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• Using HBase or Cassandra for a token server

  - by crippy

  I've been trying to figure out how to use HBase/Cassandra for a token system we're re-implementing. I can probably squeeze quite a lot more from MySQL, but it just seems it has come to clinging on to the wrong tool for the task just because we know it well. Eventually will hit a wall (like happened to us in other areas). Naturally I started looking into possible NoSQL solutions. The prominent ones (at least in terms of buzz) are HBase and Cassandra. The story is more or less like this: A user can send a gift other users. Each gift has a list of recipients or is public in which case limited by number or expiration date For each gift sent we generate some token that uniquely identifies that gift. For each gift we track the list of potential recipients and their current status relating to that gift (accepted, declinded etc). A user can request to see all his currently pending gifts A can request a list of users he has sent a gift to today (used to limit number of gifts sent) Required the ability to "dump" or "ignore" expired gifts (x day old gifts are considered expired) There are some other requirements but I believe the above covers the essentials. How would I go and model that using HBase or Cassandra? Well, the wall was performance. A few 10s of millions of records per day over 2 tables kept for 2 weeks (wish I could have kept it for more but there was no way). The response times kept getting slower and slower until eventually we had to start cutting down number of days we kept data. Caching helps here but it's not an ideal solution since a big part of the ops are updates. Also, as I hinted in my original post. We use MySQL extensively. We know exactly what it can and can't do both in naive implementations followed by native partitioning and finally by horizontally sharding our dataset on the application level to reside on multiple DB nodes. It can be done, but that's not really what I'm trying to get from this. I asked a very specific question about designing a solution using a NoSQL solution since it's very hard to find examples for designs out there. Brainlag, not trying to come off as rude. I actually appreciate it a lot that you are the only one who even bothered to respond. but I see it over and over again. People ask questions and others assume they have no idea what they're talking about and give an irrelevant answer. Ignore RDBMS please. The question is about nosql.

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• What Counts For a DBA: Fitness

  - by Louis Davidson

  If you know me, you can probably guess that physical exercise is not really my thing. There was a time in my past when it a larger part of my life, but even then never in the same sort of passionate way as a number of our SQL friends.  For me, I find that mental exercise satisfies what I believe to be the same inner need that drives people to run farther than I like to drive on most Saturday mornings, and it is certainly just as addictive. Mental fitness shares many common traits with physical fitness, especially the need to attain it through repetitive training. I only wish that mental training burned off a bacon cheeseburger in the same manner as does jogging around a dewy park on Saturday morning. In physical training, there are at least two goals, the first of which is to be physically able to do a task. The second is to train the brain to perform the task without thinking too hard about it. No matter how long it has been since you last rode a bike, you will be almost certainly be able to hop on and start riding without thinking about the process of pedaling or balancing. If you’ve never ridden a bike, you could be a physics professor /Olympic athlete and still crash the first few times you try, even though you are as strong as an ox and your knowledge of the physics of bicycle riding makes the concept child’s play. For programming tasks, the process is very similar. As a DBA, you will come to know intuitively how to backup, optimize, and secure database systems. As a data programmer, you will work to instinctively use the clauses of Transact-SQL DML so that, when you need to group data three ways (and not four), you will know to use the GROUP BY clause with GROUPING SETS without resorting to a search engine.  You have the skill. Making it naturally then requires repetition and experience is the primary requirement, not just simply learning about a topic. The hardest part of being really good at something is this difference between knowledge and skill. I have recently taken several informative training classes with Kimball University on data warehousing and ETL. Now I have a lot more knowledge about designing data warehouses than before. I have also done a good bit of data warehouse designing of late and have started to improve to some level of proficiency with the theory. Yet, for all of this head knowledge, it is still a struggle to take what I have learned and apply it to the designs I am working on.  Data warehousing is still a task that is not yet deeply ingrained in my brain muscle memory. On the other hand, relational database design is something that no matter how much or how little I may get to do it, I am comfortable doing it. I have done it as a profession now for well over a decade, I teach classes on it, and I also have done (and continue to do) a lot of mental training beyond the work day. Sometimes the training is just basic education, some reading blogs and attending sessions at PASS events.  My best training comes from spending time working on other people’s design issues in forums (though not nearly as much as I would like to lately). Working through other people’s problems is a great way to exercise your brain on problems with which you’re not immediately familiar. The final bit of exercise I find useful for cultivating mental fitness for a data professional is also probably the nerdiest thing that I will ever suggest you do.  Akin to running in place, the idea is to work through designs in your head. I have designed more than one database system that would revolutionize grocery store operations, sales at my local Target store, the ordering process at Amazon, and ways to improve Disney World operations to get me through a line faster (some of which they are starting to implement without any of my help.) Never are the designs truly fleshed out, but enough to work through structures and processes.  On “paper”, I have designed database systems to catalog things as trivial as my Lego creations, rental car companies and my audio and video collections. Once I get the database designed mentally, sometimes I will create the database, add some data (often using Red-Gate’s Data Generator), and write a few queries to see if a concept was realistic, but I will rarely fully flesh out the database since I have no desire to do any user interface programming anymore.  The mental training allows me to keep in practice for when the time comes to do the work I love the most for real…even if I have been spending most of my work time lately building data warehouses.  If you are really strong of mind and body, perhaps you can mix a mental run with a physical run; though don’t run off of a cliff while contemplating how you might design a database to catalog the trees on a mountain…that would be contradictory to the purpose of both types of exercise.

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• Randomly generate directed graph on a grid

  - by Talon876

  I am trying to randomly generate a directed graph for the purpose of making a puzzle game similar to the ice sliding puzzles from Pokemon. This is essentially what I want to be able to randomly generate: http://bulbanews.bulbagarden.net/wiki/Crunching_the_numbers:_Graph_theory. I need to be able to limit the size of the graph in an x and y dimension. In the example given in the link, it would be restricted to an 8x4 grid. The problem I am running into is not randomly generating the graph, but randomly generating a graph, which I can properly map out in a 2d space, since I need something (like a rock) on the opposite side of a node, to make it visually make sense when you stop sliding. The problem with this is that sometimes the rock ends up in the path between two other nodes or possibly on another node itself, which causes the entire graph to become broken. After discussing the problem with a few people I know, we came to a couple of conclusions that may lead to a solution. Including the obstacles in the grid as part of the graph when constructing it. Start out with a fully filled grid and just draw a random path and delete out blocks that will make that path work. The problem then becomes figuring out which ones to delete to avoid introducing an additional, shorter path. We were also thinking a dynamic programming algorithm may be beneficial, though none of us are too skilled with creating dynamic programming algorithms from nothing. Any ideas or references about what this problem is officially called (if it's an official graph problem) would be most helpful. Here are some examples of what I have accomplished so far by just randomly placing blocks and generating the navigation graph from the chosen start/finish. The idea (as described in the previous link) is you start at the green S and want to get to the green F. You do this by moving up/down/left/right and you continue moving in the direction chosen until you hit a wall. In these pictures, grey is a wall, white is the floor, and the purple line is the minimum length from start to finish, and the black lines and grey dots represented possible paths. Here are some bad examples of randomly generated graphs: http://i.stack.imgur.com/9uaM6.png Here are some good examples of randomly generated (or hand tweaked) graphs: i.stack.imgur.com/uUGeL.png (can't post another link, sorry) I've also seemed to notice the more challenging ones when actually playing this as a puzzle are ones which have lots of high degree nodes along the minimum path.

