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• CQRS - Benefits

  - by Dylan Smith

  Thanks to all the comments and feedback from the last post I think I have a better understanding now of the benefits of CQRS (separate from the benefits of Event Sourcing). I’m going to try and sum it up here, and point out some areas where I could still use some advice: CQRS Benefits Sounds like the primary benefit of CQRS as an architecture is it allows you to create a simpler domain model by sucking out everything related to queries. I can definitely see the benefit to this, in general the domain logic related to commands is the high-value behavior in the software, but the logic required to service the queries would add a lot of low-value “noise” to the domain model that would dilute the high-value (command) behavior – sorting, paging, filtering, pre-fetch paths, etc. Also the most appropriate domain structure for implementing commands might not be the most optimal for implementing queries. To paraphrase Greg, this usually results in a domain model that is mediocre at both, piss-poor at one, or more likely piss-poor at both commands and queries. Not only will you be able to simplify your domain model by pulling out all the query logic, but at least a handful of commands in most systems will probably be “pass-though” type commands with little to no logic that just generate events. If these can be implemented directly in the command-handler and never touch the domain model, this allows you to slim down the domain model even more. Also, if you were to do event sourcing without CQRS, you no longer have a database containing the current state (only the domain model would) which makes it difficult (or impossible) to support ad-hoc querying and/or reporting that is common in most business software. Of course CQRS provides some great scalability benefits, not only scalability but I have to assume that it provides extremely low latency for most operations, especially if you have an asynchronous event bus. I know Greg says that you get a 3x scaling (Commands, Queries, Client) of your ability to perform parallel development, but IMHO, it seems like it only provides 1.5x scaling since even without CQRS you’re going to have your client loosely coupled to your domain - which is still a great benefit to be able to realize. Questions / Concerns If all the queries against an aggregate get pulled out to the Query layer, what if the only commands for that aggregate can be handled in a “pass-through” manner with the command handler directly generating events. Is it possible to have an aggregate that isn’t modeled in the domain model? Are there any issues or downsides to this? I know in the feedback from my previous posts it was suggested that having one domain model handling both commands and queries requires implementing a lot of traversals between objects that wouldn’t be necessary if it was only servicing commands. My question is, do you include traversals in your domain model based on the needs of the code, or based on the conceptual domain model? If none of my Commands require a Customer.Orders traversal, but the conceptual domain includes the concept of a set of orders belonging to a customer – should I model that in my domain model or not? I like the idea of using the Query side of the architecture as a place to put junior devs where the risk of them screwing something up has minimal impact. But I’m not sold on the idea that you can actually outsource it. Like I said in one of my comments on my previous post, the code to handle a query and generate DTO’s is going to be dead simple, but the code to process events and apply them to the tables on the query side is going to require a significant amount of domain knowledge to know which events to listen for to update each of the de-normalized tables (and what changes need to be made when each event is processed). I don’t know about everybody else, but having Indian/Russian/whatever outsourced developers have to do anything that requires significant domain knowledge has never been successful in my experience. And if you need to spec out for each new query which events to listen to and what to do with each one, well that’s probably going to be just as much work to document as it would be to just implement it. Greg made the point in a comment that doing an aggregate query like “Total Sales By Customer” is going to be inefficient if you use event sourcing but not CQRS. I don’t understand why that would be the case. I imagine in that case you’d simply have a method/property on the Customer object that calculated total sales for that customer by enumerating over the Orders collection. Then the application services layer would generate DTO’s off of the Customers collection that included say the CustomerID, CustomerName, TotalSales, or whatever the case may be. As long as you use a snapshotting implementation, I don’t see why that would be anymore inefficient in a DDD+Event Sourcing implementation than in a typical DDD implementation. Like I mentioned in my last post I still have some questions about query logic that haven’t been answered yet, but before I start asking those I want to make sure I have a strong grasp on what benefits CQRS provides.  My main concern with the query logic was that I know I could just toss it all into the query side, but I was concerned that I would be losing the benefits of using CQRS in the first place if I did that.  I want to elaborate more on this though with some example situations in an upcoming post.

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• SQL SERVER – Solution – Puzzle – SELECT * vs SELECT COUNT(*)

