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  • Fastest sort of fixed length 6 int array

    - by kriss
    Answering to another StackOverflow question (this one) I stumbled upon an interresting sub-problem. What is the fastest way to sort an array of 6 ints ? As the question is very low level (will be executed by a GPU): we can't assume libraries are available (and the call itself has it's cost), only plain C to avoid emptying instruction pipeline (that has a very high cost) we should probably minimize branches, jumps, and every other kind of control flow breaking (like those hidden behind sequence points in && or ||). room is constrained and minimizing registers and memory use is an issue, ideally in place sort is probably best. Really this question is a kind of Golf where the goal is not to minimize source length but execution speed. I call it 'Zening` code as used in the title of the book Zen of Code optimization by Michael Abrash and it's sequels.

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  • SQL Server: how to optimize "like" queries?

    - by duke84
    I have a query that searches for clients using "like" with wildcard. For example: SELECT TOP (10) [t0].[CLIENTNUMBER], [t0].[FIRSTNAME], [t0].[LASTNAME], [t0].[MI], [t0].[MDOCNUMBER] FROM [dbo].[CLIENT] AS [t0] WHERE (LTRIM(RTRIM([t0].[DOCREVNO])) = '0') AND ([t0].[FIRSTNAME] LIKE '%John%') AND ([t0].[LASTNAME] LIKE '%Smith%') AND ([t0].[SSN] LIKE '%123%') AND ([t0].[CLIENTNUMBER] LIKE '%123%') AND ([t0].[MDOCNUMBER] LIKE '%123%') AND ([t0].[CLIENTINDICATOR] = 'ON') It can also use less parameters in "where" clause, for example: SELECT TOP (10) [t0].[CLIENTNUMBER], [t0].[FIRSTNAME], [t0].[LASTNAME], [t0].[MI], [t0].[MDOCNUMBER] FROM [dbo].[CLIENT] AS [t0] WHERE (LTRIM(RTRIM([t0].[DOCREVNO])) = '0') AND ([t0].[FIRSTNAME] LIKE '%John%') AND ([t0].[CLIENTINDICATOR] = 'ON') Can anybody tell what is the best way to optimize performance of such query? Maybe I need to create an index? This table can have up to 1000K records in production.

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  • Programmer's editor or IDE for C code

    - by Yktula
    I feel like this question has been repeated here, but I couldn't find it. What open-source programmer's editor or IDE is best for writing code in C? A GUI and integration with Clang for static code analysis or git for version control would be convenient, but aren't necessary. I would ideally use two editors: one feature-filled IDE and one with a small memory footprint, but editors like jEdit, Geany, Diakonos, nano, etc. don't satisfy many of my needs, which include: Good support for refactoring and code completion. Extensibility in C or a "modern" scripting language (i.e. Ruby or Python) Relatively good performance and lack of bloated-ness

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  • How do I prevent jagged edges alongside the surfaces of my 3d model?

    - by badcodenotreat
    Lets say I've implemented in openGL a crude model viewer with shading which renders a series of blocks, such that I have something that looks like this. http://i.imgur.com/TsF7K.jpg Whenever I rotate my model to the side, it causes an unwanted jagged effect along any surface with a steep viewing angle. http://i.imgur.com/Bgl9o.jpg I'm pretty sure this is due to the polygon offset I used to prevent z-fighting between the model and the wireframe, however I'm not able to find the factor/unit parameters in openGL which prevent this unwanted effect. what are the best values of factor and unit for glPolygonOffset to prevent this? would implementing anti-aliasing alleviate the problem? is the trade off in performance trivial/significant? is this perhaps a shading issue? should i try a solution along this line of thought?

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  • MS SQL Server: how to optimize "like" queries?

