the lazy dba - Developer IT

Using Lazy<T> and abstract wrapper class to lazy-load complex system parameters

- by DigiMortal

.NET Framework 4.0 introduced new class called Lazy<T> and I wrote blog post about it: .Net Framework 4.0: Using System.Lazy<T>. One thing is annoying for me – we have to keep lazy loaded value and its value loader as separate things. In this posting I will introduce you my Lazy<T> wrapper for complex to get system parameters that uses template method to keep lazy value loader in parameter class. Problem with original implementation Here’s the sample code that shows you how Lazy<T> is usually used. This is just sample code, don’t focus on the fact that this is dummy console application. class Program { static void Main(string[] args) { var temperature = new Lazy<int>(LoadMinimalTemperature); Console.WriteLine("Minimal room temperature: " + temperature.Value); Console.ReadLine(); } protected static int LoadMinimalTemperature() { var returnValue = 0; // Do complex stuff here return true; } } The problem is that our class with many lazy loaded properties will grow messy if it has all value loading code inside it. This code may be complex for more than one parameter and in this case it is better to use separate class for this parameter. Defining base class for parameters As a first step I will define base class for all lazy-loaded parameters. This class is wrapper around Lazy<T> and it also offers one template method that parameter classes have to override to provide loaded data. public abstract class LazyParameter<T> { private Lazy<T> _lazyParam; public LazyParameter() { _lazyParam = new Lazy<T>(Load); } protected abstract T Load(); public T Value { get { return _lazyParam.Value; } } } It is also possible to extend Lazy<T> but I don’t prefer to do it as Lazy<T> has six constructors we have to take care of. Also I don’t like to expose Lazy<T> public interface to users of my parameter classes. Creating parameter class Now it’s time to create our first parameter class. Notice how few stuff we have in this class besides overridden Load() method. public class MinimalRoomTemperature : LazyParameter<int> { protected override int Load() { var returnValue = 0; // Do complex stuff here return returnValue; } } Using parameter class is simple. Here’s my test code. class Program { static void Main(string[] args) { var parameter = new MinimalRoomTemperature(); Console.WriteLine("Minimal room temperature: " + parameter.Value); Console.ReadLine(); } } Conclusion Lazy<T> is useful class that you usually don’t want to use outside from API-s. I like this class but I don’t like when people are using this class directly in application code. In this posting I showed you how to use Lazy<T> with wrapper class to get complex parameter loading code out from classes that use this parameter. We ended up with generic base class for parameters that you can also use as base for other similar classes (you have to find better name to base class in this case).

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Lazy Sequences that "Look Ahead" for Project Euler Problem 14

- by ivar

I'm trying to solve Project Euler Problem 14 in a lazy way. Unfortunately, I may be trying to do the impossible: create a lazy sequence that is both lazy, yet also somehow 'looks ahead' for values it hasn't computed yet. The non-lazy version I wrote to test correctness was: (defn chain-length [num] (loop [len 1 n num] (cond (= n 1) len (odd? n) (recur (inc len) (+ 1 (* 3 n))) true (recur (inc len) (/ n 2))))) Which works, but is really slow. Of course I could memoize that: (def memoized-chain (memoize (fn [n] (cond (= n 1) 1 (odd? n) (+ 1 (memoized-chain (+ 1 (* 3 n)))) true (+ 1 (memoized-chain (/ n 2))))))) However, what I really wanted to do was scratch my itch for understanding the limits of lazy sequences, and write a function like this: (def lazy-chain (letfn [(chain [n] (lazy-seq (cons (if (odd? n) (+ 1 (nth lazy-chain (dec (+ 1 (* 3 n))))) (+ 1 (nth lazy-chain (dec (/ n 2))))) (chain (+ n 1)))))] (chain 1))) Pulling elements from this will cause a stack overflow for n2, which is understandable if you think about why it needs to look 'into the future' at n=3 to know the value of the tenth element in the lazy list because (+ 1 (* 3 n)) = 10. Since lazy lists have much less overhead than memoization, I would like to know if this kind of thing is possible somehow via even more delayed evaluation or queuing?

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Implicit Lazy Loading vs Explicit Lazy Loading

- by Tarik

I've been reading Entity Framework and people were crying over why there was not implicit lazy loading or something. Basically I've been searching things about Lazy Loading and now I know what it is : It is a design pattern which allows us to load objects when they are really needed. But what is the difference between Explicit Lazy Loading and Implicit Lazy Loading. Thanks in advance...

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SQLAuthority Book Review DBA Survivor: Become a Rock Star DBA

DBA Survivor: Become a Rock Star DBA – Thomas LaRock Link to Amazon Link to Flipkart First of all, I thank all my readers when I wrote that I could not get this book in any local book stores, because they offered me to send a copy of this good book. A very special mention [...]...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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SQLAuthority News – Best Complements – DBA Survivor: Become a Rock Star DBA

- by pinaldave

Today’s blog post is about the biggest complement I have ever received. I am very very happy and would like to share my feelings with you. Thomas Larock (Blog | Twitter) (known as SQLRockstar) keeps the excellent ranking of the blogger in SQL Server Arena. I am big fan of this list and have been referring lots of people. I was in the msdb database since the very first day of the ranking. Two days ago, I noticed that I am promoted to Model Database. I often receive complements about my blog but this is the biggest complement I have ever received. I have taken the snapshot of the same and listed here. Thomas is a SQL Server MVP and Board of Directors for the Professional Association for SQL Server. He is the author of DBA Survivor: Become a Rock Star DBA. The book is designed to give a junior to mid-level DBA a better understanding of what skills are needed in order to survive (and thrive) in their career. This book is currently not available in India, I am waiting for someone traveling from USA to bring the copy for me. I am very eager to read the book and promise to share the book review with all of you once I am done reading. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, SQLServer, T SQL, Technology

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SQLAuthority Book Review – DBA Survivor: Become a Rock Star DBA

- by pinaldave

DBA Survivor: Become a Rock Star DBA – Thomas LaRock Link to Amazon Link to Flipkart First of all, I thank all my readers when I wrote that I could not get this book in any local book stores, because they offered me to send a copy of this good book. A very special mention goes to Sripada and Jayesh for they gave so much effort in finding my home address and sending me the hard copy. Before, I did not have the copy of the book, but now I have two of it already! It surprises me how my readers were able to find my home address, which I have not publicly shared. Quick Review: This is indeed a one easy-to-read and fun book. We all work day and night with technology yet we should not forget to show our love and care for our family at home. For our souls that starve for peace and guidance, this one book is the “it” book for all the technology enthusiasts. Though this book was specifically written for DBAs, the reach is not limited to DBAs only because the lessons incorporated in it actually applies to all. This is one of the most motivating technical books I have read. Detailed Review: Let us go over a few questions first: Who wants to be as famous as rockstars in the field of Database Administration? How can one learn what it takes to become a top notch software developer? If you are a beginner in your field, how will you go to next level? Your boss may be very kind or like Dilbert’s Boss, what will you do? How do you keep growing when Eco-system around you does not support you? You are almost at top but there is someone else at the TOP, what do you do and how do you avoid office politics? As a database developer what should be your basic responsibility? and many more… I was able to completely read book in one sitting and I loved it. Before I continue with my opinion, I want to echo the opinion of Kevin Kline who has written the Forward of the book. He has truly suggested that “You hold in your hands a collection of insights and wisdom on the topic of database administration gained through many years of hard-won experience, long nights of study, and direct mentorship under some of the industry’s most talented database professionals and information technology (IT) experts.” Today, IT field is getting bigger and better, while talking about terabytes of the database becomes “more” normal every single day. The gods and demigods of database professionals are taking care of these large scale databases and are carefully maintaining them. In this world, there are only a few beginnings on the first step. There are many experts in different technology fields who are asked to address the issues with databases. There is YOU and ME, who is just new to this work. So we ask ourselves WHERE to begin and HOW to begin. We adore and follow the religion of our rockstars, but oftentimes we really have no idea about their background and their struggles. Every rockstar has his success story which needs to be digested before learning his tricks and tips. This book starts with the same note and teaches the two most important lessons for anybody who wants to be a DBA Rockstar – to focus on their single goal of learning and to excel the technology. The story starts with three simple guidelines – Get Prepared, Get Trained, Get Certified. Once a person learns the skills, and then, it would be about time that he needs to enrich or to improve those skills you have learned. I am sure that the right opportunity will come finding themselves and they will not have to go run behind it. However, the real challenge for any person is the first day or first week. A new employee, no matter how much experienced he is, sometimes has no clue about what should one do at new job. Chapter 2 and chapter 3 precisely talk about what one should do as soon as the new job begins. It is also written with keeping the fact in focus that each job can be very much different but there are few infrastructure setups and programming concepts are the same. Learning basics of database was really interesting. I like to focus on the roots of any technology. It is important to understand the structure of the database before suggesting what indexes needs to be created, the same way this book covers the most essential knowledge one must learn by most database developers. I think the title of the fourth chapter is my favorite sentence in this book. I can see that I will be saying this again and again in the future – “A Development Server Is a Production Server to a Developer“. I have worked in the software industry for almost 8 years now and I have seen so many developers sitting on their chairs and waiting for instructions from their lead about how to improve the code or what to do the next. When I talk to them, I suggest that the experiment with their server and try various techniques. I think they all should understand that for them, a development server is their production server and needs to pay proper attention to the code from the beginning. There should be NO any inappropriate code from the beginning. One has to fully focus and give their best, if they are not sure they should ask but should do something and stay active. Chapter 5 and 6 talks about two essential skills for any developer and database administration – what are the ethics of developers when they are working with production server and how to support software which is running on the production server. I have met many people who know the theory by heart but when put in front of keyboard they do not know where to start. The first thing they do opening the browser and searching online, instead of opening SQL Server Management Studio. This can very well happen to anybody who is experienced as well. Chapter 5 and 6 addresses that situation as well includes the handy scripts which can solve almost all the basic trouble shooting issues. “Where’s the Buffet?” By far, this is the best chapter in this book. If you have ever met me, you would know that I love food. I think after reading this chapter, I felt Thomas has written this just keeping me in mind. I think there will be many other people who feel the same way, too. Even my wife who read this chapter thought this was specifically written for me. I will not talk any more about this chapter as this is one must read chapter. And of course this is about real ‘FOOD‘. I am an SQL Server Trainer and Consultant and I totally agree with the point made in the chapter 8 of this book. Yes, it says here that what is necessary to train employees and people. Millions of dollars worth the labor is continuously done in the world which has faults and incorrect. Once something goes wrong, very expensive consultant comes in and fixes the problem. This whole cycle which can be stopped and improved if proper training is done. There is plenty of free trainings available as well, if one cannot afford paid training. “Connect. Learn. Share” – I think this is a great summary and bird’s eye view of this book. Networking is the key. Everything which is discussed in this book can be taken to next level if one properly uses this tips and continuously grow with it. Connecting with others, helping learn each other and building the good knowledge sharing environment should be the goal of everyone. Before I end the review I want to share a real experience. I have personally met one DBA who has worked in a single department in a company for so long that when he was put in a different department in his company due to closing that department, he could not adjust and quit the job despite the same people and company around him. Adjusting in the new environment gets much tougher as one person gets more and more experienced. This book precisely addresses the same issue along with their solutions. I just cannot stop comparing the book with my personal journey. I found so many things which are coincidently in the book is written as how we developer and DBA think. I must express special thanks to Thomas for taking time in his personal life and write this book for us. This book is indeed a book for everybody who wants to grow healthy in the tough and competitive environment. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Book Review, SQLAuthority News, SQLServer, T SQL, Technology

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Interviewing a DBA

- by kev

Our Company is in the Process of recuiting a DBA. I have built a group test of questions from basic questions such as Pk and Fk constraints, simple querries(fizzbuzz style) to more advanced things such as indexes, Collation, isolation levels and how to trace deadlocks. However, that is the limit of my knowledge. So my question to all the DBA's is what is the base level knowledge that all DBA's should have? We are really looking for someone that will be able to manage our replication, analyzing some of our slower running queries(that the devs can go to for help) and someone that can trace some of the deadlock issues that we are having. Any help would be most appreciated!