  - by pinaldave

  Earlier I have published Puzzle Why SELECT * throws an error but SELECT COUNT(*) does not. This question have received many interesting comments. Let us go over few of the answers, which are valid. Before I start the same, let me acknowledge Rob Farley who has not only answered correctly very first but also started interesting conversation in the same thread. The usual question will be what is the right answer. I would like to point to official Microsoft Connect Items which discusses the same. RGarvao https://connect.microsoft.com/SQLServer/feedback/details/671475/select-test-where-exists-select tiberiu utan http://connect.microsoft.com/SQLServer/feedback/details/338532/count-returns-a-value-1 Rob Farley count(*) is about counting rows, not a particular column. It doesn’t even look to see what columns are available, it’ll just count the rows, which in the case of a missing FROM clause, is 1. “select *” is designed to return columns, and therefore barfs if there are none available. Even more odd is this one: select ‘blah’ where exists (select *) You might be surprised at the results… Koushik The engine performs a “Constant scan” for Count(*) where as in the case of “SELECT *” the engine is trying to perform either Index/Cluster/Table scans. amikolaj When you query ‘select * from sometable’, SQL replaces * with the current schema of that table. With out a source for the schema, SQL throws an error. so when you query ‘select count(*)’, you are counting the one row. * is just a constant to SQL here. Check out the execution plan. Like the description states – ‘Scan an internal table of constants.’ You could do ‘select COUNT(‘my name is adam and this is my answer’)’ and get the same answer. Netra Acharya SELECT * Here, * represents all columns from a table. So it always looks for a table (As we know, there should be FROM clause before specifying table name). So, it throws an error whenever this condition is not satisfied. SELECT COUNT(*) Here, COUNT is a Function. So it is not mandetory to provide a table. Check it out this: DECLARE @cnt INT SET @cnt = COUNT(*) SELECT @cnt SET @cnt = COUNT(‘x’) SELECT @cnt Naveen Select 1 / Select ‘*’ will return 1/* as expected. Select Count(1)/Count(*) will return the count of result set of select statement. Count(1)/Count(*) will have one 1/* for each row in the result set of select statement. Select 1 or Select ‘*’ result set will contain only 1 result. so count is 1. Where as “Select *” is a sysntax which expects the table or equauivalent to table (table functions, etc..). It is like compilation error for that query. Ramesh Hi Friends, Count is an aggregate function and it expects the rows (list of records) for a specified single column or whole rows for *. So, when we use ‘select *’ it definitely give and error because ‘*’ is meant to have all the fields but there is not any table and without table it can only raise an error. So, in the case of ‘Select Count(*)’, there will be an error as a record in the count function so you will get the result as ’1'. Try using : Select COUNT(‘RAMESH’) and think there is an error ‘Must specify table to select from.’ in place of ‘RAMESH’ Pinal : If i am wrong then please clarify this. Sachin Nandanwar Any aggregate function expects a constant or a column name as an expression. DO NOT be confused with * in an aggregate function.The aggregate function does not treat it as a column name or a set of column names but a constant value, as * is a key word in SQL. You can replace any value instead of * for the COUNT function.Ex Select COUNT(5) will result as 1. The error resulting from select * is obvious it expects an object where it can extract the result set. I sincerely thank you all for wonderful conversation, I personally enjoyed it and I am sure all of you have the same feeling. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: CodeProject, Pinal Dave, PostADay, Readers Contribution, Readers Question, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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• Handy SQL Server Function Series: Part 1

  - by Most Valuable Yak (Rob Volk)

  I've been preparing to give a presentation on SQL Server for a while now, and a topic that was recommended was SQL Server functions.  More specifically, the lesser-known functions (like @@OPTIONS), and maybe some interesting ways to use well-known functions (like using PARSENAME to split IP addresses)  I think this is a veritable goldmine of useful information, and researching for the presentation has confirmed that beyond my initial expectations.I even found a few undocumented/underdocumented functions, so for the first official article in this series I thought I'd start with 2 of each, COLLATIONPROPERTY() and COLLATIONPROPERTYFROMID().COLLATIONPROPERTY() provides information about (wait for it) collations, SQL Server's method for handling foreign character sets, sort orders, and case- or accent-sensitivity when sorting character data.  The Books Online entry for  COLLATIONPROPERTY() lists 4 options for code page, locale ID, comparison style and version.  Used in conjunction with fn_helpcollations():SELECT *, COLLATIONPROPERTY(name,'LCID') LCID, COLLATIONPROPERTY(name,'CodePage') CodePage, COLLATIONPROPERTY(name,'ComparisonStyle') ComparisonStyle, COLLATIONPROPERTY(name,'Version') Version FROM fn_helpcollations()You can get some excellent information. (c'mon, be honest, did you even know about fn_helpcollations?)Collations in SQL Server have a unique name and ID, and you'll see one or both in various system tables or views like syscolumns, sys.columns, and INFORMATION_SCHEMA.COLUMNS.  Unfortunately they only link the ID and name for collations of existing columns, so if you wanted to know the collation ID of Albanian_CI_AI_WS, you'd have to declare a column with that collation and query the system table.While poking around the OBJECT_DEFINITION() of sys.columns I found a reference to COLLATIONPROPERTYFROMID(), and the unknown property "Name".  Not surprisingly, this is how sys.columns finds the name of the collation, based on the ID stored in the system tables.  (Check yourself if you don't believe me)Somewhat surprisingly, the "Name" property also works for COLLATIONPROPERTY(), although you'd already know the name at that point.  Some wild guesses and tests revealed that "CollationID" is also a valid property for both functions, so now:SELECT *, COLLATIONPROPERTY(name,'LCID') LCID, COLLATIONPROPERTY(name,'CodePage') CodePage, COLLATIONPROPERTY(name,'ComparisonStyle') ComparisonStyle, COLLATIONPROPERTY(name,'Version') Version, COLLATIONPROPERTY(name,'CollationID') CollationID FROM fn_helpcollations() Will get you the collation ID-name link you…probably didn't know or care about, but if you ever get on Jeopardy! and this question comes up, feel free to send some of your winnings my way. :)And last but not least, COLLATIONPROPERTYFROMID() uses the same properties as COLLATIONPROPERTY(), so you can use either one depending on which value you have available.Keep an eye out for Part 2!

