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  • SQL SERVER – Manage Help Settings – CTRL + ALT + F1

    - by pinaldave
    It is a miracle that curiosity survives formal education. ~ Albert Einstein I have 3 years old daughter and she never misses any chance to play with the system. I have multiple computers and I always make sure that if I am working with production server, I never leave it open but when I am doing some experiment I often leave my computer open. My daughter loves the part when I have left the computer open and I am not observing her. Recently I had the same scenario, I got urgent call and I moved away from my computer and when I returned she was playing with SSMS left open my computer. Here is the screen which was visible on the screen. For a moment, I could not figure out what was this screen and what was about to get updated. I tried to ask her what keys she pressed the reaction was “I wanted – eya eya o”. Well, what more I expect from 3 years old. She is no computer genius – she just learned to use notepad and paint on my machine. Finally, when I saw the above screen in detail, I realize that this screen was from the help screen and something got updated. I have been using SQL Server for a long time but I never updated help on the screen. When I need to search something if I remember that I have written it earlier I will go to http://search.sqlauthority.com and will search there or will search on Google. As this computer was already updated I fired up Virtual Machine and tried to look recreate how my daughter was reached to above screen. Here are the steps which I have to do to reach to above screen. Go to SSMS >> Toolbar >> Help >> Manage Help Settings (or type CTRL+ALT+F1) and click it. Above click brought up following screen. I clicked on Check for update online brought following screen up. When I clicked on Update it brought me back to original screen which my daughter was able to bring up earlier. I found it so interesting that what took me 2-3 minutes to figure out and the screen which I have never come across in my career I learned from my curiosity like my daughter. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Tricks to Replace SELECT * with Column Names – SQL in Sixty Seconds #017 – Video

    - by pinaldave
    You might have heard many times that one should not use SELECT * as there are many disadvantages to the usage of the SELECT *. I also believe that there are always rare occasion when we need every single column of the query. In most of the cases, we only need a few columns of the query and we should retrieve only those columns. SELECT * has many disadvantages. Let me list a few and remaining you can add as a comment.  Retrieves unnecessary columns and increases network traffic When a new columns are added views needs to be refreshed manually Leads to usage of sub-optimal execution plan Uses clustered index in most of the cases instead of using optimal index It is difficult to debug. There are two quick tricks I have discussed in the video which explains how users can avoid using SELECT * but instead list the column names. 1) Drag the columns folder from SQL Server Management Studio to Query Editor 2) Right Click on Table Name >> Script TAble AS >> SELECT To… >> Select option It is extremely easy to list the column names in the table. In today’s sixty seconds video, you will notice that I was able to demonstrate both the methods very quickly. From now onwards there should be no excuse for not listing ColumnName. Let me ask a question back – is there ever a reason to SELECT *? If yes, would you please share that as a comment. More on SELECT *: SQL SERVER – Solution – Puzzle – SELECT * vs SELECT COUNT(*) SQL SERVER – Puzzle – SELECT * vs SELECT COUNT(*) SQL SERVER – SELECT vs. SET Performance Comparison I encourage you to submit your ideas for SQL in Sixty Seconds. We will try to accommodate as many as we can. If we like your idea we promise to share with you educational material. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL in Sixty Seconds, SQL Query, SQL Scripts, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology, Video

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  • SQLAuthority News – New Book Released – SQL Server Interview Questions And Answers

    - by pinaldave
    Two days ago, on birthday of my blog – I asked simple question – Guess! What is in this box? I have received lots of interesting comments on the blog about what is in it. Many of you got it absolutely incorrect and many got it close to the right answer but no one got it 100% correct. Well, no issue at all, I am going to give away the price to whoever has the closest answer first in personal email. Here is the answer to the question about what is in the box? Here it is – the box has my new book. In fact, I should say our new book as I co-authored this book with my very good friend Vinod Kumar. We had real blast writing this book together and had lots of interesting conversation when we were writing this book. This book has one simple goal – “master the basics.” This book is not only for people who are preparing for interview. This book is for every one who wants to revisit the basics and wants to prepare themselves to the technology. One always needs to have practical knowledge to do their duty efficiently. This book talks about more than basics. There are multiple ways to present learning – either we can create simple book or make it interesting. We have decided the learning should be interactive and have opted for Interview Questions and Answer format. Here is quick interview which we have done together. Details of the books are here The core concept of this book will continue to evolve over time. I am sure many of you will come along with us on this journey and submit your suggestions to us to make this book a key reference for anybody who wants to start with SQL server. Today we want to acknowledge the fact that you will help us keep this book alive forever with the latest updates. We want to thank everyone who participates in this journey with us. You can get the books from [Amazon] | [Flipkart]. Read Vinod‘s blog post. Do not forget to wish him happy birthday as today is his birthday and also book release day – two reason to wish him congratulations. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Best Practices, Data Warehousing, Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL Interview Questions and Answers, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Book Review, SQLAuthority News, SQLServer, T SQL, Technology

