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  • does mysql stored procedures support data types like array, hash,etc?

    - by Yang
    i am creating a mysql function which takes in a varchar and change it to a int based on a mapping table. select name, convert_to_code(country) from users where sex = 'male' here, the convert_to_code() function takes in a country name (e.g. Japan, Finland..) and change it to country code which is an integer (e.g. 1001, 2310..) based on a mapping table called country_maping like below: country_name (varchar) | country_code (int) Japan | 1001 Finland | 2310 Canada | 8756 currently, the stored function need to select country_code from country_mapping where country_name = country_name and return the query result. is that possible to create a hash data struct in SP to optimize the process so that it will not need to perform the query for each row matches the where clause. thanks in advance!

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  • Does Ruby on Rails "has_many" array provide data on a "need to know" basis?

    - by Jian Lin
    On Ruby on Rails, say, if the Actor model object is Tom Hanks, and the "has_many" fans is 20,000 Fan objects, then actor.fans gives an Array with 20,000 elements. Probably, the elements are not pre-populated with values? Otherwise, getting each Actor object from the DB can be extremely time consuming. So it is on a "need to know" basis? So does it pull data when I access actor.fans[500], and pull data when I access actor.fans[0]? If it jumps from each record to record, then it won't be able to optimize performance by doing sequential read, which can be faster on the hard disk because those records could be in the nearby sector / platter layer -- for example, if the program touches 2 random elements, then it will be faster just to read those 2 records, but what if it touches all elements in random order, then it may be faster just to read all records in a sequential way, and then process the random elements. But how will RoR know whether I am doing only a few random elements or all elements in random?

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  • Simple neon optimization in Android

    - by Peter
    In my Android application, I use a bunch of open source libraries such as libyuv, libvpx, libcrypto, libssl, etc. Some of them come with Android.mk. For others, I hand-crafted Android.mk. The code is built only for arm for now. Here is my Application.mk: APP_ABI := armeabi-v7a APP_OPTIM := release APP_STL := gnustl_static APP_CPPFLAGS := -frtti I am looking for way to generate binaries that are optimized for neon. Browsing the net, I found the following setting that someone is using in his Android.mk: LOCAL_CFLAGS += -mfloat-abi=softfp -mfpu=neon -march=armv7 I wonder if I simply put this setting in Application.mk, will it automatically get applied across all the libraries? A step before each library is built is the following: include $(CLEAR_VARS) Is it better to include LOCAL_CFLAGS directive after this line (instead of including it in Application.mk)? Finally, why doesn't ndk-build automatically optimize for neon when it sees armabi in Application.mk? Regards.

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  • wpf style converter : "Convert" called by every datagrid column using it

    - by Sonic Soul
    I created a converter, and assigned it to a style. than i assigned that style, to the columns i want affected. as rows are added, and while stepping through debugger, i noticed that the converter convert method gets called 1 time per column (each time it is used). is there a way to optimize it better, so that it gets called only once and all columns using it get the same value? <Style x:Key="ConditionalColorStyle" TargetType="{x:Type DataGridCell}" BasedOn="{StaticResource CellStyle}"> <Setter Property="Foreground"> <Setter.Value> <Binding> <Binding.Converter> <local:ConditionalColorConverter /> </Binding.Converter> </Binding> </Setter.Value> </Setter> </Style>

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  • What is the cost in bytes for the overhead of a sql_variant column in SQL Server?

    - by Elan
    I have a table, which contains many columns of float data type with 15 digit precision. Each column consumes 8 bytes of storage. Most of the time the data does not require this amount of precision and could be stored as a real data type. In many cases the value can be 0, in which case I could get away with storing a single byte. My goal here is to optimize space storage requirements, which is an issue I am facing working with a SQL Express 4GB database size limit. If byte, real and float data types are stored in a sql_variant column there is obviously some overhead involved in storing these values. What is the cost of this overhead? I would then need to evaluate whether I would actually end up in significant space savings (or not) switching to using sql_variant column data types. Thanks, Elan

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  • Android: 2D. OpenGl or android.graphics.drawable?

    - by DroidIn.net
    I'm working with my friend on our first Android game. Basic idea is that every frame the whole surface is redrawn (1 large bitmap) which then sprinkled all over with large number of particles which produces effect of soapy bubbles where there's a pool of about 20 bitmaps which randomly gets picked to produce illusion that all bubbles (between 200 - 300) are all different. The math engine is in C (JNI) and currently all drawing is done using android.graphics package very similar (since that was the example I was using) to Lunar Lander. It works but animation is somewhat jerky and I can feel by temperature of my phone that it is very busy. Will we benefit from switching to OpenGL? And as a bonus question: what would be a good way to optimize the drawing mechanism (Lunar Lander like) we have now?