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• Oracle Database In-Memory

  - by Mike.Hallett(at)Oracle-BI&EPM

  Normal 0 false false false EN-GB X-NONE X-NONE Larry Ellison unveiled the next major milestone in database technology, Oracle Database In-Memory, on June 10, 2014. Oracle Database In-Memory will be generally available in July 2014 and can be used with all hardware platforms on which Oracle Database 12c is supported. This option will accelerate database performance by orders of magnitude for analytics, data warehousing, and reporting while also speeding up online transaction processing (OLTP). It allows any existing Oracle Database-compatible application to automatically and transparently take advantage of columnar in-memory processing, without additional programming or application changes. Benefits Fast ad-hoc analytics without the need to pre-create indexes Completely transparent to existing applications Faster mixed workload OLTP No database size limit Industrial strength availability and security Robustness and maturity of Oracle Database 12c To find out more see Oracle Database In-Memory Comment from Rittman Mead on Oracle In-Memory Option Launch  ... and I will let you know how this unfolds in regards to advantages for OBI11g and Exalytics and Big Data over the coming months. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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• Updating an Entity through a Service

  - by GeorgeK

  I'm separating my software into three main layers (maybe tiers would be a better term): Presentation ('Views') Business logic ('Services' and 'Repositories') Data access ('Entities' (e.g. ActiveRecords)) What do I have now? In Presentation, I use read-only access to Entities, returned from Repositories or Services, to display data. $banks = $banksRegistryService->getBanksRepository()->getBanksByCity( $city ); $banksViewModel = new PaginatedList( $banks ); // some way to display banks; // example, not real code I find this approach quite efficient in terms of performance and code maintanability and still safe as long as all write operations (create, update, delete) are preformed through a Service: namespace Service\BankRegistry; use Service\AbstractDatabaseService; use Service\IBankRegistryService; use Model\BankRegistry\Bank; class Service extends AbstractDatabaseService implements IBankRegistryService { /** * Registers a new Bank * * @param string $name Bank's name * @param string $bik Bank's Identification Code * @param string $correspondent_account Bank's correspondent account * * @return Bank */ public function registerBank( $name, $bik, $correspondent_account ) { $bank = new Bank(); $bank -> setName( $name ) -> setBik( $bik ) -> setCorrespondentAccount( $correspondent_account ); if( null === $this->getBanksRepository()->getDefaultBank() ) $this->setDefaultBank( $bank ); $this->getEntityManager()->persist( $bank ); return $bank; } /** * Makes the $bank system's default bank * * @param Bank $bank * @return IBankRegistryService */ public function setDefaultBank( Bank $bank ) { $default_bank = $this->getBanksRepository()->getDefaultBank(); if( null !== $default_bank ) $default_bank->setDefault( false ); $bank->setDefault( true ); return $this; } } Where am I stuck? I'm struggling about how to update certain fields in Bank Entity. Bad solution #1: Making a series of setters in Service for each setter in Bank; - seems to be quite reduntant, increases Service interface complexity and proportionally decreases it's simplicity - something to avoid if you care about code maitainability. I try to follow KISS and DRY principles. Bad solution #2: Modifying Bank directly through it's native setters; - really bad. If you'll ever need to move modification into the Service, it will be pain. Business logic should remain in Business logic layer. Plus, there are plans on logging all of the actions and maybe even involve user permissions (perhaps, through decorators) in future, so all modifications should be made only through the Service. Possible good solution: Creating an updateBank( Bank $bank, $array_of_fields_to_update) method; - makes the interface as simple as possible, but there is a problem: one should not try to manually set isDefault flag on a Bank, this operation should be performed through setDefaultBank method. It gets even worse when you have relations that you don't want to be directly modified. Of course, you can just limit the fields that can be modified by this method, but how do you tell method's user what they can and cannot modify? Exceptions?

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• Using the @ in SQL Azure Connections

  - by BuckWoody

  The other day I was working with a client on an application they were changing to a hybrid architecture – some data on-premise and other data in SQL Azure and Windows Azure Blob storage. I had them make a couple of corrections - the first was that all communications to SQL Azure need to be encrypted. It’s a simple addition to the connection string, depending on the library you use. Which brought up another interesting point. They had been using something that looked like this, using the .NET provider: Server=tcp:[serverName].database.windows.net;Database=myDataBase; User ID=LoginName;Password=myPassword; Trusted_Connection=False;Encrypt=True; This includes most of the formatting needed for SQL Azure. It specifies TCP as the transport mechanism, the database name is included, Trusted_Connection is off, and encryption is on. But it needed one more change: Server=tcp:[serverName].database.windows.net;Database=myDataBase; User ID=[LoginName]@[serverName];Password=myPassword; Trusted_Connection=False;Encrypt=True; Notice the difference? It’s the User ID parameter. It includes the @ symbol and the name of the server – not the whole DNS name, just the server name itself. The developers were a bit surprised, since it had been working with the first format that just used the user name. Why did both work, and why is one better than the other? It has to do with the connection library you use. For most libraries, the user name is enough. But for some libraries (subject to change so I don’t list them here) the server name parameter isn’t sent in the way the load balancer understands, so you need to include the server name right in the login, so the system can parse it correctly. Keep in mind, the string limit for that is 128 characters – so take the @ symbol and the server name into consideration for user names. The user connection info is detailed here: http://msdn.microsoft.com/en-us/library/ee336268.aspx Upshot? Include the @servername on your connection string just to be safe. And plan for that extra space…  

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• Isometric layer moving inside map

  - by gronzzz

  i'm created isometric map and now trying to limit layer moving. Main idea, that i have left bottom, right bottom, left top, right top points, that camera can not move outside, so player will not see map out of bounds. But i can not understand algorithm of how to do that. It's my layer scale/moving code. - (void)touchBegan:(UITouch *)touch withEvent:(UIEvent *)event { _isTouchBegin = YES; } - (void)touchMoved:(UITouch *)touch withEvent:(UIEvent *)event { NSArray *allTouches = [[event allTouches] allObjects]; UITouch *touchOne = [allTouches objectAtIndex:0]; CGPoint touchLocationOne = [touchOne locationInView: [touchOne view]]; CGPoint previousLocationOne = [touchOne previousLocationInView: [touchOne view]]; // Scaling if ([allTouches count] == 2) { _isDragging = NO; UITouch *touchTwo = [allTouches objectAtIndex:1]; CGPoint touchLocationTwo = [touchTwo locationInView: [touchTwo view]]; CGPoint previousLocationTwo = [touchTwo previousLocationInView: [touchTwo view]]; CGFloat currentDistance = sqrt( pow(touchLocationOne.x - touchLocationTwo.x, 2.0f) + pow(touchLocationOne.y - touchLocationTwo.y, 2.0f)); CGFloat previousDistance = sqrt( pow(previousLocationOne.x - previousLocationTwo.x, 2.0f) + pow(previousLocationOne.y - previousLocationTwo.y, 2.0f)); CGFloat distanceDelta = currentDistance - previousDistance; CGPoint pinchCenter = ccpMidpoint(touchLocationOne, touchLocationTwo); pinchCenter = [self convertToNodeSpace:pinchCenter]; CGFloat predictionScale = self.scale + (distanceDelta * PINCH_ZOOM_MULTIPLIER); if([self predictionScaleInBounds:predictionScale]) { [self scale:predictionScale scaleCenter:pinchCenter]; } } else { // Dragging _isDragging = YES; CGPoint previous = [[CCDirector sharedDirector] convertToGL:previousLocationOne]; CGPoint current = [[CCDirector sharedDirector] convertToGL:touchLocationOne]; CGPoint delta = ccpSub(current, previous); self.position = ccpAdd(self.position, delta); } } - (void)touchEnded:(UITouch *)touch withEvent:(UIEvent *)event { _isDragging = NO; _isTouchBegin = NO; // Check if i need to bounce _touchLoc = [touch locationInNode:self]; } #pragma mark - Update - (void)update:(CCTime)delta { CGPoint position = self.position; float scale = self.scale; static float friction = 0.92f; //0.96f; if(_isDragging && !_isScaleBounce) { _velocity = ccp((position.x - _lastPos.x)/2, (position.y - _lastPos.y)/2); _lastPos = position; } else { _velocity = ccp(_velocity.x * friction, _velocity.y *friction); position = ccpAdd(position, _velocity); self.position = position; } if (_isScaleBounce && !_isTouchBegin) { float min = fabsf(self.scale - MIN_SCALE); float max = fabsf(self.scale - MAX_SCALE); int dif = max > min ? 1 : -1; if ((scale > MAX_SCALE - SCALE_BOUNCE_AREA) || (scale < MIN_SCALE + SCALE_BOUNCE_AREA)) { CGFloat newSscale = scale + dif * (delta * friction); [self scale:newSscale scaleCenter:_touchLoc]; } else { _isScaleBounce = NO; } } }