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  • SQLAuthority News – SQL Server Wait Stats – eBook to Download on Kindle – Answer to FREE PDF Download Request

    - by pinaldave
    Being a book author is a completely new experience for me. I am yet to come across the issues faced by expert book authors. I assume that these interesting issues can be routine ones for expert book authors. One of the biggest requests I am getting for my SQL Server Wait Stats [Amazon] | [Flipkart] | [Kindle] book is my humble attempt to write a book. This is our very first experiment, and the book is beginning of the subject of SQL Server Wait Stats; we will come up with a new version of the book later next year when we have enough information for the SQL Server 2012 version. Following are the top 2 requests that I keep on receiving in emails, on blogs, Twitter, and Facebook. “Please send us FREE PDF of your book so we do not have to purchase it.” “If you can share with us the eBook (free and downloadable) format of your book, we will share it with everybody we know and you will get additional exposure.” Here is my response for the abovementioned requests: If you really need my book and cannot purchase it due to financial trouble, then feel free to let me know and I will purchase it myself and ship it to you. If you are in a country where the print book not available, then you can buy the Kindle book, which is available online in any country, and you can just read it on your computer and mobile devices. You DO NOT have to own a Kindle to read a Kindle format book. You can freely download Kindle software on your desired format and purchase the book online. For next 5 days, the kindle book is available at 3.99 in USA, and in other countries, the price is anywhere between 3.99 and 5.99. The price will go up by USD 2 everywhere across the world after 1st November, 2011. Here is the link to download Kindle Software for free PC, WP7, and in marketplace for various other mobile devices. I thank you for giving warm response to SQL Server Wait Stats book. I am motivated to write the next expanded version of this book. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Validating Spatial Object with IsValidDetailed Function

    - by pinaldave
    What do you prefer – error or warning indicating error may happen with the reason for the error. While writing the previous statement I remember the movie “Minory Report”. This blog post is not about minority report but I will still cover the concept in a single statement “Let us predict the future and prevent the crime which is about to happen in future”. (Please feel free to correct me if I am wrong about the movie concept, I really do not want to hurt your sentiment if you are dedicated fan). Let us switch to the SQL Server world. Spatial data types are interesting concepts. I love writing about spatial data types because it allows me to be creative with shapes (just like toddlers). When working with Spatial Datatypes it is all good when the spatial object works fine. However, when the spatial object has issue or it is created with invalid coordinates it used to give a simple error that there is an issue with the object but did not provide much information. This made it very difficult to debug. If this spatial object was used in the big procedure and while this big procedural error out because of the invalid spatial object, it is indeed very difficult to debug it. I always wished that the more information provided regarding what is the problem with spatial datatype. SQL Server 2012 has introduced the new function IsValidDetailed(). This function has made my life very easy. In simple words this function will check if the spatial object passed is valid or not. If it is valid it will give information that it is valid. If the spatial object is not valid it will return the answer that it is not valid and the reason for the same. This makes it very easy to debug the issue and make the necessary correction. DECLARE @p GEOMETRY = 'Polygon((2 2, 6 6, 4 2, 2 2))' SELECT @p.IsValidDetailed() GO DECLARE @p GEOMETRY = 'Polygon((2 2, 3 3, 4 4, 5 5, 6 6, 2 2))' SELECT @p.IsValidDetailed() GO DECLARE @p GEOMETRY = 'Polygon((2 2, 4 4, 4 2, 2 3, 2 2))' SELECT @p.IsValidDetailed() GO DECLARE @p GEOMETRY = 'CIRCULARSTRING(2 2, 4 4, 0 0)' SELECT @p.IsValidDetailed() GO DECLARE @p GEOMETRY = 'CIRCULARSTRING(2 2, 4 4, 0 0)' SELECT @p.IsValidDetailed() GO DECLARE @p GEOMETRY = 'LINESTRING(2 2, 4 4, 0 0)' SELECT @p.IsValidDetailed() GO Here is the resultset of the above query. You can see any valid query and some invalid query. If the query is invalid it also demonstrates the reason along with the error message. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Spatial Database, SQL Spatial

