROM vw WHERE Color = 'Gray'; --query 2: subquery for Color is first WITH vw AS ( SELECT p.[ID], (SELECT TOP(1) [Color] FROM [Preference] WHERE p.ID = ID AND [Color] IS NOT NULL ORDER BY [LastModified] DESC) [Color], (SELECT TOP(1) [FirstName] FROM [Preference] WHERE p.ID = ID AND [FirstName] IS NOT NULL ORDER BY [LastModified] DESC) [FirstName] FROM Person p ) SELECT ID, Color, FirstName FROM vw WHERE Color = 'Gray'; If you look at the two query plans, you'll see that an outer join is used for each subquery and that the order of the joins is the same as the order the subqueries are written. There is a filter applied to the result of the outer join for color, to filter out rows where the color is not 'Gray'. (It's odd to me that SQL would use an outer join for the color subquery since I have a non-null constraint on the result of the color subquery, but OK.) Most of the rows are removed by the color filter. The result is that query 2 is significantly cheaper than query 1 because fewer rows are involved with the second join. All reasons for constructing such a statement aside, is this an expected behavior? Shouldn't SQL server opt to move the filter as early as possible in the query plan, regardless of the order the subqueries are written?

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• sort the "rollup" in group by

  - by shantanuo

  I found that the "with rollup" option used with group by is very useful. But it does not behave with "order by" clause. Is there any way to order by the way I want as well as calculate the sub-totals? CREATE TABLE `mygroup` ( `id` int(11) default NULL, `country` varchar(100) default NULL ) ENGINE=MyISAM ; INSERT INTO `mygroup` VALUES (1,'India'),(5,'India'),(8,'India'),(18,'China'),(28,'China'),(28,'China'); mysql>select country, sum(id) from mygroup group by country with rollup; +---------+---------+ | country | sum(id) | +---------+---------+ | China | 74 | | India | 14 | | NULL | 88 | +---------+---------+ 3 rows in set (0.00 sec) mysql>select country, sum(id) as cnt from mygroup group by country order by cnt ; +---------+------+ | country | cnt | +---------+------+ | India | 14 | | China | 74 | +---------+------+ 2 rows in set (0.00 sec) mysql>select country, sum(id) as cnt from mygroup group by country with rollup order by cnt; ERROR 1221 (HY000): Incorrect usage of CUBE/ROLLUP and ORDER BY Expected Result: +---------+------+ | country | cnt | +---------+------+ | India | 14 | | China | 74 | | NULL | 88 | +---------+---------+ 3 rows in set (0.00 sec)

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• Windows.Networking.EndpointPair constructor parameters

  - by ComFreek

  I want to create a new EndpointPair object: // hostname is a string // port is an integer var endpointPair = new Windows.Networking.EndpointPair(null, null, hostname, port); But I always get this error: 0x800a000d - JavaScript runtime error: Type mismatch I've already tried the following: converting port to a string passing "" instead of null for the first two Parameters. (null should be okay if the documentation here, under the section Remarks, is right) passing no Parameters, but that ends up in an "too few parameters" error message Above all, the documentation about the constructor has been removed (as of September 4, 2012): http://msdn.microsoft.com/en-us/library/windows/apps/windows.networking.endpointpair.endpointpair.aspx

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• JavaScript: How to get the instance name of an object

  - by Quandary

  I use the below code to write code to query a web method in a specified interval. now in the this.Poll function I have to do this.tmo = setTimeout(this.strInstanceName + ".Poll()", this.iInterval); instead of this.tmo = setTimeout(this.Poll(), this.iInterval); because IE looses the this object after setTimeout So I have to pass the class it's instance name: var objPoll = new cPoll("objPoll"); How can I get the instance name without passing it as parameter ? I want to have it outta there ! <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head> <title>Intervall-Test</title> <script type="text/javascript" language="javascript"> function test() { alert("Test"); test.tmo = setTimeout(test, 2000); test.Clear = function() { clearTimeout(test.tmo); } } function cPoll(strInstanceName) { this.strInstanceName = strInstanceName ; this.iInterval = 2000; this.tmo=null; this.cbFunction=null; alert(this.Name ); this.Poll = function() { this.cbFunction(); this.tmo = setTimeout(this.strInstanceName + ".Poll()", this.iInterval); } this.Start = function(pCallBackFunction, iIntervalParameter) { if(this.tmo != null) this.Stop(); if(iIntervalParameter && iIntervalParameter > 0) this.iInterval=iIntervalParameter; this.cbFunction=pCallBackFunction; if(this.cbFunction!=null) this.Poll(); else alert("Invalid or no callback function specified"); } this.Stop = function() { if(this.tmo != null) { clearTimeout(this.tmo); this.tmo=null; } } } function CallBackFunction() { alert("PollCallBack"); } // test(); // test.Clear(); var objPoll = new cPoll("objPoll"); </script> </head> <body> <h1>Test</h1> <input type="Button" value="Start polling" onclick="objPoll.Start(CallBackFunction,3000);" /> <input type="Button" value="Stop polling" onclick="objPoll.Stop();" /> </body> </html>