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  • Is there alternative way to write this query?

    - by Kugel
    I have tables A, B, C, where A represents items which can have zero or more sub-items stored in C. B table only has 2 foreign keys to connect A and C. I have this sql query: select * from A where not exists (select * from B natural join C where B.id = A.id and C.value > 10); Which says: "Give me every item from table A where all sub-items have value less than 10. Is there a way to optimize this? And is there a way to write this not using exists operator?

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  • make: invoke command for multiple targets of multiple files?

    - by marvin2k
    Hi, I looking to optimize an existing Makefile. It's used to create multiple plots (using Octave) for every logfile in a given directory using an scriptfile for every plot which takes a logfilename as an argument. In the Moment, I use one single rule for every kind of plot available, with a handwritten call to Octave, giving the specific scriptfile/logfile as an argument. It would be nice, if every plot has "his" octave-script as a dependency (plus the logfile, of course), so only one plot is regenerated if his script is changed. Since I don't want to type that much, I wonder how I can simplifiy this by using only one general rule to build "a" plot? To make it clearer: Logfile: "$(LOGNAME).log" Scriptfile: "plot$(PLOTNAME).m" creates "$(LOGNAME)_$(PLOTNAME).png" The first thing I had in mind: %1_%2.png: %1.log $(OCTAVE) --eval "plot$<2('$<1')" But this seems not to be allowed. Could someone give me a hint?

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  • Does MVC replace traditional manually created UI, BLL, DAL ?

    - by used2could
    I'm use to creating the UI, BLL, DAL by hand (some times i've used LINQ-SQL or SubSonic for the DAL). I've done several small projects using MVC since it's release. On these projects i've still continued to write a BLL and DAL by hand and then incorporate those into the MVC's models/controllers. Looking to optimize my time on projects this seems like over kill and a potential waste of time. My question is: Would it be acceptable to roll a DAL such as SubSonic and directly use it in the Models/Controllers of my MVC web app? Now the models & controllers would act as the BLL. I just see this as a major time savor to not have to worry about another tier. (Agree ? "Please state way" : "Make argument")

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  • Premature optimization is the root of all evil, but can it ever be too late?

    - by polygenelubricants
    "We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil" So what is that 3% like? Can the avoidance of premature optimization ever be taken too extreme that it does more harm than good? Even if it's rare, has there been a case of a real measurable software engineering disaster due to complete negligence to optimize early in the process? Bonus question: is software engineering pretty much the only field that has such a counter intuitive principle regarding doing something earlier rather than later before things potentially become too big a problem to fix? Personal question: how do you justify something as premature optimization and not just a case of you being lazy/ignorant/dumb?

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  • How do I maximize a function in Mathematica which takes in a variable length list as input?

    - by Mike
    I have a time-series like function which gives an output based on a list of real numbers(i.e. you can run the function on a list of 1,2,3,... real numbers). The issue I'm encountering is how to maximize the function for a given list length(subject to a set of constraints). I could fix the function to a fixed number of real numbers(i.e. f [x_Real, y_Real] instead of f[x_List]) and treat x and y as the first two elements of the list, and call Maximize on the function, but this is not really elegant. I want to be able to easily change the number of elements in the list. What is the best way to optimize a function like I described, which takes a list as an argument, for a fixed list length?

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  • when is java faster than c++ (or when is JIT faster then precompiled)?

    - by kostja
    I have heard that under certain circumstances, Java programs or rather parts of java programs are able to be executed faster than the "same" code in C++ (or other precompiled code) due to JIT optimizations. This is due to the compiler being able to determine the scope of some variables, avoid some conditionals and pull similar tricks at runtime. Could you give an (or better - some) example, where this applies? And maybe outline the exact conditions under which the compiler is able to optimize the bytecode beyond what is possible with precompiled code? NOTE : This question is not about comparing Java to C++. Its about the possibilities of JIT compiling. Please no flaming. I am also not aware of any duplicates. Please point them out if you are.

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  • Improve performance of sorting files by extension

    - by DxCK
    With a given array of file names, the most simpliest way to sort it by file extension is like this: Array.Sort(fileNames, (x, y) => Path.GetExtension(x).CompareTo(Path.GetExtension(y))); The problem is that on very long list (~800k) it takes very long to sort, while sorting by the whole file name is faster for a couple of seconds! Theoretical, there is a way to optimize it: instead of using Path.GetExtension() and compare the newly created extension-only-strings, we can provide a Comparison than compares starting from the LastIndexOf('.') without creating new strings. Now, suppose i found the LastIndexOf('.'), i want to reuse native .NET's StringComparer and apply it only to the part on string after the LastIndexOf('.'). Didn't found a way to do that. Any ideas?