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  • Monitoring Your Servers

    - by Grant Fritchey
    If you are the DBA in a large scale enterprise, you’re probably already monitoring your servers for up-time and performance. But if you work for a medium-sized business, a small shop, or even a one-man operation, chances are pretty good that you’re not doing that sort of monitoring. You know that you’re supposed to be doing it, but other things, more important at-the-moment things, keep getting in the way. After all, which is more important, some monitoring or backup testing?  Backup testing, of course. Monitoring is frequently one of those things that you do when can get around to it.  Well, as you can see at the right, I have your round tuit ready to go. What if I told you that you could get monitoring on your servers for up-time, job completion, performance, all the standard stuff? And what if I told you that you wouldn’t need to install and configure another server in your environment to get it done? And what if I told you that you’d be able to set up and customize your alerts so you could know if your server was offline or a drive was full? Almost nothing for you to do, and you’ll have a full-blown monitoring process. Sounds to good to be true doesn’t it? Well, it’s coming. We’re creating an online, remote, monitoring system here at Red Gate. You’ll be able to use our SQL Monitor tool (which you can see here, monitoring SQL Server Central in real time) to keep track of your systems, but without having to set up a server and a database for storing the information collected. Instead, we’re taking advantage of services available through the internet to enable collection and storage of this information remotely, off your systems. All you have to do is install a piece of software that will communicate between our service and your servers and you’ll be off and running. It’s that easy. Before you get too excited, let me break the news that this is the near future I’m talking about. We’re setting up the program and there’s a sign-up you can use to get in on the initial tests.

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  • How to suggest using an ORM instead of stored procedures?

    - by Wayne M
    I work at a company that only uses stored procedures for all data access, which makes it very annoying to keep our local databases in sync as every commit we have to run new procs. I have used some basic ORMs in the past and I find the experience much better and cleaner. I'd like to suggest to the development manager and rest of the team that we look into using an ORM Of some kind for future development (the rest of the team are only familiar with stored procedures and have never used anything else). The current architecture is .NET 3.5 written like .NET 1.1, with "god classes" that use a strange implementation of ActiveRecord and return untyped DataSets which are looped over in code-behind files - the classes work something like this: class Foo { public bool LoadFoo() { bool blnResult = false; if (this.FooID == 0) { throw new Exception("FooID must be set before calling this method."); } DataSet ds = // ... call to Sproc if (ds.Tables[0].Rows.Count > 0) { foo.FooName = ds.Tables[0].Rows[0]["FooName"].ToString(); // other properties set blnResult = true; } return blnResult; } } // Consumer Foo foo = new Foo(); foo.FooID = 1234; foo.LoadFoo(); // do stuff with foo... There is pretty much no application of any design patterns. There are no tests whatsoever (nobody else knows how to write unit tests, and testing is done through manually loading up the website and poking around). Looking through our database we have: 199 tables, 13 views, a whopping 926 stored procedures and 93 functions. About 30 or so tables are used for batch jobs or external things, the remainder are used in our core application. Is it even worth pursuing a different approach in this scenario? I'm talking about moving forward only since we aren't allowed to refactor the existing code since "it works" so we cannot change the existing classes to use an ORM, but I don't know how often we add brand new modules instead of adding to/fixing current modules so I'm not sure if an ORM is the right approach (too much invested in stored procedures and DataSets). If it is the right choice, how should I present the case for using one? Off the top of my head the only benefits I can think of is having cleaner code (although it might not be, since the current architecture isn't built with ORMs in mind so we would basically be jury-rigging ORMs on to future modules but the old ones would still be using the DataSets) and less hassle to have to remember what procedure scripts have been run and which need to be run, etc. but that's it, and I don't know how compelling an argument that would be. Maintainability is another concern but one that nobody except me seems to be concerned about.

