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• A basic load test question

  - by user236131

  I have a very basic load test question. I am running a load test using VSTS 2008 and I have test rig with controller + 10 agents. This load test is against a SharePoint farm I have. My goal of the load test is to find out the resource utilization on web+app+db tiers of my farm for any given load scenario. An example of a load scenario is Usage profile: Average collaboration (as defined by SCCP) User Load: 500 (using step load pattern=a step of 50 every 2 mins and a warm up time of 2mins for every step) Think time: 0 Load duration: 8hrs Now, the question is: Is it fair to expect that metrics like Requests/sec, %processor time on web front end / App / DB, Test/sec, and etc become flat or enter a steady state at one point in time during the load test. Like I said, the goal is not to create a bottleneck but to only measure the utilization of resources by the above load profile. I am asking this question because I see something different. At one point in the load test, requests/sec becomes more or less flat. But processor utilization on the web/DB servers keeps increasing. After digging through the data a bit, I see that "tests running" counter also steadily increased over time. So, if I run the load test for more than 8hrs, %processor may go up further. This way, I don't know what to consider as the load excreted by the load profile. What does this "tests running" counter really signify? How is this different from tests/sec? Another question is: how can I find out why "tests running" counter shows an increase overtime? Thanks for your time

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• Android - How to decide wether to run a Service in a separate Process?

  - by pableu

  I am working on an Android application that collects sensor data over the course of multiple hours. For that, we have a Service that collects the Sensor Data (e.g. Acceleration, GPS, ..), does some processing and stores them remotely on a server. Currently, this Service runs in a separate process (using android:service=":background" in the manifest). This complicates the communication between the Activities and the Service, but my predecessors created the Application this way because they thought that separating the Service from the Activities would make it more stable. I would like some more factual reasons for the effort of running a separate process. What are the advantages? Does it really run more stable? Is the Service less likely to be killed by the OS (to free up resources) if it's in a separate process? Our Application uses startForeground() and friends to minimize the chance of getting killed by the OS. The Android docs are not very specific about this, the mostly state that it depends on the Application's purpose ;-) TL;DR What are objective reasons to put a long-running Service in a separate process (in Android)?

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• How can I define an irregular area of the screen and find the closest point to the mouse in that area?

  - by JonathonG

  I'm looking for a method to define an area of the screen that the mouse cannot leave. I have been directed by rob mayoff, the answerer of this question, that I can use a Quartz Event Tap to detect mouse events. This puts me part of the way to the solution to THIS question. I need to define an irregular area of the screen, not just a rectangle, that the mouse cannot leave. I have been researching this and the only idea I can come up with is using a bitmap to define the irregular area, as it will be very oddly shaped. However, I am open to solutions other than using a bitmap. Since this must be done on a Mac, I've determined that I will have to use objective C / Cocoa . I need to know how to define the area and, equally importantly, how to find the closest point in the area to the mouse (so that I can move the mouse to it if the mouse tries to move outside of the area). This is similar to what the restricted area will look like: [edit:] Okay, I've come up with part of the answer to this. If I can do a basic (light-weight) point collision detection on the image mask, I can use a simple algorithm to detect the closest point to the mouse on the black area of the image. I could do this by calculating distance between a pre-defined point (P) inside the black area of the image and the target mouse position (T), taking the midpoint (M), then checking if the midpoint is inside or outside of the shape (black or white, respectively). If M is inside the shape, then move the P to M, otherwise move T to the M, continuously recalculate this until the distance between T and P is 1 pixel or less, then move the mouse to the final calculated position. All of that being said, I still need some way to test the position of the mouse against that same position on the bitmap (assume the bitmap is the same resolution as the monitor), and check if that point is black or white. All of this needs to be done in the background, without this application actually having focus, or the bitmap being visible... is this possible?

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• Which DVCS would work best on Windows for my scenario?

