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• How can I "store" an operator inside a variable in Perl?

  - by Ricky

  I'm looking for a way to do this in Perl: $a = "60"; $b = "< 80"; if ( $a $b ) { then .... } Here, $b "holds" an operator... can I do this? Maybe some other way?

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• lambda vs. operator.attrgetter('xxx') as sort key function in Python

  - by Paul McGuire

  I am looking at some code that has a lot of sort calls using comparison functions, and it seems like it should be using key functions. If you were to change seq.sort(lambda x,y: cmp(x.xxx, y.xxx)), which is preferable: seq.sort(key=operator.attrgetter('xxx')) or: seq.sort(key=lambda a:a.xxx) I would also be interested in comments on the merits of making changes to existing code that works.

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• C++ template function specialization using TCHAR on Visual Studio 2005

  - by Eli

  I'm writing a logging class that uses a templatized operator<< function. I'm specializing the template function on wide-character string so that I can do some wide-to-narrow translation before writing the log message. I can't get TCHAR to work properly - it doesn't use the specialization. Ideas? Here's the pertinent code: // Log.h header class Log { public: template <typename T> Log& operator<<( const T& x ); template <typename T> Log& operator<<( const T* x ); template <typename T> Log& operator<<( const T*& x ); ... } template <typename T> Log& Log::operator<<( const T& input ) { printf("ref"); } template <typename T> Log& Log::operator<<( const T* input ) { printf("ptr"); } template <> Log& Log::operator<<( const std::wstring& input ); template <> Log& Log::operator<<( const wchar_t* input ); And the source file // Log.cpp template <> Log& Log::operator<<( const std::wstring& input ) { printf("wstring ref"); } template <> Log& Log::operator<<( const wchar_t* input ) { printf("wchar_t ptr"); } template <> Log& Log::operator<<( const TCHAR*& input ) { printf("tchar ptr ref"); } Now, I use the following test program to exercise these functions // main.cpp - test program int main() { Log log; log << "test 1"; log << L"test 2"; std::string test3( "test3" ); log << test3; std::wstring test4( L"test4" ); log << test4; TCHAR* test5 = L"test5"; log << test4; } Running the above tests reveals the following: // Test results ptr wchar_t ptr ref wstring ref ref Unfortunately, that's not quite right. I'd really like the last one to be "TCHAR", so that I can convert it. According to Visual Studio's debugger, the when I step in to the function being called in test 5, the type is wchar_t*& - but it's not calling the appropriate specialization. Ideas? I'm not sure if it's pertinent or not, but this is on a Windows CE 5.0 device.

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• Combining two operators in Evil-mode Emacs

  - by Dyslexic Tangent

  In vim I've remapped > and < when in visual mode to >gv and <gv respectively, like so: vnoremap > >gv vnoremap < <gv Since my target for this question are folks experienced with emacs and not vim, what > and < do is indent/dedent visually selected text. What gv does is reselect the previously selected text. These maps cause > and < to indent/dedent and then reselect the previously selected text. I'm trying out emacs with evil-mode and I'd like to do the same, but I'm having some difficulty figuring out how, exactly, to accomplish the automatic reselection. It looks like I need to somehow call evil-shift-right and evil-visual-restore sequentially, but I don't know how to create a map that will do both, so I tried creating my own function which would call both sequentially and map that instead, but it didn't work, possibly due to the fact that both of them are defined, not as functions with defun but instead as operators with evil-define-operator. I tried creating my own operators: (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) (evil-visual-restore)) (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) (evil-visual-restore)) but that doesn't restore visual as expected. A stab in the dark gave me this: (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) ('evil-visual-restore)) (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) ('evil-visual-restore)) but that selects one additional line whenever it is supposed to reselect. For now I've been using the following, which only has the problem where it reselects an additional line in the < operator. (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) (evil-visual-make-selection beg end)) (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) (evil-visual-make-selection beg end)) and I've mapped them: (define-key evil-visual-state-map ">" 'shift-right-reselect) (define-key evil-visual-state-map "<" 'shift-left-reselect) any help / pointers / tips would be greatly appreciated. Thanks in advance.