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Interviewing a DBA

- by kev

Our Company is in the Process of recuiting a DBA. I have built a group test of questions from basic questions such as Pk and Fk constraints, simple querries(fizzbuzz style) to more advanced things such as indexes, Collation, isolation levels and how to trace deadlocks. However, that is the limit of my knowledge. So my question to all the DBA's is what is the base level knowledge that all DBA's should have? We are really looking for someone that will be able to manage our replication, analyzing some of our slower running queries(that the devs can go to for help) and someone that can trace some of the deadlock issues that we are having. Any help would be most appreciated!

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You Might Be a DBA

- by BuckWoody

With all apologies to Jeff Foxworthy, I was up late Friday night on a holiday weekend (which translated into T-SQL becomes “Maintenance Window”) and I got bored in between the two or three minutes I had between clicks. So I started a “Twitter” meme – and it just took off. I haven’t cleaned these up much, but here, in author order as of Saturday the 29th of May is the list “You might be a DBA” from around the Twitterverse: buckwoody Your two main enemies are developers and SAN admins #youmightbeaDBA buckwoody People can use Access as a cross or garlic on you #youmightbeaDBA buckwoody You always plan an exit strategy, even when entering a McDonald's #youmightbeaDBA buckwoody You can't explain to your family what you really do for a living #youmightbeaDBA buckwoody You have at least one set of scripts you won't share #youmightbeaDBA buckwoody You have an opinion on the best code-beautifier #youmightbeaDBA buckwoody You have children older than the rest of your team #youmightbeaDBA buckwoody You and the Oracle DBA would kill each other, but you'll happily fight off a developer together first #youmightbeaDBA buckwoody You've threatened to quit if they give anyone the sa password on production #youmightbeaDBA buckwoody You've sent a vendor suggestions on improving their database design or code (and been ignored) #youmightbeaDBA buckwoody You've sent a vendor suggestions on improving their database design or code (and been ignored) #youmightbeaDBA buckwoody You have an opinion on the best code-beautifier #youmightbeaDBA buckwoody You have at least one set of scripts you won't share #youmightbeaDBA buckwoody You refer to co-workers as "carbon-units" #youmightbeaDBA buckwoody Being paranoid is on your resume at the top #youmightbeaDBA buckwoody Everyone comes to your cube to find the MSDN DVD's #youmightbeaDBA buckwoody You always plan an exit strategy, even when entering a McDonald's #youmightbeaDBA buckwoody You've worn down developers to get your way by explaining normalization levels #youmightbeaDBA buckwoody You refer to clothes as "Data Abstractions" #youmightbeaDBA buckwoody Users pester you to be able to put data in a database, then they pester you to take it out and put it in Excel #youmightbeaDBA buckwoody Others try to de-duplicate data, you try to copy it to more than three locations #youmightbeaDBA buckwoody You have at least one DLT tape in the trunk of your car #youmightbeaDBA buckwoody You use twitter and facebook to talk with colleagues because there's no one else in your company that does what you do #youmightbeaDBA buckwoody Your spouse knows what "ETL" means #youmightbeaDBA buckwoody You've referred to yourself as the "Data Janitor" #youmightbeaDBA buckwoody You don't have positive connotations of the word "upgrade" #youmightbeaDBA buckwoody You get your coffee before you check your servers, because you know you won't get any if you don't #youmightbeaDBA buckwoody You always come to work through the back door so no one hijacks you on the way to your cube #youmightbeaDBA buckwoody You check your server logs before you check your e-mail in the morning so you can reply "Yeah, I already fixed that." #youmightbeaDBA buckwoody You have more conference badges than clean socks #youmightbeaDBA buckwoody Your coffee mug says "It depends" #youmightbeaDBA buckwoody You can convince a boss that you need 16GB of RAM in your laptop #youmightbeaDBA buckwoody You've used ebay to find production equipment #youmightbeaDBA buckwoody You pad all project timelines by 2X, and you still miss them #youmightbeaDBA buckwoody You know when your company is acquiring another even before the CFO #youmightbeaDBA buckwoody You pad all project timelines by 2X, and you still miss them #youmightbeaDBA buckwoody You call aspirin "work vitamins" #youmightbeaDBA buckwoody You get the same amount of sleep even after you have a child #youmightbeaDBA buckwoody You obsess about performance metrics from over one year ago #youmightbeaDBA buckwoody The first thing you buy after the database software is aftermarket tools to manage the database software #youmightbeaDBA buckwoody You've tried to convince someone else to become a DBA #youmightbeaDBA buckwoody You use twitter and facebook to talk with colleagues because there's no one else in your company that does what you do #youmightbeaDBA buckwoody You only know other DBA's by their Tweet Handle #youmightbeaDBA buckwoody You've explained the difference between 32 and 64-bit to more than one manager in terms they can understand, using puppets #youmightbeaDBA buckwoody Your two main enemies are developers and SAN admins #youmightbeaDBA buckwoody You've driven to the Datacenter to install SQL Server because "you don't trust those NOC admins" #youmightbeaDBA buckwoody You pay more for faster Internet connections than cable at home so you don't have to drive in #youmightbeaDBA buckwoody You call texting a "queuing system" #youmightbeaDBA buckwoody You know that if someone can read Perl, they manage an Oracle system #youmightbeaDBA buckwoody You have an e-mail rule for backup notifications #youmightbeaDBA buckwoody Your food pyramid includes coffee, salt and fat #youmightbeaDBA buckwoody You wish everything had a graphical query plan #youmightbeaDBA buckwoody You refactor your e-mails #youmightbeaDBA buckwoody You've gotten more help from twitter and facebook than all your years in college #youmightbeaDBA buckwoody You would pay money for a license plate that has the letters S-Q-L together #youmightbeaDBA buckwoody You have actually considered making a RAID array from thumb drives #youmightbeaDBA buckwoody Everything on your laptop is installed from your MSDN subscription #youmightbeaDBA buckwoody You've written blog posts on technology you've never actually implemented in production #youmightbeaDBA buckwoody Everything on your laptop is installed from your MSDN subscription #youmightbeaDBA buckwoody @MidnightDBA Click the #youmightbeaDBA tag. I've had WAY too much coffee today. buckwoody There is no other position that is 1-deep except you and the CEO #youmightbeaDBA buckwoody When you watch "The Office" you call it "OJT" #youmightbeaDBA buckwoody You would pay money for a license plate that has the letters S-Q-L together #youmightbeaDBA buckwoody Your blog would make a "best practices" or "worst practices" book #youmightbeaDBA buckwoody You have actually considered making a RAID array from thumb drives #youmightbeaDBA buckwoody The first thing you install on your netbook is SSMS #youmightbeaDBA buckwoody Everything on your laptop is installed from your MSDN subscription #youmightbeaDBA buckwoody Your watch is set to UTC because it's just easier #youmightbeaDBA buckwoody You make plenty of money, but you're excited to get a $2.00 squeeze-ball from Quest and Redgate #youmightbeaDBA buckwoody You make plenty of money, but you're excited to get a $2.00 squeeze-ball from Quest and Redgate #youmightbeaDBA buckwoody You think data can be represented as something OTHER than XML #youmightbeaDBA buckwoody You tell people that you made a database query go faster, and expect them to be happy for you #youmightbeaDBA buckwoody You take the word "NoSQL" as a personal attack #youmightbeaDBA buckwoody People can use Access as a cross or garlic on you #youmightbeaDBA buckwoody * == bad #youmightbeaDBA buckwoody * == bad #youmightbeaDBA buckwoody There are just as many females in your technical field as males #youmightbeaDBA buckwoody People can use Access as a cross or garlic on you #youmightbeaDBA buckwoody You've gotten more help from twitter and facebook than all your years in college #youmightbeaDBA buckwoody You think that something OTHER than the database might be the performance bottleneck #youmightbeaDBA buckwoody You refer to time as a "Clustered Index" #youmightbeaDBA buckwoody You know why "user" refers to both business people and crack addicts #youmightbeaDBA buckwoody You make plenty of money, but you're excited to get a $2.00 squeeze-ball from Quest and Redgate #youmightbeaDBA buckwoody You can't explain to your family what you really do for a living #youmightbeaDBA buckwoody You tell people that you made a database query go faster, and expect them to be happy for you #youmightbeaDBA buckwoody You think a millisecond is a really long time #youmightbeaDBA buckwoody You're sitting and typing #youmightbeaDBA when you could be outside #youmightbeaDBA buckwoody You can't wait for a technical conference so you can wear a kilt - and you're not Scottish #youmightbeaDBA buckwoody You know that "DBA" stands for "Default Blame Acceptor" #youmightbeaDBA buckwoody People can use Access as a cross or garlic on you #youmightbeaDBA buckwoody You know what "the truth, thole truth and nothing but the truth, so help me Codd" means #youmightbeaDBA buckwoody You've gotten more help from twitter and facebook than all your years in college #youmightbeaDBA buckwoody You can't talk fast enough to get a concept out of your head so you tweet it instead #youmightbeaDBA buckwoody You cry when someone doesn't use a WHERE clause #youmightbeaDBA buckwoody You think data can be represented as something OTHER than XML #youmightbeaDBA buckwoody You think "Set theory" is not an verb but a noun #youmightbeaDBA buckwoody You try to convince random strangers to vote on your Connect item #youmightbeaDBA buckwoody You think 3 hours of contiguous sleep is a good thing #youmightbeaDBA or #youmightbeamother buckwoody You don't like Oracle, and not just because of what she did to Neo #youmightbeaDBA buckwoody You know when to say "sequel" and "s-q-l" #youmightbeaDBA buckwoody You know where the data is #youmightbeaDBA buckwoody You refer to your children as "Fully Redundant Mirrors" #youmightbeaDBA buckwoody Holiday == "Maintenance Window" #youmightbeaDBA buckwoody Your laptop is more powerful than the servers in most companies - including your own #youmightbeaDBA buckwoody You capitalize SELECTed words #youmightbeaDBA buckwoody You take the word "NoSQL" as a personal attack #youmightbeaDBA buckwoody You know why "user" refers to both business people and crack addicts #youmightbeaDBA buckwoody You cringe in public when the word "upgrade" is used in a sentence #youmightbeaDBA buckwoody Holiday == "Maintenance Window" #youmightbeaDBA buckwoody All Data Is MetaData means something to you #youmightbeaDBA buckwoody You've never seen the driveway to your house in the daylight #youmightbeaDBA buckwoody You think that something OTHER than the database might be the performance bottleneck #youmightbeaDBA buckwoody Most of your bloodstream is composed of caffeine #youmightbeaDBA buckwoody Your task list is labeled "CRUD Matrix" #youmightbeaDBA buckwoody You call your wife/husband a "Linked Server" #youmightbeaDBA anonythemouse When someone tells you they are going to take a dump and you wonder of which database then #youmightbeaDBA anonythemouse When it's 11pm on a holiday weekend and you are working #youmightbeaDBA anonythemouse When you sit down at a table and look for it's primary key #youmightbeaDBA anonythemouse When getting milk from the fridge you check the expiry date is > getdate() #youmightbeaDBA blakmk when you wake up dreaming about sql #youmightbeaDBA CharlesGarver You think a @buckwoody bobblehead would be a cool thing to have on the dashboard of your car #youmightbeaDBA CharlesGarver Your friends don't understand why you think there's a difference between single and double quotes #youmightbeaDBA CharlesGarver Even the newest employees know your name from all the downtime notices you've sent out #youmightbeaDBA CharlesGarver You sometimes feel anxious and think "I should test restoring those backups" and then the feeling passes #youmightbeadba CharlesGarver You know what a co-worker means when they ask "how is your squirrel server?" #youmightbeadba CharlesGarver You can't sleep at night and you ponder the logisitcs of collecting every copy of Access for the world's biggest bonfire #youmightbeaDBA CharlesGarver You can't sleep at night and you ponder the logisitcs of collecting every copy of Access for the world's biggest bonfire #youmightbeaDBA CharlesGarver You're willing to move someone's job up in priority for a box of #voodoodonuts #youmightbeaDBA CharlesGarver Each person in your company seems to think you work for THEM #youmightbeaDBA CharlesGarver You have a Love/Hate relationship going on with #Microsoft #youmightbeaDBA CharlesGarver People ask you to troubleshoot their Access program #youmightbeaDBA CharlesGarver The first words you hear in the morning are 'your voicemail box is full' #youmightbeaDBA CharlesGarver The thought of disrupting 500 people's work so you can do something doesn't phase you #youmightbeaDBA CharlesGarver You can't sleep at night and you ponder the logisitcs of collecting every copy of Access for the world's biggest bonfire #youmightbeaDBA CharlesGarver Your home computer is backed up in 3 different places #youmightbeaDBA CharlesGarver Your wardrobe for work includes pajamas #youmightbeaDBA CharlesGarver Someone tells you to look in the INDEX and you look puzzled before finally going to the back of the book. #youmightbeaDBA chuckboycejr If you have ever set up a SQLAgent job to email your mobile phone to serve as an alarm clock #youmightbeaDBA chuckboycejr If you'd rather meet Itzik than Jay Z #youmightbeaDBA chuckboycejr If you'd rather meet Itzik than Jay Z #youmightbeaDBA chuckboycejr If you'd wrestle a SysAdmin to the ground to implement #DPA best practices as per @aspiringgeek #youmightbeaDBA databaseguy I need to be up in 7 hours, so I'm off to bed! I'll have to read the rest of @buckwoody's #youmightbeaDBA posts in the AM. (g'night Buck!) databaseguy When people ask you about your house, the first thing you describe is the network. #youmightbeaDBA databaseguy The last thing you say at the office each day is, "is anybody else here? I'm shutting off the lights!" #youmightbeaDBA databaseguy Your blood pressure rises when you read application specs drafted by marketing. #youmightbeaDBA databaseguy A good day at work is one when nobody pays you no mind. #youmightbeaDBA databaseguy You care about latches and wait states. #youmightbeaDBA databaseguy You have worked over 200 hours on a performance tuning project that required no application changes at all. #youmightbeaDBA databaseguy The late-night security guard knows the names of your spouse and kids. #youmightbeaDBA databaseguy You have had vigorous debates about whether it should be pronounced "sequel" or "ess-queue-ell". #youmightbeaDBA databaseguy You have VPN and RDP software installed on your phone ... just in case. #youmightbeaDBA databaseguy You have edited a data file by hand, just to see what would happen. #youmightbeaDBA databaseguy You decorate your office walls with database catalog posters. #youmightbeaDBA databaseguy You've built programs that access data just to keep other developers from asking you to run queries all the time. #youmightbeaDBA databaseguy When you watch movies like The Matrix, you find yourself calculating the fasibility of storing all that data. #youmightbeaDBA databaseguy You have tried to convince someone to spend money on an SSD storage array. #youmightbeaDBA databaseguy When CPU is spiked on a server, you want to gather forensic evidence. #youmightbeaDBA databaseguy You have to remind developers not to push code to production without checking if the database is ready. #youmightbeaDBA databaseguy Nobody cares what you wear to work, as long as the thing keeps running. #youmightbeaDBA databaseguy Telepathy is a job requirement when working with app dev teams. #youmightbeaDBA databaseguy You read database statistics for the educational value. #youmightbeaDBA databaseguy And your boss freely admits this to anyone within earshot. #youmightbeaDBA databaseguy Your boss cannot explain or understand what you do. #youmightbeaDBA databaseguy You envision ERDs when you see a GUI. #youmightbeaDBA databaseguy You say things like "applications come and go, but data lasts forever." #youmightbeaDBA databaseguy You have memorized the names of several of the AdventureWorks employees. #youmightbeaDBA databaseguy You know what MAXDOP setting you can get away with for a big query based on current server load. #youmightbeaDBA databaseguy And you immediately recognize the recursion in my last tweet. #youmightbeaDBA databaseguy You find 50 simultaneous tweets from @buckwoody about #youmightbeaDBA :O) DBAishness You have "funny stories" about the times your developers accidentally deleted the T-log in their test environment. #youmightbeaDBA DBAishness Planning to slice and dice your MDW data with PowerPivot makes you giggle like a schoolgirl. #youmightbeaDBA donalddotfarmer You think @buckwoody lives in the "real world." #youmightbeaDBA jamach09 @buckwoody #youmightbeaDBA Why go outside when you can sit in the nice cool server room? jamach09 If you refer to procreation as "Replication", #youmightbeaDBA. jamach09 If you think ORM is a four-letter word, #youmightbeaDBA JamesMarsh If you have ever preached the value of Source Code Control, #YouMightBeADBA jethrocarr @venzann You store your shopping list in a ACID compliant DB #youmightbeaDBA joe_positive @buckwoody thought it stood for "Don't Bother Asking" #youmightbeaDBA joe_positive when you check your IT Events Calendar before making weekend plans #youmightbeaDBA LadyRuna You cringe whenever someone calls Excel a database #youmightbeaDBA LadyRuna When the waiter says he'll be your server today, you ask how many terabytes he is #youmightbeaDBA LadyRuna you always call the asterisk a "Star" #youmightbeaDBA LadyRuna You walk into a server room, say "Nice RACK!" and everyone there knows you're talking about server rack... #youmightbeaDBA LadyRuna You receive more messages from servers than from friends #youmightbeaDBA LadyRuna hmmm... #youmightbeaDBA if your recipe for gumbo is "SELECT * FROM Refrigerator" markjholmes @SQLSoldier Heh. #youmightbeaDBA if you correct other DBAs' spelling of @PaulRandal markjholmes #youmightbeaDBA if you actually test RAID5 vs RAID10 on your SAN because when it comes to configuration, "it depends." markjholmes #youmightbeaDBA if you have at least 3 definitions of the word "cluster" MarlonRibunal 3 Words: @BrentO, snicker, & Access #youmightbeaDBA MarlonRibunal @onpnt @mikeSQL my appeal was a couple of mins late. Enjoying #youmightbeaDBA MarlonRibunal @mikeSQL @onpnt pls, don't mention bacon #youmightbeaDBA merv @buckwoody You HATE 3-way joins #youmightbeaDBA MidnightDBA If you're up at midnight Tweeting about SQL #youmightbeaDBA MidnightDBA @buckwoody I'd noticed that. :) #youmightbeaDBA mikeSQL when people talk about "their type" you're thinking varchar, bigint, binary, etc #youmightbeadba mikeSQL people ask you to go to lunch , but you can't go because you're attending #SQLlunch #youmightbeadba mikeSQL you laugh for hours at all of the #sqlmoviequotes ....things in which a normal individual would scratch their head at. #youmightbeadba mikeSQL you laugh for hours at all of the #sqlmoviequotes ....things in which a normal individual would scratch their head at. #youmightbeadba mrdenny If you think that @buckwoody's demo using PowerPivot to analyze index usage data from DMVs is awesome then #youmightbeaDBA mrdenny You wish @PaulRandal still worked at Microsoft so that they would make a bobble head of him #youmightbeadba mrdenny When it's 11pm on a holiday weekend, and your posting stupid jokes on Twitter then #youmightbeadba mrdenny If you go out with friends and wonder why no one's wearing a kilt then #YouMightBeADBA mrdenny You can't do basic math, but you know off the top of your head how many CALs $14,412 can buy you. #YoumightbeaDBA mrdenny If you've ever setup a SQL Job to email you to get you out of a regularly scheduled meeting #YouMightBeADBA. mrdenny You throw up in your mouth a little when ever you here the word "Access". Even if it doesn't relate to a MS product. #YouMightBeADBA msdtjones You spend more time listening to @buckwoody than your wife #youmightbeaDBA NFDotCom You perform "hail deltas" on a regular basis. #YouMightBeADBA NoelMcKinney If you tell your wife you want to go to Columbus Ohio for your wedding anniversary so you can attend #sqlsat42 then #youmightbeaDBA NoelMcKinney You read a union is on strike and wonder if it's a UNION ALL #youmightbeaDBA NoelMcKinney You read a union is on strike and wonder if it's a UNION ALL #youmightbeaDBA NoelMcKinney Someone asks you to throw another log on the fire and you tell them not to worry about it because Autogrowth is turned on #youmightbeaDBA Nuurdygirl Even if you have a girlfriend...its possible #youmightbeadba. Yeah-i said its possible! Nuurdygirl When your girlfriend has to lean around the laptop to kiss you goodnight #youmightbeadba Old_Man_Fish If you worry about how big your package is and how long it takes to finish #youmightbeaDBA Old_Man_Fish If you no longer wonder if someone is in trouble or died if you are getting calls at 2AM #youmightbeaDBA Old_Man_Fish If, when you hear the word ACCESS with no connotation you blood pressure jumps 50 points, #youmightbeaDBA onpnt When you hear the word inject you immediately get concerned if your databases are OK #youmightbeaDBA onpnt Your servers haven't been rebooted in a year #youmightbeaDBA onpnt You know why it's funny when @PaulRandal has the word, "Sheep" in a tweet #youmightbeaDBA onpnt You have read BOL without actually having a problem to figure out #youmightbeaDBA onpnt You can type "SELECT columns FROM tables" without typos but tipen ni Banglish ares a messis #youmightbeaDBA onpnt DR strategies doesn't include the word, RAID in them #youmightbeaDBA onpnt you can move a SQL Server instance to a new server without the users ever knowing #youmightbeaDBA onpnt You have made an SSIS package that is more than one step #youmightbeaDBA onpnt You have the balls to say no to your boss when they ask for the sa password #youmightbeaDBA onpnt you google to trouble shoot a problem and end up at your own blog (and it fixes it) #youmightbeaDBA onpnt You talk your wife into moving the family vacation a week earlier so you can attend the areas local SSUG meeting #youmightbeaDBA onpnt you can explain to a nontechnical person what a deadlock is #youmightbeaDBA onpnt You hope a girl asks you what your collation is #youmightbeaDBA onpnt you make jokes that include the words shrink, truncate and 1205. And you are the only one that laughs at them #youmightbeaDBA onpnt You rate your ability to stay awake to work longer on blogs, twitter, forums and your day to day job with the 5 9's goal #youmightbeaDBA onpnt you have major surgery and beg the doctor to release you back to work 5 days later because you miss your servers #youmightbeaDBA #TrueStory onpnt You do have backups and you know how to use them #youmightbeaDBA onpnt It's the network #youmightbeaDBA onpnt When the developers get to work your mood changes rapidly #youmightbeaDBA onpnt When someone says, "PASS", you first think of karaoke #youmightbeaDBA onpnt Recruiters try to get you to call them *just* because they think you'll give them @BrentO contact info #youmightbeaDBA onpnt You chuckle every time you go to grab the "CLR" Calcium, Lime and Rust Remover to clean something #youmightbeaDBA onpnt @MarlonRibunal @mikeSQL Sorry man, it was already in motion ;-) #youmightbeaDBA onpnt When you have an "I love bacon" sticker on your laptop. #youmightbeaDBA http://twitpic.com/1ry671 onpnt You sing SELECT statements in the shower #youmightbeaDBA onpnt When you see a chicken it doesn't remind you of food. It reminds you of a guy named Jorge #youmightbeaDBA onpnt At time, SQL is your mistress #youmightbeaDBA onpnt Your wife wonders if SQL is the code name of your mistress at times #youmightbeaDBA onpnt it's Friday and you are on twitter thinking really hard about what would be funny for hash tag #youmightbeaDBA onpnt You organize your wife's "decorative"pillows on the bed in a B-Tree structure #youmightbeaDBA PaulWhiteNZ If you: SELECT TOP (1) milk FROM fridge WHERE use_by_date >= GET_DATE() ORDER BY use_by_date ASC #YouMightBeaDBA RonDBA #youmightbeaDBA if you read @buckwoody's and @BrentO's blogs. ryaneastabrook @buckwoody omg, you have to stand up a website with these on them, they are awesome #youmightbeaDBA soulvy @StrateSQL @LadyRuna Or a "Splat" #youmightbeaDBA speedracer