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  • SQL SERVER – Simple Example of Snapshot Isolation – Reduce the Blocking Transactions

    - by pinaldave
    To learn any technology and move to a more advanced level, it is very important to understand the fundamentals of the subject first. Today, we will be talking about something which has been quite introduced a long time ago but not properly explored when it comes to the isolation level. Snapshot Isolation was introduced in SQL Server in 2005. However, the reality is that there are still many software shops which are using the SQL Server 2000, and therefore cannot be able to maintain the Snapshot Isolation. Many software shops have upgraded to the later version of the SQL Server, but their respective developers have not spend enough time to upgrade themselves with the latest technology. “It works!” is a very common answer of many when they are asked about utilizing the new technology, instead of backward compatibility commands. In one of the recent consultation project, I had same experience when developers have “heard about it” but have no idea about snapshot isolation. They were thinking it is the same as Snapshot Replication – which is plain wrong. This is the same demo I am including here which I have created for them. In Snapshot Isolation, the updated row versions for each transaction are maintained in TempDB. Once a transaction has begun, it ignores all the newer rows inserted or updated in the table. Let us examine this example which shows the simple demonstration. This transaction works on optimistic concurrency model. Since reading a certain transaction does not block writing transaction, it also does not block the reading transaction, which reduced the blocking. First, enable database to work with Snapshot Isolation. Additionally, check the existing values in the table from HumanResources.Shift. ALTER DATABASE AdventureWorks SET ALLOW_SNAPSHOT_ISOLATION ON GO SELECT ModifiedDate FROM HumanResources.Shift GO Now, we will need two different sessions to prove this example. First Session: Set Transaction level isolation to snapshot and begin the transaction. Update the column “ModifiedDate” to today’s date. -- Session 1 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN UPDATE HumanResources.Shift SET ModifiedDate = GETDATE() GO Please note that we have not yet been committed to the transaction. Now, open the second session and run the following “SELECT” statement. Then, check the values of the table. Please pay attention on setting the Isolation level for the second one as “Snapshot” at the same time when we already start the transaction using BEGIN TRAN. -- Session 2 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that the values in the table are still original values. They have not been modified yet. Once again, go back to session 1 and begin the transaction. -- Session 1 COMMIT After that, go back to Session 2 and see the values of the table. -- Session 2 SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that the values are yet not changed and they are still the same old values which were there right in the beginning of the session. Now, let us commit the transaction in the session 2. Once committed, run the same SELECT statement once more and see what the result is. -- Session 2 COMMIT SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that it now reflects the new updated value. I hope that this example is clear enough as it would give you good idea how the Snapshot Isolation level works. There is much more to write about an extra level, READ_COMMITTED_SNAPSHOT, which we will be discussing in another post soon. If you wish to use this transaction’s Isolation level in your production database, I would appreciate your comments about their performance on your servers. I have included here the complete script used in this example for your quick reference. ALTER DATABASE AdventureWorks SET ALLOW_SNAPSHOT_ISOLATION ON GO SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 1 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN UPDATE HumanResources.Shift SET ModifiedDate = GETDATE() GO -- Session 2 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 1 COMMIT -- Session 2 SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 2 COMMIT SELECT ModifiedDate FROM HumanResources.Shift GO Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Transaction Isolation

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  • Tokenizing JavaScript: A look at what’s left after minification

    - by InfinitiesLoop
    Minifiers JavaScript minifiers are popular these days. Closure , YUI Compressor , Microsoft Ajax Minifier , to name a few. Using one is essential for any site that uses more than a little script and cares about performance. Each tool of course has advantages and disadvantages. But they all do a pretty good job. The results vary only slightly in the grand scheme of things. Not enough to make so much of a difference that I’d say you should always use one over the other – use whatever fits in with your...(read more)

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  • Implementing algorithms via compute shaders vs. pipeline shaders

    - by TravisG
    With the availability of compute shaders for both DirectX and OpenGL it's now possible to implement many algorithms without going through the rasterization pipeline and instead use general purpose computing on the GPU to solve the problem. For some algorithms this seems to become the intuitive canonical solution because they're inherently not rasterization based, and rasterization-based shaders seemed to be a workaround to harness GPU power (simple example: creating a noise texture. No quad needs to be rasterized here). Given an algorithm that can be implemented both ways, are there general (potential) performance benefits over using compute shaders vs. going the normal route? Are there drawbacks that we should watch out for (for example, is there some kind of unusual overhead to switching from/to compute shaders at runtime)? Are there perhaps other benefits or drawbacks to consider when choosing between the two?