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• LINQ To SQL exception: Local sequence cannot be used in LINQ to SQL implementation of query operator

  - by pcampbell

  Consider this LINQ To SQL query. It's intention is to take a string[] of search terms and apply the terms to a bunch of different fields on the SQL table: string[] searchTerms = new string[] {"hello","world","foo"}; List<Cust> = db.Custs.Where(c => searchTerms.Any(st => st.Equals(c.Email)) || searchTerms.Any(st => st.Equals(c.FirstName)) || searchTerms.Any(st => st.Equals(c.LastName)) || searchTerms.Any(st => st.Equals(c.City)) || searchTerms.Any(st => st.Equals(c.Postal)) || searchTerms.Any(st => st.Equals(c.Phone)) || searchTerms.Any(st => c.AddressLine1.Contains(st)) ) .ToList(); An exception is raised: Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator Question: Why is this exception raised, and how can the query be rewritten to avoid this exception?

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• Why does the minus operator give different result than the TIMESTAMPDIFF() function in mysql?

  - by f3r3nc

  Since TIMESTAMP in mysql is stored as a 32bit value representing the time interval from 1970-jan-1 0:00:00 in seconds, I assumed that using minus (-) operator on TIMESTAMP values would give the difference of these values in seconds. Actually not: +---------------------------------------------------------------------+ | TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:29:59") | +---------------------------------------------------------------------+ | 41.000000 | +---------------------------------------------------------------------+ 1 row in set (0.05 sec) mysql> select timestampdiff(SECOND,TIMESTAMP("2010-04-02 10:30:00"),TIMESTAMP("2010-04-02 10:29:59")); +-----------------------------------------------------------------------------------------+ | timestampdiff(SECOND,TIMESTAMP("2010-04-02 10:30:00"),TIMESTAMP("2010-04-02 10:29:59")) | +-----------------------------------------------------------------------------------------+ | -1 | +-----------------------------------------------------------------------------------------+ mysql> select TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:30:01") ; +---------------------------------------------------------------------+ | TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:30:01") | +---------------------------------------------------------------------+ | -1.000000 | +---------------------------------------------------------------------+ +---------------------------------------------------------------------+ | TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:31:00") | +---------------------------------------------------------------------+ | -100.000000 | +---------------------------------------------------------------------+ It seems like one minute difference is 100 instead of 60. Why is this?

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• Equality and Assigment Operators

  - by Jeremy Smith

  I have a assembly compiled in VB.NET that contains two operators: Public Shared Operator =(quarterA As CalendarQuarter, quarterB As CalendarQuarter) As Boolean Return quarterA.StartDate = quarterB.StartDate AndAlso quarterA.EndDate = quarterB.EndDate AndAlso quarterA.Quarter = quarterB.Quarter End Operator Public Shared Operator <>(quarterA As CalendarQuarter, quarterB As CalendarQuarter) As Boolean Return Not (quarterA = quarterB) End Operator However, when using the assembly in C# to perform equality checks if (qtr != null) I receive the error: Cannot implicity convert type 'object' to 'bool' My original intent with the = operator was only for assignment purposes in VB, so I may be way off base (I don't use custom operators too often). What do I need to do to make the operator behave with both equality and assignment operations?

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• No whitespace between a cast and a namespace operator?

  - by Pod

  Hello. Could anyone please explain the following line of code, found on http://docs.openttd.org/ai__cargo_8cpp_source.html return (AICargo::TownEffect)::CargoSpec::Get(cargo_type)->town_effect; If this line was: return (AICargo::TownEffect) ::CargoSpec::Get(cargo_type)->town_effect; (note the space between TownEffect) and the ::) then I would understand it fine. However there is no whitespace in that document*, which would mean (AICargo::TownEffect) is the left operand of the :: operator. How does this code work/compile? Or are the two things equivilent due to some obscure C++ rule? *It's the same in the cpp file as well.

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• How is the ">" operator implemented (on 32 bit integers)?

  - by Ron Klein

  Let's say that the environment is x86. How do compilers compile the "" operator on 32 bit integers. Logically, I mean. Without any knowledge of Assembly. Let's say that the high level language code is: int32 x, y; x = 123; y = 456; bool z; z = x > y; What does the compiler do for evaluating the expression x > y? Does it perform something like (assuming that x and y are positive integers): w = sign_of(x - y); if (w == 0) // expression is 'false' else if (w == 1) // expression is 'true' else // expression is 'false' Is there any reference for such information?

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• Simple Scala syntax - trying to define "==" operator - what am I missing?