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• i want to search in sql server with must have parameter in one colunm

  - by sherif4csharp

  hello i am usning c# and ms SQL server 2008 i have table like this id | propertyTypeId | FinishingQualityId | title | Description | features 1 1 2 prop1 propDEsc1 1,3,5,7 2 2 3 prop2 propDEsc2 1,3 3 6 5 prop3 propDEsc3 1 4 5 4 prop4 propDEsc4 3,5 5 4 6 prop5 propDEsc5 5,7 6 4 6 prop6 propDEsc6 and here is my stored code (search in the same table) create stored procdures propertySearch as @Id int = null, @pageSize float , @pageIndex int, @totalpageCount int output, @title nvarchar(150) =null , @propertyTypeid int = null , @finishingqualityid int = null , @features nvarchar(max) = null , -- this parameter send like 1,3 ( for example) begin select row_number () as TempId over( order by id) , id,title,description,propertyTypeId,propertyType.name,finishingQualityId,finishingQuality.Name,freatures into #TempTable from property join propertyType on propertyType.id= property.propertyTypeId join finishingQuality on finishingQuality.id = property.finishingQualityId where property.id = isnull(@id,property.id ) and proprty.PropertyTypeId= isnull(@propertyTypeid,property.propertyTypeId) select totalpageconunt = ((select count(*) from #TempTable )/@pageSize ) select * from #TempTable where tempid between (@pageindex-1)*@pagesize +1 and (@pageindex*@pageSize) end go i can't here filter the table by feature i sent. this table has to many rows i want to add to this stored code to filter data for example when i send 1,3 in features parameter i want to return row number one and two in the example table i write in this post (want to get the data from table must have the feature I send) many thanks for every one helped me and will help

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• How to create nonclustered index in Create Table.

  - by isthatacode

  Create table FavoriteDish ( FavID int identity (1,1) primary key not null, DishID int references Dishes(DishID) not null , CelebrityName nvarchar(100) nonclustered not null ) This results in - Incorrect syntax near the keyword 'nonclustered'. I referred the MSDN help for create table syntax. I am not sure whats wrong here? Thanks for reading.

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• recv returns old data

  - by anon

  This loop is supposed to take data from a socket line by line and put it in a buffer. For some reason, when there is no new data to return, recv returns the last couple lines it got. I was able to stop the bug by commenting out the first recv, but then I cant tell how long the next line will be. I know it's not a while(this->connected){ memset(buf, '\0', sizeof(buf)); recv(this->sock, buf, sizeof(buf), MSG_PEEK); //get length of next message ptr = strstr(buf, "\r\n"); if (ptr == NULL) continue; err = recv(this->sock, buf, (ptr-buf), NULL); //get next message printf("--%db\n%s\n", err, buf); tok[0] = strtok(buf, " "); for(i=1;tok[i-1]!=NULL;i++) tok[i] = strtok(NULL, " "); //do more stuff }

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• How would I best address this object type heirachy? Some kind of enum heirarchy?

  - by FerretallicA

  I'm curious as to any solutions out there for addressing object heirarchies in an ORM approach (in this instance, using Entity Framework 4). I'm working through some docs on EF4 and trying to apply it to a simple inventory tracking program. The possible types for inventory to fall into are as follows: INVENTORY ITEM TYPES: Hardware PC Desktop Server Laptop Accessory Input (keyboards, scanners etc) Output (monitors, printers etc) Storage (USB sticks, tape drives etc) Communication (network cards, routers etc) Software What recommendations are there for handling enums in a situation like this? Are enums even the solution? I don't really want to have a ridiculously normalised database for such a relatively simple experiment (eg tables for InventoryType, InventorySubtype, InventoryTypeToSubtype etc). I don't really want to over-complicate my data model with each subtype being inherited even though no additional properties or methods are included (except PC types which would ideally have associated accessories and software but that's probably out of scope here). It feels like there should be a really simple, elegant solution to this but I can't put my finger on it. Any assistance or input appreciated!