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• Polite busy-waiting with WRPAUSE on SPARC

  - by Dave

  Unbounded busy-waiting is an poor idea for user-space code, so we typically use spin-then-block strategies when, say, waiting for a lock to be released or some other event. If we're going to spin, even briefly, then we'd prefer to do so in a manner that minimizes performance degradation for other sibling logical processors ("strands") that share compute resources. We want to spin politely and refrain from impeding the progress and performance of other threads — ostensibly doing useful work and making progress — that run on the same core. On a SPARC T4, for instance, 8 strands will share a core, and that core has its own L1 cache and 2 pipelines. On x86 we have the PAUSE instruction, which, naively, can be thought of as a hardware "yield" operator which temporarily surrenders compute resources to threads on sibling strands. Of course this helps avoid intra-core performance interference. On the SPARC T2 our preferred busy-waiting idiom was "RD %CCR,%G0" which is a high-latency no-nop. The T4 provides a dedicated and extremely useful WRPAUSE instruction. The processor architecture manuals are the authoritative source, but briefly, WRPAUSE writes a cycle count into the the PAUSE register, which is ASR27. Barring interrupts, the processor then delays for the requested period. There's no need for the operating system to save the PAUSE register over context switches as it always resets to 0 on traps. Digressing briefly, if you use unbounded spinning then ultimately the kernel will preempt and deschedule your thread if there are other ready threads than are starving. But by using a spin-then-block strategy we can allow other ready threads to run without resorting to involuntary time-slicing, which operates on a long-ish time scale. Generally, that makes your application more responsive. In addition, by blocking voluntarily we give the operating system far more latitude regarding power management. Finally, I should note that while we have OS-level facilities like sched_yield() at our disposal, yielding almost never does what you'd want or naively expect. Returning to WRPAUSE, it's natural to ask how well it works. To help answer that question I wrote a very simple C/pthreads benchmark that launches 8 concurrent threads and binds those threads to processors 0..7. The processors are numbered geographically on the T4, so those threads will all be running on just one core. Unlike the SPARC T2, where logical CPUs 0,1,2 and 3 were assigned to the first pipeline, and CPUs 4,5,6 and 7 were assigned to the 2nd, there's no fixed mapping between CPUs and pipelines in the T4. And in some circumstances when the other 7 logical processors are idling quietly, it's possible for the remaining logical processor to leverage both pipelines. Some number T of the threads will iterate in a tight loop advancing a simple Marsaglia xor-shift pseudo-random number generator. T is a command-line argument. The main thread loops, reporting the aggregate number of PRNG steps performed collectively by those T threads in the last 10 second measurement interval. The other threads (there are 8-T of these) run in a loop busy-waiting concurrently with the T threads. We vary T between 1 and 8 threads, and report on various busy-waiting idioms. The values in the table are the aggregate number of PRNG steps completed by the set of T threads. The unit is millions of iterations per 10 seconds. For the "PRNG step" busy-waiting mode, the busy-waiting threads execute exactly the same code as the T worker threads. We can easily compute the average rate of progress for individual worker threads by dividing the aggregate score by the number of worker threads T. I should note that the PRNG steps are extremely cycle-heavy and access almost no memory, so arguably this microbenchmark is not as representative of "normal" code as it could be. And for the purposes of comparison I included a row in the table that reflects a waiting policy where the waiting threads call poll(NULL,0,1000) and block in the kernel. Obviously this isn't busy-waiting, but the data is interesting for reference. _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } _td { border: 1px green solid; } _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } Aggregate progress T = #worker threads Wait Mechanism for 8-T threadsT=1T=2T=3T=4T=5T=6T=7T=8 Park thread in poll() 32653347334833483348334833483348 no-op 415 831 124316482060249729303349 RD %ccr,%g0 "pause" 14262429269228623013316232553349 PRNG step 412 829 124616702092251029303348 WRPause(8000) 32443361333133483349334833483348 WRPause(4000) 32153308331533223347334833473348 WRPause(1000) 30853199322432513310334833483348 WRPause(500) 29173070315032223270330933483348 WRPause(250) 26942864294930773205338833483348 WRPause(100) 21552469262227902911321433303348

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• Business Intelligence: "Building a Cube"

  Learn the basics of building an Oracle Essbase aggregate storage database.