  - by Alex R

  While experimenting with some stuff on the REPL, I got to a point where I needed something like this: scala class A(x:Int) { println(x); def ==(a:A) : Boolean = { this.x == a.x; } } Just a simple class with an "==" operator. Why doesn't it work??? Here's the result: :10: error: type mismatch; found : A required: ?{val x: ?} Note that implicit conversions are not applicable because they are ambiguous: both method any2ArrowAssoc in object Predef of type [A](x: A)ArrowAssoc[A] and method any2Ensuring in object Predef of type [A](x: A)Ensuring[A] are possible conversion functions from A to ?{val x: ?} class A(x:Int) { println(x); def ==(a:A) : Boolean = { this.x == a.x; } } ^ This is scala 2.8 RC1. Thanks

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• netbeans autocompletion when using singleton to retrieve object instead of new operator?

  - by fayer

  when i use the 'new' operator to instantiate a class, netbeans has no problem to autocomplete the members of the object. $instance = new Singleton(); $instance-> // shows test() method but when i use a singleton to retrieve an object it cannot autocomplete the members in the object retrieved. the getInstance code looks like this: public function test() { echo "hello"; } public static function getInstance() { if ( ! is_object(self::$_instance)) { self::$_instance = new self(); self::$_instance->initialize(); } return self::$_instance; } so i use: $instance = Singleton::getInstance(); $instance-> // no autocompletion! does anyone have the same problem? how do i work around it? thanks!

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• C# Bug or Brain Teaser? Cast working only with Coalesce (??) Operator

  - by Alex

  This is very strange, maybe someone can explain what's happening, or this is a bug (though I tend to think that this is probably just something intricate about C#). The following code throws the error "Cannot implicitly convert type 'uint?' to 'uint'.": public void Test(UInt32? p) { UInt32 x = p; } However, this code works without error: public void Test(UInt32? p) { UInt32 x = p ?? 1; } Huh? Why does this work? Why would the coalesce operator cause implicit conversion of UInt32? (nullable) to UInt32 (non-nullable), while the first error message says that there is no implicit conversion between those types?

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• C# string equality operator returns false, but I'm pretty sure it should be true... What?!

  - by Daniel Schaffer

  I'm trying to write a unit test for a piece of code that generates a large amount of text. I've run into an issue where the "expected" and "actual" strings appear to be equal, but Assert.AreEqual throws, and both the equality operator and Equals() return false. The result of GetHashCode() is different for both values as well. However, putting both strings into text files and comparing with DiffMerge tells me they're the same. Additionally, using Encoding.ASCII.GetBytes() on both values and then using SequenceEquals to compare the resulting byte arrays returns true. The values are 34KB each, so I'll hold off putting them here for now. Any ideas? I'm completely stumped.

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• How does C++ free the memory when a constructor throws an exception and a custom new is used

  - by Joshua

  I see the following constructs: new X will free the memory if X constructor throws. operator new() can be overloaded. The canonical definition of an operator new overload is void *operator new(heap h) and the corrisponding operator delete. The most common operator new overload is pacement new, which is void *operator new(void *p) { return p; } You almost always cannot call delete on the pointer given to placement new. This leads to a single question. How is memory cleaned up when X constructor throws and an overloaded new is used?

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• Template class + virtual function = must implement?

  - by sold

  This code: template <typename T> struct A { T t; void DoSomething() { t.SomeFunction(); } }; struct B { }; A<B> a; is easily compiled without any complaints, as long as I never call a.DoSomething(). However, if I define DoSomething as a virtual function, I will get a compile error saying that B doesn't declare SomeFunction. I can somewhat see why it happens (DoSomething should now have an entry in the vtable), but I can't help feeling that it's not really obligated. Plus it sucks. Is there any way to overcome this? EDIT 2: Okay. I hope this time it makes sence: Let's say I am doing intrusive ref count, so all entities must inherit from base class Object. How can I suuport primitive types too? I can define: template <typename T> class Primitive : public Object { T value; public: Primitive(const T &value=T()); operator T() const; Primitive<T> &operator =(const T &value); Primitive<T> &operator +=(const T &value); Primitive<T> &operator %=(const T &value); // And so on... }; so I can use Primitive<int>, Primitive<char>... But how about Primitive<float>? It seems like a problem, because floats don't have a %= operator. But actually, it isn't, since I'll never call operator %= on Primitive<float>. That's one of the deliberate features of templates. If, for some reason, I would define operator %= as virtual. Or, if i'll pre-export Primitive<float> from a dll to avoid link errors, the compiler will complain even if I never call operator %= on a Primitive<float>. If it would just have fill in a dummy value for operator %= in Primitive<float>'s vtable (that raises an exception?), everything would have been fine.