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  • latest intel graphics driver?

    - by Anwar Shah
    I have Intel Graphics Card, which have model number GM965. It is on a Notebook, (Lenovo 3000 Y410). My Ubuntu Installation worked good until I upgraded to 12.04. It was a fresh install. The Graphics performance is poor compared to Natty, Oneiric. In the details tab of System Settings, Graphics driver is shown as "Unknown". I have upgraded the xserver-xorg-video-intel package to version 2.19.. from 2.17. But still same. So, My question is How can I install latest Intel graphics driver for my Chipset? or Is there any other method to fix the problem with graphics.

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  • Optimizing collision engine bottleneck

    - by Vittorio Romeo
    Foreword: I'm aware that optimizing this bottleneck is not a necessity - the engine is already very fast. I, however, for fun and educational purposes, would love to find a way to make the engine even faster. I'm creating a general-purpose C++ 2D collision detection/response engine, with an emphasis on flexibility and speed. Here's a very basic diagram of its architecture: Basically, the main class is World, which owns (manages memory) of a ResolverBase*, a SpatialBase* and a vector<Body*>. SpatialBase is a pure virtual class which deals with broad-phase collision detection. ResolverBase is a pure virtual class which deals with collision resolution. The bodies communicate to the World::SpatialBase* with SpatialInfo objects, owned by the bodies themselves. There currenly is one spatial class: Grid : SpatialBase, which is a basic fixed 2D grid. It has it's own info class, GridInfo : SpatialInfo. Here's how its architecture looks: The Grid class owns a 2D array of Cell*. The Cell class contains two collection of (not owned) Body*: a vector<Body*> which contains all the bodies that are in the cell, and a map<int, vector<Body*>> which contains all the bodies that are in the cell, divided in groups. Bodies, in fact, have a groupId int that is used for collision groups. GridInfo objects also contain non-owning pointers to the cells the body is in. As I previously said, the engine is based on groups. Body::getGroups() returns a vector<int> of all the groups the body is part of. Body::getGroupsToCheck() returns a vector<int> of all the groups the body has to check collision against. Bodies can occupy more than a single cell. GridInfo always stores non-owning pointers to the occupied cells. After the bodies move, collision detection happens. We assume that all bodies are axis-aligned bounding boxes. How broad-phase collision detection works: Part 1: spatial info update For each Body body: Top-leftmost occupied cell and bottom-rightmost occupied cells are calculated. If they differ from the previous cells, body.gridInfo.cells is cleared, and filled with all the cells the body occupies (2D for loop from the top-leftmost cell to the bottom-rightmost cell). body is now guaranteed to know what cells it occupies. For a performance boost, it stores a pointer to every map<int, vector<Body*>> of every cell it occupies where the int is a group of body->getGroupsToCheck(). These pointers get stored in gridInfo->queries, which is simply a vector<map<int, vector<Body*>>*>. body is now guaranteed to have a pointer to every vector<Body*> of bodies of groups it needs to check collision against. These pointers are stored in gridInfo->queries. Part 2: actual collision checks For each Body body: body clears and fills a vector<Body*> bodiesToCheck, which contains all the bodies it needs to check against. Duplicates are avoided (bodies can belong to more than one group) by checking if bodiesToCheck already contains the body we're trying to add. const vector<Body*>& GridInfo::getBodiesToCheck() { bodiesToCheck.clear(); for(const auto& q : queries) for(const auto& b : *q) if(!contains(bodiesToCheck, b)) bodiesToCheck.push_back(b); return bodiesToCheck; } The GridInfo::getBodiesToCheck() method IS THE BOTTLENECK. The bodiesToCheck vector must be filled for every body update because bodies could have moved meanwhile. It also needs to prevent duplicate collision checks. The contains function simply checks if the vector already contains a body with std::find. Collision is checked and resolved for every body in bodiesToCheck. That's it. So, I've been trying to optimize this broad-phase collision detection for quite a while now. Every time I try something else than the current architecture/setup, something doesn't go as planned or I make assumption about the simulation that later are proven to be false. My question is: how can I optimize the broad-phase of my collision engine maintaining the grouped bodies approach? Is there some kind of magic C++ optimization that can be applied here? Can the architecture be redesigned in order to allow for more performance? Actual implementation: SSVSCollsion Body.h, Body.cpp World.h, World.cpp Grid.h, Grid.cpp Cell.h, Cell.cpp GridInfo.h, GridInfo.cpp