  - by PoorLuzer

  At work I use ClearCase and SourceSafe, but have found some time to do some time to code for myself enroute thanks to a disposable laptop. However, I wish I had a lightweight VCS on my system using which I would be able to make changes to my code during the commute and then push/grab them from my Linux systems. I use git on my home system, but I can't really get it working on Windows. I don't want all that cygwin hack. If it does not run natively on Windows, it just won't do. What have you guys tried on your Windows system? Something that YOU use. The big player at the moment seems to be Mercurial? What would be best for a one (or maybe two) man team? I just need to maintain : Versioned copies of source code. Checking in and out should be as less obtrusive as possible. I am looking forward to a multiple Undo kind of feature (like that in an EMacs buffer) but persistent. I really like the way git keeps track of lines moving between files in a source code set I should be able to move part(s)/sub tree(s) of the source tree (each sub tree implies a module/plugin to my the main software I am building) to an archival system either completly or partially and restore them back from the archive as and when required and the system should track any changes to this tree as well. I actually want to experiment with my code as much as possible without me manually keeping track of what I modified and what I need to undo once I try out some idea, so that I am back to where I want to continue from. Notes : A similar topic came up a year ago : http://stackoverflow.com/questions/4670/dvcs-choices-whats-good-for-windows I hope things have changed, and I really want people to share their own, real life experiences. Not something they recommend without using it or they think will work.

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• Querying for a unique value based on the aggregate of another value while grouping on a third value

  - by Justin Swartsel

  So I know this problem isn't a new one, but I'm trying to wrap my head around it and understand the best way to deal with scenarios like this. Say I have a hypothetical table 'X' that looks like this: GroupID ID (identity) SomeDateTime -------------------------------------------- 1 1000 1/1/01 1 1001 2/2/02 1 1002 3/3/03 2 1003 4/4/04 2 1004 5/5/05 I want to query it so the result set looks like this: ---------------------------------------- 1 1002 3/3/03 2 1004 5/5/05 Basically what I want is the MAX SomeDateTime value grouped by my GroupID column. The kicker is that I DON'T want to group by the ID column, I just want to know the 'ID' that corresponds to the MAX SomeDateTime. I know one pseudo-solution would be: ;WITH X1 as ( SELECT MAX(SomeDateTime) as SomeDateTime, GroupID FROM X GROUP BY GroupID ) SELECT X1.SomeDateTime, X1.GroupID, X2.ID FROM X1 INNER JOIN X as X2 ON X.DateTime = X2.DateTime But this doesn't solve the fact that a DateTime might not be unique. And it seems sloppy to join on a DateTime like that. Another pseudo-solution could be: SELECT X.GroupID, MAX(X.ID) as ID, MAX(X.SomeDateTime) as SomeDateTime FROM X GROUP BY X.GroupID But there are no guarantees that ID will actually match the row that SomeDateTime comes from. A third less useful option might be: SELECT TOP 1 X.GroupID, X.ID, X.SomeDateTime FROM X WHERE X.GroupID = 1 ORDER BY X.SomeDateTime DESC But obviously that only works with a single, known, GroupID. I want to be able to join this result set on GroupID and/or ID. Does anyone know of any clever solutions? Any good uses of windowing functions? Thanks!

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• Chat app vs REST app - use a thread in an Activity or a thread in a Service?

  - by synic

  In Virgil Dobjanschi's talk, "Developing Android REST client applications" (link here), he said a few things that took me by surprise. Including: Don't run http queries in threads spawned by your activities. Instead, communicate with a service to do them, and store the information in a ContentProvider. Use a ContentObserver to be notified of changes. Always perform long running tasks in a Service, never in your Activity. Stop your Service when you're done with it. I understand that he was talking about a REST API, but I'm trying to make it fit with some other ideas I've had for apps. One of APIs I've been using uses long-polling for their chat interface. There is a loop http queries, most of which will time out. This means that, as long as the app hasn't been killed by the OS, or the user hasn't specifically turned off the chat feature, I'll never be done with the Service, and it will stay open forever. This seems less than optimal. Long question short: For a chat application that uses long polling to simulate push and immediate response, is it still best practice to use a Service to perform the HTTP queries, and store the information in a ContentProvider?