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  • Real-Time Multi-User Gaming Platform

    - by Victor Engel
    I asked this question at Stack Overflow but was told it's more appropriate here, so I'm posting it again here. I'm considering developing a real-time multi-user game, and I want to gather some information about possibilities before I do some real development. I've thought about how best to ask the question, and for simplicity, the best way that occurred to me was to make an analogy to the field (or playground) game darebase. In the field game of darebase, there are two or more bases. To start, there is one team on each base. The game is a fancy game of tag. When two people meet out in the field, the person who left his base most recently timewise captures the other person. They then return to that person's base. Play continues until everyone is part of the same team. So, analogizing this to an online computer game, let's suppose there are an indefinite number of bases. When a person starts up the game, he has a team that is located at, for example, his current GPS coordinates. It could be a virtual world, but for sake of argument, let's suppose the virtual world corresponds to the player's actual GPS coordinates. The game software then consults the database to see where the closest other base is that is online, and the two teams play their game of virtual tag. Note that the user of the other base could have a different base than the one run by the current user as the closest base to him, in which case, he would be in two simultaneous battles, one with each base. When they go offline, the state of their players is saved on a server somewhere. Game logic calls for the players to have some automaton-logic of some sort, so they can fend for themselves in a limited way using basic rules, until their user goes online again. The user doesn't control the players' movements directly, but issues general directives that influence the players' movement logic. I think this analogy is good enough to frame my question. What sort of platforms are available to develop this sort of game? I've been looking at smartfoxserver, but I'm not convinced yet that it is the best option or even that it will work at all. One possibility, of course, would be to roll out my own web server, but I'd rather not do that if there is an existing service out there already that I could tap into. I will be developing for iOS devices at first. So any suggestions would be greatly appreciated. I think I need to establish the architecture first before proceeding with this project. Note that darbase is not the game I intend to implement, but, upon reflection, that might not be a bad idea either.

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  • [JAVA]How to make my Oracle update/insert action through JAVA faster?

    - by gunbuster363
    [JAVA]How to make my Oracle update/insert action through JAVA faster? Hi everyone, I am facing a problem in my company that is - our program's speed is not fast enough. To be more specific, we are telecommunication company and this program handle call/internet serfing transaction made by every mobile phone users in our city. Because the amount of download content made by the iphone users is just too much, our program cannot handle them fast enough. The situation is, the amount of transaction made by users are double of the transaction processed by our program. Most of the running time of the program are dominated by DB transactions. I've search through the internet and browsed some sites ( for example: http://www.javaperformancetuning.com/tips/rawtips.shtml ) talking about java performace in DB, but I cannot find a suggestion suitable for us. these advices are not applicable/already used, for instance: 1)Use prepared statements. Use parametrized SQL Already used prepared statement. Each time will use different parameter by clear parameters and set parameters. 2)Tune the SQL to minimize the data returned (e.g. not 'SELECT *'). Sure, already used. 3)Use connection pooling. We hold a single connection during the program's execution. And I doubt that pooling cannot solve the problem because our program act as 1 user, so there are no problem for concurrent access to DB. If anyone of you think pooling is good, please tell me why. Thanks. 4)Try to combine queries and batch updates. Cannot do it. Every query/insert/update is depend on the database's information. For example, we look up the DB for the client's information, if we cannot find his usage, we insert the usage into DB, otherwise we do update. 5)Close resources (Connections, Statements, ResultSets) when finished Sure. 6)Select the fastest JDBC driver. I don't know. I've search on the internet about the type of driver available and I am very confused. We use oracle.jdbc.driver.OracleDriver and we use thin instead of oci, that's all I know. In addition, our program is a two-tier way ( java <- oracle ) 7)turn off auto-commit already done that. Looking forwards to any helps, thank you very much.