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  • Better drivers for SiS 650/740 integrated video?

    - by Bart van Heukelom
    I installed Xubuntu 10.10 on an old box today and the graphical performance is horrid. According to lspci, the video card is this: 01:00.0 VGA compatible controller: Silicon Integrated Systems [SiS] 65x/M650/740 PCI/AGP VGA Display Adapter (prog-if 00 [VGA controller]) Subsystem: ASUSTeK Computer Inc. Device 8081 Flags: 66MHz, medium devsel, IRQ 11 BIST result: 00 Memory at f0000000 (32-bit, prefetchable) [size=128M] Memory at e7800000 (32-bit, non-prefetchable) [size=128K] I/O ports at d800 [size=128] Expansion ROM at <unassigned> [disabled] Capabilities: <access denied> Kernel modules: sisfb Is there a way to make it faster? Alternative drivers? The additional drivers tool shows nothing. I'm specifically interested in improving Java's Java2D rendering speed, because I'll be running a "stat screen" written in that language on it.

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  • Does Ubuntu Touch consume less than Android?

    - by Eduard Florinescu
    One of the problems of new OSs is power consumption. That is because power and performance requires a lot of tweaks and experience with the kernel, drivers and OS code-base on one hand, and a lot of extensive long-term test and quality assurance on the other hand. Given that Android is a rather old and established OS I saw that it has pretty good power consumption. Phoronix does this kind of comparissions but I was not able to find to much about Ubuntu Touch. Does Ubuntu Touch consume less than Android in general, do you have data on some platforms compared?

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  • Create new variable or make multiple chained calls?

    - by Rodrigo
    What is the best way to get this attributes, thinking in performance and code quality? Using chained calls: name = this.product.getStock().getItems().get(index).getName(); id = this.product.getStock().getItems().get(index).getId(); Creating new variable: final item = this.product.getStock().getItems().get(index); name = item.getName(); it = item.getId(); I prefer the second way, to let the code cleaner. But I would like to see some opinions about it. Thank you!

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  • SQLSat65, Great Perf Counters Poster from Quest

    - by merrillaldrich
    I was fortunate to be able to attend the Vancouver BC SQLSaturday this past weekend, and it was excellent! Great sessions, good facility, well attended. Nice work, and a huge thank you to the volunteers that made that happen. One side perk: I got a copy of this terrific performance counters poster from Quest, which you can download as a PDF for free. Very handy, especially as a teaching tool. I'm using it for my SCOM MP work. Check it out....(read more)

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  • Does Ubuntu Touch consume less power than Android?

    - by Eduard Florinescu
    One of the problems of new OSs is power consumption. That is because power and performance requires a lot of tweaks and experience with the kernel, drivers and OS code-base on one hand, and a lot of extensive long-term test and quality assurance on the other hand. Given that Android is a rather old and established OS I saw that it has pretty good power consumption. Phoronix does this kind of comparissions but I was not able to find much about Ubuntu Touch. Does Ubuntu Touch consume less than Android, do you have data on some platforms compared?

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  • Drag and drop fearture for a website

    - by gpuguy
    I have to design a website which will have drag and drop features for creating an e-card. So you select items from a tool box and drag and drop this item on the card area. Once you have completed the design you can publish the e-card on the web by clicking "Save and publish" button. What are the possible technologies for implementing this feature? The requirement is that the application should not degrade the performance of the website, and should not take much time in publishing once the user click "Save and publish" button.

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  • Does Ubuntu run well on an USB HDD?