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• How to call operator<< on "this" in a descendant of std::stringstream?

  - by romkyns

  class mystream : public std::stringstream { public: void write_something() { this << "something"; } }; This results in the following two compile errors on VC++10: error C2297: '<<' : illegal, right operand has type 'const char [10]' error C2296: '<<' : illegal, left operand has type 'mystream *const ' Judging from the second one, this is because what this points at can't be changed, but the << operator does (or at least is declared as if it does). Correct? Is there some other way I can still use the << and >> operators on this?

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• C++ volatile required when spinning on boost::shared_ptr operator bool()?

  - by JaredC

  I have two threads referencing the same boost::shared_ptr: boost::shared_ptr<Widget> shared; On thread is spinning, waiting for the other thread to reset the boost::shared_ptr: while(shared) boost::thread::yield(); And at some point the other thread will call: shared.reset(); My question is whether or not I need to declare the shared pointer as volatile to prevent the compiler from optimizing the call to shared.operator bool() out of the loop and never detecting the change? I know that if I were simply looping on a variable, waiting for it to reach 0 I would need volatile, but I'm not sure if boost::shared_ptr is implemented in such a way that it is not necessary here.

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• Shortcut to get all private field names combined with && operator as a generated line of code?

  - by burak ozdogan

  Hi, Is it possible to use reflection when we write a code-template? I was just thinking if it is possible to write a piece of code-template that will return me a list of all private field in the class separated by && operator in Visual Stuudio? Let's say, I will enter "getAllPrivates&&" (or press a shortcut key) in the VS editor and it will return me something like this: private bool _privateFiel1 = false; private bool _privateFiel2 = true; private bool _privateFiel3 = false; private bool _privateFiel4 = false; private bool _privateFiel5 = true; // Here I press the shortcut or call the code-template and get his: _privateFiel1 && _privateFiel2 && _privateFiel3 && _privateFiel4 && _privateFiel5

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• How to implement copy operator for such C++ structure?

  - by Kabumbus

  So having struct ResultStructure { ResultStructure(const ResultStructure& other) { // copy code in here ? using memcpy ? how??? } ResultStructure& operator=(const ResultStructure& other) { if (this != &other) { // copy code in here ? } return *this } int length; char* ptr; }; How to implement copy? (sorry - I am C++ nube)

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• Is it possible to apply NOT(!) operator while DataBinding a property of a control ?

  - by Ashish Ashu

  I have Button control and I have to set the IsEanbled property based on the bool variable. bool IsBoolVariable I want if IsBoolVariable property is true then I want to set the IsEnabled property to false AND when IsBoolVariable property is false then I want to set the IsEnabled property to true. Is it possible to apply not(!) operator while defining the binding as given below <Button IsEnabled = "{Binding Path = **!**IsBoolVariable}" /> I can very well do that by applying convertors , but that is the only way to do that?

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• can I acces a struct inside of a struct without using the dot operator?

  - by yan bellavance

  I have 2 structures that have 90% of their fields the same. I want to group those fields in a structure but I do not want to use the dot operator to access them. The reason is I already coded with the first structure and have just created the second one. before: struct{ int a; int b; int c; object1 name; }str1; struct{ int a; int b; int c; object2 name; }str2; now I would create a third struct: struct{ int a; int b; int c; }str3; and would change the str1 and atr2 to this: struct{ str3 str; object1 name; }str1; struct { str3 str; object2 name; }str2; Finally I would like to be able to access a,b and c by doing: str1 myStruct; myStruct.a; myStruct.b; myStruct.c; and not: myStruct.str.a; myStruct.str.b; myStruct.str.c; Is there a way to do such a thing. The reason for doing this is I want keep the integrety of the data if chnges to the struct were to occur and to not repeat myself and not have to change my existing code and not have fields nested too deeply.

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• Does operator precedence in C++ differ for pointers and iterators?

  - by oraz

  The code below demonstrates this difference: #include <iostream> #include <string> int main() { char s[] = "ABCD"; std::string str(s); char *p = s; while(*p) { *p++ = tolower(*p); // <-- incr after assignment } std::cout << s << std::endl; std::string::iterator it = str.begin(), end = str.end(); while(it != end) { *it++ = tolower(*it); // <-- incr before assignment ? } std::cout << str << std::endl; return 0; } the code above outputs: abcd bcd if we separate assignment operation and increment operator: while(it != end) { *it = tolower(*it); // <-- incr before assignment ? it++; } the output will be as expected. What's wrong with the original code? $ g++ --version g++ (GCC) 3.4.4 (cygming special, gdc 0.12, using dmd 0.125) Copyright (C) 2004 Free Software Foundation, Inc.