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• How to track many in-game statistics

  - by Alex Schearer

  I am looking to track many in-game events, e.g. the score of each move, how many moves are taken, what types of moves, etc. A lot of stats can simply be tracked with a counter. In some cases I need to aggregate data in order to calculate the value (e.g. most common move). How are you tracking in-game stats for your games? How do you avoid creating a class with tens or hundreds of fields? How do you avoid littering the code with tracking invocations? How do you abstract the aggregate data so as to avoid rewriting it for each scenario?

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• Applying DDD principles in a RESTish web service

  - by Andy

  I am developing an RESTish web service. I think I got the idea of the difference between aggregation and composition. Aggregation does not enforce lifecycle/scope on the objects it references. Composition does enforce lifecycle/scope on the objects it contain/own. If I delete a composite object then all the objects it contain/own are deleted as well, while the deleting an aggregate root does not delete referenced objects. 1) If it is true that deleting aggregate roots does not necessary delete referenced objects, what sense does it make to not have a repository for the references objects? Or are aggregate roots as a term referring to what is known as composite object? 2) When you create an web service you will have multiple endpoints, in my case I have one entity Book and another named Comment. It does not make sense to leave the comments in my application if the book is deleted. Therefore, book is a composite object. I guess I should not have a repository for comments since that would break the enforcement of lifecycle and rules that the book class may have. However I have URL such as (examples only): GET /books/1/comments POST /books/1/comments Now, if I do not have a repository for comments, does that mean I have to load the book object and then return the referenced comments? Am I allowed to return a list of Comment entities from the BookRepository, does that make sense? The repository for Book may eventually become rather big with all sorts of methods. Am I allowed to write JPQL (JPA queries) that targets comments and not books inside the repository? What about pagination and filtering of comments. When adding a new comment triggered by the POST endpoint, do you need to load the book, add the comment to the book, and then update the whole book object? What I am currently doing is having a own CommentRepository, even though the comments are deleted with the book. I could need some direction on how to do it correct. Since you are exposing not only root objects in RESTish services I wonder how to handle this at the backend. I am using Hibernate and Spring.

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• Architecture for dashbaord showing aggregated stats

  - by soulnafein

  I'm trying to find the best architecture for an application that shows a dashboard with aggregated stats that come from another one (e.g. number of sales in the last 12 months, current sales this month, a fairly complex score, performance of users over last 30 days, etc.) There is a fair bit of business logic that lives in Application 1 but the aggregated data gets saved in Application 2 (dashboard). What's the best way to create the aggregate data? 1) Pull data directly from Application 1 database and duplicate business logic for score calculation etc. 2) Push data from Application 1 to Application 2 somehow 3) Aggregate data in Application 1 on the fly and provide and api for Application 2 4) Other (probably) Please suggest solutions, Thanks.

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• Script to calculate the Median value for SQL Server data

  The standard SQL language has a number of aggregate functions like: SUM, MIN, MAX, AVG, but a common statistics function that SQL Server does not have is a built-in aggregate function for median. The median is the value that falls in the middle of a sorted resultset with equal parts that are smaller and equal parts that are greater. Since there is no built-in implementation for the median, the following is a simple solution I put together to find the median. Get smart with SQL Backup ProPowerful centralised management, encryption and more.SQL Backup Pro was the smartest kid at school. Discover why.

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• DDD: service contains two repository

  - by tikhop

  Does it correct way to have two repository inside one service and will it be an application or domain service? Suppose I have a Passenger object that should contains Passport (government id) object. I am getting Passenger from PassengerRepository. PassengerRepository create request to server and obtain data (json) than parse received data and store inside repository. I have confused because I want to store Passport as Entity and put it to PassportRepository but all information about password contains inside json than i received above. I guess that I should create a PassengerService that will be include PassengerRepository and PassportRepository with several methods like removePassport, addPassport, getAllPassenger and etc. UPDATE: So I guess that the better way is represent Passport as VO and store all passports inside Passenger aggregate. However there is another question: Where I should put the methods (methods calls server api) for management passenger's passport. I think the better place is so within Passenger aggregate.

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• Pivoting DataTable Simplified

  A class to pivot a DataTable with various aggregate functions.

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• functional dependencies vs type families

  - by mhwombat

  I'm developing a framework for running experiments with artificial life, and I'm trying to use type families instead of functional dependencies. Type families seems to be the preferred approach among Haskellers, but I've run into a situation where functional dependencies seem like a better fit. Am I missing a trick? Here's the design using type families. (This code compiles OK.) {-# LANGUAGE TypeFamilies, FlexibleContexts #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u => a -> StateT u IO a -- plus other functions class Universe u where type MyAgent u :: * withAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } defaultWithAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () defaultWithAgent = undefined -- stub -- plus default implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- .. and they'll also need to make SimpleUniverse an instance of Universe -- for their agent type. -- instance Universe SimpleUniverse where type MyAgent SimpleUniverse = Bug withAgent = defaultWithAgent -- boilerplate -- plus similar boilerplate for other functions Is there a way to avoid forcing my users to write those last two lines of boilerplate? Compare with the version using fundeps, below, which seems to make things simpler for my users. (The use of UndecideableInstances may be a red flag.) (This code also compiles OK.) {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, UndecidableInstances #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u a => a -> StateT u IO a -- plus other functions class Universe u a | u -> a where withAgent :: Agent a => (a -> StateT u IO a) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } instance Universe SimpleUniverse a where withAgent = undefined -- stub -- plus implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- And now my users only have to write stuff like... -- u :: SimpleUniverse u = SimpleUniverse "mydir"