    - by Klaus
    I have here a company notebook, and because the HDD is full encrypted, I cannot install an extra partition for another system that I would like to use in my free time. And I really need another system, because this crap Windows here with that much of anti-virus, anti-spyware, anti-whatever on it is so slow and annoying. What can I do? I could use an external USB HDD with another system. Because I would like to handle big files and so on, I don't want to use a USB stick. A USB 2.5 HDD + Ubuntu is what I think the best option. Here are my questions: Do I have to note something? Does Ubuntu run well on an external HDD? Do I have big performance problems (because of the USB HDD)? Should I buy a very fast HDD for much money or it is not that important? Any suggestions?

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  • how to do partial updates in OpenGL?

    - by Will
    It is general wisdom that you redraw the entire viewport on each frame. I would like to use partial updates; what are the various ways can do that, and what are their pros, cons and relative performance? (Using textures, FBOs, the accumulator buffer, any kind of scissors that can affect swapbuffers etc?) A scenario: a scene with a fair few thousand visible trees; although the textures are mipmapped and they are drawn via VBOs roughly front-to-back with so on, its still a lot of polys. Would streaming a single screen-sized texture be better than throwing them at the screen every frame? You'd have to redraw and recapture them only on camera movement or as often as your wind model updates or whatever, which need not be every frame.

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  • Why is chunk size often a power of two?

    - by danijar
    There are many Minecraft clones out there and I am working on my own implementation. A principle of terrain rendering is tiling the whole world in fixed size chunks to reduce the effort of localized changes. In Minecraft the chunk size is 16 x 16 x 256 as far as I now. And in clones I also always saw chunk sizes of a power of the number 2. Is there any reason for that, maybe performance or memory related? I know that powers of 2 play a special role in binary computers but what has that to do with the chunk size?

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  • Implementing set of processes in a stored procedure or through the code?

    - by just_name
    I want to know what's the suitable method to implement the following case (best practice). If i make a set of processes like this : 1- select data from set of DB tables. 2- loop on the selected result . 3- Make some checks on each iteration . 4- Insert the result in another table . Implementing the previous steps in a stored procedure or in a transaction through my code (asp.net) . ? Concerning the performance , security and reliability issues .

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  • How do I avoid "Developer's Bad Optimization Intuition"?

    - by Mona
    I saw on a article that put forth this statement: Developers love to optimize code and with good reason. It is so satisfying and fun. But knowing when to optimize is far more important. Unfortunately, developers generally have horrible intuition about where the performance problems in an application will actually be. How can a developer avoid this bad intuition? Are there good tools to find which parts of your code really need optimization (for Java)? Do you know of some articles, tips, or good reads on this subject?

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  • Is Ubuntu running well on an usb hdd? Need suggestions

    - by Klaus
    Dear Linux and Ubuntu pros, I have here a company notebook, and because the hdd is full encrypted I cannot install an extra partition for another system that I would like to use in my free time. And I really need another system, because this crap windows here with that much of antivirus, antispyware, anti-whatever on it is sooo slow and anoying. What can I do? I could use an external usb hdd with another system. Because I would like to handle big files and so on, I dont want to use an sub stick. An usb 2.5hdd + ubuntu is what I think the best option. Here are my question: Do I have to note something? Is Ubuntu running well on an external hdd? Do I have big performance problems (because of the usb hdd)? Should I buy a very fast hdd for much money or is it not that important? Any suggestions? Thank you :)

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  • Data Loading Issues? Try the new Demantra Data Load Guided Resolution

    - by user702295
    Hello!   Do you have data loading issues?  Perhaps you are trying the new partial schema export tool.   New to Demantra, the Data Load Guided Resolution, document 1461899.1.  This interactive guide will help you locate known solutions to previously discovered issues quickly.  From performance, ORA and ODPM errors to collections related issues that have no known hard number error.   This guide includes the diagnosis of data being imported into Demantra and data being exported from Demantra.  Contact me with any questions or suggestions.   Thank You!

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  • why would you use textures that are not a power of 2?

