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  • Preprocessor "macro function" vs. function pointer - best practice?

    - by Dustin
    I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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  • MVP pattern. Presenter requires new view instance. Best practice

    - by Andrew Florko
    I try to apply MVP pattern for win.forms application. I have 2 forms: main & child. Main has a button and when you click it - child form should appear. There are 2 views interfaces that forms implement IMainView { event OnClick; ... } IChildView { ... } There are two presenters MainPresenter(IMainView) & ChildPresenter(IChildView) MainPresenter listens to OnClick event and then should create IChildView implementation. MainPresenter { ... MainClicked() { // it's required to create IChildView instance here } } How would you implement such creation typically? Shall IMainView has factory method for IChildView or may be it should be separate Views factory. What would you advise? Or maybe there is some misunderstanding of MVP here? Thank you in advance!

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  • How to Inserting message into View that depends on session value. ASP.NET MVC. Best practice

    - by Andrew Florko
    User have to populate multistep questionnaire web-forms and step messages depend on the option chosen by user at the very beginning. Messages are stored in web.config file. I use asp.net mvc project, strong typed views and keep business logic separated from controller in static class. I don't want to make business logic dependency on web.config. Well, I have to insert message into view that depends on session value. There are at least 2 options how to implement this: View model has property that is populated in controller/businessLogic and rendered in view like <%: Model.HelpMessage1 %>. I have to pass web.config values from controller to businessLogic that makes business logic methods signature too complex. I don't want to make configuration source abstract (in order to let business logic read configuration values from its methods directly) also. Create static helper class that is called from view like <%: ViewHelper.HelpMessage1(Model.Option1) %>. But in this case logic what to show seems to be separated into two classes: business logic & viewHelper. What will you suggest? Thank you in advance!

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  • Preprocessor #define vs. function pointer - best practice?

    - by Dustin
    I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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  • Best practice: How to persist simple data without a database in django?

    - by Infinity
    I'm building a website that doesn't require a database because a REST API "is the database". (Except you don't want to be putting site-specific things in there, since the API is used by mostly mobile clients) However there's a few things that normally would be put in a database, for example the "jobs" page. You have master list view, and the detail views for each job, and it should be easy to add new job entries. (not necessarily via a CMS, but that would be awesome) e.g. example.com/careers/ and example.com/careers/77/ I could just hardcode this stuff in templates, but that's no DRY- you have to update the master template and the detail template every time. What do you guys think? Maybe a YAML file? Or any better ideas? Thx

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  • What's the best practice in case something goes wrong in Perl code?

    - by Geo
    I saw code which works like this: do_something($param) || warn "something went wrong\n"; and I also saw code like this: eval { do_something_else($param); }; if($@) { warn "something went wrong\n"; } Should I use eval/die in all my subroutines? Should I write all my code based on stuff returned from subroutines? Isn't eval'ing the code ( over and over ) gonna slow me down?

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  • When using out parameters in a function, is it good practice to initialize them in the function?

    - by adambox
    I have a function that uses out parameters to return multiple values to the caller. I would like to initialize them in the function, but I wasn't sure if that's a bad idea since you don't know when you call the function that it's going to change the values right away. The caller might assume that after the function returns, if whatever it was doing didn't work, the values would be whatever they were initialized to in the caller. Is it ok / good for me to initialize in the function? Example: public static void SomeFunction(int ixID, out string sSomething) { sSomething = ""; sSomething = something(ixID); if (sSomething = "") { somethingelse(); sSomething = "bar" } }

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  • Is it the best practice to extract an interface for every class?

    - by the_drow
    I have seen code where every class has an interface that it implements. Sometimes there is no common interface for them all. They are just there and they are used instead of concreate objects. They do not offer a generic interface for two classes and are specific to the domain of the problem that the class solves. Is there any reason to do that?