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  • MongoDB vs CouchDB (Speed optimization)

    - by Edward83
    Hi! I made some tests of speed to compare MongoDB and CouchDB. Only inserts were while testing. I got MongoDB 15x faster than CouchDB. I know that it is because of sockets vs http. But, it is very interesting for me how can I optimize inserts in CouchDB? Test platform: Windows XP SP3 32 bit. I used last versions of MongoDB, MongoDB C# Driver and last version of installation package of CouchDB for Windows. Thanks!

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  • Database indexes - what should they be

    - by WebweaverD
    Most of my database tables have a clear unique index through which lookups are done 90% of the time but I am a bit unsure on this one - I have a table which keeps track of user rating totals for items in my database, I now want to add another table, to track individual ratings with an ip address column to make sure no one can rate something twice. Since I can see this becoming a big, high use table it is important to optimize it correctly. (MYSQL table) This table will have the following fields: rating_id(always - unique), item_id (always - not unique), user_id (optional - not unique), ip_address (always - not unique), rating_value(always - not unique), has_review(bool) Now I envisions 90% the queries going something like this: When a user rates something - select where item_id = x and ip_address = y, (if rows = 0) insert rating When in user account pages - select where ip_address = x or username = y Now none of the fields searched on are unique, can I still use them as indexes (for example item _id and ip_address), can I have two indexes and will this still improve performance over a non indexed table?

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  • "Anagram solver" based on statistics rather than a dictionary/table?

    - by James M.
    My problem is conceptually similar to solving anagrams, except I can't just use a dictionary lookup. I am trying to find plausible words rather than real words. I have created an N-gram model (for now, N=2) based on the letters in a bunch of text. Now, given a random sequence of letters, I would like to permute them into the most likely sequence according to the transition probabilities. I thought I would need the Viterbi algorithm when I started this, but as I look deeper, the Viterbi algorithm optimizes a sequence of hidden random variables based on the observed output. I am trying to optimize the output sequence. Is there a well-known algorithm for this that I can read about? Or am I on the right track with Viterbi and I'm just not seeing how to apply it?

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  • Faster way to clone.

    - by AngryHacker
    I am trying to optimize a piece of code that clones an object: #region ICloneable public object Clone() { MemoryStream buffer = new MemoryStream(); BinaryFormatter formatter = new BinaryFormatter(); formatter.Serialize(buffer, this); // takes 3.2 seconds buffer.Position = 0; return formatter.Deserialize(buffer); // takes 2.1 seconds } #endregion Pretty standard stuff. The problem is that the object is pretty beefy and it takes 5.4 seconds (according ANTS Profiler - I am sure there is the profiler overhead, but still). Is there a better and faster way to clone?

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  • C++: concatenate ints in an array?

    - by Nate
    As part of a homework assignment I need to concatenate certain values in an array in C++. So, for example if I have: int v[] = {0,1,2,3,4} I may need at some point to concatenate v[1] - v[4] so that I get an int with the value 1234. I got it working using stringstream, by appending the values onto the stringstream and then converting back to an integer. However, throughout the program there will eventually be about 3 million different permutations of v[] passed to my toInt() function, and the stringstream seems rather expensive (at least when dealing with that many values). it's working, but very slow and I'm trying to do whatever I can to optimize it. Is there a more optimal way to concatenate ints in an array in C++? I've done some searching and nearly everywhere seems to just suggest using stringstream (which works, but seems to be slowing my program down a lot). EDIT: Just clarifying, I do need the result to be an int.

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  • change Magento to new server, images of existing product do not shown in frontend

    - by forrest gump
    I have moved a Magento website to a new server to optimize speed. All images appear to be replaced by image placeholders. I tried to set permission for media to 777, when I delete cache media folder and refresh, a new cache folder is created automatically, but only with placeholder images inside. I flushed image cache, reindex in magento backend but still no hope. What should I do now? Somethings might be helpful: . It's fine to create new product with images . Flush cache, only placeholders images are created . tried to use magento-cleanup.php, no hope . tried to remove .htaccess in media folder . the images of products are there in the media folder, just not in cache folder. Magento only looks at the cache folder for image :(

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  • Unicorn: Which number of worker processes to use?