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• kernel software trap handling

  - by Tony

  I'm reading a book on Windows Internals and there's something I don't understand: "The kernel handles software interrupts either as part of hardware interrupt handling or synchronously when a thread invokes kernel functions related to the software interrupt." So does this mean that software interrupts or exceptions will only be handled under these conditions: a. When the kernel is executing a function from said thread related to the software exception(trap) b. when it is already handling a hardware trap Is my understanding of this correct? The next bit: "In most cases, the kernel installs front-end trap handling functions that perform general trap handling tasks before and after transferring control to other functions that field the trap." I don't quite understand what it means by 'front-end trap handling functions' and 'field the trap'? Can anyone help me?

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• Can't escape single quotes in shell

  - by user13743

  I'm trying to make a command to do a perl substitution on a batch of php files in a directory. The string I want to replace has single quotes in it, and I can't get it to properly escape the in shell. I tried echoing the string with unescaped quotes, to see what perl would be getting: echo 's/require_once('include.constants.php');/require_once('include.constants.php');require_once("./functions/include.session.inc.php");/g' and it doesn't have the single-quotes in the result: s/require_once\(include.constants.php\);/require_once\(include.constants.php\);require_once\("\./functions/include\.session\.inc\.php"\);/g However, when I try to escape the single quotes: echo 's/require_once\(\'include\.constants\.php\'\);/require_once\(\'include\.constants\.php\'\);require_once\("\./functions/include\.session\.inc\.php"\);/g' I get the prompt to complete the command: > What I want it to parse to is this: What am I doing wrong? s/require_once\('include.constants.php'\);/require_once\('include.constants.php'\);require_once\("\./functions/include\.session\.inc\.php"\);/g

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• Platform Builder: Cloning – the Linker is your Friend

  - by Bruce Eitman

  I was tasked this week with making a minor change to NetMsgBox() behavior. NetMsgBox() is a little function in NETUI that handles MessageBox() for the Network User Interface.  The obvious solution is to clone the entire NETUI directory from Public\Common\Oak\Drivers (see Platform Builder: Clone Public Code for more on cloning). If you haven’t already, take a minute to look in that folder. There are a lot of files in the folder, but I only needed to modify one function in one of those files. There must be a better way. Enter the linker. Instead of cloning the entire folder, here is what I did: Create a new folder in my Platform named NETUI (but the name isn’t important) Copy the C file that I needed to modify to the new folder, in this case netui.c Copy a makefile from one of the other folder (really they are all the same) Run Sysgen_capture Open a build window (see Platform Builder: Build Tools, Opening a Build Window) Change directories to the new folder Run “Sysgen_capture netui” Rename sources.netui to sources Add the C file to sources as SOURCES=netui.c Modify the code Build the code Done That is it, the functions from my new folder now replace the functions from the Public code and link with the rest to create NETUI.dll. There is a catches. If you remove any of the functions from the C file, linking will fail because the remaining functions will be found twice.   Copyright © 2010 – Bruce Eitman All Rights Reserved

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• SQLAuthority News – Learning, Community and Book Signing at #SQLPASS 2012

  - by pinaldave

  SQLPASS event is going excellent we are having great great fun! We are having book signing events and the response is overwhelmingly positive. I am glad that all of you love our books and I totally appreciate your support. Rick and I both are feeling very motivated to write more books in future. Here is our schedule for book signing. SQL Queries 2012 Joes 2 Pros Volume1 Finally a book for the true SQL Server beginner! Whether you are brand new to databases and are thinking of getting your 70-461 certification or already a semi-pro working in the field and need some fingertip support, this is this is the book for you. Joes 2 Pros does not assume you already know anything about databases or SQL server.  This book builds on the success of the previous series and will help anyone transform themselves from a beginner “Joe” into a SQL 2012 “Pro”. Wednesday, November 7, 2012 12pm-1pm – Book Signing at Exhibit Hall Joes Pros booth#117 (FREE BOOK) Rest all the time – I will be at Exhibition Hall Joes 2 Pros Booth #117. Stop by for the goodies! This book is also available on Amazon. SQL 2012 Functions Joes 2 Pros Functions have been around for many years to make our lives easier. Because of them, thousands of lines of valuable programming can be done with one statement. When we know what functions are offered in SQL Server we can get powerful projects done very quickly. Often times, the functions you wished you had are released in the next version. Wednesday, November 7, 2012 7pm-8pm - Embarcadero Booth Book Signing (FREE BOOK) Thursday, November 8, 2012 12pm-1pm - Embarcadero Booth Book Signing (FREE BOOK) This book is also available on Amazon. If you are at SQLPASS stop by Booth #117 – I will be there and many be you can get one of my signed book! Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL PASS, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Book Review, SQLAuthority News, SQLServer, T SQL, Technology