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• Dictionary keys don't contain a key that's already contained in keys

  - by ran

  Why is the following 'exist' boolean variable getting a value of false??? foreach (Cell existCell in this.decoratorByCell.Keys) { //this call yield the same hashcode for both cells. still exist==false bool exist = this.decoratorByCell.ContainsKey(existCell); } I've overridden GetHashCode() & Equals() Methods as follows: public override int GetHashCode() { string nodePath = GetNodePath(); return nodePath.GetHashCode() + m_ownerColumn.GetHashCode(); } public bool Equals(Cell other) { bool nodesEqual = (other.OwnerNode == null && this.OwnerNode == null) || (other.GetNodePath() == this.GetNodePath()); bool columnsEqual = (other.OwnerColumn == null && this.OwnerColumn == null) || (other.OwnerColumn == this.OwnerColumn); bool treesEqual = (this.m_ownerTree == other.m_ownerTree); return (nodesEqual && columnsEqual && treesEqual); }

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• Linq to sql Error "Data at the root level is invalid " for nullable xml column

  - by Mukesh

  I have Created a table like CREATE TABLE [dbo].[tab1]( [Id] [int] NOT NULL, [Name] [varchar](100) NOT NULL, [Meta] [xml] NULL, CONSTRAINT [PK_tab1] PRIMARY KEY CLUSTERED ( [Id] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY] When I am doing linq to sql query to fetch a data it throw an error "data at the root level is invalid linq". In further investigation I come to know that the meta column is null in that case. In real it is nullable Do I have to remove the nullable and set some blank root node as default or there is some another way to get rid of the error. My linq Query which throws error var obj1= (from obj in dbContext.tab1s where obj.id== 123 select obj).FirstOrDefault<Tab1>();

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• sqllite - sql question 101

  - by qstar

  Hi, I would do something like this* select * from cars_table where body not equal to null. select * from cars_table where values not equal to null And id = "3" I know the syntax for 'not equal' is <, but i get an empty results. For the second part, I want to get a result set where it only returns the columns that have a value. So, if the value is null, then don't include that column. Thanks

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• How to select the first row for each group in MySQL?

  - by Jader Dias

  In C# it would be like this: table .GroupBy(row => row.SomeColumn) .Select(group => group .OrderBy(row => row.AnotherColumn) .First() ) Linq-To-Sql translates it to the following T-SQL code: SELECT [t3].[AnotherColumn], [t3].[SomeColumn] FROM ( SELECT [t0].[SomeColumn] FROM [Table] AS [t0] GROUP BY [t0].[SomeColumn] ) AS [t1] OUTER APPLY ( SELECT TOP (1) [t2].[AnotherColumn], [t2].[SomeColumn] FROM [Table] AS [t2] WHERE (([t1].[SomeColumn] IS NULL) AND ([t2].[SomeColumn] IS NULL)) OR (([t1].[SomeColumn] IS NOT NULL) AND ([t2].[SomeColumn] IS NOT NULL) AND ([t1].[SomeColumn] = [t2].[SomeColumn])) ORDER BY [t2].[AnotherColumn] ) AS [t3] ORDER BY [t3].[AnotherColumn] But it is uncompatible with MySQL.

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• Select Multiple Images Using GalleryView

  - by hwrdprkns

  Hi guys, I was just wondering if Android had built in code so that I could select multiple images in a gallery-view and then have those images exported as filenames in a string array(ex /sdcard/~f1.jpg, /sdcard/~f2.jpg,...). I have the gallery code here, but I'm not sure what modifications need to be made. Any help is appreciated. Thanks! // take_picture = (Button)findViewById(R.id.take_picture); // Here we set up a string array of the thumbnail ID column we want to // get back String[] proj = { MediaStore.Images.Thumbnails._ID }; if(proj.length == 0) { nopic.setVisibility(View.VISIBLE); } // Now we create the cursor pointing to the external thumbnail store cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, proj, // Which // columns // to // return null, // WHERE clause; which rows to return (all rows) null, // WHERE clause selection arguments (none) null); // Order-by clause (ascending by name) /* take_picture.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { Intent i = new Intent(GalleryActivity.this, CameraActivity.class); startActivity(i); } }); */ // We now get the column index of the thumbnail id column_index = cursor .getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID); // Reference the Gallery view g = (Gallery) findViewById(R.id.gallery); if(proj.length == 0) { nopic.setVisibility(View.VISIBLE); g.setVisibility(View.GONE); } // Set the adapter to our custom adapter (below) g.setAdapter(new ImageAdapter(this)); // Set a item click listener, and just Toast the clicked position g.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView parent, View v, int position, long id) { // Now we want to actually get the data location of the file String[] proj = { MediaStore.Images.Media.DATA }; // We request our cursor again cursor = managedQuery( MediaStore.Images.Media.EXTERNAL_CONTENT_URI, proj, // Which // columns // to // return null, // WHERE clause; which rows to return (all rows) null, // WHERE clause selection arguments (none) null); // Order-by clause (ascending by name) // We want to get the column index for the data uri column_index = cursor .getColumnIndexOrThrow(MediaStore.Images.Media.DATA); // Lets move to the selected item in the cursor cursor.moveToPosition((int) g.getSelectedItemId()); // And here we get the filename String filename = cursor.getString(column_index); Log.v("GalleryActivity", filename); Toast.makeText(GalleryActivity.this, filename, Toast.LENGTH_SHORT).show(); setPrefs(filename); Intent i = new Intent(GalleryActivity.this, OtherClass.class); startActivity(i); } }); } And the ImageAdapter code here: public class ImageAdapter extends BaseAdapter { int mGalleryItemBackground; public ImageAdapter(Context c) { mContext = c; // See res/values/attrs.xml for the that defines // Gallery1. TypedArray a = obtainStyledAttributes(R.styleable.Gallery); mGalleryItemBackground = a.getResourceId( R.styleable.Gallery_android_galleryItemBackground, 0); a.recycle(); } public int getCount() { return cursor.getCount(); } public Object getItem(int position) { return position; } public long getItemId(int position) { return position; } public View getView(int position, View convertView, ViewGroup parent) { ImageView i = new ImageView(mContext); if (convertView == null) { cursor.moveToPosition(position); int id = cursor.getInt(column_index); i.setImageURI(Uri.withAppendedPath( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, "" + id)); i.setScaleType(ImageView.ScaleType.FIT_XY); i.setLayoutParams(new Gallery.LayoutParams(200, 200)); // The preferred Gallery item background i.setBackgroundResource(mGalleryItemBackground); } return i; } } Again any help is appreciateds! Just to let you guys know, the gallery works fine (for one image) as in it exports the filename correctly. Just need to know if there is an easy way to select multiples and export them. Thanks again!