You can still fall asleep after three cups of coffee #youmightbeaDBA speedracer You retweet @buckwoody on a Friday night #youmightbeaDBA speedracer You can still fall asleep after three cups of coffee #youmightbeaDBA speedracer Developers make you twitch #youmightbeaDBA sqlagentman You know what X/1024*8 is. #YouMightBeADBA SqlAsylum Your still in the office at 5:00 on memorial day weekend. #youmightbeadba :) SQLBob Whenever someone you know gets pregnant you bring up INNER JOINs or SQL Injection attacks... #youmightbeaDBA SQLChicken You know one or more SQL folks in the community with an animal in their username #youmightbeaDBA SQLChicken You've used one or more car analogies to explain how a database works #youmightbeaDBA SQLChicken “@sqljoe: #youmightbeaDBA if you applied to attend #sqlu and requested @SQLChicken to pull strings for you” lmao nice! SQLChicken When talking about SSIS your discussions break down into various jokes about packages #youmightbeaDBA SQLChicken Just SEEING the code for cursors makes you break out in hives #youmightbeaDBA SQLChicken Just SEEING the code for cursors makes you break out in hives #youmightbeaDBA SQLCraftsman You coined the phrase "Magic SAN Dust" because calling a vendor's marketing claims BS is not acceptable in a meeting. #YouMightBeADBA SQLCraftsman If you hear about a new feature with the acronym "DAC" and wonder what disaster of a feature it is attached to this time. #YouMightBeADBA SQLCraftsman You really own a "Stick of Much Developer Whacking" #YouMightBeADBA SQLCraftsman You coined the phrase "Magic SAN Dust" because calling a vendor's marketing claims BS is not acceptable in a meeting. #YouMightBeADBA SQLCraftsman Default Blame Acceptor #YouMightBeADBA SQLCraftsman If you hear about a new feature with the acronym "DAC" and wonder what disaster of a feature it is attached to this time. #YouMightBeADBA SQLCraftsman Default Blame Acceptor #YouMightBeADBA SQLCraftsman If you hear about a new feature with the acronym "DAC" and wonder what disaster of a feature it is attached to this time. #YouMightBeADBA sqljoe #youmightbeaDBA if you wished your wife knew T-sql. USE ShoppingList SELECT NecessaryItems from Supermarket WHERE Category<> ("junk food") sqljoe #youmightbeaDBA if the first thing you kiss when you wake up is your mobile for not waking you up in the middle of the night sqljoe #youmightbeaDBA if your wife has a "Do Not Fly" family vacation list of her own including your laptop and mobile sqljoe #youmightbeaDBA if you have researched for DBA Anonymous groups and attended a #SSUG willing to drop your database (vice) sqljoe #youmightbeaDBA if your only maintenance windows are staff meetings sqljoe #youmightbeaDBA if you think of yourself as "The One" in The Matrix "balancing the equation" from The Architect's (developers) poor coding sqljoe #youmightbeaDBA if you think @PaulRandal should have played the Oracle in The Matrix sqljoe #youmightbeaDBA if home CD & Movie collection is stored in secured containers,in logical order & naming convention,and with a backup copy sqljoe #youmightbeaDBA if you applied to attend #sqlu and requested @SQLChicken to pull strings for you sqljoe #youmightbeaDBA if you have tried to TiVo @MidnightDBA broadcasts sqljoe #youmightbeaDBA if your #sql user group feels like #AA meetings sqljoe #youmightbeaDBA if you thought of bringing your #sql books to #sqlsaturday and #sqlpass for autographs sqljoe #youmightbeaDBA if #sqlpass feels like the #oscars sqljoe #youmightbeaDBA if you are proud of your small package SQLLawman #youmightbeaDBA when you hear MDX and Acura is not first thought that comes to mind. sqlrunner If your wife double checks that there isn't a SQLSat within 200 miles of your vacation destination #youmightbeaDBA sqlrunner When you're on a conference call and your wife thinks your speaking in a foreign language #youmightbeaDBA sqlrunner When you're on a conference call and your wife thinks your speaking in a foreign language #youmightbeaDBA sqlrunner You treat the word 'access' as a verb, not a noun #youmightbeaDBA sqlrunner If you are happy with sub-second performance #youmightbeaDBA sqlrunner When you know the names of the NOC people AND their families #youmightbeadba sqlrunner When you know the names of the NOC people AND their families #youmightbeadba sqlrunner Your company set's up international phone coverage for your cruise #youmightbeaDBA sqlsamson @buckwoody if your manager asks you for data and you respond with "there's a script for that" #youmightbeadba sqlsamson @buckwoody If you receive more messages from your server then your spouse #youmightbeadba SQLSoldier You've spent all night Valentines Day upgrading the SQL Servers and forgot to tell your wife you'd be working late. #youmightbeadba SQLSoldier You're flattered when someone calls you a geek. #youmightbeadba SQLSoldier @llangit @mrdenny it's 11pm on a holiday weekend, & your reading stupid jokes on Twitter then #youmightbeadba SQLSoldier Your manager borrows lunch money from you because your salary is 30% higher than his. #youmightbeaDBA SQLSoldier You think "intellisense" is a double negative because it's not intelligent nor makes sense. #youmightbeaDBA SQLSoldier 75% of the emails you receive at home have the phrase "now following you on Twitter!" in the subject line. #youmightbeaDBA SQLSoldier You petition Ken Burns to remake Office Space because it should have been 18 hours long. #youmightbeaDBA SQLSoldier You select a candidate for a Jr DBA position because his resume said he's willing to get your coffee. #youmightbeaDBA SQLSoldier Somebody misquotes @PaulRandall and you call him on your cell to verify. #youmightbeaDBA SQLSoldier You wish the elevator in your building was slower because it's the last time you'll be left alone all day. #youmightbeaDBA SQLSoldier The developers sacrifice small animals before giving you their code for review. #youmightbeaDBA SQLSoldier Developers bring you coffee and a BLT when you review their code. #youmightbeaDBA #IWish SQLSoldier You can get out of any family get-together by saying you have to work and nobody questions it. #youmightbeaDBA SQLSoldier You've requested a HP Superdome for you "test" box. #youmightbeaDBA SQLSoldier Your leave work early because your internet connection to the data center is better at home #youmightbeaDBA SQLSoldier The new CEO asks you to justify your salary, so you go on vacation for 2 weeks. And he never questions you again. #youmightbeaDBA SQLSoldier You cheer when Milton burns down the company in Office Space #youmightbeaDBA SQLSoldier A dev. asks if you've heard about some great new feature in SQL and you show the 16 blog posts you wrote on it ... last year #youmightbeaDBA SQLSoldier Your dev team is still testing SQL 2008 and you're already planning for SQL 11. #youmightbeaDBA #TrueStory SQLSoldier The new CEO asks you to justify your salary, so you go on vacation for 2 weeks. And he never questions you again. #youmightbeaDBA SQLSoldier Your dev team is still testing SQL 2008 and you're already planning for SQL 11. #youmightbeaDBA SQLSoldier You use a cell phone service coverage map to plan your next vacation. #youmightbeaDBA SQLSoldier You come in to work at 7 AM because it gives you at least 3 hours without any developers around. #youmightbeaDBA SQLSoldier You figure out a way to make take your wife on a cruise and deduct it as a business expense. #youmightbeaDBA #sqlcruise SQLSoldier You name your cat SQLDog because the name @SQLCat was already taken. #youmightbeaDBA SQLSoldier You rate your blog posts based on the number of retweets you get. #youmightbeaDBA SQLSoldier You disable random logins just to mess with people. #youmightbeaDBA SQLSoldier You fall for the pickup line, "Hey baby, what's your collation?" #youmightbeaDBA SQLSoldier You can blame an outage on anyone in the company because you're the only one that knows how to find out what really happened #youmightbeaDBA SQLSoldier You can blame an outage on anyone in the company because you're the only one that knows how to find out what really happened #youmightbeaDBA SQLSoldier You cheer when Milton burns down the company in Office Space #youmightbeaDBA SQLSoldier Your leave work early because your internet connection to the data center is better at home #youmightbeaDBA SQLSoldier You cheer when Milton burns down the company in Office Space #youmightbeaDBA SQLSoldier Your think the 4 food groups are coffee, bacon, fast food, and Mountain Dew. #youmightbeaDBA SQLSoldier You tell someone your job title and they ask "What?" You describe it and they ask "What?". So you say "computer geek". #youmightbeaDBA SQLSoldier The #1 referrer to your blog is Twitter.com. #youmightbeaDBA SQLSoldier Your idea of a good time on a Saturday involves free training. #youmightbeaDBA #sqlsat43 SQLSoldier You write a book that all of your co-workers have and none have read it. #youmightbeaDBA SQLSoldier You write a book that sells a couple thousand copies and is heralded a best seller. #youmightbeaDBA SQLSoldier No matter how sick you are, you go to work if it's time to pass the pager on to the next guy. #youmightbeaDBA #TrueStory SQLSoldier You go out on the town, and strangers walk up to you and say, "Hey you're that SQL guy" #youmightbeaDBA #TrueStory SQLSoldier Your wife asks you to fix something, and you request a downtime window. #youmightbeaDBA SQLSoldier Your wife asks when you'll be home, and you tell her that you wish you knew. #youmightbeaDBA SQLSoldier Your best pickup line, "Hey baby, what's your collation?" #youmightbeaDBA SQLSoldier Your wife asks when you'll be home, and you tell her that you wish you knew. #youmightbeaDBA SQLSoldier You know that @BuckWoody is not someone's porno name. #youmightbeaDBA SQLSoldier You list TSQL as your native language on the 2010 census. #youmightbeaDBA SQLSoldier Starbucks' stock price drops every time you go on vacation. #youmightbeaDBA SQLSoldier You're happy when the web master says that the website is down. #youmightbeaDBA SQLSoldier You know that @BuckWoody is not someone's porno name. #youmightbeaDBA SQLSoldier You get mad when someone calls your car a "heap" because you've always considered it to be a "clustered index". #youmightbeaDBA SQLSoldier Your blog has more hits than your company's website. #youmightbeaDBA SQLSoldier You systematically remove the asterisk key from all keyboards in the company except yours. #youmightbeaDBA SQLSoldier When asked if you recycle, you reply that you run sp_cycle_errorlog every night at midnight #youmightbeaDBA SQLSoldier You wouldn't allow someone named @AdamMachanic to work on your car. #youmightbeaDBA SQLSoldier You switch offices every 3 days to avoid developers #youmightbeaDBA SQLSoldier PSS has your number on speed dial. #youmightbeaDBA SQLSoldier You frown when you they tell Neo that he's going to the Oracle #youmightbeaDBA swhaley you regretted saying "This shouldn't effect production" #youmightbeaDBA swhaley you regretted saying "This shouldn't effect production" #youmightbeaDBA Tarwn A pleasurable saturday means spending the day learning more about what you already do the rest of the week #youmightbeaDBA ...oh, wait... thelostforum For great justice; all our base are belong to YOU !! #youmightbeadba thelostforum @SQLSoldier: You need a witness to use a mirror #youmightbeaDBA ;) TimCost you capitalize key words. always. everywhere. you can't help it, usually don't even notice. #youmightbeaDBA Toshana Your the only one in your company not impressed with the developers new application. #youmightbeaDBA venzann Coming soon from a (respected) book publisher - @buckwoody's #youmightbeaDBA venzann He's on a role tonight. @buckwoody is summing up my life with his #youmightbeaDBA tweets... venzann I love the #youmightbeaDBA tag. Found at least 6 new DBAs to follow.. venzann He's on a role tonight. @buckwoody is summing up my life with his #youmightbeaDBA tweets... venzann You use #sqlhelp as a primary resource during troubleshooting #youmightbeaDBA venzann You insist on stricter password security for your sql servers than you implement on your own laptop #youmightbeaDBA WesBrownSQL @buckwoody you are up so late the only tweets you see are from @buckwoody #youmightbeaDBA WesBrownSQL @SQLSoldier you are upgrading all your 2005 prod servers to 2008 R2 on a three day weekend... #youmightbeaDBA zippy1981 #youmightbeaDBA if everytime you do something with #mongodb you think of the Vulcan proverb "only Nixon could go to China." Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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How does 'lazy' work?