    - by duke84
    I have a query that searches for clients using "like" with wildcard. For example: SELECT TOP (10) [t0].[CLIENTNUMBER], [t0].[FIRSTNAME], [t0].[LASTNAME], [t0].[MI], [t0].[MDOCNUMBER] FROM [dbo].[CLIENT] AS [t0] WHERE (LTRIM(RTRIM([t0].[DOCREVNO])) = '0') AND ([t0].[FIRSTNAME] LIKE '%John%') AND ([t0].[LASTNAME] LIKE '%Smith%') AND ([t0].[SSN] LIKE '%123%') AND ([t0].[CLIENTNUMBER] LIKE '%123%') AND ([t0].[MDOCNUMBER] LIKE '%123%') AND ([t0].[CLIENTINDICATOR] = 'ON') It can also use less parameters in "where" clause, for example: SELECT TOP (10) [t0].[CLIENTNUMBER], [t0].[FIRSTNAME], [t0].[LASTNAME], [t0].[MI], [t0].[MDOCNUMBER] FROM [dbo].[CLIENT] AS [t0] WHERE (LTRIM(RTRIM([t0].[DOCREVNO])) = '0') AND ([t0].[FIRSTNAME] LIKE '%John%') AND ([t0].[CLIENTINDICATOR] = 'ON') Can anybody tell what is the best way to optimize performance of such query? Maybe I need to create an index? This table can have up to 1000K records in production.

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  • SqlServer / MySql Connection pool: is it really important ?

    - by stighy
    Hy guys, after a lot of problem with my hoster, i decided to disable connection pooling of my application. The problem was related to the number of concurrent connections : only five. So i decided to disable connection pooling: the result is that my web app don't crash. So i'm asking you: are there some "collateral" effect disabling connection pooling ? Is it so important ? I didn't noticed bad performance after disabling it. Thank you for your (i'm sure) precious advice!

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  • Implementing a linear, binary SVM (support vector machine)

    - by static_rtti
    I want to implement a simple SVM classifier, in the case of high-dimensional binary data (text), for which I think a simple linear SVM is best. The reason for implementing it myself is basically that I want to learn how it works, so using a library is not what I want. The problem is that most tutorials go up to an equation that can be solved as a "quadratic problem", but they never show an actual algorithm! So could you point me either to a very simple implementation I could study, or (better) to a tutorial that goes all the way to the implementation details? Thanks a lot!

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  • How to setup RAM disk drive using python or WMI?

    - by Ming Xie
    Hi, The background of my question is associated with Tesseract, the free OCR engine (1985-1995 by HP, now hosting in Google). It specifically requires an input file and an output file; the argument only takes filename (not stream / binary string), so in order to use the wrapper API such as pytesser and / or python-tesser.py, the OCR temp files must be created. I, however, have a lot of images need to OCR; frequent disk write and remove is inevitable (and of course the performance hit). The only choice I could think about is changing the wrapper class and point the temp file to RAM disk, which bring this problem up. If you have better solution, please let me know. Thanks a lot. -M

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  • Retrieve input and output parameters for SQL stored procs and functions?

    - by Darth Continent
    For a given SQL stored proc or function, I'm trying to obtain its input and output parameters, where applicable, in a Winforms app I'm creating to browse objects and display their parameters and other attributes. So far I've discovered the SQL system function object_definition, which takes a given sysobjects.id and returns the text of that object; also discovered via search this post which describes extracting the parameters in the context of a app using the ADO.NET method DeriveParameters in conjunction with some caching for better performance; and for good measure found some helpful system stored procs from this earlier post on Hidden Features of SQL Server. I'm leaning towards implementing the DeriveParameters method in my C# app, since parsing the output of object_definition seems messy, and I haven't found a hidden feature in that post so far that would do the trick. Is DeriveParameters applicable to both functions and stored procs for purposes of retreiving their parameters, and if so, could someone please provide an example?

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  • Indexing only one MySQL column value

    - by BrainCore
    I have a MySQL InnoDB table with a status column. The status can be 'done' or 'processing'. As the table grows, at most .1% of the status values will be 'processing,' whereas the other 99.9% of the values will be 'done.' This seems like a great candidate for an index due to the high selectivity for 'processing' (though not for 'done'). Is it possible to create an index for the status column that only indexes the value 'processing'? I do not want the index to waste an enormous amount of space indexing 'done.'