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  • Assessing Relative Maintainability

    - by João Bragança
    We (a contractor, actually) are implementing an off the shelf system to replace a legacy homegrown system for the core domain of the company (designing widgets). Unfortunately both systems will have to run concurrently for some time, as the product just isn't ready yet. Also, the decision was made to only migrate some of the widgets from the legacy system, based on date of last sale activity. Later on a new requirement came down: certain people in the company, most of them outside of the widget development context, want to search all widgets. The search results screen has 3 pieces of data: a GUID, a human readable id that is searchable, and a brief description (may need to be searchable in the future). In the widget details, there will be multiple screens. These screens align very well along SOA / bounded context lines - a screen for marketing data, a screen for sales history, etc. UML ahead! I am probably using the wrong kind of arrows here so please forgive me. The current solution - which is not in production yet - is something like the following: Both systems will be queried and the controller will merge the results. The new system has its own proprietary query language (we've alleviated this a bit with a LINQ provider). It also puts a lot of data on the wire. 15 search results typically run about 60k of unintelligible SOAP-wrapped xml. So I would prefer to avoid querying this system directly. These two systems publish events to help us integrate with other systems, mainly an ERP system. One of these events contains all the data necessary for the search screen. I proposed the following alternative: However I am being told that 'adding another database' will create more maintenance down the road. However, I believe this to be false, as I had to add a relatively simple feature that took several hours longer than anticipated because of this merging code. I want to get a feel for which system is more maintainable in the long run. I personally have not had the burden of maintaining any large system. I want something more than my gut. Specifically I'd like to know if having more, specialized physical databases is more or less maintainable than having less larger physical databases.

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  • How to make my Oracle update/insert action through Java faster?

    - by gunbuster363
    I am facing a problem in my company that is - our program's speed is not fast enough. To be more specific, we are telecommunication company and this program handle call/internet serfing transaction made by every mobile phone users in our city. Because the amount of download content made by the iphone users is just too much, our program cannot handle them fast enough. The situation is, the amount of transaction made by users are double of the transaction processed by our program. Most of the running time of the program are dominated by DB transactions. I've search through the internet and browsed some sites ( for example: http://www.javaperformancetuning.com/tips/rawtips.shtml ) talking about Java performace in DB, but I cannot find a suggestion suitable for us. These advices are not applicable/already used, for instance: 1. Use prepared statements. Use parameterized SQL Already used prepared statement. Each time will use different parameter by clear parameters and set parameters. 2. Tune the SQL to minimize the data returned (e.g. not 'SELECT *'). Sure, already used. 3. Use connection pooling. We hold a single connection during the program's execution. And I doubt that pooling cannot solve the problem because our program act as 1 user, so there are no problem for concurrent access to DB. If anyone of you think pooling is good, please tell me why. Thanks. 4. Try to combine queries and batch updates. Cannot do it. Every query/insert/update is depend on the database's information. For example, we look up the DB for the client's information, if we cannot find his usage, we insert the usage into DB, otherwise we do update. 5. Close resources (Connections, Statements, ResultSets) when finished Sure. 6. Select the fastest JDBC driver. I don't know. I've search on the internet about the type of driver available and I am very confused. We use oracle.jdbc.driver.OracleDriver and we use thin instead of oci, that's all I know. In addition, our program is a two-tier way ( java <- oracle ) 7. Turn off auto-commit already done that. Looking forwards to any help.

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  • Storing a looong lookup table

    - by inquisitive
    Background The product i am working on has a very long lookup-table. the table contains static data and cannot be auto generated. there are about 500 rows and 10 columns. columns have mostly integers and strings. to complicate the matters, there are actually two such tables. every row in table-1 maps to zero-or-more rows in table-2. we use an SQLite database with two tables. the product installer places the SQLite file in the installation directory. the application is written in dot-net and we use ADO to load the data once on startup. now, the lookup table grows. in each release a month, we add about 10 new entries existing entries are adjusted. every release we fine tune existing entries. The problem a team of (10) developers work on the lookup table. Code goes in the SVN, but the little devil the SQLite does not. this prevents multiple developers to work on it. we do take regular backups of the file, but proper versioning is not possible. we never know who did the breaking change. the worse thing is we dont know if there is any change at all. diff'ing databases is tedious if not impossible. the tables are expected to grow quite large in years to come and we would need developers to work in parallel on it. the data is business critical. we need to be able to audit changes made to it. Question What would be a solution for the problems outlines above? one idea was to transform the whole thing to XML and treat it like just another source file. that way SVN can do the versioning and we can work in parallel. but the data shows relational behavior. with XML we loose the unique and foreign-key constraints. also we cant query it with sql like ease. any help here will be appreciated.