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• How to write to a varchar(max) column using ODBC

  - by andyjohnson

  Summary: I'm trying to write a text string to a column of type varchar(max) using ODBC and SQL Server 2005. It fails if the length of the string is greater than 8000. Help! I have some C++ code that uses ODBC (SQL Native Client) to write a text string to a table. If I change the column from, say, varchar(100) to varchar(max) and try to write a string with length greater than 8000, the write fails with the following error [Microsoft][ODBC SQL Server Driver]String data, right truncation So, can anyone advise me on if this can be done, and how? Some example (not production) code that shows what I'm trying to do: SQLHENV hEnv = NULL; SQLRETURN iError = SQLAllocEnv(&hEnv); HDBC hDbc = NULL; SQLAllocConnect(hEnv, &hDbc); const char* pszConnStr = "Driver={SQL Server};Server=127.0.0.1;Database=MyTestDB"; UCHAR szConnectOut[SQL_MAX_MESSAGE_LENGTH]; SWORD iConnectOutLen = 0; iError = SQLDriverConnect(hDbc, NULL, (unsigned char*)pszConnStr, SQL_NTS, szConnectOut, (SQL_MAX_MESSAGE_LENGTH-1), &iConnectOutLen, SQL_DRIVER_COMPLETE); HSTMT hStmt = NULL; iError = SQLAllocStmt(hDbc, &hStmt); const char* pszSQL = "INSERT INTO MyTestTable (LongStr) VALUES (?)"; iError = SQLPrepare(hStmt, (SQLCHAR*)pszSQL, SQL_NTS); char* pszBigString = AllocBigString(8001); iError = SQLSetParam(hStmt, 1, SQL_C_CHAR, SQL_VARCHAR, 0, 0, (SQLPOINTER)pszBigString, NULL); iError = SQLExecute(hStmt); // Returns SQL_ERROR if pszBigString len > 8000 The table MyTestTable contains a single colum defined as varchar(max). The function AllocBigString (not shown) creates a string of arbitrary length. I understand that previous versions of SQL Server had an 8000 character limit to varchars, but not why is this happening in SQL 2005? Thanks, Andy

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• Import Contacts from .vcf file in Android 2.1

  - by Prateek Jain

  Hi All, I am able to retrieve all contacts from android in .vcf file using following code. ContentResolver cr = getContentResolver(); Cursor cur = cr.query(ContactsContract.Contacts.CONTENT_URI,null, null, null, null); String lookupKey = cur.getString(cur.getColumnIndex(ContactsContract.Contacts.LOOKUP_KEY)); Uri uri = Uri.withAppendedPath(ContactsContract.Contacts.CONTENT_VCARD_URI, lookupKey); System.out.println("The value is " + cr.getType(uri)); AssetFileDescriptor fd = this.getContentResolver().openAssetFileDescriptor(uri, "r"); FileInputStream fis = fd.createInputStream(); I don't know how to use this .vcf file to import all these contacts using code. The .vcf file contains all the details of all contacts including photos etc. Cheers, Prateek

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• Valgrind says "stack allocation," I say "heap allocation"