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  • Coding in large chunks ... Code verification skills

    - by Andrew
    As a follow up to my prev question: What is the best aproach for coding in a slow compilation environment To recap: I am stuck with a large software system with which a TDD ideology of "test often" does not work. And to make it even worse the features like pre-compiled headers/multi-threaded compilation/incremental linking, etc is not available to me - hence I think that the best way out would be to add the extensive logging into the system and to start "coding in large chunks", which I understand as code for a two-three hours first (as opposed to 15-20 mins in TDD) - thoroughly eyeball the code for a 15 minutes and only after all that do the compilation and run the tests. As I have been doing TDD for a quite a while, my code eyeballing / code verification skills got rusty (you don't really need this that much if you can quickly verify what you've done in 5 seconds by running a test or two) - so I am after a recommendations on how to learn these source code verification/error spotting skills again. I know I was able to do that easily some 5-10 years ago when I din't have much support from the compiler/unit testing tools I had until recently, thus there should be a way to get back to the basics.

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  • SQLAuthority News – Community Tech Days – TechEd on The Road – Ahmedabad – June 11, 2011

    - by pinaldave
    TechEd on Road is back! In Ahmedabad June 11, 2011! Inviting all Professional Developers, Project Managers, Architects, IT Managers, IT Administrators and Implementers of Ahmedabad to be a part of Tech•Ed on the Road, on 11th June, 2011. We have put together the best sessions from Tech•Ed India 2011 for you in your city. Focal point will be technologies like Database and BI, Windows 7, ASP.NET. REGISTER HERE! Venue: Venue: Ahmedabad Management Association (AMA) Dr. Vikram Sarabhai Marg, University Area, Ahmedabad, Gujarat 380 015 Time: 9:30AM – 5:30PM The biggest attraction of the event is session HTML5 – Future of the Web by Harish Vaidyanathan. He is Evangelist Lead in Microsoft and hands on developer himself. I strongly urge all of you to attend his session to understand direction of the web and Microsoft’s take on the subject. I (Pinal Dave) will be presenting on the session of SQL Server Performance Tuning and Jacob Sebastian will be presenting on T-SQL Worst Practices. Do not miss this opportunity. Those who have attended in the past know that from last two years the venue is jam packed in first few minutes. Do come in early to get better seat and reserve your spot. We will have QUIZ during the event and we will have various gifts – Watches, USB Drives, T-Shirts and many more interesting gifts. Refer the agenda today and register right away. There will be no video recording so come and visit the event in person. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, Best Practices, Database, DBA, MVP, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • SQLAuthority News – SQL Server Interview Questions And Answers Book Summary

    - by pinaldave
    Today we are using computers for various activities, motor vehicles for traveling to places, and mobile phones for conversation. How many of us can claim the invention of micro-processor, a basic wheel, or the telegraph? Similarly, this book was not written overnight. The journey of this book goes many years back with many individuals to be thanked for. To begin with, we want to thank all those interviewers who reject interviewees by saying they need to know ‘the key things’ regardless of having high grades in class. The whole concept of interview questions and answers revolves around knowing those ‘key things’. The core concept of this book will continue to evolve over time. I am sure many of you will come along with us on this journey and submit your suggestions to us to make this book a key reference for anybody who wants to start with SQL Server. Today we want to acknowledge the fact that you will help us keep this book alive forever with the latest updates. We want to thank everyone who participates in this journey with us. Though each of these chapters are geared towards convenience we highly recommend reading each of the sections irrespective of the roles you might be doing since each of the sections have some interesting trivia about working with SQL Server. In the industry the role of accidental DBA’s (especially with SQL Server) is very common. Hence if you have performed the role of DBA for a short stint and want to brush-up your fundamentals then the upcoming sections will be a great review. Table Of Contents Database Concepts With Sql Server Common Generic Questions & Answers Common Developer Questions Common Tricky Questions Miscellaneous Questions On Sql Server 2008 Dba Skills Related Questions Data Warehousing Interview Questions & Answers General Best Practices [Amazon] | [Flipkart] Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Best Practices, Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL Interview Questions and Answers, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL, Technology

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  • SQL Rally Pre-Con: Data Warehouse Modeling – Making the Right Choices