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  • Running MS Access Programs

    - by fredhappier
    I have an old program developed in MS Access and would like to convert it to Kexi somehow. The program on Windows is launched with Access. Is there any way that Kexi can launch this program? I know my way around Ubuntu and the terminal, but not well versed on databases. Once you make something in Kexi how do you "run" it or "view" what you've made? So far I am able to import the MDB file into Kexi and see all of the database data, but that is as far I have gone. The program was made by a relative years ago for my dad. I myself am an Ubuntu only user for 6+ years now and have no intentions to touch Windows and am looking for a linux solution. My dad is also an Ubuntu user, hence why Im looking for a solution. If Kexi cannot launch and run an MDB file, what else can I try? Anything browser based? Any tips or direction would be extremely helpful. I spoke to my brother who originally made the program. I told him about Kexi and here is what he said. Does any of this make sense? Thanks. This is how I would try to get them to work: Stand alone setup - after import, look for an option where you designate which form object you want to open upon startup. It might be in the tools tab in the picture below. After you save that change, it re-start it and it should work. Front end/back end setup - Do what I suggested for the stand alone setup to the "front-end" MDB file. After you do that, put the other file (table MDB file) where you want it to reside on the network. Now, open back up the "front end" file and look for an option that will allow you to "connect" to those tables in the other file. It looks like it could be in the "External data" tab in the picture below. For this setup, you may need to do these two tasks in the reverse order I just mentioned. Thanks! Fred

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  • Removing Left Recursion in ANTLR

    - by prosseek
    As is explained in http://stackoverflow.com/questions/2652060/removing-left-recursion , there are two ways to remove the left recursion. Modify the original grammar to remove the left recursion using some procedure Write the grammar originally not to have the left recursion What people normally use for removing (not having) the left recursion with ANTLR? I've used flex/bison for parser, but I need to use ANTLR. The only thing I'm concerned about using ANTLR (or LL parser in genearal) is left recursion removal. In practical sense, how serious of removing left recursion in ANTLR? Is this a showstopper in using ANTLR? Or, nobody cares about it in ANTLR community? I like the idea of AST generation of ANTLR. In terms of getting AST quick and easy way, which method (out of the 2 removing left recursion methods) is preferable?

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  • Boosting my GA with Neural Networks and/or Reinforcement Learning

    - by AlexT
    As I have mentioned in previous questions I am writing a maze solving application to help me learn about more theoretical CS subjects, after some trouble I've got a Genetic Algorithm working that can evolve a set of rules (handled by boolean values) in order to find a good solution through a maze. That being said, the GA alone is okay, but I'd like to beef it up with a Neural Network, even though I have no real working knowledge of Neural Networks (no formal theoretical CS education). After doing a bit of reading on the subject I found that a Neural Network could be used to train a genome in order to improve results. Let's say I have a genome (group of genes), such as 1 0 0 1 0 1 0 1 0 1 1 1 0 0... How could I use a Neural Network (I'm assuming MLP?) to train and improve my genome? In addition to this as I know nothing about Neural Networks I've been looking into implementing some form of Reinforcement Learning, using my maze matrix (2 dimensional array), although I'm a bit stuck on what the following algorithm wants from me: (from http://people.revoledu.com/kardi/tutorial/ReinforcementLearning/Q-Learning-Algorithm.htm) 1. Set parameter , and environment reward matrix R 2. Initialize matrix Q as zero matrix 3. For each episode: * Select random initial state * Do while not reach goal state o Select one among all possible actions for the current state o Using this possible action, consider to go to the next state o Get maximum Q value of this next state based on all possible actions o Compute o Set the next state as the current state End Do End For The big problem for me is implementing a reward matrix R and what a Q matrix exactly is, and getting the Q value. I use a multi-dimensional array for my maze and enum states for every move. How would this be used in a Q-Learning algorithm? If someone could help out by explaining what I would need to do to implement the following, preferably in Java although C# would be nice too, possibly with some source code examples it'd be appreciated.