  - by Joel J. Adamson

  Dear Friends, I am trying to trace a segfault with valgrind. I get the following message from valgrind: ==3683== Conditional jump or move depends on uninitialised value(s) ==3683== at 0x4C277C5: sparse_mat_mat_kron (sparse.c:165) ==3683== by 0x4C2706E: rec_mating (rec.c:176) ==3683== by 0x401C1C: age_dep_iterate (age_dep.c:287) ==3683== by 0x4014CB: main (age_dep.c:92) ==3683== Uninitialised value was created by a stack allocation ==3683== at 0x401848: age_dep_init_params (age_dep.c:131) ==3683== ==3683== Conditional jump or move depends on uninitialised value(s) ==3683== at 0x4C277C7: sparse_mat_mat_kron (sparse.c:165) ==3683== by 0x4C2706E: rec_mating (rec.c:176) ==3683== by 0x401C1C: age_dep_iterate (age_dep.c:287) ==3683== by 0x4014CB: main (age_dep.c:92) ==3683== Uninitialised value was created by a stack allocation ==3683== at 0x401848: age_dep_init_params (age_dep.c:131) However, here's the offending line: /* allocate mating table */ age_dep_data->mtable = malloc (age_dep_data->geno * sizeof (double *)); if (age_dep_data->mtable == NULL) error (ENOMEM, ENOMEM, nullmsg, __LINE__); for (int j = 0; j < age_dep_data->geno; j++) { 131=> age_dep_data->mtable[j] = calloc (age_dep_data->geno, sizeof (double)); if (age_dep_data->mtable[j] == NULL) error (ENOMEM, ENOMEM, nullmsg, __LINE__); } What gives? I thought any call to malloc or calloc allocated heap space; there is no other variable allocated here, right? Is it possible there's another allocation going on (the offending stack allocation) that I'm not seeing? You asked to see the code, here goes: /* Copyright 2010 Joel J. Adamson <[email protected]> $Id: age_dep.c 1010 2010-04-21 19:19:16Z joel $ age_dep.c:main file Joel J. Adamson -- http://www.unc.edu/~adamsonj Servedio Lab University of North Carolina at Chapel Hill CB #3280, Coker Hall Chapel Hill, NC 27599-3280 This file is part of an investigation of age-dependent sexual selection. This code is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with haploid. If not, see <http://www.gnu.org/licenses/>. */ #include "age_dep.h" /* global variables */ extern struct argp age_dep_argp; /* global error message variables */ char * nullmsg = "Null pointer: %i"; /* error message for conversions: */ char * errmsg = "Representation error: %s"; /* precision for formatted output: */ const char prec[] = "%-#9.8f "; const size_t age_max = AGEMAX; /* maximum age of males */ static int keep_going_p = 1; int main (int argc, char ** argv) { /* often used counters: */ int i, j; /* read the command line */ struct age_dep_args age_dep_args = { NULL, NULL, NULL }; argp_parse (&age_dep_argp, argc, argv, 0, 0, &age_dep_args); /* set the parameters here: */ /* initialize an age_dep_params structure, set the members */ age_dep_params_t * params = malloc (sizeof (age_dep_params_t)); if (params == NULL) error (ENOMEM, ENOMEM, nullmsg, __LINE__); age_dep_init_params (params, &age_dep_args); /* initialize frequencies: this initializes a list of pointers to initial frqeuencies, terminated by a NULL pointer*/ params->freqs = age_dep_init (&age_dep_args); params->by = 0.0; /* what range of parameters do we want, and with what stepsize? */ /* we should go from 0 to half-of-theta with a step size of about 0.01 */ double from = 0.0; double to = params->theta / 2.0; double stepsz = 0.01; /* did you think I would spell the whole word? */ unsigned int numparts = floor(to / stepsz); do { #pragma omp parallel for private(i) firstprivate(params) \ shared(stepsz, numparts) for (i = 0; i < numparts; i++) { params->by = i * stepsz; int tries = 0; while (keep_going_p) { /* each time through, modify mfreqs and mating table, then go again */ keep_going_p = age_dep_iterate (params, ++tries); if (keep_going_p == ERANGE) error (ERANGE, ERANGE, "Failure to converge\n"); } fprintf (stdout, "%i iterations\n", tries); } /* for i < numparts */ params->freqs = params->freqs->next; } while (params->freqs->next != NULL); return 0; } inline double age_dep_pmate (double age_dep_t, unsigned int genot, double bp, double ba) { /* the probability of mating between these phenotypes */ /* the female preference depends on whether the female has the preference allele, the strength of preference (parameter bp) and the male phenotype (age_dep_t); if the female lacks the preference allele, then this will return 0, which is not quite accurate; it should return 1 */ return bits_isset (genot, CLOCI)? 