    - by Davide Mauri
    As you may have already learned from my old post or Adam’s or Kalen’s posts, there will be two SQL Rally in North Europe. In the Stockholm SQL Rally, with my friend Thomas Kejser, I’ll be delivering a pre-con on Data Warehouse Modeling: Data warehouses play a central role in any BI solution. It's the back end upon which everything in years to come will be created. For this reason, it must be rock solid and yet flexible at the same time. To develop such a data warehouse, you must have a clear idea of its architecture, a thorough understanding of the concepts of Measures and Dimensions, and a proven engineered way to build it so that quality and stability can go hand-in-hand with cost reduction and scalability. In this workshop, Thomas Kejser and Davide Mauri will share all the information they learned since they started working with data warehouses, giving you the guidance and tips you need to start your BI project in the best way possible?avoiding errors, making implementation effective and efficient, paving the way for a winning Agile approach, and helping you define how your team should work so that your BI solution will stand the test of time. You'll learn: Data warehouse architecture and justification Agile methodology Dimensional modeling, including Kimball vs. Inmon, SCD1/SCD2/SCD3, Junk and Degenerate Dimensions, and Huge Dimensions Best practices, naming conventions, and lessons learned Loading the data warehouse, including loading Dimensions, loading Facts (Full Load, Incremental Load, Partitioned Load) Data warehouses and Big Data (Hadoop) Unit testing Tracking historical changes and managing large sizes With all the Self-Service BI hype, Data Warehouse is become more and more central every day, since if everyone will be able to analyze data using self-service tools, it’s better for him/her to rely on correct, uniform and coherent data. Already 50 people registered from the workshop and seats are limited so don’t miss this unique opportunity to attend to this workshop that is really a unique combination of years and years of experience! http://www.sqlpass.org/sqlrally/2013/nordic/Agenda/PreconferenceSeminars.aspx See you there!

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  • Why do some bad websites rank well?

    - by BradB
    Consider the following scenario: you are pitching SEO/Website Optimisation to a prospective client and you explain to them the importance of great copy and content, how acquiring links (ethically) can increase page rank, why the quality of the HTML build matters (H1, H2 tags, w3c validation etc), why keyword research is beneficial, you may drop in a few Google Webmaster Guideline or Matt Cutts references to back up your claims and rubbish the "back hat" approach as being no longer effective for good measure. Your advice is ethical and in the eyes of best practices, spot on. Then, the client points out to you some of their long established competitors on Google and you see these competitor websites ranking in the top spots (1 to 3) for medium to highly competitive search phrases that your client wants to compete for. These websites totally contradict your ethical approach and pretty much violate every best practice previously noted. They even out perform other "white hat" competitors who are in accordance with the above guidelines. I experienced this today. One of these well ranking websites had: About six microsites with more or less the same copy and a slightly varied layout Little or not textual content I would almost say duplicate content across the sites, but there was so little of it it could barely qualify for being duplicate All the content in Flash (with a music track that kicked in on each page load, not so much of an SEO issue - but it helps paint the picture) Keyword stuffing behind the Flash file with a bunch of black text on black background in the style of keyword 1 keyword 2,keyword1,keyword 2,keyword 2 keyword 3 and so on... The exact keyword stuffed combination present on every page of the website A bunch of clearly self made links from poor quality forums and directories with little or no Page Rank Links exchanged across the microsites How do you explain your way out of this when this hard evidence is sat in front of you undermining your great pitch?

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  • IOUG SIG Webcast on October 30th : Performance Tuning your DB Cloud

    - by Anand Akela
    The Oracle Enterprise Manager Special Interest Group (SIG) is a growing body of IOUG members who manage or are interested in all aspects of Oracle Enterprise Manager. This IOUG SIG is managed by volunteers and supported by Oracle Enterprise Manager product managers and developers. The purpose of the SIG is to bring relevant information and education through webcasts, discussions and networking to users interested in learning more about the product, and to share user experiences. On October 30th at 10 AM pacific time, Oracle Enterprise Manager SIG is hosting a webcast on "Performance Tuning your DB Cloud in OEM 12c Cloud Control - 360 Degrees". In this webcast, Tariq Farooq , CEO, BrainSurface and Mike Ault, Oracle  will provide a tutorial on how to monitor and perform performance tuning of the Oracle database cloud environment. You will learn how to leverage Oracle Enterprise Manager for tuning, trouble-shooting & monitoring your Oracle Database Cloud Ecosystem. The session covers lessons learned, tips/tricks, recommendations, best practices, gotchas and a whole lot more on how to effectively use Oracle Enterprise Manager Cloud Control 12c for quick, easy & intuitive performance tuning of your Oracle Database Cloud. Session Objectives:• Leveraging OEM12c Cloud Control for Oracle DB Tuning/Monitoring • Limited Deep-Dive on AWR • Oracle DB Cloud Performance Tuning • Best Practices for DB Cloud Maintenance/Monitoring Register Now ! Stay Connected: Twitter |  Face book |  You Tube |  Linked in |  Google+ |  Newsletter

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  • Is it OK to use dynamic typing to reduce the amount of variables in scope?