- by Matt Fenwick

What is the difference between these two functions? I see that lazy is intended to be lazy, but I don't understand how that is accomplished. -- | Identity function. id :: a -> a id x = x -- | The call '(lazy e)' means the same as 'e', but 'lazy' has a -- magical strictness property: it is lazy in its first argument, -- even though its semantics is strict. lazy :: a -> a lazy x = x -- Implementation note: its strictness and unfolding are over-ridden -- by the definition in MkId.lhs; in both cases to nothing at all. -- That way, 'lazy' does not get inlined, and the strictness analyser -- sees it as lazy. Then the worker/wrapper phase inlines it. -- Result: happiness Tracking down the note in MkId.lhs (hopefully this is the right note and version, sorry if it's not): Note [lazyId magic] ~~~~~~~~~~~~~~~~~~~ lazy :: forall a?. a? -> a? (i.e. works for unboxed types too) Used to lazify pseq: pseq a b = a `seq` lazy b Also, no strictness: by being a built-in Id, all the info about lazyId comes from here, not from GHC.Base.hi. This is important, because the strictness analyser will spot it as strict! Also no unfolding in lazyId: it gets "inlined" by a HACK in CorePrep. It's very important to do this inlining after unfoldings are exposed in the interface file. Otherwise, the unfolding for (say) pseq in the interface file will not mention 'lazy', so if we inline 'pseq' we'll totally miss the very thing that 'lazy' was there for in the first place. See Trac #3259 for a real world example. lazyId is defined in GHC.Base, so we don't have to inline it. If it appears un-applied, we'll end up just calling it. I don't understand that because it refers to lazyId instead of lazy. How does lazy work?

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What proportion of DBA skills are platform-independent?

- by Arkaaito

Problem: we've grown to the point where we need a real DBA. Real DBAs are hard to find. Possible solution: I know someone with extensive experience (currently working on MSSQL) who is looking for a new DBA job. He might be willing to consider working for a MySQL shop (I haven't asked). Snag: I don't know to what extent MSSQL DBA skills map to MySQL DBA skills. I'm a developer, so I know enough about MySQL to develop apps which use it (including the basic performance-tuning, index selection, etc.), do schema design, and perform simple utility tasks (backup with mysqldump, scripting, etc.). I don't know anything about MSSQL. Nor do I actually know much about the boundaries of the DBA role. Can anyone with more experience - perhaps as a DBA - weigh in on this? Are there enough similarities between MSSQL and MySQL that it's worth asking a MSSQL DBA if he'd be interested in applying for a MySQL position?

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Migrating SQL Server Databases – The DBA’s Checklist (Part 1)

- by Sadequl Hussain

It is a fact of life: SQL Server databases change homes. They move from one instance to another, from one version to the next, from old servers to new ones. They move around as an organisation’s data grows, applications are enhanced or new versions of the database software are released. If not anything else, servers become old and unreliable and databases eventually need to find a new home. Consider the following scenarios: 1. A new database application is rolled out in a production server from the development or test environment 2. A copy of the production database needs to be installed in a test server for troubleshooting purposes 3. A copy of the development database is regularly refreshed in a test server during the system development life cycle 4. A SQL Server is upgraded to a newer version. This can be an in-place upgrade or a side-by-side migration 5. One or more databases need to be moved between different instances as part of a consolidation strategy. The instances can be running the same or different version of SQL Server 6. A database has to be restored from a backup file provided by a third party application vendor 7. A backup of the database is restored in the same or different instance for disaster recovery 8. A database needs to be migrated within the same instance: a. Files are moved from direct attached storage to storage area network b. The same database is copied under a different name for another application Migrating SQL Server database applications is a complex topic in itself. There are a number of components that can be involved: jobs, DTS or SSIS packages, logins or linked servers are only few pieces of the puzzle. However, in this article we will focus only on the central part of migration: the installation of the database itself. Unless it is an in-place upgrade, typically the database is taken from a source server and installed in a destination instance. Most of the time, a full backup file is used for the rollout. The backup file is either provided to the DBA or the DBA takes the backup and restores it in the target server. Sometimes the database is detached from the source and the files are copied to and attached in the destination. Regardless of the method of copying, moving, refreshing, restoring or upgrading the physical database, there are a number of steps the DBA should follow before and after it has been installed in the destination. It is these post database installation steps we are going to discuss below. Some of these steps apply in almost every scenario described above while some will depend on the type of objects contained within the database. Also, the principles hold regardless of the number of databases involved. Step 1: Make a copy of data and log files when attaching and detaching When detaching and attaching databases, ensure you have made copies of the data and log files if the destination is running a newer version of SQL Server. This is because once attached to a newer version, the database cannot be detached and attached back to an older version. Trying to do so will give you a message like the following: Server: Msg 602, Level 21, State 50, Line 1 Could not find row in sysindexes for database ID 6, object ID 1, index ID 1. Run DBCC CHECKTABLE on sysindexes. Connection Broken If you try to backup the attached database and restore it in the source, it will still fail. Similarly, if you are restoring the database in a newer version, it cannot be backed up or detached and put back in an older version of SQL. Unlike detach and attach method though, you do not lose the backup file or the original database here. When detaching and attaching a database, it is important you keep all the log files available along with the data files. It is possible to attach a database without a log file and SQL Server can be instructed to create a new log file, however this does not work if the database was detached when the primary file group was read-only. You will need all the log files in such cases. Step 2: Change database compatibility level Once the database has been restored or attached to a newer version of SQL Server, change the database compatibility level to reflect the newer version unless there is a compelling reason not to do so. When attaching or restoring from a previous version of SQL, the database retains the older version’s compatibility level. The only time you would want to keep a database with an older compatibility level is when the code within your database is no longer supported by SQL Server. For example, outer joins with *= or the =* operators were still possible in SQL 2000 (with a warning message), but not in SQL 2005 anymore. If your stored procedures or triggers are using this form of join, you would want to keep the database with an older compatibility level. For a list of compatibility issues between older and newer versions of SQL Server databases, refer to the Books Online under the sp_dbcmptlevel topic. Application developers and architects can help you in deciding whether you should change the compatibility level or not. You can always change the compatibility mode from the newest to an older version if necessary. To change the compatibility level, you can either use the database’s property from the SQL Server Management Studio or use the sp_dbcmptlevel stored procedure. Bear in mind that you cannot run the built-in reports for databases from SQL Server Management Studio if you keep the database with an older compatibility level. The following figure shows the error message I received when trying to run the “Disk Usage by Top Tables” report against a database. This database was hosted in a SQL Server 2005 system and still had a compatibility mode 80 (SQL 2000). Continues…