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  • Invoke ngen from NSIS installer

    - by BlackStar
    I am using NSIS to deploy a .Net application. The installation/uninstallation process works fine, but I would like to add a final ngen step to improve startup performance. Unfortunately, Google didn't reveal any relevant material. It's unlikely that noone has ever done this before - maybe someone here has some idea? In the unlikely case that this is impossible to support without ugly hacks, I would be willing to use a different installer technology provided it can run on my Linux build server. (This rules out WiX, for example.) Any ideas?

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  • Reasons why one should not call the garbage collector directly.

    - by Shimrod
    Hi everyone, I'm currently writing a paper for my company, about how to avoid calling the garbage collector directly from the code (when playing with COM objects for instance). I know this is a bad practice, and should be only considered in very rare cases, but I can't seem to find a way to tell why it should be avoided. And I don't want to rely on the "The G.C. is smarter than you" principle (even if it is the truth :-) ) So can you tell me some clues about why you think one should avoid to call the garbage collector directly ? (performance impact?) Or maybe if you have links about this particular topic, they would be very helpful. Thanks in advance !

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  • How can I provide a different rendering target to Direct2D?

    - by fingerprint211b
    I'm using Direct2D in C# to render a small gui framework for my research project. I'm not very used to working on Windows or with DirectX. I'm using a Windows Forms control to create a render target, and msdn warns that since it uses BindDC, a the larger the rendering target, the worse the performance will be (which turned out to be a dramatic difference, when I maximize the window, I get around 15 fps). What would be a better way to create a render target for Direct2D? Is there a way to create a window and render directly to it, instead of rendering to a control's buffer first, and then rendering that? If so, how? Sorry if my English sucks, not my native language.

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  • What is technically more advanced: Python or Assembler? [closed]

    - by el ka es
    I wondered which of these languages is more powerful. With powerful I don't mean the readability, assembler would be naturally the winner here, but something resulting from, for example, the following factors: Which of them is more high-level? (Both aren't really but one has to be more) Who would be the possibly fastest in compiled state? (There is no Python compiler out there as far as I know but it wouldn't be hard writing one I suppose) Which of the both has the better code length/code action ratio? What I mean is If you get to distracted by the, compared to Python, improved readability of assembler, just think of writing plain binary/machine code as what assembler assembles to. Both languages are so basic that it should be possible to answer the question(s) in a rather objective view, I hope.

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  • Seeking tuturial: introduction to ODBC with Delphi

    - by mawg
    I have a lot of embedded C/C++/Ada experience and an outdated smattering of Delphi plus some database stuff. Now I have to implement an app in Delphi which can manipulate MySql, Oracle, maybe MS Acess. In short, I need ODBC. I need to programatically created a database, define its structure and populate its contents, then later query its existence and programatically search. I would prefer not to use 3rd party components, unless there is a compelling reason to do so (performance ought not to be an issue for the app, it won't have much data or be run often, at least not in v1.0) . Can anyone point me at a tutorial which can get me up to speed? Thanks

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  • How to benchmark apache/nginx setup

    - by Saif Bechan
    I am planning to setup nginx as reverse proxy. I will have apache to deliver my dynamic content, and nginx will deliver the static content. My configuration i have now is just Apache with fastCGI. This gives me no configuration problems and runs great. After I have set up nginx I want to run some benchmarks to see if I really got some performance increases, else i will switch back. Does anyone know how I can benchmark this type of setup? Or maybe someone did this already and have some canned results, I will be glad to hear them. PS. I know this is more a serverfault type of question, but i have seen numerous posts about apache and nginx so i thought i give it a try

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  • Gallery items become off-center when switching into landscape orientation.