    - by missingno
    Often, when I am initializing something I have to use a temporary variable, for example: file_str = "path/to/file" file_file = open(file) or regexp_parts = ['foo', 'bar'] regexp = new RegExp( regexp_parts.join('|') ) However, I like to reduce the scope my variables to the smallest scope possible so there is less places where they can be (mis-)used. For example, I try to use for(var i ...) in C++ so the loop variable is confined to the loop body. In these initialization cases, if I am using a dynamic language, I am then often tempted to reuse the same variable in order to prevent the initial (and now useless) value from being used latter in the function. file = "path/to/file" file = open(file) regexp = ['...', '...'] regexp = new RegExp( regexp.join('|') ) The idea is that by reducing the number of variables in scope I reduce the chances to misuse them. However this sometimes makes the variable names look a little weird, as in the first example, where "file" refers to a "filename". I think perhaps this would be a non issue if I could use non-nested scopes begin scope1 filename = ... begin scope2 file = open(filename) end scope1 //use file here //can't use filename on accident end scope2 but I can't think of any programming language that supports this. What rules of thumb should I use in this situation? When is it best to reuse the variable? When is it best to create an extra variable? What other ways do we solve this scope problem?

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  • How to implement Restricted access to application features

    - by DroidUser
    I'm currently developing a web application, that provides some 'service' to the user. The user will have to select a 'plan' according to which she/he will be allowed to perform application specific actions but up to a limit defined by the plan. A Plan will also limit access to certain features, which will not be available at all for some plans. As an example : say there are 3 plans, 2 actions throughout the application users in plan-1 can perform action-1 3 times, and they can't perform action-2 at all users in plan-2 can perform action-1 10 times, action-2 5 times users in plan-3 can perform action-1 20 times, action-2 10 times So i'm looking for the best way to get this done, and my main concerns besides implementing it, are the following(in no particular order) maintainability/changeability : the number of plans, and type of features/actions will change in the final product industry standard/best practice : for future readiness!! efficiency : ofcourse, i want fast code!! I have never done anything like this before, so i have no clue about how do i go about implementing these functionalities. Any tips/guides/patterns/resources/examples? I did read a little about ACL, RBAC, are they the patterns that i need to follow? Really any sort of feedback will help.

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  • BGP Multihomed/Multi-location best practice

    - by Tom O'Connor
    We're in the process of designing a new iteration of our network where we improve resilliency by adding a second datacentre. We'll be adding a second datacentre, with an identical configuration of servers as our primary location. To achieve network connectivity, we're looking into a couple of possible methods. See earlier questions http://serverfault.com/questions/86736/best-way-to-improve-resilience and http://serverfault.com/questions/101582/dns-round-robin-failover-and-load-balancing I'm pretty convinced that BGP is the right way to go about this, and this question is not about RRDNS. 1) If we have 2 locations, do we announce the same IP address block from both locations? 2) If we did this, but had a management ssh interface on x.x.x.50 from datacentre A, but it was on x.x.x.150 in datacentre B. What is the best practice mechanism for achieving this? Because if I were nearest to A, then all my traffic would go to x.50, but if i attempted to connect to x.150, I'd not be able to connect, because this address wouldn't be valid at A, but only at B. Is the best solution to announce 2 different netblocks, one at each location, facilitating the need for RRDNS, or to announce a single block, and run some form of VPN between the two sites for managment traffic?