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• Need help implementing this algorithm with map reduce(hadoop)

  - by Julia

  Hi all! i have algorithm that will go through a large data set read some text files and search for specific terms in those lines. I have it implemented in Java, but I didnt want to post code so that it doesnt look i am searching for someone to implement it for me, but it is true i really need a lot of help!!! This was not planned for my project, but data set turned out to be huge, so teacher told me I have to do it like this. I was reading about MapReduce and thaught that i first do the standard implementation and then it will be more/less easier to do it with mapreduce. But didnt happen, since algorithm is quite stupid and nothing special, and map reduce...i cant wrap my mind around it. So here is shortly pseudo code of my algorithm LIST termList (there is method that creates this list from lucene index) FOLDER topFolder INPUT topFolder IF it is folder and not empty list files (there are 30 sub folders inside) FOR EACH sub folder GET file "CheckedFile.txt" analyze(CheckedFile) ENDFOR END IF Method ANALYZE(CheckedFile) read CheckedFile WHILE CheckedFile has next line GET line FOR(loops through termList) GET third word from line IF third word = term from list append whole line to string buffer ENDIF ENDFOR END WHILE OUTPUT string buffer to file Also, as you can see, each time when "analyze" is called, new file has to be created, i understood that map reduce is difficult to write to many outputs??? I understand mapreduce intuition, and my example seems perfectly suited for mapreduce, but when it comes to do this, obviously I do not know enough and i am STUCK! Please please help.

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• Why is the 'var' keyword bad? Or am I just old school?

  - by WaggingSiberian

  Recently I overheard junior developer ask "why do you use 'var' so much?". The mid-level developer responded "I use VAR all the time. I love it! I don't have to figure out the type." I didn't have the time or energy to get into a religious war and hey, I'm still the new guy here :-) I understand var has its place. LINQ comes to mind. But I have also always been told the use of var represents lazy programming and I should just use the correct type to begin with. If it's an int, define it as an int, not a var. When reviewing code, seeing the type makes it easier to follow. My opinion is, it's just lazy but there are exception. Var also reminds me of the VB/VBA variant type. It also had its place. I recall (from many years ago) its usage being less-than-desirable type and it was rather resource hungry. Am I just being stuck in my ways? Should we start using var all the time as my co-worker does?

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• Optimizing near-duplicate value search

  - by GApple

  I'm trying to find near duplicate values in a set of fields in order to allow an administrator to clean them up. There are two criteria that I am matching on One string is wholly contained within the other, and is at least 1/4 of its length The strings have an edit distance less than 5% of the total length of the two strings The Pseudo-PHP code: foreach($values as $value){ foreach($values as $match){ if( ( $value['length'] < $match['length'] && $value['length'] * 4 > $match['length'] && stripos($match['value'], $value['value']) !== false ) || ( $match['length'] < $value['length'] && $match['length'] * 4 > $value['length'] && stripos($value['value'], $match['value']) !== false ) || ( abs($value['length'] - $match['length']) * 20 < ($value['length'] + $match['length']) && 0 < ($match['changes'] = levenshtein($value['value'], $match['value'])) && $match['changes'] * 20 <= ($value['length'] + $match['length']) ) ){ $matches[] = &$match; } } } I've tried to reduce calls to the comparatively expensive stripos and levenshtein functions where possible, which has reduced the execution time quite a bit. However, as an O(n^2) operation this just doesn't scale to the larger sets of values and it seems that a significant amount of the processing time is spent simply iterating through the arrays. Some properties of a few sets of values being operated on Total | Strings | # of matches per string | | Strings | With Matches | Average | Median | Max | Time (s) | --------+--------------+---------+--------+------+----------+ 844 | 413 | 1.8 | 1 | 58 | 140 | 593 | 156 | 1.2 | 1 | 5 | 62 | 272 | 168 | 3.2 | 2 | 26 | 10 | 157 | 47 | 1.5 | 1 | 4 | 3.2 | 106 | 48 | 1.8 | 1 | 8 | 1.3 | 62 | 47 | 2.9 | 2 | 16 | 0.4 | Are there any other things I can do to reduce the time to check criteria, and more importantly are there any ways for me to reduce the number of criteria checks required (for example, by pre-processing the input values), since there is such low selectivity?

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• Visual C++ function suddenly 170x slower

  - by Mikael

  For the past few months I've been working on a Visual C++ project to take images from cameras and process them. Up until today this has taken about 65 ms to update the data but now it has suddenly increased significantly. What happens is: I launch my program and for the first 30 or so iterations it performs as expected, then suddenly the loop time increases from 65 ms to 250 ms. The odd thing is, after timing each function I found out that the part of the code which is causing the slowdown is fairly basic and has not been modified in over a month. The data which goes into it is unchanged and identical every iteration but the execution time which is initially less than 1 ms suddenly increases to 170 ms while the rest of the code is still performing as expected (time-wise). Basically, I am calling the same function over and over, for the first 30 calls it performs as it should, after that it slows down for no apparent reason. It might also be worth noting that it is a sudden change in execution time, not a gradual increase. What could be causing this? The code is leaking some memory (~50 kb/s) but not nearly enough to warrant a sudden 4x slowdown. If anyone has any ideas I'd love to hear them!