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• No wireless connection using a conceptronic c54i (RT2561/RT61 rev B)

  - by jrosell

  Detected but not working. New install on ubuntu 11.10 using coneptronic C54Ri. As documentation says it uses Ralink drivers.... Any ideas why my wireless does not work? $ lspci -nn | grep -i 'ralink' 01:05.0 Network controller: Ralink corp. RT2561/RT61 rev B 802.11g ifconfig eth0 Link encap:Ethernet HWaddr 00:1e:90:e5:af:13 inet addr:192.168.0.197 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::21e:90ff:fee5:af13/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:28361 errors:0 dropped:0 overruns:0 frame:0 TX packets:16858 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:39812172 (39.8 MB) TX bytes:1633405 (1.6 MB) Interrupt:43 Base address:0xc000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:80 errors:0 dropped:0 overruns:0 frame:0 TX packets:80 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:6608 (6.6 KB) TX bytes:6608 (6.6 KB) iwconfig wlan0 wlan0 IEEE 802.11abg ESSIDff/any Mode:Managed Access Point: Not-Associated Tx-Power=0 dBm Retry long limit:7 RTS thrff Fragment thrff Power Managementff lsmod | grep rt rt61pci 27493 0 crc_itu_t 12627 1 rt61pci rt2x00pci 14202 1 rt61pci rt2x00lib 48114 2 rt61pci,rt2x00pci mac80211 272785 2 rt2x00pci,rt2x00lib cfg80211 172392 2 rt2x00lib,mac80211 eeprom_93cx6 12653 1 rt61pci parport_pc 32114 1 parport 40930 3 ppdev,parport_pc,lp lsmod | grep rt [ 2497.816989] phy0 -> rt2x00pci_regbusy_read: Error - Indirect register access failed: offset=0x0000308c, value=0xffffffff [ 2497.827112] phy0 -> rt2x00pci_regbusy_read: Error - Indirect register access failed: offset=0x0000308c, value=0xffffffff [ 2497.837430] phy0 -> rt2x00pci_regbusy_read: Error - Indirect register access failed: offset=0x0000308c, value=0xffffffff [ 2497.847528] phy0 -> rt2x00pci_regbusy_read: Error - Indirect register access failed: offset=0x0000308c, value=0xffffffff [ 2497.847632] phy0 -> rt61pci_wait_bbp_ready: Error - BBP register access faile d, aborting. [ 2497.847637] phy0 -> rt61pci_set_device_state: Error - Device failed to enter state 4 (-5). sudo lshw -C network *-network DISABLED description: Wireless interface product: RT2561/RT61 rev B 802.11g vendor: Ralink corp. physical id: 5 bus info: pci@0000:01:05.0 logical name: wlan0 version: 00 serial: fa:b8:14:58:62:35 width: 32 bits clock: 33MHz capabilities: pm cap_list ethernet physical wireless configuration: broadcast=yes driver=rt61pci driverversion=3.0.0-12-generic firmware=0.8 latency=0 link=no multicast=yes wireless=IEEE 802.11abg resources: irq:16 memory:fdef8000-fdefffff iwlist scan lo Interface doesn't support scanning. eth0 Interface doesn't support scanning. wlan0 Failed to read scan data : Network is down uname -mr 3.0.0-12-generic i686 Edit 1 $ rfkill list all 0: phy0: Wireless LAN Soft blocked: no Hard blocked: no On reboot, sudo lshw -C network returns network is ok. Hovever, WPA keeps on asking the wireless key

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• Developing Schema Compare for Oracle (Part 4): Script Configuration

  - by Simon Cooper

  If you've had a chance to play around with the Schema Compare for Oracle beta, you may have come across this screen in the synchronization wizard: This screen is one of the few screens that, along with the project configuration form, doesn't come from SQL Compare. This screen was designed to solve a couple of issues that, although aren't specific to Oracle, are much more of a problem than on SQL Server: Datatype conversions and NOT NULL columns. 1. Datatype conversions SQL Server is generally quite forgiving when it comes to datatype conversions using ALTER TABLE. For example, you can convert from a VARCHAR to INT using ALTER TABLE as long as all the character values are parsable as integers. Oracle, on the other hand, only allows ALTER TABLE conversions that don't change the internal data format. Essentially, every change that requires an actual datatype conversion has to be done using a rebuild with a conversion function. That's OK, as we can simply hard-code the various conversion functions for the valid datatype conversions and insert those into the rebuild SELECT list. However, as there always is with Oracle, there's a catch. Have a look at the NUMTODSINTERVAL function. As well as specifying the value (or column) to convert, you have to specify an interval_unit, which tells oracle how to interpret the input number. We can't hardcode a default for this parameter, as it is entirely dependent on the user's data context! So, in order to convert NUMBER to INTERVAL DAY TO SECOND/INTERVAL YEAR TO MONTH, we need to have feedback from the user as to what to put in this parameter while we're generating the sync script - this requires a new step in the engine action/script generation to insert these values into the script, as well as new UI to allow the user to specify these values in a sensible fashion. In implementing the engine and UI infrastructure to allow this it made much more sense to implement it for any rebuild datatype conversion, not just NUMBER to INTERVALs. For conversions which we can do, we pre-fill the 'value' box with the appropriate function from the documentation. The user can also type in arbitary SQL expressions, which allows the user to specify optional format parameters for the relevant conversion functions, or indeed call their own functions to convert between values that don't have a built-in conversion defined. As the value gets inserted as-is into the rebuild SELECT list, any expression that is valid in that context can be specified as the conversion value. 2. NOT NULL columns Another problem that is solved by the new step in the sync wizard is adding a NOT NULL column to a table. If the table contains data (as most database tables do), you can't just add a NOT NULL column, as Oracle doesn't know what value to put in the new column for existing rows - the DDL statement will fail. There are actually 3 separate scenarios for this problem that have separate solutions within the engine: Adding a NOT NULL column to a table without a rebuild Here, the workaround is to add a column default with an appropriate value to the column you're adding: ALTER TABLE tbl1 ADD newcol NUMBER DEFAULT <value> NOT NULL; Note, however, there is something to bear in mind about this solution; once specified on a column, a default cannot be removed. To 'remove' a default from a column you change it to have a default of NULL, hence there's code in the engine to treat a NULL default the same as no default at all. Adding a NOT NULL column to a table, where a separate change forced a table rebuild Fortunately, in this case, a column default is not required - we can simply insert the default value into the rebuild SELECT clause. Changing an existing NULL to a NOT NULL column To implement this, we run an UPDATE command before the ALTER TABLE to change all the NULLs in the column to the required default value. For all three, we need some way of allowing the user to specify a default value to use instead of NULL; as this is essentially the same problem as datatype conversion (inserting values into the sync script), we can re-use the UI and engine implementation of datatype conversion values. We also provide the option to alter the new column to allow NULLs, or to ignore the problem completely. Note that there is the same (long-running) problem in SQL Compare, but it is much more of an issue in Oracle as you cannot easily roll back executed DDL statements if the script fails at some point during execution. Furthermore, the engine of SQL Compare is far less conducive to inserting user-supplied values into the generated script. As we're writing the Schema Compare engine from scratch, we used what we learnt from the SQL Compare engine and designed it to be far more modular, which makes inserting procedures like this much easier.