    - by Sandile
    Hey Guys, Thanks for your time. I'm writing an application for android 2.2 and I'm using a gallery to circulate through a list of images that the user can then click to navigate other portions of the application. In portrait orientation, everything is kosher: the images are displaying correctly (completely in the center of the screen as I intended); however, in landscape orientation, all the images in the gallery are strangely displaced a fixed distance to the left of the center of the screen. I've been researching this issue for hours now and haven't found a solution. I'm hoping that some android guru can aid me in the resolution of this bizarre rendering issue. MainMenuActivity.java relevant code snippet (the activity in which the gallery resides) Gallery optionList = (Gallery)findViewById(R.id.mainMenuOptionList); GalleryItem[] optionListItemIdArray = new GalleryItem[] { new GalleryItem(R.drawable.icon_main_menu_option_list_blackboard, "Start Next Lesson", "Start the next planned vocab lesson."), new GalleryItem(R.drawable.icon_main_menu_option_list_index_cards, "Review Words", "Manually look over old words."), new GalleryItem(R.drawable.icon_main_menu_option_list_dice, "Play Vocab Games", "Play games to reinforce knowledge."), new GalleryItem(R.drawable.icon_main_menu_option_list_calendar, "View Lesson Plan", "View the schedule for coming lessons."), new GalleryItem(R.drawable.icon_main_menu_option_list_pie_chart, "View Performance Report", "Evaluate your overall performance statistics."), new GalleryItem(R.drawable.icon_main_menu_option_list_settings, "Manage Settings", "Change and modify application settings.") }; optionList.setAdapter(new GalleryImageAdapter(this, optionListItemIdArray)); NOTE: A GalleryItem is a POJO with an image resource id, title and description. GalleryImageAdapter.java: public class GalleryImageAdapter extends BaseAdapter { private Context context; private GalleryItem[] galleryItemArray; public GalleryImageAdapter(Context context, GalleryItem[] galleryItemArray) { this.context = context; this.galleryItemArray = galleryItemArray; } @Override public int getCount() { return galleryItemArray.length; } @Override public Object getItem(int position) { return position; } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { ImageView imageView = new ImageView(context); imageView.setImageResource(galleryItemArray[position].getImageId()); imageView.setScaleType(ImageView.ScaleType.FIT_START); imageView.setLayoutParams(new Gallery.LayoutParams(Gallery.LayoutParams.WRAP_CONTENT, Gallery.LayoutParams.WRAP_CONTENT)); return imageView; } } Portrait version of main_menu.xml <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/mainMenuLinearLayout" android:background="#3067a8" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:id="@+id/mainMenuHeadingTextView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:paddingLeft="10dip" android:textColor="#ffffff" android:textSize="50sp" android:text="@string/main_menu_heading" android:shadowColor="#555555" android:shadowDx="0" android:shadowDy="0" android:shadowRadius="2" /> <TextView android:id="@+id/mainMenuSubHeadingTextView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:paddingLeft="15dip" android:textColor="#ffffff" android:textSize="15sp" android:text="@string/main_menu_sub_heading" android:shadowColor="#555555" android:shadowDx="0" android:shadowDy="0" android:shadowRadius="2" /> <Gallery xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/mainMenuOptionList" android:layout_width="fill_parent" android:layout_height="wrap_content" android:paddingTop="20dip" android:paddingBottom="10dip" android:spacing="40dip" /> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/mainMenuOptionListDetailLinearLayout" android:gravity="center_vertical|center_horizontal" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:id="@+id/mainMenuOptionListLabelTextView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textColor="#ffffff" android:textSize="25sp" android:shadowColor="#555555" android:shadowDx="0" android:shadowDy="0" android:shadowRadius="2" /> <TextView android:id="@+id/mainMenuOptionListDescriptionTextView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textColor="#ffffff" android:textSize="15sp" android:shadowColor="#555555" android:shadowDx="0" android:shadowDy="0" android:shadowRadius="2" /> </LinearLayout> </LinearLayout> Landscape version of main_menu.xml <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/mainMenuLinearLayout" android:background="#3067a8" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:id="@+id/mainMenuHeadingTextView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:paddingLeft="10dip" android:textColor="#ffffff" android:textSize="50sp" android:text="@string/main_menu_heading" android:shadowColor="#555555" android:shadowDx="0" android:shadowDy="0" android:shadowRadius="2" /> <TextView android:id="@+id/mainMenuSubHeadingTextView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:paddingLeft="15dip" android:textColor="#ffffff" android:textSize="15sp" android:text="@string/main_menu_sub_heading" android:shadowColor="#555555" android:shadowDx="0" android:shadowDy="0" android:shadowRadius="2" /> <Gallery xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/mainMenuOptionList" android:layout_width="fill_parent" android:layout_height="128dip" android:paddingLeft="0dip" android:paddingTop="5dip" android:spacing="10dip" /> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/mainMenuOptionListDetailLinearLayout" android:gravity="center_vertical|center_horizontal" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:id="@+id/mainMenuOptionListLabelTextView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textColor="#ffffff" android:textSize="25sp" android:shadowColor="#555555" android:shadowDx="0" android:shadowDy="0" android:shadowRadius="2" /> <TextView android:id="@+id/mainMenuOptionListDescriptionTextView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textColor="#ffffff" android:textSize="15sp" android:shadowColor="#555555" android:shadowDx="0" android:shadowDy="0" android:shadowRadius="2" /> </LinearLayout> </LinearLayout> Thank you for your time!