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• Hive performance increase

  - by Sagar Nikam

  I am dealing with a database (2.5 GB) having some tables only 40 row to some having 9 million rows data. when I am doing any query for large table it takes more time. I want results in less time small query on table which have 90 rows only-- hive> select count(*) from cidade; Time taken: 50.172 seconds hdfs-site.xml <configuration> <property> <name>dfs.replication</name> <value>3</value> <description>Default block replication. The actual number of replications can be specified when the file is created. The default is used if replication is not specified in create time. </description> </property> <property> <name>dfs.block.size</name> <value>131072</value> <description>Default block replication. The actual number of replications can be specified when the file is created. The default is used if replication is not specified in create time. </description> </property> </configuration> does these setting affects performance of hive? dfs.replication=3 dfs.block.size=131072 can i set it from hive prompt as hive>set dfs.replication=5 Is this value remains for a perticular session only ? or Is it better to change it in .xml file ?

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• Cannot Resize DIV to anything smaller than maximum width

  - by MxmastaMills

  Quick CSS Question. I cannot seem to figure out a very simple CSS/HTML problem. Here's a JSFiddle. http://jsfiddle.net/BmM6t/ Basically, these two divs are not resizing to anything less than 100% width: <div id="main_pic" class="main_div"> THIS IS WHERE THE MAIN PIC WILL GO. </div> <div id="signin" class="main_div"> SIGN IN TO THE SITE! <form> <label for="name">EMAIL/USERNAME:</label> <input type="text" name="name" id="name"> <label for="email">PASSWORD:</label> <input type="text" name="email" id="email"> <br /> <input type="submit" value="Let's Play!"> </form> </div> You'll see that the two divs with class main_div actually take up the entire width of the screen for some reason (you can see that if you inspect the element) even though their widths are clearly written. When you try to change the width of one of the main_div's it changes the width but if you inspect the element, it just changes the width of the object and adds padding around it to make sure it still takes up the entire width of the screen. I'm sure it's some little error I've made but I can't find it. Thanks for the help!

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• Need a set based solution to group rows

  - by KM

  I need to group a set of rows based on the Category column, and also limit the combined rows based on the SUM(Number) column to be less than or equal to the @Limit value. For each distinct Category column I need to identify "buckets" that are <=@limit. If the SUM(Number) of all the rows for a Category column are <=@Limit then there will be only 1 bucket for that Category value (like 'CCCC' in the sample data). However if the SUM(Number)@limit, then there will be multiple bucket rows for that Category value (like 'AAAA' in the sample data), and each bucket must be <=@Limit. There can be as many buckets as necessary. Also, look at Category value 'DDDD', its one row is greater than @Limit all by itself, and gets split into two rows in the result set. Given this simplified data: DECLARE @Detail table (DetailID int primary key, Category char(4), Number int) SET NOCOUNT ON INSERT @Detail VALUES ( 1, 'AAAA',100) INSERT @Detail VALUES ( 2, 'AAAA', 50) INSERT @Detail VALUES ( 3, 'AAAA',300) INSERT @Detail VALUES ( 4, 'AAAA',200) INSERT @Detail VALUES ( 5, 'BBBB',500) INSERT @Detail VALUES ( 6, 'CCCC',200) INSERT @Detail VALUES ( 7, 'CCCC',100) INSERT @Detail VALUES ( 8, 'CCCC', 50) INSERT @Detail VALUES ( 9, 'DDDD',800) INSERT @Detail VALUES (10, 'EEEE',100) SET NOCOUNT OFF DECLARE @Limit int SET @Limit=500 I need one of these result set: DetailID Bucket | DetailID Category Bucket -------- ------ | -------- -------- ------ 1 1 | 1 'AAAA' 1 2 1 | 2 'AAAA' 1 3 1 | 3 'AAAA' 1 4 2 | 4 'AAAA' 2 5 3 OR 5 'BBBB' 1 6 4 | 6 'CCCC' 1 7 4 | 7 'CCCC' 1 8 4 | 8 'CCCC' 1 9 5 | 9 'DDDD' 1 9 6 | 9 'DDDD' 2 10 7 | 10 'EEEE' 1