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  • Determining the maximum stack depth

    - by Joa Ebert
    Imagine I have a stack-based toy language that comes with the operations Push, Pop, Jump and If. I have a program and its input is the toy language. For instance I get the sequence Push 1 Push 1 Pop Pop In that case the maximum stack would be 2. A more complicated example would use branches. Push 1 Push true If .success Pop Jump .continue .success: Push 1 Push 1 Pop Pop Pop .continue: In this case the maximum stack would be 3. However it is not possible to get the maximum stack by walking top to bottom as shown in this case since it would result in a stack-underflow error actually. CFGs to the rescue you can build a graph and walk every possible path of the basic blocks you have. However since the number of paths can grow quickly for n vertices you get (n-1)! possible paths. My current approach is to simplify the graph as much as possible and to have less possible paths. This works but I would consider it ugly. Is there a better (read: faster) way to attack this problem? I am fine if the algorithm produces a stack depth that is not optimal. If the correct stack size is m then my only constraint is that the result n is n = m. Is there maybe a greedy algorithm available that would produce a good result here?

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  • SyncFramework upgrade from 1.0 to 2.0 Sql Server CE database change tracking issue

    - by Andronicus
    I'm trying to upgrade an application that uses Sync Framework 1.0 to synchronise a SqlServerCe database with SqlServer 2005. On the client, the existing database already has change tracking enabled, but when the sync is initiated SyncFramework 2.0 fails to find the last Sync Received anchor and then tries to re=initialize the Change tracking, which fails. I get the exception... {System.Exception} = {"The specified change tracking operation is not supported. To carry out this operation on the table, disable the change tracking on the table, and enable the change tracking."} It seems like all I can do is delete the local database and recreate it. Which is not a great solution for us, since some of the data in the clients database is not synced with the server, and our users would prefer not to loose this data in the upgrade. Is there any reason why SyncFramework 2.0 cannot locate the existing Last received sync anchor?

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  • Advantages of compilers for functional languages over compilers for imperative languages

    - by Onorio Catenacci
    As a follow up to this question What are the advantages of built-in immutability of F# over C#?--am I correct in assuming that the F# compiler can make certain optimizations knowing that it's dealing with largely immutable code? I mean even if a developer writes "Functional C#" the compiler wouldn't know all of the immutability that the developer had tried to code in so that it couldn't make the same optimizations, right? In general would the compiler of a functional language be able to make optimizations that would not be possible with an imperative language--even one written with as much immutability as possible?

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  • What are modern and old compilers written in?

    - by ulum
    As a compiler, other than an interpreter, only needs to translate the input and not run it the performance of itself should be not that problematic as with an interpreter. Therefore, you wouldn't write an interpreter in, let's say Ruby or PHP because it would be far too slow. However, what about compilers? If you would write a compiler in a scripting language maybe even featuring rapid development you could possibly cut the source code and initial development time by halv, at least I think so. To be sure: With scripting language I mean interpreted languages having typical features that make programming faster, easier and more enjoyable for the programmer, usually at least. Examples: PHP, Ruby, Python, maybe JavaScript though that may be an odd choice for a compiler What are compilers normally written in? As I suppose you will respond with something low-level like C, C++ or even Assembler, why? Are there compilers written in scripting languages? What are the (dis)advantages of using low or high level programming languages for compiler writing?

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  • Translate a<b to IR Trees

    - by drozzy
    I have to translate the mini-java (java like language) statements into intermediate-representation trees. But for this question I have no idea what it is asking... a>b moves a 1 or 0 into some newly defined temporary, and whose right-hand side is a temporary Does the wording make sense to anyone? (I am using the Java compilers book, and it is question 7.2d) in ch7.)

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  • Microsoft Sync Framework with Mutliple Client and Server Database

    - by David Osborn
    I'm working on changes to an application to have a local data store instead of connecting directly to the database server. The client app will then sync changes both ways between the server database and its local data store. I'm trying to implement the syncing solution using Microsoft Sync Framework. To be clear there is no server application, only the database server, but there are multiple clients. I have started implementing two classes that implement FullEnumerationSimpleSyncProvider, one called LocalSyncProvider and one called ServerSyncProvider. The LocalSyncProvider knows how to enumerate, insert, update, delete items from the local data store, and the ServerSyncProvider knows how to enumerate, insert, update, delete items from the database server. They each use the provided SqlMetadataStore and store the two metadata stores (one for the local and one for the server) on the local drive of the client. This means that each client will have its own metadata store for its local data store and its own metadata store for the server database. Is this actually going to work, does there need to exists only one server metadata store, or do I need to be using the Sync Framework differently?

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