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• Why do I always think I know much less than others? [closed]

  - by John Kenedy

  I have been in programming since primary 6. Since the time DOS comes, I have been doing programming in quickbasic 4.5, then to VB 6, then to C#. In between I also do programming in C++. But every time I open Stack Overflow and trying to help others answering their problems, it seems that I know nothing. I feel that I am so stupid even I have been in programming for so long. I would shock reading all the questions and unable to find any clue. Is technology moving too fast that left out me? I feel that technology changes too fast and I can't keep up, when I know ASP.NET web form, MVC is out, when I know MVC, android/iphone/HTML5 app is popular. It seems that I am chasing something and never reach 'it'. I don't know whether this is correct place for me to talk about this. I just wish to listen to opinion like you, how do you think technology should grow instead of recreating language, adding bug here and there to let programmer figure it out, while big company share the solution among themselves. This is exactly how I feel. The simple example is how do you think why doesn't Dictionary<> in .NET provide iterating the object using index? Why must we use Key or GetEnumerator(). Developer has to google and read wasted hour of hour of time to find pieces of hack code to use reflection to achieve reading from index. Where developer will keep it as collection and valuable code. HOwever when times come, everything changes again, developer has to find answer for new silly problems again! Yes, I really hate it! I hate how many big companies are playing with the developer by cutting a big picture into small puzzle and messing it up and asking developer to place it together themselves. As if they are creating problems for us to solve it, so we are unable to grow upfront, we are being manipulated by those silly problems they have created. Another sample would how difficult to collect Cookies from CookieContainer without passing the URL, yes without the URL and I WANT to get all cookie in the cookiecontainer without knowing the URL, I want to iterate all. Why does micros0ft have to limit me from doing that?

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• 5.1 surround sound

  - by rocker9455

  Ok, So i've always had trouble with enabling 5.1 in ubuntu. Running 'alsamixer': I have: Master, Heaphones, PCM, Front, Front Mi, Front Mi, Surround, Center All are at 100% Card:HDA Intel Chip:Realtek ALC888 (This is my onboard sound, Its a dell studio, with 7.1 integrated sound) Running "speaker-test -c6 -twav" I only get the front 2 speakers (Right/Left) making any noise. The others make no noise at all. I have no other sound card to use as all my PCI slots are used up. Daemon.conf: ; daemonize = no ; fail = yes ; allow-module-loading = yes ; allow-exit = yes ; use-pid-file = yes ; system-instance = no ; enable-shm = yes ; shm-size-bytes = 0 # setting this 0 will use the system-default, usually 64 MiB ; lock-memory = no ; cpu-limit = no ; high-priority = yes ; nice-level = -11 ; realtime-scheduling = yes ; realtime-priority = 5 ; exit-idle-time = 20 ; scache-idle-time = 20 ; dl-search-path = (depends on architecture) ; load-default-script-file = yes ; default-script-file = ; log-target = auto ; log-level = notice ; log-meta = no ; log-time = no ; log-backtrace = 0 resample-method = speex-float-1 ; enable-remixing = yes ; enable-lfe-remixing = no flat-volumes = no ; rlimit-fsize = -1 ; rlimit-data = -1 ; rlimit-stack = -1 ; rlimit-core = -1 ; rlimit-as = -1 ; rlimit-rss = -1 ; rlimit-nproc = -1 ; rlimit-nofile = 256 ; rlimit-memlock = -1 ; rlimit-locks = -1 ; rlimit-sigpending = -1 ; rlimit-msgqueue = -1 ; rlimit-nice = 31 ; rlimit-rtprio = 9 ; rlimit-rttime = 1000000 ; default-sample-format = s16le ; default-sample-rate = 44100 ; default-sample-channels = 6 ; default-channel-map = front-left,front-right default-fragments = 8 default-fragment-size-msec = 10

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• Why wifi doesn't work in this case?

  - by xRobot

  I have a brand new notebook where I have installed Windows 7 and Ubuntu 12.04 LTS 64bit in dual boot. In windows 7 wifi works but in Ubuntu not. Could you help me please ? iwconfig lo no wireless extensions. wlan0 IEEE 802.11bgn ESSID:off/any Mode:Managed Access Point: Not-Associated Tx-Power=20 dBm Retry long limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Management:off eth0 no wireless extensions. lshw -C network *-network description: Ethernet interface product: RTL8111/8168B PCI Express Gigabit Ethernet controller vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:01:00.0 logical name: eth0 version: 07 serial: b4:b5:1f:1b:9a:56 size: 10Mbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=half firmware=rtl8168e-3_0.0.4 03/27/12 latency=0 link=no multicast=yes port=MII speed=10Mbit/s resources: irq:41 ioport:3000(size=256) memory:c2404000-c2404fff memory:c2400000-c2403fff *-network description: Wireless interface product: Ralink corp. vendor: Ralink corp. physical id: 0 bus info: pci@0000:02:00.0 logical name: wlan0 version: 00 serial: 84:4b:f4:0a:3a:22 width: 32 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=rt2800pci driverversion=3.2.0-31-generic firmware=0.34 latency=0 link=no multicast=yes wireless=IEEE 802.11bgn resources: irq:18 memory:c2500000-c250ffff lspci | grep -i net 01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 07) 02:00.0 Network controller: Ralink corp. Device 539a iwlist scan lo Interface doesn't support scanning. wlan0 Interface doesn't support scanning : Device or resource busy eth0 Interface doesn't support scanning. lsmod Module Size Used by rfcomm 47604 0 bnep 18281 2 bluetooth 180104 10 rfcomm,bnep parport_pc 32866 0 ppdev 17113 0 snd_hda_codec_hdmi 32474 1 snd_hda_codec_realtek 224173 1 joydev 17693 0 hp_wmi 18092 0 sparse_keymap 13890 1 hp_wmi snd_hda_intel 33773 3 snd_hda_codec 127706 3 snd_hda_codec_hdmi,snd_hda_codec_realtek,snd_hda_intel snd_hwdep 13668 1 snd_hda_codec snd_pcm 97188 3 snd_hda_codec_hdmi,snd_hda_intel,snd_hda_codec snd_seq_midi 13324 0 snd_rawmidi 30748 1 snd_seq_midi snd_seq_midi_event 14899 1 snd_seq_midi snd_seq 61896 2 snd_seq_midi,snd_seq_midi_event snd_timer 29990 2 snd_pcm,snd_seq snd_seq_device 14540 3 snd_seq_midi,snd_rawmidi,snd_seq psmouse 97362 0 snd 78855 16 snd_hda_codec_hdmi,snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_seq_device arc4 12529 2 rt2800pci 18715 0 rt2800lib 58925 1 rt2800pci crc_ccitt 12667 1 rt2800lib rt2x00pci 14577 1 rt2800pci rt2x00lib 51144 3 rt2800pci,rt2800lib,rt2x00pci mac80211 506816 3 rt2800lib,rt2x00pci,rt2x00lib soundcore 15091 1 snd mac_hid 13253 0 uvcvideo 72627 0 videodev 98259 1 uvcvideo v4l2_compat_ioctl32 17128 1 videodev wmi 19256 1 hp_wmi i915 473240 3 cfg80211 205544 2 rt2x00lib,mac80211 eeprom_93cx6 12725 1 rt2800pci drm_kms_helper 46978 1 i915 drm 242038 4 i915,drm_kms_helper i2c_algo_bit 13423 1 i915 snd_page_alloc 18529 2 snd_hda_intel,snd_pcm mei 41616 0 serio_raw 13211 0 video 19596 1 i915 lp 17799 0 parport 46562 3 parport_pc,ppdev,lp usbhid 47199 0 hid 99559 1 usbhid r8169 62099 0 rfkill list: # rfkill list 0: phy0: Wireless LAN Soft blocked: no Hard blocked: no 1: hp-wifi: Wireless LAN Soft blocked: no Hard blocked: no