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• C++ assignment operators dynamic arrays

  - by user2905445

  First off i know the multiplying part is wrong but i have some questions about the code. 1. When i am overloading my operator+ i print out the matrix using cout << *this then right after i return *this and when i do a+b on matix a and matix b it doesnt give me the same thing this is very confusing. 2. When i make matrix c down in my main i cant use my default constructor for some reason because when i go to set it = using my assignment operator overloaded function it gives me an error saying "expression must be a modifiable value. although using my constructor that sets the row and column numbers is the same as my default constructor using (0,0). 3. My assignment operator= function uses a copy constructor to make a new matrix using the values on the right hand side of the equal sign and when i print out c it doesn't give me anything Any help would be great this is my hw for a algorithm class which i still need to do the algorithm for the multiplying matrices but i need to solve these issues first and im having a lot of trouble please help. //Programmer: Eric Oudin //Date: 10/21/2013 //Description: Working with matricies #include <iostream> using namespace std; class matrixType { public: friend ostream& operator<<(ostream&, const matrixType&); const matrixType& operator*(const matrixType&); matrixType& operator+(const matrixType&); matrixType& operator-(const matrixType&); const matrixType& operator=(const matrixType&); void fillMatrix(); matrixType(); matrixType(int, int); matrixType(const matrixType&); ~matrixType(); private: int **matrix; int rowSize; int columnSize; }; ostream& operator<< (ostream& osObject, const matrixType& matrix) { osObject << endl; for (int i=0;i<matrix.rowSize;i++) { for (int j=0;j<matrix.columnSize;j++) { osObject << matrix.matrix[i][j] <<", "; } osObject << endl; } return osObject; } const matrixType& matrixType::operator=(const matrixType& matrixRight) { matrixType temp(matrixRight); cout << temp; return temp; } const matrixType& matrixType::operator*(const matrixType& matrixRight) { matrixType temp(rowSize*matrixRight.columnSize, columnSize*matrixRight.rowSize); if(rowSize == matrixRight.columnSize) { for (int i=0;i<rowSize;i++) { for (int j=0;j<columnSize;j++) { temp.matrix[i][j] = matrix[i][j] * matrixRight.matrix[i][j]; } } } else { cout << "Cannot multiply matricies that have different size rows from the others columns." << endl; } return temp; } matrixType& matrixType::operator+(const matrixType& matrixRight) { if(rowSize == matrixRight.rowSize && columnSize == matrixRight.columnSize) { for (int i=0;i<rowSize;i++) { for (int j=0;j<columnSize;j++) { matrix[i][j] += matrixRight.matrix[i][j]; } } } else { cout << "Cannot add matricies that are different sizes." << endl; } cout << *this; return *this; } matrixType& matrixType::operator-(const matrixType& matrixRight) { matrixType temp(rowSize, columnSize); if(rowSize == matrixRight.rowSize && columnSize == matrixRight.columnSize) { for (int i=0;i<rowSize;i++) { for (int j=0;j<columnSize;j++) { matrix[i][j] -= matrixRight.matrix[i][j]; } } } else { cout << "Cannot subtract matricies that are different sizes." << endl; } return *this; } void matrixType::fillMatrix() { for (int i=0;i<rowSize;i++) { for (int j=0;j<columnSize;j++) { cout << "Enter the matix number at (" << i << "," << j << "):"; cin >> matrix[i][j]; } } } matrixType::matrixType() { rowSize=0; columnSize=0; matrix = new int*[rowSize]; for (int i=0; i < rowSize; i++) { matrix[i] = new int[columnSize]; } } matrixType::matrixType(int setRows, int setColumns) { rowSize=setRows; columnSize=setColumns; matrix = new int*[rowSize]; for (int i=0; i < rowSize; i++) { matrix[i] = new int[columnSize]; } } matrixType::matrixType(const matrixType& otherMatrix) { rowSize=otherMatrix.rowSize; columnSize=otherMatrix.columnSize; matrix = new int*[rowSize]; for (int i = 0; i < rowSize; i++) { for (int j = 0; j < columnSize; j++) { matrix[i]=new int[columnSize]; matrix[i][j]=otherMatrix.matrix[i][j]; } } } matrixType::~matrixType() { delete [] matrix; } int main() { matrixType a(2,2); matrixType b(2,2); matrixType c(0,0); cout << "fill matrix a:"<< endl;; a.fillMatrix(); cout << "fill matrix b:"<< endl;; b.fillMatrix(); cout << a; cout << b; c = a+b; cout <<"matrix a + matrix b =" << c; system("PAUSE"); return 0; }