1.0 - exp (-bp * age_dep_t) + ba: 1.0; } inline double age_dep_trait (int age, unsigned int genot, double by) { /* return the male trait, a function of the trait locus, age, the age-dependent scaling parameter (bx) and the males condition genotype */ double C; double T; /* get the male's condition genotype */ C = (double) bits_popcount (bits_extract (0, CLOCI, genot)); /* get his trait genotype */ T = bits_isset (genot, CLOCI + 1)? 1.0: 0.0; /* return the trait value */ return T * by * exp (age * C); } int age_dep_iterate (age_dep_params_t * data, unsigned int tries) { /* main driver routine */ /* number of bytes for female frequencies */ size_t geno = data->age_dep_data->geno; size_t genosize = geno * sizeof (double); /* female frequencies are equal to male frequencies at birth (before selection) */ double ffreqs[geno]; if (ffreqs == NULL) error (ENOMEM, ENOMEM, nullmsg, __LINE__); /* do not set! Use memcpy (we need to alter male frequencies (selection) without altering female frequencies) */ memmove (ffreqs, data->freqs->freqs[0], genosize); /* for (int i = 0; i < geno; i++) */ /* ffreqs[i] = data->freqs->freqs[0][i]; */ #ifdef PRMTABLE age_dep_pr_mfreqs (data); #endif /* PRMTABLE */ /* natural selection: */ age_dep_ns (data); /* normalized mating table with new frequencies */ age_dep_norm_mtable (ffreqs, data); #ifdef PRMTABLE age_dep_pr_mtable (data); #endif /* PRMTABLE */ double * newfreqs; /* mutate here */ /* i.e. get the new frequency of 0-year-olds using recombination; */ newfreqs = rec_mating (data->age_dep_data); /* return block */ { if (sim_stop_ck (data->freqs->freqs[0], newfreqs, GENO, TOL) == 0) { /* if we have converged, stop the iterations and handle the data */ age_dep_sim_out (data, stdout); return 0; } else if (tries > MAXTRIES) return ERANGE; else { /* advance generations */ for (int j = age_max - 1; j < 0; j--) memmove (data->freqs->freqs[j], data->freqs->freqs[j-1], genosize); /* advance the first age-class */ memmove (data->freqs->freqs[0], newfreqs, genosize); return 1; } } } void age_dep_ns (age_dep_params_t * data) { /* calculate the new frequency of genotypes given additive fitness and selection coefficient s */ size_t geno = data->age_dep_data->geno; double w[geno]; double wbar, dtheta, ttheta, dcond, tcond; double t, cond; /* fitness parameters */ double mu, nu; mu = data->wparams[0]; nu = data->wparams[1]; /* calculate fitness */ for (int j = 0; j < age_max; j++) { int i; for (i = 0; i < geno; i++) { /* calculate male trait: */ t = age_dep_trait(j, i, data->by); /* calculate condition: */ cond = (double) bits_popcount (bits_extract(0, CLOCI, i)); /* trait-based fitness term */ dtheta = data->theta - t; ttheta = (dtheta * dtheta) / (2.0 * nu * nu); /* condition-based fitness term */ dcond = CLOCI - cond; tcond = (dcond * dcond) / (2.0 * mu * mu); /* calculate male fitness */ w[i] = 1 + exp(-tcond) - exp(-ttheta); } /* calculate mean fitness */ /* as long as we calculate wbar before altering any values of freqs[], we're safe */ wbar = gen_mean (data->freqs->freqs[j], w, geno); for (i = 0; i < geno; i++) data->freqs->freqs[j][i] = (data->freqs->freqs[j][i] * w[i]) / wbar; } } void age_dep_norm_mtable (double * ffreqs, age_dep_params_t * params) { /* this function produces a single mating table that forms the input for recombination () */ /* i is female genotype; j is male genotype; k is male age */ int i,j,k; double norm_denom; double trait; size_t geno = params->age_dep_data->geno; for (i = 0; i < geno; i++) { double norm_mtable[geno]; /* initialize the denominator: */ norm_denom = 0.0; /* find the probability of mating and add it to the denominator */ for (j = 0; j < geno; j++) { /* initialize entry: */ norm_mtable[j] = 0.0; for (k = 0; k < age_max; k++) { trait = age_dep_trait (k, j, params->by); norm_mtable[j] += age_dep_pmate (trait, i, params->bp, params->ba) * (params->freqs->freqs)[k][j]; } norm_denom += norm_mtable[j]; } /* now calculate entry (i,j) */ for (j = 0; j < geno; j++) params->age_dep_data->mtable[i][j] = (ffreqs[i] * norm_mtable[j]) / norm_denom; } } My current suspicion is the array newfreqs: I can't memmove, memcpy or assign a stack variable then hope it will persist, can I? rec_mating() returns double *.