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  • Strip tags (with tags inside attributes and nested tags) using javascript

    - by Kokizzu
    What the fastest (in performance) way to strip strings from tags, most solution i've tried that uses regexp not resulting correct values for tags inside attributes (yes, i know it's wrong), example test case: var str = "<div data-content='yo! press this: <br/> <button type=\"button\"><i class=\"glyphicon glyphicon-disk\"></i> Save</button>' data-title='<div>this one for tooltips <div>seriously</div></div>'> this is the real content<div> with another nested</div></div>" that should resulting: this is the real content with another nested

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  • Strategies to use Database Sequences?

    - by Bruno Brant
    Hello all, I have a high-end architecture which receives many requests every second (in fact, it can receive many requests every millisecond). The architecture is designed so that some controls rely on a certain unique id assigned to each request. To create such UID we use a DB2 Sequence. Right now I already understand that this approach is flawed, since using the database is costly, but it makes sense to do so because this value will also be used to log information on the database. My team has just found out an increase of almost 1000% in elapsed time for each transaction, which we are assuming happened because of the sequence. Now I wonder, using sequences will serialize access to my application? Since they have to guarantee that increments works the way they should, they have to, right? So, are there better strategies when using sequences? Please assume that I have no other way of obtaining a unique id other than relying on the database.

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  • Can you recommend an effective and cheap CDN for video streaming?

    - by Shaul Dar
    I am looking for a streaming CDN recommendation. Cost and performance are my chief concerns. Video viewers may be all over the globe, with the, US, Europe, Russia and South America topping the list (yes, I know that leaves out a little :-). I saw the following list of streaming CDNs in LinkedIn: Akamai, BitGravity, EdgeCast, Highwinds, Internap, Level3, Limelight, Mirror Image, Move Networks, Qbrick, SimpleCDN, StreamZilla, Swarmcast (streaming via HTTP), WINK Streaming... (+Amazon's S3 and CloudFront) Can anyone recommend any of these or others? Or a different type of technology (e.g. P2P).