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• How to send multiple MVP matrices to a vertex shader in OpenGL ES 2.0

  - by Carbon Crystal

  I'm working my way through optimizing the rendering of sprites in a 2D game using OpenGL ES and I've hit the limit of my knowledge when it comes to GLSL and vertex shaders. I have two large float buffers containing my vertex coordinates and texture coordinates (eventually this will be one buffer) for multiple sprites in order to perform a single glDrawArrays call. This works but I've hit a snag when it comes to passing the transformation matrix into the vertex shader. My shader code is: uniform mat4 u_MVPMatrix; attribute vec4 a_Position; attribute vec2 a_TexCoordinate; varying vec2 v_TexCoordinate; void main() { v_TexCoordinate = a_TexCoordinate; gl_Position = u_MVPMatrix * a_Position; } In Java (Android) I am using a FloatBuffer to store the vertex/texture data and this is provided to the shader like so: mGlEs20.glVertexAttribPointer(mVertexHandle, Globals.GL_POSITION_VERTEX_COUNT, GLES20.GL_FLOAT, false, 0, mVertexCoordinates); mGlEs20.glVertexAttribPointer(mTextureCoordinateHandle, Globals.GL_TEXTURE_VERTEX_COUNT, GLES20.GL_FLOAT, false, 0, mTextureCoordinates); (The Globals.GL_POSITION_VERTEX_COUNT etc are just integers with the value of 2 right now) And I'm passing the MVP (Model/View/Projection) matrix buffer like this: GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mModelCoordinates); (mModelCoordinates is a FloatBuffer containing 16-float sequences representing the MVP matrix for each sprite) This renders my scene but all the sprites share the same transformation, so it's obviously only picking the first 16 elements from the buffer which makes sense since I am passing in "1" as the second parameter. The documentation for this method says: "This should be 1 if the targeted uniform variable is not an array of matrices, and 1 or more if it is an array of matrices." So I tried modifying the shader with a fixed size array large enough to accomodate most of my scenarios: uniform mat4 u_MVPMatrix[1000]; But this lead to an error in the shader: cannot convert from 'uniform array of 4X4 matrix of float' to 'Position 4-component vector of float' This just seems wrong anyway as it's not clear to me how the shader would know when to transition to the next matrix anyway. Anyone have an idea how I can get my shader to pick up a different MVP matrix (i.e. the NEXT 16 floats) from my MVP buffer for every 4 vertices it encounters? (I am using GL_TRIANGLE_STRIP so each sprite has 4 vertices). Thanks!

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• Joining on NULLs

  - by Dave Ballantyne

  A problem I see on a fairly regular basis is that of dealing with NULL values.  Specifically here, where we are joining two tables on two columns, one of which is ‘optional’ ie is nullable.  So something like this: i.e. Lookup where all the columns are equal, even when NULL.   NULL’s are a tricky thing to initially wrap your mind around.  Statements like “NULL is not equal to NULL and neither is it not not equal to NULL, it’s NULL” can cause a serious brain freeze and leave you a gibbering wreck and needing your mummy. Before we plod on, time to setup some data to demo against. Create table #SourceTable ( Id integer not null, SubId integer null, AnotherCol char(255) not null ) go create unique clustered index idxSourceTable on #SourceTable(id,subID) go with cteNums as ( select top(1000) number from master..spt_values where type ='P' ) insert into #SourceTable select Num1.number,nullif(Num2.number,0),'SomeJunk' from cteNums num1 cross join cteNums num2 go Create table #LookupTable ( Id integer not null, SubID integer null ) go insert into #LookupTable Select top(100) id,subid from #SourceTable where subid is not null order by newid() go insert into #LookupTable Select top(3) id,subid from #SourceTable where subid is null order by newid() If that has run correctly, you will have 1 million rows in #SourceTable and 103 rows in #LookupTable.  We now want to join one to the other. First attempt – Lets just join select * from #SourceTable join #LookupTable on #LookupTable.id = #SourceTable.id and #LookupTable.SubID = #SourceTable.SubID OK, that’s a fail.  We had 100 rows back,  we didn’t correctly account for the 3 rows that have null values.  Remember NULL <> NULL and the join clause specifies SUBID=SUBID, which for those rows is not true. Second attempt – Lets deal with those pesky NULLS select * from #SourceTable join #LookupTable on #LookupTable.id = #SourceTable.id and isnull(#LookupTable.SubID,0) = isnull(#SourceTable.SubID,0) OK, that’s the right result, well done and 99.9% of the time that is where its left. It is a relatively trivial CPU overhead to wrap ISNULL around both columns and compare that result, so no problems.  But, although that’s true, this a relational database we are using here, not a procedural language.  SQL is a declarative language, we are making a request to the engine to get the results we want.  How we ask for them can make a ton of difference. Lets look at the plan for our second attempt, specifically the clustered index seek on the #SourceTable   There are 2 predicates. The ‘seek predicate’ and ‘predicate’.  The ‘seek predicate’ describes how SQLServer has been able to use an Index.  Here, it has been able to navigate the index to resolve where ID=ID.  So far so good, but what about the ‘predicate’ (aka residual probe) ? This is a row-by-row operation.  For each row found in the index matching the Seek Predicate, the leaf level nodes have been scanned and tested using this logical condition.  In this example [Expr1007] is the result of the IsNull operation on #LookupTable and that is tested for equality with the IsNull operation on #SourceTable.  This residual probe is quite a high overhead, if we can express our statement slightly differently to take full advantage of the index and make the test part of the ‘Seek Predicate’. Third attempt – X is null and Y is null So, lets state the query in a slightly manner: select * from #SourceTable join #LookupTable on #LookupTable.id = #SourceTable.id and ( #LookupTable.SubID = #SourceTable.SubID or (#LookupTable.SubID is null and #SourceTable.SubId is null) ) So its slightly wordier and may not be as clear in its intent to the human reader, that is what comments are for, but the key point is that it is now clearer to the query optimizer what our intention is. Let look at the plan for that query, again specifically the index seek operation on #SourceTable No ‘predicate’, just a ‘Seek Predicate’ against the index to resolve both ID and SubID.  A subtle difference that can be easily overlooked.  But has it made a difference to the performance ? Well, yes , a perhaps surprisingly high one. Clever query optimizer well done. If you are using a scalar function on a column, you a pretty much guaranteeing that a residual probe will be used.  By re-wording the query you may well be able to avoid this and use the index completely to resolve lookups. In-terms of performance and scalability your system will be in a much better position if you can.