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• Blackberry - application settings save/load

  - by Max Gontar

  Hi! I know two ways to save/load application settings: use PersistentStore use filesystem (store, since SDCard is optional) I'd like to know what are you're practicies of working with application settings? Using PersistentStore to save/load application settings The persistent store provides a means for objects to persist across device resets. A persistent object consists of a key-value pair. When a persistent object is committed to the persistent store, that object's value is stored in flash memory via a deep copy. The value can then be retrieved at a later point in time via the key. Example of helper class for storing and retrieving settings: class PSOptions { private PersistentObject mStore; private LongHashtableCollection mSettings; private long KEY_URL = 0; private long KEY_ENCRYPT = 1; private long KEY_REFRESH_PERIOD = 2; public PSOptions() { // "AppSettings" = 0x71f1f00b95850cfeL mStore = PersistentStore.getPersistentObject(0x71f1f00b95850cfeL); } public String getUrl() { Object result = get(KEY_URL); return (null != result) ? (String) result : null; } public void setUrl(String url) { set(KEY_URL, url); } public boolean getEncrypt() { Object result = get(KEY_ENCRYPT); return (null != result) ? ((Boolean) result).booleanValue() : false; } public void setEncrypt(boolean encrypt) { set(KEY_ENCRYPT, new Boolean(encrypt)); } public int getRefreshPeriod() { Object result = get(KEY_REFRESH_PERIOD); return (null != result) ? ((Integer) result).intValue() : -1; } public void setRefreshRate(int refreshRate) { set(KEY_REFRESH_PERIOD, new Integer(refreshRate)); } private void set(long key, Object value) { synchronized (mStore) { mSettings = (LongHashtableCollection) mStore.getContents(); if (null == mSettings) { mSettings = new LongHashtableCollection(); } mSettings.put(key, value); mStore.setContents(mSettings); mStore.commit(); } } private Object get(long key) { synchronized (mStore) { mSettings = (LongHashtableCollection) mStore.getContents(); if (null != mSettings && mSettings.size() != 0) { return mSettings.get(key); } else { return null; } } } } Example of use: class Scr extends MainScreen implements FieldChangeListener { PSOptions mOptions = new PSOptions(); BasicEditField mUrl = new BasicEditField("Url:", "http://stackoverflow.com/"); CheckboxField mEncrypt = new CheckboxField("Enable encrypt", false); GaugeField mRefresh = new GaugeField("Refresh period", 1, 60 * 10, 10, GaugeField.EDITABLE|FOCUSABLE); ButtonField mLoad = new ButtonField("Load settings", ButtonField.CONSUME_CLICK); ButtonField mSave = new ButtonField("Save settings", ButtonField.CONSUME_CLICK); public Scr() { add(mUrl); mUrl.setChangeListener(this); add(mEncrypt); mEncrypt.setChangeListener(this); add(mRefresh); mRefresh.setChangeListener(this); HorizontalFieldManager hfm = new HorizontalFieldManager(USE_ALL_WIDTH); add(hfm); hfm.add(mLoad); mLoad.setChangeListener(this); hfm.add(mSave); mSave.setChangeListener(this); loadSettings(); } public void fieldChanged(Field field, int context) { if (field == mLoad) { loadSettings(); } else if (field == mSave) { saveSettings(); } } private void saveSettings() { mOptions.setUrl(mUrl.getText()); mOptions.setEncrypt(mEncrypt.getChecked()); mOptions.setRefreshRate(mRefresh.getValue()); } private void loadSettings() { mUrl.setText(mOptions.getUrl()); mEncrypt.setChecked(mOptions.getEncrypt()); mRefresh.setValue(mOptions.getRefreshPeriod()); } }

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• Invert linear linked list

  - by ArtWorkAD

  Hi, a linear linked list is a set of nodes. This is how a node is defined (to keep it easy we do not distinguish between node an list): class Node{ Object data; Node link; public Node(Object pData, Node pLink){ this.data = pData; this.link = pLink; } public String toString(){ if(this.link != null){ return this.data.toString() + this.link.toString(); }else{ return this.data.toString() ; } } public void inc(){ this.data = new Integer((Integer)this.data + 1); } public void lappend(Node list){ Node child = this.link; while(child != null){ child = child.link; } child.link = list; } public Node copy(){ if(this.link != null){ return new Node(new Integer((Integer)this.data), this.link.copy()); }else{ return new Node(new Integer((Integer)this.data), null); } } public Node invert(){ Node child = this.link; while(child != null){ child = child.link; } child.link = this;.... } } I am able to make a deep copy of the list. Now I want to invert the list so that the first node is the last and the last the first. The inverted list has to be a deep copy. I started developing the invert function but I am not sure. Any Ideas? Update: Maybe there is a recursive way since the linear linked list is a recursive data structure. I would take the first element, iterate through the list until I get to a node that has no child and append the first element, I would repeat this for the second, third....