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• Initializing an object to all zeroes

  - by dash-tom-bang

  Oftentimes data structures' valid initialization is to set all members to zero. Even when programming in C++, one may need to interface with an external API for which this is the case. Is there any practical difference between: some_struct s; memset(s, 0, sizeof(s)); and simply some_struct s = { 0 }; Do folks find themselves using both, with a method for choosing which is more appropriate for a given application? For myself, as mostly a C++ programmer who doesn't use memset much, I'm never certain of the function signature so I find the second example is just easier to use in addition to being less typing, more compact, and maybe even more obvious since it says "this object is initialized to zero" right in the declaration rather than waiting for the next line of code and seeing, "oh, this object is zero initialized." When creating classes and structs in C++ I tend to use initialization lists; I'm curious about folks thoughts on the two "C style" initializations above rather than a comparison against what is available in C++ since I suspect many of us interface with C libraries even if we code mostly in C++ ourselves.

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• WINDOWS: Your computer hangs. You can windows + R (run dialog) but performance is so halted taskMGR

  - by John Sullivan

  The question is, what process are available to try to recover from total system instability before pulling the plug when we can do nothing but programs or batches in the path from the run dialog (windows + r key), and performance is so dead that taskMGR / procEXP / other programs with visual guis are not usable? I am not a windows expert, but ideally someone out there has written a program that does more or less stuff like this: Immediately set (or perhaps I can set from the run prompt) its priority to extremely high, evaluate performance bottlenecks. E.g. is CPU 100%? If so identify offending program(s) or problems. Attempt / log fixes, then provide crude feedback asking the user if his performance has stabilized enough to abort, wait a few seconds, if no feedback continue, etc. etc. Eventually try to do any "system cleanup" if the program decides it cannot recover and perhaps finally provide a series of beeps to the user, or what have you, to say "OK, I give up, time to pull the plug". Ideally create a log, when able. These kinds of horrible hangs are a situation where surely trying something, anything, is better than nothing -- as long as that something is intelligent -- when the alternative is ripping out the power coord. Again, I am not a windows expert, so perhaps there is a much more elegant "hands on" approach I am not aware of.

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• Integrating jQuery autocomplete with Google site search

  - by user1715700

  I have a bit of an odd situation. I have to implement search on a public facing website -but, that search must be able to search both web pages and have an autocomplete/suggestion functionality that comes from a list of terms that are in a DB table. So, I'm wondering a couple things: 1) should I be looking at Google search and jQuery autocomplete? 2) is there something else I should be looking at instead? 3) if this is the right path to be heading down are the enough pointers on implementation? The crux of my problem is that the terms that I need to use for the autocomplete/suggest functionality reside within a database and not on the webpages. So, I thought Google would be appropriate for search the webpages and that I could sort of fill in the blanks so to speak with these terms from the DB. I'm going to say that there are roughly 20-40,000 terms or so that need autocomplete. But that is really just a very rough guess -it could be less. I'm open to ideas and not really married to any particular solution. However, I will admit to liking the ideas of offloading the search to Google. I hear they have a good algorithm ;) Any ideas, thoughts, or leads are greatly appreciated!

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• How do you protect yourself from runaway memory consumption bringing down the PC?

  - by romkyns

  Every now and again I find myself doing something moderately dumb that results in my program allocating all the memory it can get and then some. This kind of thing used to cause the program to die fairly quickly with an "out of memory" error, but these days Windows will go out of its way to give this non-existent memory to the application, and in fact is apparently prepared to commit suicide doing so. Not literally of course, but it will starve itself of usable physical RAM so badly that even running the task manager will require half an hour of swapping (after all the runaway application is still allocating more and more memory all the time). This doesn't happen too often, but when it does it's disastrous. I usually have to reset my machine, causing data loss from time to time and generally a lot of inconvenience. Do you have any practical advice on making the consequences of such a mistake less dire? Perhaps some registry tweak to limit the max amount of virtual memory an app is allowed to allocate? Or some CLR flag that will limit this only for the current application? (It's usually in .NET that I do this to myself.) ("Don't run out of RAM" and "Buy more RAM" are no use - the former I have no control over, and the latter I've already done.)