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• Part 5: Choose the right tool - or - why

  - by volker.eckardt(at)oracle.com

  Consider the following client request “Please create a report for us to list expenses”. Which Oracle EBS tool would you choose? There are plenty of options available: Oracle Reports, or BI Publisher with PDF or Excel layout, or Discoverer, or BI Publisher Stand Alone, or PDF online generation, or Oracle WebADI, or Plain SQL*Plus as Concurrent Program, or Online review option … Assuming, you as development lead have to decide, you may decide by available skill set in your development team. However, is this a good decision? An important question to influence the decision is the “Why” question: why do you need this report, what process is behind, what exactly you like to achieve? We see often data created or printed, although it would be much better to get the data in Excel, and upload changes via WebADI directly. There are more points that should drive your decision: How many of such requirements you have got? Has this technique been used in the project already? Are there related reusable’s you may gain from? How difficult is it to maintain your solution? Can you merge this report with another one, to reduce test and maintenance work? In addition, also your own development standards should guide you a bit to come to a good decision. In one of my own projects, we discussed such topics in our weekly team meeting. By utilizing the team knowledge best, you may come to a better decision, and additionally, your team supports your decision. Unfortunately, I have rarely seen dedicated team trainings or planned knowledge transfer to support such processes. Often the pressure to deliver on time is too high to have discussion and decision time left. But exactly this can help keeping maintenance costs low by limiting the number of alternative solutions for similar requirements. Lastly, design decisions should be documented to allow another person taking this over easily. Decisions shall be reviewed and updated regularly, to reflect related procedures or Oracle products respective product versions. Summary: Oracle EBS offers plenty of alternatives to implement customizations. Create and maintain a decision tree to support the design process. Do not leave the decision just on developer side. Limit the number of alternative solutions as best as possible; choose one which is the most appropriate also from future maintenance perspective.

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• Problem trying to lock framerate at 60 FPS

  - by shad0w

  I've written a simple class to limit the framerate of my current project. But it does not work as it should. Here is the code: void FpsCounter::Process() { deltaTime = static_cast<double>(frameTimer.GetMsecs()); waitTime = 1000.0/fpsLimit - deltaTime; frameTimer.Reset(); if(waitTime <= 0) { std::cout << "error, waittime: " << waitTime << std::endl; } else { SDL_Delay(static_cast<Uint32>(waitTime)); } if(deltaTime == 0) { currFps = -1; } else { currFps = 1000/deltaTime; } std::cout << "--Timings--" << std::endl; std::cout << "Delta: \t" << deltaTime << std::endl; std::cout << "Delay: \t" << waitTime << std::endl; std::cout << "FPS: \t" << currFps << std::endl; std::cout << "-- --" << std::endl; } Timer::Timer() { startMsecs = 0; } Timer::~Timer() { // TODO Auto-generated destructor stub } void Timer::Start() { started = true; paused = false; Reset(); } void Timer::Pause() { if(started && !paused) { paused = true; pausedMsecs = SDL_GetTicks() - startMsecs; } } void Timer::Resume() { if(paused) { paused = false; startMsecs = SDL_GetTicks() - pausedMsecs; pausedMsecs = 0; } } int Timer::GetMsecs() { if(started) { if(paused) { return pausedMsecs; } else { return SDL_GetTicks() - startMsecs; } } return 0; } void Timer::Reset() { startMsecs = SDL_GetTicks(); } The "FpsCounter::Process()" Method is called everytime at the end of my gameloop. I've got the problem that the loop is correctly delayed only every second frame, so it runs one frame delayed at 60 FPS and the next without delay at over 1000 fps. I am searching the error quite a while now, but I do not find it. I hope somebody can point me in the right direction.

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• Wireless connection by using command screen

  - by Amadeus

  I installed Ubuntu 12.04 armhf to my beagleboard-xm and now trying to connect to a wireless network. First, I checked if I can search for available networks: ubuntu@arm:~$ iwlist scan lo Interface doesn't support scanning. usb0 Interface doesn't support scanning. wlan0 Scan completed : Cell 01 - Address: EA:7D:EF:60:C9:0B Channel:1 Frequency:2.412 GHz (Channel 1) Quality=70/70 Signal level=-23 dBm Encryption key:on ESSID:"ghostrider" Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s 24 Mb/s; 36 Mb/s; 54 Mb/s Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s Mode:Ad-Hoc Extra:tsf=000000005a1ab50e Extra: Last beacon: 6242ms ago IE: Unknown: 000A67686F73747269646572 IE: Unknown: 010882848B962430486C IE: Unknown: 030101 IE: Unknown: 06020000 IE: Unknown: 2A0100 IE: Unknown: 2F0100 IE: Unknown: 32040C121860 IE: Unknown: 2D1A2C181BFF00000000000000000000000000000000000000000000 IE: Unknown: 3D16010800000000FF000000000000000000000000000000 IE: Unknown: DD09001018020000000000 Then I edited /etc/network/interfaces file to the following: root@arm:/etc/wpa_supplicant# cat /etc/network/interfaces auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet dhcp # Example to keep MAC address between reboots #hwaddress ether DE:AD:BE:EF:CA:FE # WiFi Example auto wlan0 iface wlan0 inet dhcp wpa-ssid "ghostrider" wpa-psk "b34d373eb2fb836a43b0afffe783c7d0af694724506c9e77b06d1021302905bf" But I cannot still connect to the wireless network: root@arm:/etc/wpa_supplicant# iwconfig lo no wireless extensions. usb0 no wireless extensions. wlan0 IEEE 802.11bgn ESSID:off/any Mode:Managed Access Point: Not-Asociated Tx-Power=20 dBm Retry long limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Management:on eth0 no wireless extensions. root@arm:/etc/network# ifup wlan0 Failed to bring up wlan0. What is wrong? Should I change any other files also? But I think it was enough. By the way if you are curious about where that wpa-psk came from: zero@ghostrider:~$ wpa_passphrase ghostrider 34bddf67c2 network={ ssid="ghostrider" #psk="34bddf67c2" psk=b34d373eb2fb836a43b0afffe783c7d0af694724506c9e77b06d1021302905bf } I will appreciate any effort to help. Regards, Amadeus ps: Also I tried to connect manually: root@arm:/etc/network# iwconfig wlan0 essid ghostrider key s:34bddf67c2 But this did not solve my problem also.

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• SMTP POP3 & PST. Acronyms from Hades.