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SQLAuthority News Best Complements DBA Survivor: Become a Rock Star DBA

Today’s blog post is about the biggest complement I have ever received. I am very very happy and would like to share my feelings with you.Thomas Larock (Blog | Twitter) (known as SQLRockstar) keeps the excellent ranking of the blogger in SQL Server Arena. I am big fan of this list and have been referring [...]...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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SQL Server for the Oracle DBA Links

- by BuckWoody

I do a presentation (and a class) called "SQL Server for the Oracle DBA". It's a non-marketing overview that gives you the basics of working with SQL Server if you're already familiar wtih how Oracle works. This class and these links DO NOT help you with "Why should I use Oracle/SQL Server instead of Oracle/SQL Server" - I'll assume you're already there, and if not, there are LOTS of sites to help you make that decision. Although these links might contain slight marketing slants (I don't control them) I've tried to get the best links I can. Feel free to comment here to add more/better links. As such, these aren't links that help you work with Oracle - they are links to help you work with SQL Server. Some of them contain more information than you actually need, others don't have near enough. Taken together (and with the class) you're able to get done what you need to do. "Practical SQL Server for Oracle Professionals" - A Microsoft Whitepaper, probably the best place to get started: http://download.microsoft.com/download/6/9/d/69d1fea7-5b42-437a-b3ba-a4ad13e34ef6/SQLServer2008forOracle.docx Free Training: http://technet.microsoft.com/en-us/sqlserver/dd548020.aspx Classroom training (will cost you): http://www.microsoft.com/learning/en/us/course.aspx?ID=50068A&locale=en-us Terminology Differences: http://www.associatedcontent.com/article/2383466/oracle_and_sql_server_basic_terminology.html Datatype mapping between Oracle and SQL Server: http://msdn.microsoft.com/en-us/library/ms151817.aspx The "other" direction - can still be useful for the Oracle professional to see the other side: http://blog.benday.com/archive/2008/10/23/23195.aspx Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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Best methods for Lazy Initialization with properties

- by Stuart Pegg

I'm currently altering a widely used class to move as much of the expensive initialization from the class constructor into Lazy Initialized properties. Below is an example (in c#): Before: public class ClassA { public readonly ClassB B; public void ClassA() { B = new ClassB(); } } After: public class ClassA { private ClassB _b; public ClassB B { get { if (_b == null) { _b = new ClassB(); } return _b; } } } There are a fair few more of these properties in the class I'm altering, and some are not used in certain contexts (hence the Laziness), but if they are used they're likely to be called repeatedly. Unfortunately, the properties are often also used inside the class. This means there is a potential for the private variable (_b) to be used directly by a method without it being initialized. Is there a way to make only the public property (B) available inside the class, or even an alternative method with the same initialized-when-needed?

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Linq to SQL Lazy Loading in ASP.Net applications

- by nikolaosk

In this post I would like to talk about LINQ to SQL and its native lazy loading functionality. I will show you how you can change this behavior. We will create a simple ASP.Net application to demonstrate this. I have seen a lot of people struggling with performance issues. That is mostly due to the lack of knowledge of how LINQ internally works.Imagine that we have two tables Products and Suppliers (Northwind database). There is one to many relationship between those tables-entities. One supplier...(read more)

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Problem with lazy loading implementation

- by Mehran

Hi, I have implemented lazy loading in my program. it's done through a proxy class like: class Order { public virtual IList<Item> Items {get; set;} } class OrderProxy { public override IList<Item> Items { get { if (base.Items == null) Items = GetItems(base.OrderID); return base.Items; } set { base.Items = value; } } } the problem is that whenever i instantiate proxy class,without even touching the Items property, it tries to load Items! as you may know,i want to instantiate proxy class and return the instance to BLL instead of domain object itself. what's the problem? Does .NET CLR access(read) properties in a class, when it's instatiating the class? any other methods? Thanks

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Whats the point of lazy-seq in clojure?

- by dbyrne

I am looking through some example Fibonacci sequence clojure code: (def fibs (lazy-cat [1 2] (map + fibs (rest fibs)))) I generally understand what is going on, but don't quite understand the point of lazy-cat. I know that lazy-cat is a macro that is translating to something like this: (def fibs (concat (lazy-seq [1 2]) (lazy-seq (map + fibs (rest fibs))))) What exactly is lazy-seq accomplishing? It would still be evaluated lazily even without lazy-seq? Is this strictly for caching purposes?

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Migrating SQL Server Databases – The DBA’s Checklist (Part 3)

- by Sadequl Hussain

Continuing from Part 2 of the Database Migration Checklist series: Step 10: Full-text catalogs and full-text indexing This is one area of SQL Server where people do not seem to take notice unless something goes wrong. Full-text functionality is a specialised area in database application development and is not usually implemented in your everyday OLTP systems. Nevertheless, if you are migrating a database that uses full-text indexing on one or more tables, you need to be aware a few points. First of all, SQL Server 2005 now allows full-text catalog files to be restored or attached along with the rest of the database. However, after migration, if you are unable to look at the properties of any full-text catalogs, you are probably better off dropping and recreating it. You may also get the following error messages along the way: Msg 9954, Level 16, State 2, Line 1 The Full-Text Service (msftesql) is disabled. The system administrator must enable this service. This basically means full text service is not running (disabled or stopped) in the destination instance. You will need to start it from the Configuration Manager. Similarly, if you get the following message, you will also need to drop and recreate the catalog and populate it. Msg 7624, Level 16, State 1, Line 1 Full-text catalog ‘catalog_name‘ is in an unusable state. Drop and re-create this full-text catalog. A full population of full-text indexes can be a time and resource intensive operation. Obviously you will want to schedule it for low usage hours if the database is restored in an existing production server. Also, bear in mind that any scheduled job that existed in the source server for populating the full text catalog (e.g. nightly process for incremental update) will need to be re-created in the destination. Step 11: Database collation considerations Another sticky area to consider during a migration is the collation setting. Ideally you would want to restore or attach the database in a SQL Server instance with the same collation. Although not used commonly, SQL Server allows you to change a database’s collation by using the ALTER DATABASE command: ALTER DATABASE database_name COLLATE collation_name You should not be using this command for no reason as it can get really dangerous. When you change the database collation, it does not change the collation of the existing user table columns. However the columns of every new table, every new UDT and subsequently created variables or parameters in code will use the new setting. The collation of every char, nchar, varchar, nvarchar, text or ntext field of the system tables will also be changed. Stored procedure and function parameters will be changed to the new collation and finally, every character-based system data type and user defined data types will also be affected. And the change may not be successful either if there are dependent objects involved. You may get one or multiple messages like the following: Cannot ALTER ‘object_name‘ because it is being referenced by object ‘dependent_object_name‘. That is why it is important to test and check for collation related issues. Collation also affects queries that use comparisons of character-based data. If errors arise due to two sides of a comparison being in different collation orders, the COLLATE keyword can be used to cast one side to the same collation as the other. Continues…

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Migrating SQL Server Databases – The DBA’s Checklist (Part 2)

- by Sadequl Hussain

Continuing from Part 1 , our Migration Checklist continues: Step 5: Update statistics It is always a good idea to update the statistics of the database that you have just installed or migrated. To do this, run the following command against the target database: sp_updatestats The sp_updatestats system stored procedure runs the UPDATE STATISTICS command against every user and system table in the database. However, a word of caution: running the sp_updatestats against a database with a compatibility level below 90 (SQL Server 2005) will reset the automatic UPDATE STATISTICS settings for every index and statistics of every table in the database. You may therefore want to change the compatibility mode before you run the command. Another thing you should remember to do is to ensure the new database has its AUTO_CREATE_STATISTICS and AUTO_UPDATE_STATISTICS properties set to ON. You can do so using the ALTER DATABASE command or from the SSMS. Step 6: Set database options You may have to change the state of a database after it has been restored. If the database was changed to single-user or read-only mode before backup, the restored copy will also retain these settings. This may not be an issue when you are manually restoring from Enterprise Manager or the Management Studio since you can change the properties. However, this is something to be mindful of if the restore process is invoked by an automated job or script and the database needs to be written to immediately after restore. You may want to check the database’s status programmatically in such cases. Another important option you may want to set for the newly restored / attached database is PAGE_VERIFY. This option specifies how you want SQL Server to ensure the physical integrity of the data. It is a new option from SQL Server 2005 and can have three values: CHECKSUM (default for SQL Server 2005 and latter databases), TORN_PAGE_DETECTION (default when restoring a pre-SQL Server 2005 database) or NONE. Torn page detection was itself an option for SQL Server 2000 databases. From SQL Server 2005, when PAGE_VERIFY is set to CHECKSUM, the database engine calculates the checksum for a page’s contents and writes it to the page header before storing it in disk. When the page is read from the disk, the checksum is computed again and compared with the checksum stored in the header. Torn page detection works much like the same way in that it stores a bit in the page header for every 512 byte sector. When data is read from the page, the torn page bits stored in the header is compared with the respective sector contents. When PAGE_VERIFY is set to NONE, SQL Server does not perform any checking, even if torn page data or checksums are present in the page header. This may not be something you would want to set unless there is a very specific reason. Microsoft suggests using the CHECKSUM page verify option as this offers more protection. Step 7: Map database users to logins A common database migration issue is related to user access. Windows and SQL Server native logins that existed in the source instance and had access to the database may not be present in the destination. Even if the logins exist in the destination, the mapping between the user accounts and the logins will not be automatic. You can use a special system stored procedure called sp_change_users_login to address these situations. The procedure needs to be run against the newly attached or restored database and can accept four parameters. Depending on what you want to do, you may be using less than four though. The first parameter, @Action, can take three values. When you specify @Action = ‘Report’, the system will provide you with a list of database users which are not mapped to any login. If you want to map a database user to an existing SQL Server login, the value for @Action will be ‘Update_One’. In this case, you will only need to provide the database user name and the login it will map to. So if your newly restored database has a user account called “bob” and there is already a SQL Server login with the same name and you want to map the user to the login, you will execute a query like the following: sp_change_users_login @Action = ‘Update_One’, @UserNamePattern = ‘bob’, @LoginName = ‘bob’ If the login does not exist, you can instruct SQL Server to create the login with the same name. In this case you will need to provide a password for the login and the value of the @Action parameter will be ‘Auto_Fix’. If the login already exists, it will be automatically mapped to the user account. Unfortunately sp_change_users_login system stored procedure cannot be used to map database users to trusted logins (Windows accounts) in SQL Server. You will need to follow a manual process to re-map the database user accounts. Continues…

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Any merit to a lazy-ish juxt function?