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• I am using relational division with EAV, but I need to find results in EAV that have some of the cat

  - by NewToDB

  I have two tables: CREATE TABLE EAV ( subscriber_id INT(1) NOT NULL DEFAULT '0', attribute_id CHAR(62) NOT NULL DEFAULT '', attribute_value CHAR(62) NOT NULL DEFAULT '', PRIMARY KEY (subscriber_id,attribute_id) ) INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (1,'color','red') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (1,'size','xl') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (1,'garment','shirt') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (2,'color','red') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (2,'size','xl') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (2,'garment','pants') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (3,'garment','pants') CREATE TABLE CRITERIA ( attribute_id CHAR(62) NOT NULL DEFAULT '', attribute_value CHAR(62) NOT NULL DEFAULT '' ) INSERT INTO CRITERIA (attribute_id, attribute_value) VALUES ('color', 'red') INSERT INTO CRITERIA (attribute_id, attribute_value) VALUES ('size', 'xl') To find all subscribers in the EAV that match my criteria, I use relational division: SELECT DISTINCT(subscriber_id) FROM EAV WHERE subscriber_id IN (SELECT E.subscriber_id FROM EAV AS E JOIN CRITERIA AS CR ON E.attribute_id = CR.attribute_id AND E.attribute_value = CR.attribute_value GROUP BY E.subscriber_id HAVING COUNT() = (SELECT COUNT() FROM CRITERIA)) This gives me an unique list of subscribers who have all the criteria. So that means I get back subscriber 1 and 2 since they are looking for the color red and size xl, and that's exactly my criteria. But what if I want to extend this so that I also get subscriber 3 since this subscriber didn't specifically say what color or size they want (ie. there is no entry for attribute 'color' or 'size' in the EAV table for subscriber 3). Given my current design, is there a way I can extend my query to include subscribers that have zero or more of the attributes defined, and if they do have the attribute defined, then it must match the criteria? Or is there a better way to design the table to aid in querying?

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• Cascading updates with business key equality: Hibernate best practices?

  - by Traphicone

  I'm new to Hibernate, and while there are literally tons of examples to look at, there seems to be so much flexibility here that it's sometimes very hard to narrow all the options down the best way of doing things. I've been working on a project for a little while now, and despite reading through a lot of books, articles, and forums, I'm still left with a bit of a head scratcher. Any veteran advice would be very appreciated. So, I have a model involving two classes with a one-to-many relationship from parent to child. Each class has a surrogate primary key and a uniquely constrained composite business key. <class name="Container"> <id name="id" type="java.lang.Long"> <generator class="identity"/> </id> <properties name="containerBusinessKey" unique="true" update="false"> <property name="name" not-null="true"/> <property name="owner" not-null="true"/> </properties> <set name="items" inverse="true" cascade="all-delete-orphan"> <key column="container" not-null="true"/> <one-to-many class="Item"/> </set> </class> <class name="Item"> <id name="id" type="java.lang.Long"> <generator class="identity"/> </id> <properties name="itemBusinessKey" unique="true" update="false"> <property name="type" not-null="true"/> <property name="color" not-null="true"/> </properties> <many-to-one name="container" not-null="true" update="false" class="Container"/> </class> The beans behind these mappings are as boring as you can possibly imagine--nothing fancy going on. With that in mind, consider the following code: Container c = new Container("Things", "Me"); c.addItem(new Item("String", "Blue")); c.addItem(new Item("Wax", "Red")); Transaction t = session.beginTransaction(); session.saveOrUpdate(c); t.commit(); Everything works fine the first time, and both the Container and its Items are persisted. If the above code block is executed again, however, Hibernate throws a ConstraintViolationException--duplicate values for the "name" and "owner" columns. Because the new Container instance has a null identifier, Hibernate assumes it is an unsaved transient instance. This is expected but not desired. Since the persistent and transient Container objects have the same business key values, what we really want is to issue an update. It is easy enough to convince Hibernate that our new Container instance is the same as our old one. With a quick query we can get the identifier of the Container we'd like to update, and set our transient object's identifier to match. Container c = new Container("Things", "Me"); c.addItem(new Item("String", "Blue")); c.addItem(new Item("Wax", "Red")); Query query = session.createSQLQuery("SELECT id FROM Container" + "WHERE name = ? AND owner = ?"); query.setString(0, c.getName()); query.setString(1, c.getOwner()); BigInteger id = (BigInteger)query.uniqueResult(); if (id != null) { c.setId(id.longValue()); } Transaction t = session.beginTransaction(); session.saveOrUpdate(c); t.commit(); This almost satisfies Hibernate, but because the one-to-many relationship from Container to Item cascades, the same ConstraintViolationException is also thrown for the child Item objects. My question is: what is the best practice in this situation? It is highly recommended to use surrogate primary keys, and it is also recommended to use business key equality. When you put these two recommendations in to practice together, however, two of the greatest conveniences of Hibernate--saveOrUpdate and cascading operations--seem to be rendered almost completely useless. As I see it, I have only two options: Manually fetch and set the identifier for each object in the mapping. This clearly works, but for even a moderately sized schema this is a lot of extra work which it seems Hibernate could easily be doing. Write a custom interceptor to fetch and set object identifiers on each operation. This looks cleaner than the first option but is rather heavy-handed, and it seems wrong to me that you should be expected to write a plug-in which overrides Hibernate's default behavior for a mapping which follows the recommended design. Is there a better way? Am I making completely the wrong assumptions? I'm hoping that I'm just missing something. Thanks.

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