  - by mikef

  A busy SysAdmin will occasionally have reason to curse SMTP. It is, certainly, one of the strangest events in the history of IT that such a deeply flawed system, designed originally purely for campus use, should have reached its current dominant position. The explanation was that it was the first open-standard email system, so SMTP/POP3 became the internet standard. We are, in consequence, dogged with a system with security weaknesses so extreme that messages are sent in plain text and you have no real assurance as to who the message came from anyway (SMTP-AUTH hasn't really caught on). Even without the security issues, the use of SMTP in an office environment provides a management nightmare to all commercial users responsible for complying with all regulations that control the conduct of business: such as tracking, retaining, and recording company documents. SMTP mail developed from various Unix-based systems designed for campus use that took the mail analogy so literally that mail messages were actually delivered to the users, using a 'store and forward' mechanism. This meant that, from the start, the end user had to store, manage and delete messages. This is a problem that has passed through all the releases of MS Outlook: It has to be able to manage mail locally in the dreaded PST file. As a stand-alone system, Outlook is flawed by its neglect of any means of automatic backup. Previous Outlook PST files actually blew up without warning when they reached the 2 Gig limit and became corrupted and inaccessible, leading to a thriving industry of 3rd party tools to clear up the mess. Microsoft Exchange is, of course, a server-based system. Emails are less likely to be lost in such a system if it is properly run. However, there is nothing to stop users from using local PSTs as well. There is the additional temptation to load emails into mobile devices, or USB keys for off-line working. The result is that the System Administrator is faced by a complex hybrid system where backups have to be taken from Servers, and PCs scattered around the network, where duplication of emails causes storage issues, and document retention policies become impossible to manage. If one adds to that the complexity of mobile phone email readers and mail synchronization, the problem is daunting. It is hardly surprising that the mood darkens when SysAdmins meet and discuss PST Hell. If you were promoted to the task of tormenting the souls of the damned in Hades, what aspects of the management of Outlook would you find most useful for your task? I'd love to hear from you. Cheers, Michael

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• What HTML and CSS markup is best for SEO for a list of questions (like on Stack Exchange sites)

  - by Oleg9

  On the StackOverflow a question block (in the q-list on the index page and so on) represented by the following html code: <div class="question-summary narrow tagged-interesting" id="question-summary-19832613"> <div onclick="window.location.href='/questions/19832613/how-to-display-only-transit-routesfor-trains-in-google-maps-api'" class="cp"> <div class="votes"> <div class="mini-counts">0</div> <div>votes</div> </div> <div class="status unanswered"> <div class="mini-counts">0</div> <div>answers</div> </div> <div class="views"> <div class="mini-counts">3</div> <div>views</div> </div> </div> <div class="summary"> <h3>...</h3> <div class="tags t-javascript t-google-maps t-google t-google-maps-api-3"> </div> <div class="started"> <a href="/questions/19832613/how-to-display-only-transit-routesfor-trains-in-google-maps-api" class="started-link"><span title="2013-11-07 09:52:29Z" class="relativetime">1 min ago</span></a> <a href="/users/1309392/shirish">Shirish</a> <span class="reputation-score" title="reputation score " dir="ltr">189</span> </div> </div> </div> It uses float positioning. My questions is: Would use of css styled tables be a better choice? (It's a table, isn't it?) Or it just depends on what are you prefer to use and doesn't affect the technical side (search engines or something)? The background information (such as number of views, votes etc.) comes first in the code. And I know that search engines have a limit at viewing each page. So would it better to place div's depending on their importance and then markup them on the page using css methods (like negative margins and absolute positioning)? Or it isn't so important in this instance?

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• Sampling SQL server batch activity

  - by extended_events

  Recently I was troubleshooting a performance issue on an internal tracking workload and needed to collect some very low level events over a period of 3-4 hours.  During analysis of the data I found that a common pattern I was using was to find a batch with a duration that was longer than average and follow all the events it produced.  This pattern got me thinking that I was discarding a substantial amount of event data that had been collected, and that it would be great to be able to reduce the collection overhead on the server if I could still get all activity from some batches. In the past I’ve used a sampling technique based on the counter predicate to build a baseline of overall activity (see Mikes post here).  This isn’t exactly what I want though as there would certainly be events from a particular batch that wouldn’t pass the predicate.  What I need is a way to identify streams of work and select say one in ten of them to watch, and sql server provides just such a mechanism: session_id.  Session_id is a server assigned integer that is bound to a connection at login and lasts until logout.  So by combining the session_id predicate source and the divides_by_uint64 predicate comparator we can limit collection, and still get all the events in batches for investigation. CREATE EVENT SESSION session_10_percent ON SERVER ADD EVENT sqlserver.sql_statement_starting(     WHERE (package0.divides_by_uint64(sqlserver.session_id,10))), ADD EVENT sqlos.wait_info (        WHERE (package0.divides_by_uint64(sqlserver.session_id,10))), ADD EVENT sqlos.wait_info_external (        WHERE (package0.divides_by_uint64(sqlserver.session_id,10))), ADD EVENT sqlserver.sql_statement_completed(     WHERE (package0.divides_by_uint64(sqlserver.session_id,10))) ADD TARGET ring_buffer WITH (MAX_DISPATCH_LATENCY=30 SECONDS,TRACK_CAUSALITY=ON) GO   There we go; event collection is reduced while still providing enough information to find the root of the problem.  By the way the performance issue turned out to be an IO issue, and the session definition above was more than enough to show long waits on PAGEIOLATCH*.        

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• AS3 - At exactly 23 empty alpha channels, images below stop drawing

  - by user46851

  I noticed, while trying to draw large numbers of circles, that occasionally, there would be some kind of visual bug where some circles wouldn't draw properly. Well, I narrowed it down, and have noticed that if there is 23 or more objects with 00 for an alpha value on the same spot, then the objects below don't draw. It appears to be on a pixel-by-pixel basis, since parts of the image still draw. Originally, this problem was noticed with a class that inherited Sprite. It was confirmed to also be a problem with Sprites, and now Bitmaps, too. If anyone can find a lower-level class than Bitmap which doesn't have this problem, please speak up so we can try to find the origin of the problem. I prepared a small test class that demonstrates what I mean. You can change the integer value at line 20 in order to see the three tests I came up with to clearly show the problem. Is there any kind of workaround, or is this just a limit that I have to work with? Has anyone experienced this before? Is it possible I'm doing something wrong, despite the bare-bones implementation? package { import flash.display.Sprite; import flash.events.Event; import flash.display.Bitmap; import flash.display.BitmapData; public class Main extends Sprite { public function Main():void { if (stage) init(); else addEventListener(Event.ADDED_TO_STAGE, init); } private function init(e:Event = null):void { removeEventListener(Event.ADDED_TO_STAGE, init); // entry point Test(3); } private function Test(testInt:int):void { if(testInt==1){ addChild(new Bitmap(new BitmapData(200, 200, true, 0xFFFF0000))); for (var i:int = 0; i < 22; i++) { addChild(new Bitmap(new BitmapData(100, 100, true, 0x00000000))); } } if(testInt==2){ addChild(new Bitmap(new BitmapData(200, 200, true, 0xFFFF0000))); for (var j:int = 0; j < 23; j++) { addChild(new Bitmap(new BitmapData(100, 100, true, 0x00000000))); } } if(testInt==3){ addChild(new Bitmap(new BitmapData(200, 200, true, 0xFFFF0000))); for (var k:int = 0; k < 22; k++) { addChild(new Bitmap(new BitmapData(100, 100, true, 0x00000000))); } var M:Bitmap = new Bitmap(new BitmapData(100, 100, true, 0x00000000)); M.x += 50; M.y += 50; addChild(M); } } } }

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• 2d, Top-down map with different levels