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• sending php mail from localhost

  - by SimplySimon

  I have installed php, mySQL, postfix and sendmail and have set up a simple email script on my local host server. mail() returns 1 (TRUE) when I send an e-mail, however the email does not arrive at the destination. Installation The mail functions are part of the PHP core. There is no installation needed to use these functions. Requirements For the mail functions to be available, PHP requires an installed and working email system. The program to be used is defined by the configuration settings in the php.ini file. Runtime Configuration The behavior of the mail functions is affected by settings in the php.ini file. Mail configuration options: Name Default Description Changeable sendmail_path NULL Unix systems only: Specifies where the sendmail program can be found (usually /usr/sbin/sendmail or /usr/lib/sendmail) PHP_INI_SYSTEM I found it at /usr/lib/sendmail however, I can not find the configuration file, which is where I assume my problem is, as I have not told anything which server I am using to send my mail through. If anyone can help me I would be grateful.

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• does my js replace view?

  - by Milla Well

  I am writing a web application which is based on Codeigniter and jQuery. I primarily use ajax to call my controller functions and it turned out, that there are just 4 view*.php files, because most of my contoller functions return JSON data, which is processed in my jQuery. So my actual code is divided in kind of MVCC model: Codeigniter model (db, computations) Codeigniter controller (filtering, xss-cleaning, checking permissions, call model functions) jQuery controller (callback functions) jQuery view (adding/removing classes, appending elements,... ) So I violate the paradigm of not using the echo function in my Codeiginter controller and simply call echo json_encode($result); because it doesn't make any sense to me to create a view*.php file for one loc. Especially because all the regular view*.php stuff is covered in my jQuery view. I was wondering if I am missing something out, or if there is a way to integrate this jQuery-controller in my Codeigniter. I found some words on this topic, but this seems pretty handmade. Are there some neat solutions? Does a MVCC model make sense?