- by NielsK

In answering a question about a function that maps over multiple functions with the same arguments (A: juxt), I came up with a function that basically took the same form as juxt, but used map: (defn could-be-lazy-juxt [& funs] (fn [& args] (map #(apply %1 %2) funs (repeat args)))) => ((juxt inc dec str) 1) [2 0 "1"] => ((could-be-lazy-juxt inc dec str) 1) (2 0 "1") => ((juxt * / -) 6 2) [12 3 4] => ((could-be-lazy-juxt * / -) 6 2) (12 3 4) As posted in the original question, I have little clue about the laziness or performance of it, but timing in the REPL does suggest something lazy-ish is going on. => (time (apply (juxt + -) (range 1 100))) "Elapsed time: 0.097198 msecs" [4950 -4948] => (time (apply (could-be-lazy-juxt + -) (range 1 100))) "Elapsed time: 0.074558 msecs" (4950 -4948) => (time (apply (juxt + -) (range 10000000))) "Elapsed time: 1019.317913 msecs" [49999995000000 -49999995000000] => (time (apply (could-be-lazy-juxt + -) (range 10000000))) "Elapsed time: 0.070332 msecs" (49999995000000 -49999995000000) I'm sure this function is not really that quick (the print of the outcome 'feels' about as long in both). Doing a 'take x' on the function only limits the amount of functions evaluated, which probably is limited in it's applicability, and limiting the other parameters by 'take' should be just as lazy in normal juxt. Is this juxt really lazy ? Would a lazy juxt bring anything useful to the table, for instance as a compositing step between other lazy functions ? What are the performance (mem / cpu / object count / compilation) implications ? Is that why the Clojure juxt implementation is done with a reduce and returns a vector ? Edit: Somehow things can always be done simpler in Clojure. (defn could-be-lazy-juxt [& funs] (fn [& args] (map #(apply % args) funs)))

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How to switch from developer to dba? [on hold]

- by lamwaiman1988

I am working as a developer for 3 years and I am thinking of switch to dba. I do not own any certificate nor received any training regarding the daily job of dba. My company also do not offer any chance of work/training related to a dba. If I want to be a dba ( because of the salary and a much stable job than developer ), should I go to get some oracle certificates? I've also heard that you can't be a good dba if you cannot get a good understanding about the working OS such as windows/unix ( and to do that you also need to get some certificate on windows administration or unix administration ) but they recommend book of Rich Stevens over certificate. I am confused on what should I do to make this happen.

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Lazy Loading,Eager Loading,Explicit Loading in Entity Framework 4

- by nikolaosk

This is going to be the ninth post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here , the third one here , the fourth one here , the fifth one here ,the sixth one here ,the seventh one here and the eighth one here . I have a post regarding ASP.Net and EntityDataSource . You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a...(read more)

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Lazy Evaluation – Why being lazy in F# blows my mind!

- by MarkPearl

First of all – shout out to Peter Adams – from the feedback I have gotten from him on the last few posts of F# that I have done – my mind has just been expanded. I did a blog post a few days ago about infinite sequences – I didn’t really understand what was going on with it, and I still don’t really get it – but I am getting closer. In Peter’s last comment he made mention of Lazy Evaluation. I am ashamed to say that up till then I had never heard about lazy evaluation – how can evaluation be lazy? I mean, I know about lazy loading and that makes sense… but surely something is either evaluated or not! Well… a bit of reading today and I have been enlightened to a point – if you do know of any good articles explaining lazy evaluation please send them to me. So what is lazy evaluation and why is it useful? Lazy evaluation is a process whereby the system only computes the values needed and “ignores” the computations not needed. I’m going out on a limb here, but with this explanation in hand, imagine the following C# code… public int CalculatedVal() { int Val1 = 0; int Val2 = 0; for (int Count = 0; Count < 1000000; Count++) { Val1++; } return Val2; } Normally, even though Val1 is never needed, the system would loop 1000000 times and add 1 to the current value of Val1. Imagine if the system realized this and so just skipped this segment of code and instead did the following…. public int CalculatedVal() { int Val1 = 0; return Val2; } A massive saving in computation and wasted effort. Now I am pretty sure it isn’t as simple as this but I think this is the basic idea. For a more detailed explanation of lazy evaluation in c#, Pedram Rezei has a wonderful post on lazy evaluation and makes some C# comparisons. I am not going to take any thunder from him by repeating everything he said since I think he did such a good job of explaining it himself. What I am interested in though is how in F# do you tell something to have lazy evalution, and how do you know if something will be eager or lazy by looking at it. I found this post was useful. From reading around F# by default uses eager evaluation unless explicitly told to use lazy evaluation. One exception to this is sequences, which are lazy by default. Now reading about lazy evaluation has helped me understand more about F# coding… From my understanding of F# because of its declarative nature, most of the actual code you are declaring properties and rules – very little code is actually saying do this right now - but when it comes to a “do this” code section, it then evaluates and optimizes code and applies the rules. So props to lazy evaluation and its optimizations…

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??OPEN CURSOR?BULK COLLECT

- by Liu Maclean(???)