    - by blackbird07
    I am running a Ruby on Rails app on a virtual Linux server that is capped at 1GB RAM. Currently, I am constantly hitting the limit and would like to optimize memory utilization. One option I am looking at is reducing the number of unicorn workers. So what is the best way to determine the number of unicorn workers to use? The current setting is 10 workers, but the maximum number of requests per second I have seen on Google Analytics Real-Time is 3 (only scored once at a peak time; in 99% of the time not going above 1 request per second). So is it a save assumption that I can - for now - go with 4 workers, leaving room for unexpected amounts of requests? What are the metrics I should have a look at for determining the number of workers and what are the tools I can use for that on my Ubuntu machine?

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  • java best way to transfer images

    - by d.raev
    I have a application that reads a PDF, transform the content to collection of TIF files, and send them to Glass Fish Server for saving. Usually there are 1-5 pages and it works nice, but when I got a input file with 100+ pages... it throws error on the transfer. Java heap space at java.util.Arrays.copyOf(Arrays.java:2786) at java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:94) Putting more resources is not a good option in my case, so I m looking for a way to optimize it somehow. I store the data in: HashMap<TifProfile, List<byte[]> Is there a better way to store or send them ? EDIT I did some tests and the final collections for PDF with 80 pages has size over 280mb (240 tiffs with different settings inside)

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  • Php efficiency question --> Database call vs. File Write vs. Calling C++ executable

    - by JP19
    Hi, What I wish to achieve is - log all information about each and every visit to every page ofmy website (like ip address, browser, referring page, etc). Now this is easy to do. What I am interested is doing this in a way so as to cause minimum overhead (runtime) in the php scripts. What is the best approach for this efficiency-wise: 1) Log all information to a database table 2) Write to a file (from php directly) 3) Call a C++ executable, that will write this info to a file in parallel [so the script can continue execution without waiting for the file write to occur ...... is this even possible] I may be trying to optimize unnecessarily/prematurely, but still - any thoughts / ideas on this would be appreciated. (I think efficiency of file write/logging can really be a concern if I have say 100 visits per minute...) Thanks & Regards, JP

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  • How can I Query only __key__ on a Google Appengine PolyModel child?

    - by Gabriel
    So the situation is: I want to optimize my code some for doing counting of records. So I have a parent Model class Base, a PolyModel class Entry, and a child class of Entry Article: How would I query Article.key so I can reduce the query load but only get the Article count. My first thought was to use: q = db.GqlQuery("SELECT __key__ from Article where base = :1", i_base) but it turns out GqlQuery doesn't like that because articles are actually stored in a table called Entry. Would it be possible to Query the class attribute? something like: q = db.GqlQuery("select __key__ from Entry where base = :1 and :2 in class", i_base, 'Article') neither of which work. Turns out the answer is even easier. But I am going to finish this question because I looked everywhere for this. q = db.GqlQuery("select __key__ from Entry where base = :1 and class = :2", i_base, 'Article')

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  • SQL query duration is longer for smaller dataset?

    - by entens
    I received reports that a my report generating application was not working. After my initial investigation, I found that the SQL transaction was timing out. I'm mystified as to why the query for a smaller selection of items would take so much longer to return results. Quick query (averages 4 seconds to return): SELECT * FROM Payroll WHERE LINEDATE >= '04-17-2010'AND LINEDATE <= '04-24-2010' ORDER BY 'EMPLYEE_NUM' ASC, 'OP_CODE' ASC, 'LINEDATE' ASC Long query (averages 1 minute 20 seconds to return): SELECT * FROM Payroll WHERE LINEDATE >= '04-18-2010'AND LINEDATE <= '04-24-2010' ORDER BY 'EMPLYEE_NUM' ASC, 'OP_CODE' ASC, 'LINEDATE' ASC I could simply increase the timeout on the SqlCommand, but it doesn't change the fact the query is taking longer than it should. Why would requesting a subset of the items take longer than the query that returns more data? How can I optimize this query?

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  • Rails/mysql SUM distinct records - optimization

    - by pepernik
    Hey. How would you optimize this SQL SELECT SUM(tmp.cost) FROM ( SELECT DISTINCT clients.id as client, countries.credits_cost AS cost FROM countries INNER JOIN clients ON clients.country_id = countries.id INNER JOIN clients_groups ON clients_groups.client_id=clients.id WHERE clients_groups.group_id IN (1,2,3,4,5,6,7,8,9) GROUP BY clients.id ) AS tmp; I'm using this example as part of my Ruby on Rails project. Note that my nested SQL (tmp) can have more then 10 milion records. You can split that in more SQLs if the performance is better. Should I add any indexes to make it quicker (i have it on IDs)?

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