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• Log Blog

  - by PointsToShare

  © 2011 By: Dov Trietsch. All rights reserved Logging – A log blog In a another blog (Missing Fields and Defaults) I spoke about not doing a blog about log files, but then I looked at it again and realized that this is a nice opportunity to show a simple yet powerful tool and also deal with static variables and functions in C#. My log had to be able to answer a few simple logging rules:   To log or not to log? That is the question – Always log! That is the answer  Do we share a log? Even when a file is opened with a minimal lock, it does not share well and performance greatly suffers. So sharing a log is not a good idea. Also, when sharing, it is harder to find your particular entries and you have to establish rules about retention. My recommendation – Do Not Share!  How verbose? Your log can be very verbose – a good thing when testing, very terse – a good thing in day-to-day runs, or somewhere in between. You must be the judge. In my Blog, I elect to always report a run with start and end times, and always report errors. I normally use 5 levels of logging: 4 – write all, 3 – write more, 2 – write some, 1 – write errors and timing, 0 – write none. The code sample below is more general than that. It uses the config file to set the max log level and each call to the log assigns a level to the call itself. If the level is above the .config highest level, the line will not be written. Programmers decide which log belongs to which level and thus we can set the .config differently for production and testing.  Where do I keep the log? If your career is important to you, discuss this with the boss and with the system admin. We keep logs in the L: drive of our server and make sure that we have a directory for each app that needs a log. When adding a new app, add a new directory. The default location for the log is also found in the .config file Print One or Many? There are two options here:   1.     Print many, Open but once once – you start the stream and close it only when the program ends. This is what you can do when you perform in “batch” mode like in a console app or a stsadm extension.The advantage to this is that starting a closing a stream is expensive and time consuming and because we use a unique file, keeping it open for a long time does not cause contention problems. 2.     Print one entry at a time or Open many – every time you write a line, you start the stream, write to it and close it. This work for event receivers, feature receivers, and web parts. Here scalability requires us to create objects on the fly and get rid of them as soon as possible.  A default value of the onceOrMany resides in the .config.  All of the above applies to any windows or web application, not just SharePoint.  So as usual, here is a routine that does it all, and a few simple functions that call it for a variety of purposes.   So without further ado, here is app.config  <?xml version="1.0" encoding="utf-8" ?> <configuration>     <configSections>         <sectionGroup name="applicationSettings" type="System.Configuration.ApplicationSettingsGroup, System, Version=2.0.0.0, Culture=neutral, ublicKeyToken=b77a5c561934e089" >         <section name="statics.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />         </sectionGroup>     </configSections>     <applicationSettings>         <statics.Properties.Settings>             <setting name="oneOrMany" serializeAs="String">                 <value>False</value>             </setting>             <setting name="logURI" serializeAs="String">                 <value>C:\staticLog.txt</value>             </setting>             <setting name="highestLevel" serializeAs="String">                 <value>2</value>             </setting>         </statics.Properties.Settings>     </applicationSettings> </configuration>   And now the code:  In order to persist the variables between calls and also to be able to persist (or not to persist) the log file itself, I created an EventLog class with static variables and functions. Static functions do not need an instance of the class in order to work. If you ever wondered why our Main function is static, the answer is that something needs to run before instantiation so that other objects may be instantiated, and this is what the “static” Main does. The various logging functions and variables are created as static because they do not need instantiation and as a fringe benefit they remain un-destroyed between calls. The Main function here is just used for testing. Note that it does not instantiate anything, just uses the log functions. This is possible because the functions are static. Also note that the function calls are of the form: Class.Function.  using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; namespace statics {       class Program     {         static void Main(string[] args)         {             //write a single line             EventLog.LogEvents("ha ha", 3, "C:\\hahafile.txt", 4, true, false);             //this single line will not be written because the msgLevel is too high             EventLog.LogEvents("baba", 3, "C:\\babafile.txt", 2, true, false);             //The next 4 lines will be written in succession - no closing             EventLog.LogLine("blah blah", 1);             EventLog.LogLine("da da", 1);             EventLog.LogLine("ma ma", 1);             EventLog.LogLine("lah lah", 1);             EventLog.CloseLog(); // log will close             //now with specific functions             EventLog.LogSingleLine("one line", 1);             //this is just a test, the log is already closed             EventLog.CloseLog();         }     }     public class EventLog     {         public static string logURI = Properties.Settings.Default.logURI;         public static bool isOneLine = Properties.Settings.Default.oneOrMany;         public static bool isOpen = false;         public static int highestLevel = Properties.Settings.Default.highestLevel;         public static StreamWriter sw;         /// <summary>         /// the program will "print" the msg into the log         /// unless msgLevel is > msgLimit         /// onceOrMany is true when once - the program will open the log         /// print the msg and close the log. False when many the program will         /// keep the log open until close = true         /// normally all the arguments will come from the app.config         /// called by many overloads of logLine         /// </summary>         /// <param name="msg"></param>         /// <param name="msgLevel"></param>         /// <param name="logFileName"></param>         /// <param name="msgLimit"></param>         /// <param name="onceOrMany"></param>         /// <param name="close"></param>         public static void LogEvents(string msg, int msgLevel, string logFileName, int msgLimit, bool oneOrMany, bool close)         {             //to print or not to print             if (msgLevel <= msgLimit)             {                 //open the file. from the argument (logFileName) or from the config (logURI)                 if (!isOpen)                 {                     string logFile = logFileName;                     if (logFileName == "")                     {                         logFile = logURI;                     }                     sw = new StreamWriter(logFile, true);                     sw.WriteLine("Started At: " + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));                     isOpen = true;                 }                 //print                 sw.WriteLine(msg);             }             //close when instructed             if (close || oneOrMany)             {                 if (isOpen)                 {                     sw.WriteLine("Ended At: " + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));                     sw.Close();                     isOpen = false;                 }             }         }           /// <summary>         /// The simplest, just msg and level         /// </summary>         /// <param name="msg"></param>         /// <param name="msgLevel"></param>         public static void LogLine(string msg, int msgLevel)         {             //use the given msg and msgLevel and all others are defaults             LogEvents(msg, msgLevel, "", highestLevel, isOneLine, false);         }                 /// <summary>         /// one line at a time - open print close         /// </summary>         /// <param name="msg"></param>         /// <param name="msgLevel"></param>         public static void LogSingleLine(string msg, int msgLevel)         {             LogEvents(msg, msgLevel, "", highestLevel, true, true);         }           /// <summary>         /// used to close. high level, low limit, once and close are set         /// </summary>         /// <param name="close"></param>         public static void CloseLog()         {             LogEvents("", 15, "", 1, true, true);         }           }     }   }   That’s all folks!

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• Customizing the NUnit GUI for data-driven testing

  - by rwong

  My test project consists of a set of input data files which is fed into a piece of legacy third-party software. Since the input data files for this software are difficult to construct (not something that can be done intentionally), I am not going to add new input data files. Each input data file will be subject to a set of "test functions". Some of the test functions can be invoked independently. Other test functions represent the stages of a sequential operation - if an earlier stage fails, the subsequent stages do not need to be executed. I have experimented with the NUnit parametrized test case (TestCaseAttribute and TestCaseSourceAttribute), passing in the list of data files as test cases. I am generally satisfied with the the ability to select the input data for testing. However, I would like to see if it is possible to customize its GUI's tree structure, so that the "test functions" become the children of the "input data". For example: File #1 CheckFileTypeTest GetFileTopLevelStructureTest CompleteProcessTest StageOneTest StageTwoTest StageThreeTest File #2 CheckFileTypeTest GetFileTopLevelStructureTest CompleteProcessTest StageOneTest StageTwoTest StageThreeTest This will be useful for identifying the stage that failed during the processing of a particular input file. Is there any tips and tricks that will enable the new tree layout? Do I need to customize NUnit to get this layout?