????T.askmaclean.com?????bulk collect?open cursor???, ????????? ??????: ???? OPEN_CURSOR ????SQL?? ???????. ?????? ????? ???????????????? ????? test_soruce create table zengfankun_temp01 as select * from dba_objects;select count(*) from zengfankun_temp01;–12,6826analyze table zengfankun_temp01 compute statistics; create or replace procedure test_open_cursor istype type_owner is table of zengfankun_temp01.owner%type index by binary_integer;type type_object_name is table of zengfankun_temp01.object_name%type index by binary_integer;type type_object_id is table of zengfankun_temp01.object_id%type index by binary_integer;type type_object_type is table of zengfankun_temp01.object_type%type index by binary_integer;type type_last_ddl_time is table of zengfankun_temp01.last_ddl_time%type index by binary_integer; l_ary_owner type_owner;l_ary_object_name type_object_name;l_ary_object_id type_object_id;l_ary_object_type type_object_type;l_ary_last_ddl_time type_last_ddl_time; cursor cur_object isselect owner,object_name,object_id,object_type,last_ddl_timefrom zengfankun_temp01order by owner,object_name,object_type,last_ddl_time;OPEN_START number;OPEN_END number;FETCH_START number;FETCH_END number;beginDBMS_OUTPUT.ENABLE (buffer_size=>null) ;OPEN_START:=dbms_utility.get_time();open cur_object;OPEN_END :=dbms_utility.get_time();dbms_output.put_line(‘OPEN_TIME:’||TO_CHAR(OPEN_END-OPEN_START));loopFETCH_START:=dbms_utility.get_time();fetch cur_object bulk collect intol_ary_owner,l_ary_object_name,l_ary_object_id,l_ary_object_type,l_ary_last_ddl_timelimit 10000;FETCH_END:=dbms_utility.get_time();dbms_output.put_line(‘FETCH_TIME:’||TO_CHAR(FETCH_END-FETCH_START)||’ ROWCOUNT:’||cur_object%rowCount); exit when cur_object%notfound or cur_object%notfound is null;end loop;end test_open_cursor; OPEN_TIME:12FETCH_TIME:21 ROWCOUNT:10000FETCH_TIME:3 ROWCOUNT:20000FETCH_TIME:3 ROWCOUNT:30000FETCH_TIME:3 ROWCOUNT:40000FETCH_TIME:3 ROWCOUNT:50000FETCH_TIME:3 ROWCOUNT:60000FETCH_TIME:3 ROWCOUNT:70000FETCH_TIME:3 ROWCOUNT:80000FETCH_TIME:3 ROWCOUNT:90000FETCH_TIME:3 ROWCOUNT:100000FETCH_TIME:3 ROWCOUNT:110000FETCH_TIME:3 ROWCOUNT:120000FETCH_TIME:1 ROWCOUNT:126826 ???? OPEN_TIME:0FETCH_TIME:18 ROWCOUNT:10000FETCH_TIME:3 ROWCOUNT:20000FETCH_TIME:3 ROWCOUNT:30000FETCH_TIME:3 ROWCOUNT:40000FETCH_TIME:3 ROWCOUNT:50000FETCH_TIME:3 ROWCOUNT:60000FETCH_TIME:3 ROWCOUNT:70000FETCH_TIME:3 ROWCOUNT:80000FETCH_TIME:3 ROWCOUNT:90000FETCH_TIME:3 ROWCOUNT:100000FETCH_TIME:3 ROWCOUNT:110000FETCH_TIME:3 ROWCOUNT:120000FETCH_TIME:2 ROWCOUNT:126826 SQL?????????, ????????????.??OPEN CURSOR ????0???????????3??.??N? ??????. ???? ?N? ?????????? ??????. ??????????????? ??????????. ?????????10000??? ???????????????????clear???, ???????????: ?OPEN CURSOR ?????, PL/SQL????SQL????PARSE SQL????????, ??????OPEN CURSOR????SNAPSHOT SCN ??SCN, ??Oracle?????FETCH?????,???????????????? ????FETCH ??????????????,???????Current Block, The most recent version of block , ?????SCN >> Snapshot scn, ????UNDO???? ???SCN ???Best Block ,???Read Consistentcy;???? ???UNDO SNAPSHOT???????????????Best Block??,???????ORA-1555??? ????????, ??????????,???????????????char(2000)????, ???????????????,????bulk collect fetch??fetch 10 ???,????????OPEN CURSOR?????PARSE??SQL????????, ??????????fetch bulk collect??????????10????,??”_trace_pin_time”????Server Process?pin CR block???,??????????Fetch Bulk Collect limit 10??10?buffer?pin? [oracle@nas ~]$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.3.0 Production on Wed Aug 1 11:36:52 2012 Copyright (c) 1982, 2011, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options SQL> select * from global_name; GLOBAL_NAME -------------------------------------------------------------------------------- http://www.askmaclean.com SQL> create table maclean (t1 char(2000)) tablespace users pctfree 99; Table created. SQL> begin 2 for i in 1..200 loop 3 insert into maclean values('MACLEAN'); 4 commit ; 5 end loop; 6 end; 7 / PL/SQL procedure successfully completed. SQL> exec dbms_stats.gather_table_stats('','MACLEAN'); PL/SQL procedure successfully completed. SQL> select count(*) from maclean; COUNT(*) ---------- 200 SQL> select blocks,num_rows from dba_tables where table_name='MACLEAN'; BLOCKS NUM_ROWS ---------- ---------- 244 200 SQL> alter system set "_trace_pin_time"=1 scope=spfile; System altered. SQL> startup force; ORACLE instance started. Total System Global Area 3140026368 bytes Fixed Size 2232472 bytes Variable Size 1795166056 bytes Database Buffers 1325400064 bytes Redo Buffers 17227776 bytes Database mounted. Database opened. SQL> alter session set events '10046 trace name context forever,level 12'; Session altered. SQL> SQL> SQL> declare 2 cursor v_cursor is 3 select * from sys.maclean; 4 type v_type is table of sys.maclean%rowtype index by binary_integer; 5 rec_tab v_type; 6 begin 7 open v_cursor; 8 dbms_lock.sleep(30); 9 loop 10 fetch v_cursor bulk collect 11 into rec_tab limit 10; 12 dbms_lock.sleep(10); 13 exit when v_cursor%notfound; 14 end loop; 15 end; 16 / ?????10046 trace+ pin trace: PARSING IN CURSOR #47499559136872 len=337 dep=0 uid=0 oct=47 lid=0 tim=1343836146412056 hv=496860239 ad='11a11dbb0' sqlid='4zh7954ftuz2g' declare cursor v_cursor is select * from sys.maclean; type v_type is table of sys.maclean%rowtype index by binary_integer; rec_tab v_type; begin open v_cursor; dbms_lock.sleep(30); loop fetch v_cursor bulk collect into rec_tab limit 10; dbms_lock.sleep(10); exit when v_cursor%notfound; end loop; end; END OF STMT PARSE #47499559136872:c=0,e=346,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=0,tim=1343836146412051 ===================== PARSING IN CURSOR #47499559126280 len=25 dep=1 uid=0 oct=3 lid=0 tim=1343836146414939 hv=3296884535 ad='11a11d250' sqlid='2mb1493284xtr' SELECT * FROM SYS.MACLEAN END OF STMT PARSE #47499559126280:c=1999,e=2427,p=0,cr=0,cu=0,mis=1,r=0,dep=1,og=1,plh=2568761675,tim=1343836146414937 EXEC #47499559126280:c=0,e=55,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,plh=2568761675,tim=1343836146415104 ????? ? SELECT * FROM SYS.MACLEAN? PARSE ????? , ????FETCH???????pin ????????, ????OPEN CURSOR????? *** 2012-08-01 11:49:36.424 WAIT #47499559136872: nam='PL/SQL lock timer' ela= 30009361 duration=0 p2=0 p3=0 obj#=-1 tim=1343836176424782 ???30s pin ktewh26: kteinpscan dba 0x10a6202:4 time 1039048805 pin ktewh27: kteinmap dba 0x10a6202:4 time 1039048847 pin kdswh11: kdst_fetch dba 0x10a6203:1 time 1039048898 pin kdswh11: kdst_fetch dba 0x10a6204:1 time 1039048961 pin kdswh11: kdst_fetch dba 0x10a6205:1 time 1039049004 pin kdswh11: kdst_fetch dba 0x10a6206:1 time 1039049042 pin kdswh11: kdst_fetch dba 0x10a6207:1 time 1039049089 pin kdswh11: kdst_fetch dba 0x10a6208:1 time 1039049123 pin kdswh11: kdst_fetch dba 0x10a6209:1 time 1039049159 pin kdswh11: kdst_fetch dba 0x10a620a:1 time 1039049191 pin kdswh11: kdst_fetch dba 0x10a620b:1 time 1039049225 pin kdswh11: kdst_fetch dba 0x10a620c:1 time 1039049260 kdst_fetch???fetch??????? , ??fetch?10?? ???????FETCH FETCH #47499559126280:c=0,e=536,p=0,cr=12,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836176425542 *** 2012-08-01 11:49:46.428 WAIT #47499559136872: nam='PL/SQL lock timer' ela= 10002694 duration=0 p2=0 p3=0 obj#=-1 tim=134383618642829 ????10s pin kdswh11: kdst_fetch dba 0x10a620d:1 time 1049052211 pin kdswh11: kdst_fetch dba 0x10a620e:1 time 1049052264 pin kdswh11: kdst_fetch dba 0x10a620f:1 time 1049052299 pin kdswh11: kdst_fetch dba 0x10a6211:1 time 1049052332 pin kdswh11: kdst_fetch dba 0x10a6212:1 time 1049052364 pin kdswh11: kdst_fetch dba 0x10a6213:1 time 1049052398 pin kdswh11: kdst_fetch dba 0x10a6214:1 time 1049052430 pin kdswh11: kdst_fetch dba 0x10a6215:1 time 1049052462 pin kdswh11: kdst_fetch dba 0x10a6216:1 time 1049052494 pin kdswh11: kdst_fetch dba 0x10a6217:1 time 1049052525 FETCH #47499559126280:c=0,e=371,p=0,cr=10,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836186428807 ??pin 10????, ???fetch ?? WAIT #47499559136872: nam='PL/SQL lock timer' ela= 10002864 duration=0 p2=0 p3=0 obj#=-1 tim=1343836196431754 pin kdswh11: kdst_fetch dba 0x10a6218:1 time 1059055662 pin kdswh11: kdst_fetch dba 0x10a6219:1 time 1059055714 pin kdswh11: kdst_fetch dba 0x10a621a:1 time 1059055748 pin kdswh11: kdst_fetch dba 0x10a621b:1 time 1059055781 pin kdswh11: kdst_fetch dba 0x10a621c:1 time 1059055815 pin kdswh11: kdst_fetch dba 0x10a621d:1 time 1059055848 pin kdswh11: kdst_fetch dba 0x10a621e:1 time 1059055883 pin kdswh11: kdst_fetch dba 0x10a621f:1 time 1059055915 pin kdswh11: kdst_fetch dba 0x10a6221:1 time 1059055953 pin kdswh11: kdst_fetch dba 0x10a6222:1 time 1059055992 FETCH #47499559126280:c=0,e=385,p=0,cr=10,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836196432274 ???? ??????? DBA????? ............................ ???? WAIT #47499559136872: nam='PL/SQL lock timer' ela= 10002933 duration=0 p2=0 p3=0 obj#=-1 tim=1343836366495589 pin kdswh11: kdst_fetch dba 0x10a62f6:1 time 1229119497 pin kdswh11: kdst_fetch dba 0x10a62f7:1 time 1229119545 pin kdswh11: kdst_fetch dba 0x10a62f8:1 time 1229119576 pin kdswh11: kdst_fetch dba 0x10a62f9:1 time 1229119610 pin kdswh11: kdst_fetch dba 0x10a62fa:1 time 1229119644 pin kdswh11: kdst_fetch dba 0x10a62fb:1 time 1229119671 pin kdswh11: kdst_fetch dba 0x10a62fc:1 time 1229119703 pin kdswh11: kdst_fetch dba 0x10a62fd:1 time 1229119730 pin kdswh11: kdst_fetch dba 0x10a62fe:1 time 1229119760 pin kdswh11: kdst_fetch dba 0x10a62ff:1 time 1229119787 FETCH #47499559126280:c=0,e=340,p=0,cr=10,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836366496067 ??????DBA? 0x10a6203 , ??DBA ? 0x10a62ff ???????DBA??MACLEAN????????,???DBA???Maclean????? getbfno?????dba??????????? CREATE OR REPLACE FUNCTION getbfno (p_dba IN VARCHAR2) RETURN VARCHAR2 IS l_str VARCHAR2 (255) DEFAULT NULL; l_fno VARCHAR2 (15); l_bno VARCHAR2 (15); BEGIN l_fno := DBMS_UTILITY.data_block_address_file (TO_NUMBER (LTRIM (p_dba, '0x'), 'xxxxxxxx' ) ); l_bno := DBMS_UTILITY.data_block_address_block (TO_NUMBER (LTRIM (p_dba, '0x'), 'xxxxxxxx' ) ); l_str := 'datafile# is:' || l_fno || CHR (10) || 'datablock is:' || l_bno || CHR (10) || 'dump command:alter system dump datafile ' || l_fno || ' block ' || l_bno || ';'; RETURN l_str; END; / Function created. SQL> select getbfno('0x10a6203') from dual; GETBFNO('0X10A6203') -------------------------------------------------------------------------------- datafile# is:4 datablock is:680451 dump command:alter system dump datafile 4 block 680451; SQL> select getbfno('0x10a62ff') from dual; GETBFNO('0X10A62FF') -------------------------------------------------------------------------------- datafile# is:4 datablock is:680703 dump command:alter system dump datafile 4 block 680703; SQL> select dbms_rowid.rowid_block_number(min(rowid)),dbms_rowid.rowid_relative_fno(min(rowid)) from maclean; DBMS_ROWID.ROWID_BLOCK_NUMBER(MIN(ROWID)) ----------------------------------------- DBMS_ROWID.ROWID_RELATIVE_FNO(MIN(ROWID)) ----------------------------------------- 680451 4 SQL> select dbms_rowid.rowid_block_number(max(rowid)),dbms_rowid.rowid_relative_fno(max(rowid)) from maclean; DBMS_ROWID.ROWID_BLOCK_NUMBER(MAX(ROWID)) ----------------------------------------- DBMS_ROWID.ROWID_RELATIVE_FNO(MAX(ROWID)) ----------------------------------------- 680703 4 ???????3???: 1.?OPEN CURSOR ?????, PL/SQL????SQL????PARSE SQL????????, ??????OPEN CURSOR????SNAPSHOT SCN ??SCN, ??Oracle?????FETCH?????,???????????????? 2.????FETCH ?????????????? 3. ???open cursor+ fetch bulk collect???”?????????”

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