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  • IOUG and Oracle Enterprise Manager User Community Twitter Chat and Sessions at OpenWorld

    - by Anand Akela
    Like last many years, we will have annual Oracle Users Forum on Sunday, September 30th, 2012 at Moscone West, Levels 2 & 3 . It will be open to all registered attendees of Oracle Open World and conferences running from September 29 to October 5, 2012 . This will be a great  opportunity to meet with colleagues, peers, and subject matter experts to share best practices, tips, and techniques around Oracle technologies. You could sit in on a special interest group (SIG) meeting or session and learn how to get more out of Oracle technologies and applications. IOUG and Oracle Enterprise Manager team invites you to join a Twitter Chat on Sunday, Sep. 30th from 11:30 AM to 12:30 PM.  IOUG leaders, Enterprise Manager SIG contributors and many Oracle Users Forum speakers will answer questions related to their experience with Oracle Enterprise Manager and the activities and resources available for  Enterprise Manager SIG members. You can participate in the chat using hash tag #em12c on Twitter.com or by going to  tweetchat.com/room/em12c      (Needs Twitter credential for participating).  Feel free to join IOUG and Enterprise team members at the User Group Pavilion on 2nd Floor, Moscone West. Here is the complete list of Oracle Enterprise Manager sessions during the Oracle Users Forum : Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Time Session Title Speakers Location 8:00AM - 8:45AM UGF4569 - Oracle RAC Migration with Oracle Automatic Storage Management and Oracle Enterprise Manager 12c VINOD Emmanuel -Database Engineering, Dell, Inc. Wendy Chen - Sr. Systems Engineer, Dell, Inc. Moscone West - 2011 8:00AM - 8:45AM UGF10389 -  Monitoring Storage Systems for Oracle Enterprise Manager 12c Anand Ranganathan - Product Manager, NetApp Moscone West - 2016 9:00AM - 10:00AM UGF2571 - Make Oracle Enterprise Manager Sing and Dance with the Command-Line Interface Ray Smith - Senior Database Administrator, Portland General Electric Moscone West - 2011 10:30AM - 11:30AM UGF2850 - Optimal Support: Oracle Enterprise Manager 12c Cloud Control, My Oracle Support, and More April Sims - DBA, Southern Utah University Moscone West - 2011 11:30AM - 12:30PM IOUG and Oracle Enterprise Manager Joint Tweet Chat  Join IOUG Leaders, IOUG's Enterprise Manager SIG Contributors and Speakers on Twitter and ask questions related to practitioner's experience with Oracle Enterprise Manager and the new IOUG 's Enterprise Manager SIG. To attend and participate in the chat, please use hash tag #em12c on twitter.com or your favorite Twitter client. You can also go to tweetchat.com/room/em12c to watch the conversation or login with your twitter credentials to ask questions. User Group Pavilion 2nd Floor, Moscone West 12:30PM-2:00PM UGF5131 - Migrating from Oracle Enterprise Manager 10g Grid Control to 12c Cloud Control    Leighton Nelson - Database Administrator, Mercy Moscone West - 2011 2:15PM-3:15PM UGF6511 -  Database Performance Tuning: Get the Best out of Oracle Enterprise Manager 12c Cloud Control Mike Ault - Oracle Guru, TEXAS MEMORY SYSTEMS INC Tariq Farooq - CEO/Founder, BrainSurface Moscone West - 2011 3:30PM-4:30PM UGF4556 - Will It Blend? Verifying Capacity in Server and Database Consolidations Jeremiah Wilton - Database Technology, Blue Gecko / DatAvail Moscone West - 2018 3:30PM-4:30PM UGF10400 - Oracle Enterprise Manager 12c: Monitoring, Metric Extensions, and Configuration Best Practices Kellyn Pot'Vin - Sr. Technical Consultant, Enkitec Moscone West - 2011 Stay Connected: Twitter |  Face book |  You Tube |  Linked in |  Newsletter

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  • Separating code logic from the actual data structures. Best practices?