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• I don't understand the definition of side effects

  - by Chris Okyen

  I don't understand the wikipedia article on Side Effects: In computer science, a function or expression is said to have a side effect if, in addition to returning a value, it also 1.) Modifies some state or 2.) Has an observable interaction with calling functions or the outside world. I know an example of the first thing that causes a function or expression to have side effects - modifying a state Function and Expression modifying a state : 1.) foo(int X) { return x = x % x; } a = a + 1; What does 2.) - Has an observable interaction with calling functions or the outside world," mean? - Please give an example. The article continues on to say, "For example, a function might modify a global or static variable, modify one of its arguments, raise an exception, write data to a display or file, read data, or call other side-effecting functions...." Are all these examples, examples of 1.) - Modifiying some state , or are they also part of 2.) - Has an observable interaction with calling functions or the outside world?

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• Standard Network Tiers in a Distributed N-Tier System

  Distributed N-Tier client/server architecture allows for segments of an application to be broken up and distributed across multiple locations on a network.  Listed below are standard tiers in a Distributed N-Tier System. End-User Client Tier The End-User Client is responsible for sending and receiving requests from web servers and other applications servers and translating the responses so that the End-User can interpret the data effectively. The primary roles for this tier are to communicate with servers and translate server responses back to the end-user to interpret. Business-Specific Functions Validate Data Display Data Send Data to Webserver Web Server Tier The Web server tier processes new requests for information coming in from the HTTP and HTTPS ports. This primarily handles the generation of user interfaces and calls the application server when needed to access Data and business logic when needed. Business-specific functions Send Data to application server Format Data for Display Validate Data Application Server Tier The application server stores and executes predefined business logic that is applied to various pieces of data as the business determines. The processed data is then returned back to the Webserver. Additionally, this server directly calls the database to obtain and store any data used by the system Business-Specific Functions Validate Data Process Data Send Data to Database Server Database Server Tier The Database Server is responsible for storing and returning all data need by the calling applications. The primary role for this this server is storage. Data is stored as needed and can be recalled at any point later in time. Business-Specific Functions Insert Data Delete Data Return Data to Application Server

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• How should I start refactoring my mostly-procedural C++ application?

  - by oob

  We have a program written in C++ that is mostly procedural, but we do use some C++ containers from the standard library (vector, map, list, etc). We are constantly making changes to this code, so I wouldn't call it a stagnant piece of legacy code that we can just wrap up. There are a lot of issues with this code making it harder and harder for us to make changes, but I see the three biggest issues being: Many of the functions do more (way more) than one thing We violate the DRY principle left and right We have global variables and global state up the wazoo. I was thinking we should attack areas 1 and 2 first. Along the way, we can "de-globalize" our smaller functions from the bottom up by passing in information that is currently global as parameters to the lower level functions from the higher level functions and then concentrate on figuring out how to removing the need for global variables as much as possible. I just finished reading Code Complete 2 and The Pragmatic Programmer, and I learned a lot, but I am feeling overwhelmed. I would like to implement unit testing, change from a procedural to OO approach, automate testing, use a better logging system, fully validate all input, implement better error handling and many other things, but I know if we start all this at once, we would screw ourselves. I am thinking the three I listed are the most important to start with. Any suggestions are welcome. We are a team of two programmers mostly with experience with in-house scripting. It is going to be hard to justify taking the time to refactor, especially if we can't bill the time to a client. Believe it or not, this project has been successful enough to keep us busy full time and also keep several consultants busy using it for client work.

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• Pure functional programming and game state

  - by Fu86

  Is there a common technique to handle state (in general) in a functional programming language? There are solutions in every (functional) programming language to handle global state, but I want to avoid this as far as I could. All state in a pure functional manner are function parameters. So I need to put the whole game state (a gigantic hashmap with the world, players, positions, score, assets, enemies, ...)) as a parameter to all functions which wants to manipulate the world on a given input or trigger. The function itself picks the relevant information from the gamestate blob, do something with it, manipulate the gamestate and return the gamestate. But this looks like a poor mans solution for the problem. If I put the whole gamestate into all functions, there is no benefit for me in contrast to global variables or the imperative approach. I could put just the relevant information into the functions and return the actions which will be taken for the given input. And one single function apply all the actions to the gamestate. But most functions need a lot of "relevant" information. move() need the object position, the velocity, the map for collision, position of all enemys, current health, ... So this approach does not seem to work either. So my question is how do I handle the massive amount of state in a functional programming language -- especially for game development?

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• DDD Modeling questions : student, classroom, seats and a favorite seat for a student.

  - by Erik Ashepa

  Hi, i'm not sure how to model this relationship... A classroom contains many seats, every student studies in a classroom and have a favorite seat within it. The way i see it, i have two aggregate roots: classroom and student, seats a are entities aggregatged by classroom... And for a student to have a fovorite seat, it must hold a reference to it (seat isn't an aggregate root). Any suggestions? Thanks in advance, Erik.

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