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• Slowing process creation under Java?

  - by oconnor0

  I have a single, large heap (up to 240GB, though in the 20-40GB range for most of this phase of execution) JVM [1] running under Linux [2] on a server with 24 cores. We have tens of thousands of objects that have to be processed by an external executable & then load the data created by those executables back into the JVM. Each executable produces about half a megabyte of data (on disk) that when read right in, after the process finishes, is, of course, larger. Our first implementation was to have each executable handle only a single object. This involved the spawning of twice as many executables as we had objects (since we called a shell script that called the executable). Our CPU utilization would start off high, but not necessarily 100%, and slowly worsen. As we began measuring to see what was happening we noticed that the process creation time [3] continually slows. While starting at sub-second times it would eventually grow to take a minute or more. The actual processing done by the executable usually takes less than 10 seconds. Next we changed the executable to take a list of objects to process in an attempt to reduce the number of processes created. With batch sizes of a few hundred (~1% of our current sample size), the process creation times start out around 2 seconds & grow to around 5-6 seconds. Basically, why is it taking so long to create these processes as execution continues? [1] Oracle JDK 1.6.0_22 [2] Red Hat Enterprise Linux Advanced Platform 5.3, Linux kernel 2.6.18-194.26.1.el5 #1 SMP [3] Creation of the ProcessBuilder object, redirecting the error stream, and starting it.

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• Improving the efficiency of multiple concurrent Core Animation animations

  - by Alex

  I have a view in my app that is very similar to the month view in the built-in Calendar app. There's a subview that holds the individual cells (a custom UIView subclass that draws text into its layer), and when the user navigates to the next "month", I create the new cells and slide the view to show them. When the animation stops, I remove the old, hidden cells and set things up so it's ready to go for the next animation. This all works nicely. However, I'd like to animate the cells' text color, as in the Calendar app, so that the outgoing ones transition to a lighter color and the incoming ones transition to a darker color. The problems is that I can have as many as 70 cells, so doing individual animations is very slow -- between 5-10 fps on my iPhone 3GS. I'm trying to find a less computationally intense way of doing this. My reading of the Shark results is that the majority of the time is spent redrawing the text for each frame for each frame. This makes sense, since text rendering is hardly the cheapest operation. I've considered creating a second view -- one holding the "outgoing" state and one holding the "incoming" state and using a single opacity animation to gradually reveal the updated cells while both are sliding. I'm concerned that instead of having 70 cells, I'll have 140, which seems like a lot of views. So, is that too many views or would there be a better way of doing this?

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• java class that simulates a simple database table

  - by ericso

  I have a collection of heterogenous data that I pull from a database table mtable. Then, for every unique value uv in column A, I compute a function of (SELECT * FROM mtable WHERE A=uv). Then I do the same for column B, and column C. There are rather a lot of unique values, so I don't want to hit the db repeatedly - I would rather have a class that replicates some of the functionality (most importantly some version of SELECT WHERE). Additionally, I would like to abstract the column names away from the class definition, if that makes any sense - the constructor should take a list of names as a parameter, and also, I suppose, a list of types (right now this is just a String[], which seems hacky). I'm getting the initial data from a RowSet. I've more or less done this by using a hashmap that maps Strings to lists/arrays of Objects, but I keep getting bogged down in comparisons and types, and am thinking that my current implementation really isn't as clean and clear as it could be. I'm pretty new to java, also, and am not sure if I'm not going down a completely incorrect path. Does anyone have any suggestions?

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• Storing large json strings to database + hash

  - by Guy

  I need to store quiete large JSON data strings to the database. I am using gzip to compress the string and therefore BLOB MySQL data type to store it. However, only 5% of all the requests contain unique data and only unique data ought to be stored to the database. My approach is as follows. array_multisort data (array [a, b, c] is virtually the same as [a, c, b]). json_encode data (json_encode is faster than serialize; we need string array representation for the step 3). sha1 data (slower than md5, though less possible the collisions). Check if the hash exists in the database. 5.1 yes – do not insert the data. 5.2. no – gzip the data and store it along the hash. Is there anything about this (apart from storing JSON data to the database in the first place) that sounds fishy or should be done a different way? p.s. We are talking about a database with roughly 1kk unique records being created every month.

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• How to structure Javascript programs in complex web applications?