    - by Will
    In the early days of OpenGL and DirectX, it was required that textures were powers of two. This meant that interpolation of float values could be done very quickly using shifting and such. Since OpenGL 2.0, and preceding that via an extension, non-power-of-two texture dimensions has been supported. Are there performance advantages to sticking to power-of-two textures on modern integrated and discrete GPUs? What advantages do non-power-of-two textures have, if any? Are there large populations of desktop users who don't have cards that support non-power-of-two textures?

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  • Do you accept counter offers when recruiting experienced programmers? [migrated]

    - by MathAttack
    It is VERY hard to find good experienced programmers. Generally if they're performing well, their employers don't want to let them go, and many don't have resumes, let alone resumes in circulation. Let's say you find one who for personal circumstances is available. And let's say you make them an offer that's fair within your salary structure. And let's say you get a modest counter. (5-10% of the total offer side) Do you accept the counter? Part of me says, "Programmers like this are so rare, why let a small sum get in the way of hiring them?" The other part says, "This precedent will set up an annual headache." Thoughts? I know it's not black and white.

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  • How well does Intel 3000 HD work on Ubuntu?

    - by Simon
    Right now i have notebook with Nvidia 8400M GS (I know, it's not good card) and it's impossible to work normally when i'll plugin external monitor (1920x1080). Windows 7 can deal with it without problems (1440x900 on notebook + 1920x1080 external). On Ubuntu i have to choose one screen and turn off the second one. Even with only one screen Ubuntu (Unity or even Gnome3) sometimes hangs for a while, I've not found solution for this yet, but nevermind, it's probably because of my card or/and nvidia's drivers. I'm going to buy new PC, but for now only with integrated Intel 3000HD, and my question is: Should i expect similar problems with this card? Here i've found link to Intel's webpage about drivers - "only community develop them", and i'm a bit concerned. I'll use then only one monitor (the bigger one), but how well does those driver work? Are there any performance tests?

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  • Why Should I Avoid Inline Scripting?

    - by thesunneversets
    A knowledgeable friend recently looked at a website I helped launch, and commented something like "very cool site, shame about the inline scripting in the source code". I'm definitely in a position to remove the inline scripting where it occurs; I'm vaguely aware that it's "a bad thing". My question is: what are the real problems with inline scripting? Is there a significant performance issue, or is it mostly just a matter of good style? Can I justify immediate action on the inline scripting front to my superiors, when there are other things to work on that might have a more obvious impact on the site? If you pulled up to a website, and took a peek at the source code, what factors would lead you to say "hmm, professional work here", and what would cause you to recoil from an obviously amateurish job? Okay, that question turned into multiple questions in the writing. But basically, inline scripting - what's the deal?

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  • System response times --- A good Service Level Agreement?

    - by mpeterson
    In order to view system performance, I have been asked by management to give page response times for a few key pages. I want to make sure I am giving a good picture of the overall health of the system, and not just narrowing in on a single measurement. So my question is: When developing software, what metrics would you provide to your stakeholders to indicate a system that is healthy and running well? (if it is not running well, that should also be evident! Not trying to hide/obscure any problems.)

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  • Browser support for internal corporate tools

    - by adam
    We are on the verge of a conversion. For years, our company supported only IE for its internal (intranet) home-built tools. Since a few of our users are still on XP, which means IE only goes up to 8... a heavily JS / jQuery site wont even load! We have been in the process of converting to use Chrome instead, to make use of its javascript performance. But, it has now been suggested that we support all common browsers... internally for these tools. Which means more development time to scale-back some of these new applications, more time to test in all browsers, and we are already under staffed. Are there any good informational sites/posts out there, that already make this argument?

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  • Why did the team at LMAX use Java and design the architecture to avoid GC at all cost?

    - by kadaj
    Why did the team at LMAX design the LMAX Disruptor in Java but all their design points to minimizing GC use? If one does not want to have GC run then why use a garbage collected language? Their optimizations, the level of hardware knowledge and the thought they put are just awesome but why Java? I'm not against Java or anything, but why a GC language? Why not use something like D or any other language without GC but allows efficient code? Is it that the team is most familiar with Java or does Java possess some unique advantage that I am not seeing? Say they develop it using D with manual memory management, what would be the difference? They would have to think low level (which they already are), but they can squeeze the best performance out of the system as it's native.

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