    - by Patrick
    I have an application that loads lots of data into memory (this is because it needs to perform some mathematical simulation on big data sets). This data comes from several database tables, that all refer to each other. The consistency rules on the data are rather complex, and looking up all the relevant data requires quite some hashes and other additional data structures on the data. Problem is that this data may also be changed interactively by the user in a dialog. When the user presses the OK button, I want to perform all the checks to see that he didn't introduce inconsistencies in the data. In practice all the data needs to be checked at once, so I cannot update my data set incrementally and perform the checks one by one. However, all the checking code work on the actual data set loaded in memory, and use the hashing and other data structures. This means I have to do the following: Take the user's changes from the dialog Apply them to the big data set Perform the checks on the big data set Undo all the changes if the checks fail I don't like this solution since other threads are also continuously using the data set, and I don't want to halt them while performing the checks. Also, the undo means that the old situation needs to be put aside, which is also not possible. An alternative is to separate the checking code from the data set (and let it work on explicitly given data, e.g. coming from the dialog) but this means that the checking code cannot use hashing and other additional data structures, because they only work on the big data set, making the checks much slower. What is a good practice to check user's changes on complex data before applying them to the 'application's' data set?

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  • Oracle BI Server Modeling, Part 1- Designing a Query Factory

    - by bob.ertl(at)oracle.com
      Welcome to Oracle BI Development's BI Foundation blog, focused on helping you get the most value from your Oracle Business Intelligence Enterprise Edition (BI EE) platform deployments.  In my first series of posts, I plan to show developers the concepts and best practices for modeling in the Common Enterprise Information Model (CEIM), the semantic layer of Oracle BI EE.  In this segment, I will lay the groundwork for the modeling concepts.  First, I will cover the big picture of how the BI Server fits into the system, and how the CEIM controls the query processing. Oracle BI EE Query Cycle The purpose of the Oracle BI Server is to bridge the gap between the presentation services and the data sources.  There are typically a variety of data sources in a variety of technologies: relational, normalized transaction systems; relational star-schema data warehouses and marts; multidimensional analytic cubes and financial applications; flat files, Excel files, XML files, and so on. Business datasets can reside in a single type of source, or, most of the time, are spread across various types of sources. Presentation services users are generally business people who need to be able to query that set of sources without any knowledge of technologies, schemas, or how sources are organized in their company. They think of business analysis in terms of measures with specific calculations, hierarchical dimensions for breaking those measures down, and detailed reports of the business transactions themselves.  Most of them create queries without knowing it, by picking a dashboard page and some filters.  Others create their own analysis by selecting metrics and dimensional attributes, and possibly creating additional calculations. The BI Server bridges that gap from simple business terms to technical physical queries by exposing just the business focused measures and dimensional attributes that business people can use in their analyses and dashboards.   After they make their selections and start the analysis, the BI Server plans the best way to query the data sources, writes the optimized sequence of physical queries to those sources, post-processes the results, and presents them to the client as a single result set suitable for tables, pivots and charts. The CEIM is a model that controls the processing of the BI Server.  It provides the subject areas that presentation services exposes for business users to select simplified metrics and dimensional attributes for their analysis.  It models the mappings to the physical data access, the calculations and logical transformations, and the data access security rules.  The CEIM consists of metadata stored in the repository, authored by developers using the Administration Tool client.     Presentation services and other query clients create their queries in BI EE's SQL-92 language, called Logical SQL or LSQL.  The API simply uses ODBC or JDBC to pass the query to the BI Server.  Presentation services writes the LSQL query in terms of the simplified objects presented to the users.  The BI Server creates a query plan, and rewrites the LSQL into fully-detailed SQL or other languages suitable for querying the physical sources.  For example, the LSQL on the left below was rewritten into the physical SQL for an Oracle 11g database on the right. Logical SQL   Physical SQL SELECT "D0 Time"."T02 Per Name Month" saw_0, "D4 Product"."P01  Product" saw_1, "F2 Units"."2-01  Billed Qty  (Sum All)" saw_2 FROM "Sample Sales" ORDER BY saw_0, saw_1       WITH SAWITH0 AS ( select T986.Per_Name_Month as c1, T879.Prod_Dsc as c2,      sum(T835.Units) as c3, T879.Prod_Key as c4 from      Product T879 /* A05 Product */ ,      Time_Mth T986 /* A08 Time Mth */ ,      FactsRev T835 /* A11 Revenue (Billed Time Join) */ where ( T835.Prod_Key = T879.Prod_Key and T835.Bill_Mth = T986.Row_Wid) group by T879.Prod_Dsc, T879.Prod_Key, T986.Per_Name_Month ) select SAWITH0.c1 as c1, SAWITH0.c2 as c2, SAWITH0.c3 as c3 from SAWITH0 order by c1, c2   Probably everybody reading this blog can write SQL or MDX.  