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  • typesafe NotifyPropertyChanged using linq expressions

    - by bitbonk
    Form Build your own MVVM I have the following code that lets us have typesafe NotifyOfPropertyChange calls: public void NotifyOfPropertyChange<TProperty>(Expression<Func<TProperty>> property) { var lambda = (LambdaExpression)property; MemberExpression memberExpression; if (lambda.Body is UnaryExpression) { var unaryExpression = (UnaryExpression)lambda.Body; memberExpression = (MemberExpression)unaryExpression.Operand; } else memberExpression = (MemberExpression)lambda.Body; NotifyOfPropertyChange(memberExpression.Member.Name); } How does this approach compare to standard simple strings approach performancewise? Sometimes I have properties that change at a very high frequency. Am I safe to use this typesafe aproach? After some first tests it does seem to make a small difference. How much CPU an memory load does this approach potentially induce?

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  • Running Awk command on a cluster

    - by alex
    How do you execute a Unix shell command (awk script, a pipe etc) on a cluster in parallel (step 1) and collect the results back to a central node (step 2) Hadoop seems to be a huge overkill with its 600k LOC and its performance is terrible (takes minutes just to initialize the job) i don't need shared memory, or - something like MPI/openMP as i dont need to synchronize or share anything, don't need a distributed VM or anything as complex Google's SawZall seems to work only with Google proprietary MapReduce API some distributed shell packages i found failed to compile, but there must be a simple way to run a data-centric batch job on a cluster, something as close as possible to native OS, may be using unix RPC calls i liked rsync simplicity but it seem to update remote notes sequentially, and you cant use it for executing scripts as afar as i know switching to Plan 9 or some other network oriented OS looks like another overkill i'm looking for a simple, distributed way to run awk scripts or similar - as close as possible to data with a minimal initialization overhead, in a nothing-shared, nothing-synchronized fashion Thanks Alex

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  • Difference between Document-oriented-DB and Bigtable clones

    - by chen
    We are looking for a suitable storage engine for our weblog history data. We looked at Bigtable's paper and understand it is suitable to us well. However, I also understand that Document-oriented-DB such as MongoDB seems to provide a little more powerful schema power -- i.e, it can model our data as well. I wonder how nowadays ppl choose a scalable NoSQL DB --- I read enough articles like "we looked at A, B and C, and we decided to use C". But I'd like to see some benchmark number. What I am saying is that if MongoDB and the like can provide same level of performance as Bigtable clones, why don't web companies choose it (preparing to deal with various potentially more complex data problem)? Thanks, By the way, I read an article (which convinced me at the moment) saying Cassandra does not fit the M/R operation, any comments?

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  • Suggest Cassandra data model for an existing schema

    - by Andriy Bohdan
    Hello guys! I hope there's someone who can help me suggest a suitable data model to be implemented using nosql database Apache Cassandra. More of than I need it to work under high loads and large amounts of data. Simplified I have 3 types of objects: Product Tag ProductTag Product: key - string key name - string .... - some other fields Tag: key - string key name - unique tag words ProductTag: product_key - foreign key referring to product tag_key - foreign key referring to tag rating - this is rating of tag for this product Each product may have 0 or many tags. Tag may be assigned to 1 or many products. Means relation between products and tags is many-to-many in terms of relational databases. Value of "rating" is updated "very" often. I need to be run the following queries Select objects by keys Select tags for product ordered by rating Select products by tag order by rating Update rating by product_key and tag_key The most important is to make these queries really fast on large amounts of data, considering that rating is constantly updated.

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  • Optimizing encrypted column search

    - by Sung Meister
    I have a table called,tblClient with an encrypted column called SSN. Due to company policy, we encrypted SSN using a symmetric key (chosen over asymmetric key due to performance reasons) using a password. Here is a partial LIKE search on SSN declare @SSN varchar(11) set @SSN = '111-22-%' open symmetric key SSN_KEY decrypt by password = 'secret' select Client_ID from tblClient (nolock) where convert(nvarchar(11), DECRYPTBYKEY(SSN)) like @SSN close symmetric key SSN_KEY Before encryption, searching thru 150,000 records took less than 1 second. but with the mix of decryption, the same search takes around 5 seconds. What strategy can I apply to try to optimize searching thru encrypted column?

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