  - by mixedpickles

  Hi there. I have a problem, which is not easily described. I'm writing a web application that makes heavy usage of jquery and ajax calls. Now I don't have experience in designing the architecture for javascript programms, but I realize that my program has not a good structure. I think I have to many identifiers referring to the same (at least more or less) thing. Let's have an exemplary look at an arbitrary UI widget: The eventhandlers use DOM elements as parameters. The DOM element represents a widget in the browser. A lot of times I use jQuery objects (I think they are basically a wrapper around DOM elements) to do something with the widget. Sometimes they are used transiently, sometimes they are stored in a variable for later purposes. The ajax function calls use strings identifiers for these widgets. They are processed server side. Beside that I have a widget class whose instances represents a widget. It is instantiated through the new operator. Now I have somehow four different object identifiers for the same thing, which needs to be kept in sync until the page is loaded anew. This seems not to be a good thing. Any advice?

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• Find Lines with N occurrences of a char

  - by Martín Marconcini

  I have a txt file that I’m trying to import as flat file into SQL2008 that looks like this: “123456”,”some text” “543210”,”some more text” “111223”,”other text” etc… The file has more than 300.000 rows and the text is large (usually 200-500 chars), so scanning the file by hand is very time consuming and prone to error. Other similar (and even more complex files) were successfully imported. The problem with this one, is that “some lines” contain quotes in the text… (this came from an export from an old SuperBase DB that didn’t let you specify a text quantifier, there’s nothing I can do with the file other than clear it and try to import it). So the “offending” lines look like this: “123456”,”this text “contains” a quote” “543210”,”And the “above” text is bad” etc… You can see the problem here. Now, 300.000 is not too much if I could perform a search using a text editor that can use regex, I’d manually remove the quotes from each line. The problem is not the number of offending lines, but the impossibility to find them with a simple search. I’m sure there are less than 500, but spread those in a 300.000 lines txt file and you know what I mean. Based upon that, what would be the best regex I could use to identify these lines? My first thought is: Tell me which lines contain more than 4 quotes (“). But I couldn’t come up with anything (I’m not good at Regex beyond the basics).

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• Migrate from Oracle to MySQL

  - by Cassy

  Hi together. We ran into serious performance problems with our Oracle database and we would like to try to migrate to a MySQL-based database (either MySQL directly or, more preferrable, Infobright). The thing is, we need to let the old and the new system overlap for at least some weeks if not months, before we actually know, if all features of the new database match our needs. So, here is our situation: The Oracle database consists of multiple tables with each millions of rows. During the day, there are literally thousands of statements, which we cannot stop for migration. Every morning, new data is imported into the Oracle database, replacing some thousands of rows. Copying this process is not a problem, so we could, in theory, import in both databases in parallel. But, and here lies the challenge, for this to work, we need to have an export from the Oracle database with a consistent state from one day. (We cannot export some tables on Monday and some others on Tuesday, etc.) This means, that at least the export should be finished in less than one day. Our first thought was to dump the schema, but I wasn't able to find a tool to import an Oracle dump file into mysql. Exporting tables in CSV files might work, but I'm afraid it could take too long. So my question now is: What should I do? Is there any tool to import Oracle dump files into MySQL? Does anybody have any experience with such a large-scale migration? Thanks in advance, Cassy PS: Please, don't suggest performance optimization techniques for Oracle, we already tried a lot :-)

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• Sending a message to nil?

  - by Ryan Delucchi

  As a Java developer who is reading Apple's Objective-C 2.0 documentation: I wonder as to what sending a message to nil means - let alone how it is actually useful. Taking an excerpt from the documentation: There are several patterns in Cocoa that take advantage of this fact. The value returned from a message to nil may also be valid: If the method returns an object, any pointer type, any integer scalar of size less than or equal to sizeof(void*), a float, a double, a long double, or a long long, then a message sent to nil returns 0. If the method returns a struct, as defined by the Mac OS X ABI Function Call Guide to be returned in registers, then a message sent to nil returns 0.0 for every field in the data structure. Other struct data types will not be filled with zeros. If the method returns anything other than the aforementioned value types the return value of a message sent to nil is undefined. Has Java rendered my brain incapable of grokking the explanation above? Or is there something that I am missing that would make this as clear as glass? Note: Yes, I do get the idea of messages/receivers in Objective-C, I am simply confused about a receiver that happens to be nil.

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