However, the trick in designing the CEIM is that you are modeling a query-generation factory.  Rather than hand-crafting individual queries, you model behavior and relationships, thus configuring the BI Server machinery to manufacture millions of different queries in response to random user requests.  This mass production requires a different mindset and approach than when you are designing individual SQL statements in tools such as Oracle SQL Developer, Oracle Hyperion Interactive Reporting (formerly Brio), or Oracle BI Publisher.   The Structure of the Common Enterprise Information Model (CEIM) The CEIM has a unique structure specifically for modeling the relationships and behaviors that fill the gap from logical user requests to physical data source queries and back to the result.  The model divides the functionality into three specialized layers, called Presentation, Business Model and Mapping, and Physical, as shown below. Presentation services clients can generally only see the presentation layer, and the objects in the presentation layer are normally the only ones used in the LSQL request.  When a request comes into the BI Server from presentation services or another client, the relationships and objects in the model allow the BI Server to select the appropriate data sources, create a query plan, and generate the physical queries.  That's the left to right flow in the diagram below.  When the results come back from the data source queries, the right to left relationships in the model show how to transform the results and perform any final calculations and functions that could not be pushed down to the databases.   Business Model Think of the business model as the heart of the CEIM you are designing.  This is where you define the analytic behavior seen by the users, and the superset library of metric and dimension objects available to the user community as a whole.  It also provides the baseline business-friendly names and user-readable dictionary.  For these reasons, it is often called the "logical" model--it is a virtual database schema that persists no data, but can be queried as if it is a database. The business model always has a dimensional shape (more on this in future posts), and its simple shape and terminology hides the complexity of the source data models. Besides hiding complexity and normalizing terminology, this layer adds most of the analytic value, as well.  This is where you define the rich, dimensional behavior of the metrics and complex business calculations, as well as the conformed dimensions and hierarchies.  It contributes to the ease of use for business users, since the dimensional metric definitions apply in any context of filters and drill-downs, and the conformed dimensions enable dashboard-wide filters and guided analysis links that bring context along from one page to the next.  The conformed dimensions also provide a key to hiding the complexity of many sources, including federation of different databases, behind the simple business model. Note that the expression language in this layer is LSQL, so that any expression can be rewritten into any data source's query language at run time.  This is important for federation, where a given logical object can map to several different physical objects in different databases.  It is also important to portability of the CEIM to different database brands, which is a key requirement for Oracle's BI Applications products. Your requirements process with your user community will mostly affect the business model.  This is where you will define most of the things they specifically ask for, such as metric definitions.  For this reason, many of the best-practice methodologies of our consulting partners start with the high-level definition of this layer. Physical Model The physical model connects the business model that meets your users' requirements to the reality of the data sources you have available. In the query factory analogy, think of the physical layer as the bill of materials for generating physical queries.  Every schema, table, column, join, cube, hierarchy, etc., that will appear in any physical query manufactured at run time must be modeled here at design time. Each physical data source will have its own physical model, or "database" object in the CEIM.  The shape of each physical model matches the shape of its physical source.  In other words, if the source is normalized relational, the physical model will mimic that normalized shape.  If it is a hypercube, the physical model will have a hypercube shape.  If it is a flat file, it will have a denormalized tabular shape. To aid in query optimization, the physical layer also tracks the specifics of the database brand and release.  This allows the BI Server to make the most of each physical source's distinct capabilities, writing queries in its syntax, and using its specific functions. This allows the BI Server to push processing work as deep as possible into the physical source, which minimizes data movement and takes full advantage of the database's own optimizer.  For most data sources, native APIs are used to further optimize performance and functionality. The value of having a distinct separation between the logical (business) and physical models is encapsulation of the physical characteristics.  This encapsulation is another enabler of packaged BI applications and federation.  It is also key to hiding the complex shapes and relationships in the physical sources from the end users.  Consider a routine drill-down in the business model: physically, it can require a drill-through where the first query is MDX to a multidimensional cube, followed by the drill-down query in SQL to a normalized relational database.  