  - by Ktash

  So, I'm creating a 2d, top down, sprite based (tiled) game, and right now I'm working on maps (well, a map editor at the moment, but it will be creating my maps, so basically the same thing). The scenario So, I'm thinking about efficiency and creating a map in pieces. In each piece, I plan on having 'layers'. Basically, I plan on rendering it down to a 'below hero' level, and an 'above hero' level, with the hero rendered in between obviously. There will likely also be a 'on level with hero' layer, but I'm not quite there yet. Not even worrying about events or interaction yet. Just looking to get a hero on the screen. Now for movement, I obviously need to know what tiles can be moved and in what direction. My plan at the moment is each tile getting 8 bits (4 'can enter in direction' bits, 4 'can leave in direction'). This will allow me to limit movement and even allow one way directional movement. The dilemma This works great for a lot of scenarios. It will allow me to store a map in essentially 3 layers, a string, and gives me flexibility going forward. However, I can't create maps that themselves have layers. A good example is a bridge where the user can go under or over the bridge without invalid moves being allowed. I can't create a platform and allow movement underneath. These are things I would like to be able to include in my game. My idea In theory, I could allow multiple hero layers and then allow multiple sets of 'below' and 'above' layers (or sandwich layers). But this complicates my system, and makes movement between maps potentially tricky (If the hero is on the third layer at the edge of a map, but that corresponds to the second layer on the other map, how can I allow or disallow movement). My question Is there a better way to manage multiple maps with multiple levels like this where a users level may be 'connected' on different levels on different maps? Or even... Am I doing this the hard way? Is there a more standard way to handle top-down 2d tiled maps that I am just not aware of? Things to note or that might be helpful This will be done in Javascript (transferred around in JSON) State will need to be transferred quickly, so a map-id and x/y/direction should be enough to get me a boolean 'can move' value Maps will not be standard sized (though they will be in a certain number of tiles) Making an editor tool so that I can have others help, so something that I can create in a tool would be helpful 'Teleportation' locations will likely need to exist to get into building maps and to and from different map sets (which will not necessarily be connected), but have not been created yet (lumping in with events at the moment).

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• Rolling With the Punches

  - by D'Arcy Lussier

  So I’ve been tweeting the last little while “Rolling with the punches” and I’ve had some people ask me what that meant. Whether you’re running a conference (like I am this week), or a project, or a birthday party for a 2 year old, you need to be ready to handle those things that are unexpected. Risk mitigation can only go so far and its at those times that you need to become resourceful. So let me tell you what the last few days have been like. Today is the first day of Prairie Dev Con Winnipeg, a conference that I run. On Friday I was informed that my keynote speaker had lost his voice, one of my speakers had a family emergency and had to back out, and I got a warning from another that he was travelling over the weekend and if there was a storm or something he may not be able to get back by Monday for his talk. A storm didn’t happen, but their car did break down and he was delayed. Finally, Saturday night I took my printing order to Staples. It was at 5 and they closed at 6, and I had a bunch of surveys to be printed and cut. The girl working said that she’d have it ready by the next day (Sunday). Her intent was to come in the next morning and finish the job. Unfortunately, she had to be hospitalized that night and never made it into work…and never informed anyone of the remaining work. They found out at 3pm when I came to pick it up and there was no way they’d be able to cut everything in time. So how did we roll with these punches? - Miguel, my keynote speaker, was a trooper and was able to do the keynote but asked that his session get moved from Monday to Tuesday. This is why I wait until the last day before printing out schedules, they can change up to the event and even later. - I was able to move some sessions around to accommodate my stranded speaker and fill the empty slot from the speaker that couldn’t make it. - Staples was able to get me half the cut surveys so I took those and my wife will pick up the rest today. I altered how we’d collect session surveys, and actually I think it’ll work better. So all of this is to say, plan but also plan for what you can’t plan for – there will be things that happen that blindside you, that you’re not sure how to handle or solve. Stop, take a deep breath, and don’t feel that you need to limit yourself to the boundaries that you initially set for yourself. Roll with the punch and learn from it so that you can avoid the blow next time. Now, back to the conference! D

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• WiFi on Ubuntu 12.04 custom: downloading unbearably slow

  - by Mark

  iwconfig reports 11 Mbps, yet I've seen as low as <1 KBps. This is the latest in my laundry list of Ubuntu problems in a dual-boot machine (cyberpowerpc custom, intel i7-3820, nvidia gtx 570). I received it two days ago, Windows 7 running fine, still having problems with Ubuntu. The browsing is intermittent but unacceptable. e.g. I could get to this site last night but I couldn't post this question. The downloading is unbearably slow, I can't download anything or install any packages because the speed is so slow. e.g. I am trying to install vim which is inexplicably missing from my 12.04 install (add another one to the problems list) and my download speed reported in the terminal was 241 B/s. Yes, bytes. iwconfig reports 11 Mbps, which further adds to the confusion. User@ubuntu:~$ iwconfig lo no wireless extensions. wlan0 IEEE 802.11bgn ESSID:"linksys" Mode:Managed Frequency:2.437 GHz Access Point: 00:18:39:76:2C:A1 Bit Rate=11 Mb/s Tx-Power=20 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=36/70 Signal level=-74 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:54 Invalid misc:18 Missed beacon:0 eth0 no wireless extensions. Any ideas? I see this is a problem a lot of people, but none of the on line solutions have worked for me so far. e.g. one site recommends editing the ath9k.conf file in /etc/modprobe.d, yet this file isn't even in the folder: User@ubuntu:/$ cd etc/modprobe.d User@ubuntu:/etc/modprobe.d$ ls alsa-base.conf blacklist-oss.conf blacklist-ath_pci.conf blacklist-rare-network.conf blacklist.conf blacklist-watchdog.conf blacklist-firewire.conf dkms.conf blacklist-framebuffer.conf nvidia-current_hybrid.conf blacklist-modem.conf nvidia-graphics-drivers.conf I think the nvidia gpu might be mucking things up. I had the "blinking cursor" problem when installing in the first place, and then I had the monitor out of range problem as well. I have my faithful Asus laptop, which is running Ubuntu 12.04 just fine. The only difference is executing host -t SOA local in the terminal gives User@ubuntu:~$ host -t SOA local local has SOA record local. nobody.localhost. 42 86400 43200 604800 10800 in my new machine, and the command reports Host local. not found in the laptop. Help would be most welcome, as I am in danger of reverting back to Windows. I'm seriously considering it. Sorry for the length, trying to show my effort in resolving the issue and include terminal snippets that might be helpful.

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• Looking for an algorithm to connect dots - shortest route

  - by e4ch

  I have written a program to solve a special puzzle, but now I'm kind of stuck at the following problem: I have about 3200 points/nodes/dots. Each of these points is connected to a few other points (usually 2-5, theoretical limit is 1-26). I have exactly one starting point and about 30 exit points (probably all of the exit points are connected to each other). Many of these 3200 points are probably not connected to neither start nor end point in any way, like a separate net, but all points are connected to at least one other point. I need to find the shortest number of hops to go from entry to exit. There is no distance between the points (unlike the road or train routing problem), just the number of hops counts. I need to find all solutions with the shortest number of hops, and not just one solution, but all. And potentially also solutions with one more hop etc. I expect to have a solution with about 30-50 hops to go from start to exit. I already tried: 1) randomly trying possibilities and just starting over when the count was bigger than a previous solution. I got first solution with 3500 hops, then it got down to about 97 after some minutes, but looking at the solutions I saw problems like unnecessary loops and stuff, so I tried to optimize a bit (like not going back where it came from etc.). More optimizations are possible, but this random thing doesn't find all best solutions or takes too long. 2) Recursively run through all ways from start (chess-problem-like) and breaking the try when it reached a previous point. This was looping at about a length of 120 nodes, so it tries chains that are (probably) by far too long. If we calculate 4 possibilities and 120 nodes, we're reaching 1.7E72 possibilities, which is not possible to calculate through. This is called Depth-first search (DFS) as I found out in the meantime. Maybe I should try Breadth-first search by adding some queue? The connections between the points are actually moves you can make in the game and the points are how the game looks like after you made the move. What would be the algorithm to use for this problem? I'm using C#.NET, but the language shouldn't matter.

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