The only difference from the user's point of view is that the 2nd query added a more detailed dimension level column - everything else was the same. Mappings Within the Business Model and Mapping Layer, the mappings provide the binding from each logical column and join in the dimensional business model, to each of the objects that can provide its data in the physical layer.  When there is more than one option for a physical source, rules in the mappings are applied to the query context to determine which of the data sources should be hit, and how to combine their results if more than one is used.  These rules specify aggregate navigation, vertical partitioning (fragmentation), and horizontal partitioning, any of which can be federated across multiple, heterogeneous sources.  These mappings are usually the most sophisticated part of the CEIM. Presentation You might think of the presentation layer as a set of very simple relational-like views into the business model.  Over ODBC/JDBC, they present a relational catalog consisting of databases, tables and columns.  For business users, presentation services interprets these as subject areas, folders and columns, respectively.  (Note that in 10g, subject areas were called presentation catalogs in the CEIM.  In this blog, I will stick to 11g terminology.)  Generally speaking, presentation services and other clients can query only these objects (there are exceptions for certain clients such as BI Publisher and Essbase Studio). The purpose of the presentation layer is to specialize the business model for different categories of users.  Based on a user's role, they will be restricted to specific subject areas, tables and columns for security.  The breakdown of the model into multiple subject areas organizes the content for users, and subjects superfluous to a particular business role can be hidden from that set of users.  Customized names and descriptions can be used to override the business model names for a specific audience.  Variables in the object names can be used for localization. For these reasons, you are better off thinking of the tables in the presentation layer as folders than as strict relational tables.  The real semantics of tables and how they function is in the business model, and any grouping of columns can be included in any table in the presentation layer.  In 11g, an LSQL query can also span multiple presentation subject areas, as long as they map to the same business model. Other Model Objects There are some objects that apply to multiple layers.  These include security-related objects, such as application roles, users, data filters, and query limits (governors).  There are also variables you can use in parameters and expressions, and initialization blocks for loading their initial values on a static or user session basis.  Finally, there are Multi-User Development (MUD) projects for developers to check out units of work, and objects for the marketing feature used by our packaged customer relationship management (CRM) software.   The Query Factory At this point, you should have a grasp on the query factory concept.  When developing the CEIM model, you are configuring the BI Server to automatically manufacture millions of queries in response to random user requests. You do this by defining the analytic behavior in the business model, mapping that to the physical data sources, and exposing it through the presentation layer's role-based subject areas. While configuring mass production requires a different mindset than when you hand-craft individual SQL or MDX statements, it builds on the modeling and query concepts you already understand. The following posts in this series will walk through the CEIM modeling concepts and best practices in detail.  We will initially review dimensional concepts so you can understand the business model, and then present a pattern-based approach to learning the mappings from a variety of physical schema shapes and deployments to the dimensional model.  Along the way, we will also present the dimensional calculation template, and learn how to configure the many additivity patterns.

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  • Software Design for Product Verticals and Service Verticals

    - by Rachel
    In every industry there are two verticals Product Vertical and Service Vertical, so my question is: How does design approach changes while designing Software for Product Vertical as compared to developing Software for Service Vertical ? What are the pros and cons for each case ? Also, in case of Product Vertical, How you go about designing Product or Features and what are steps involved ? Lastly, I was reading How Facebook Ships Code article and it appears that Product Managers have very little influence on how Product is developed and responsibility lies mainly with the Developer for the feature. So is this good practice and why one would go for this approach ? What would be your comment on this kind of approach ?

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  • Being prepared for a code review as a developer?

    - by Karthik Sreenivasan
    I am looking for some ideas here. I read the article How should code reviews be Carried Out and Code Reviews, what are the advantages? which were very informative but I still need more clarity on the question below. My Question is, Being the target developer, can you suggest some best practices a developer can incorporate before his code is going get reviewed. Currently I practice the following methods PPT for a logical flow Detailed comments. Issue: Even though I have implemented the above practices, they do not help on the review. The problem I faced is, when certain logic is referred, I keep searching for the implementation and the flow and too much time is wasted in the process and I get on people’s nerve. I think a lot of developers would be going through what I am going through as well.

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