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• SQL SERVER – 5 Tips for Improving Your Data with expressor Studio

  - by pinaldave

  It’s no secret that bad data leads to bad decisions and poor results.  However, how do you prevent dirty data from taking up residency in your data store?  Some might argue that it’s the responsibility of the person sending you the data.  While that may be true, in practice that will rarely hold up.  It doesn’t matter how many times you ask, you will get the data however they decide to provide it. So now you have bad data.  What constitutes bad data?  There are quite a few valid answers, for example: Invalid date values Inappropriate characters Wrong data Values that exceed a pre-set threshold While it is certainly possible to write your own scripts and custom SQL to identify and deal with these data anomalies, that effort often takes too long and becomes difficult to maintain.  Instead, leveraging an ETL tool like expressor Studio makes the data cleansing process much easier and faster.  Below are some tips for leveraging expressor to get your data into tip-top shape. Tip 1:     Build reusable data objects with embedded cleansing rules One of the new features in expressor Studio 3.2 is the ability to define constraints at the metadata level.  Using expressor’s concept of Semantic Types, you can define reusable data objects that have embedded logic such as constraints for dealing with dirty data.  Once defined, they can be saved as a shared atomic type and then re-applied to other data attributes in other schemas. As you can see in the figure above, I’ve defined a constraint on zip code.  I can then save the constraint rules I defined for zip code as a shared atomic type called zip_type for example.   The next time I get a different data source with a schema that also contains a zip code field, I can simply apply the shared atomic type (shown below) and the previously defined constraints will be automatically applied. Tip 2:     Unlock the power of regular expressions in Semantic Types Another powerful feature introduced in expressor Studio 3.2 is the option to use regular expressions as a constraint.   A regular expression is used to identify patterns within data.   The patterns could be something as simple as a date format or something much more complex such as a street address.  For example, I could define that a valid IP address should be made up of 4 numbers, each 0 to 255, and separated by a period.  So 192.168.23.123 might be a valid IP address whereas 888.777.0.123 would not be.   How can I account for this using regular expressions? A very simple regular expression that would look for any 4 sets of 3 digits separated by a period would be:  ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ Alternatively, the following would be the exact check for truly valid IP addresses as we had defined above:  ^(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])$ .  In expressor, we would enter this regular expression as a constraint like this: Here we select the corrective action to be ‘Escalate’, meaning that the expressor Dataflow operator will decide what to do.  Some of the options include rejecting the offending record, skipping it, or aborting the dataflow. Tip 3:     Email pattern expressions that might come in handy In the example schema that I am using, there’s a field for email.  Email addresses are often entered incorrectly because people are trying to avoid spam.  While there are a lot of different ways to define what constitutes a valid email address, a quick search online yields a couple of really useful regular expressions for validating email addresses: This one is short and sweet:  \b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b (Source: http://www.regular-expressions.info/) This one is more specific about which characters are allowed:  ^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$ (Source: http://regexlib.com/REDetails.aspx?regexp_id=26 ) Tip 4:     Reject “dirty data” for analysis or further processing Yet another feature introduced in expressor Studio 3.2 is the ability to reject records based on constraint violations.  To capture reject records on input, simply specify Reject Record in the Error Handling setting for the Read File operator.  Then attach a Write File operator to the reject port of the Read File operator as such: Next, in the Write File operator, you can configure the expressor operator in a similar way to the Read File.  The key difference would be that the schema needs to be derived from the upstream operator as shown below: Once configured, expressor will output rejected records to the file you specified.  In addition to the rejected records, expressor also captures some diagnostic information that will be helpful towards identifying why the record was rejected.  This makes diagnosing errors much easier! Tip 5:    Use a Filter or Transform after the initial cleansing to finish the job Sometimes you may want to predicate the data cleansing on a more complex set of conditions.  For example, I may only be interested in processing data containing males over the age of 25 in certain zip codes.  Using an expressor Filter operator, you can define the conditional logic which isolates the records of importance away from the others. Alternatively, the expressor Transform operator can be used to alter the input value via a user defined algorithm or transformation.  It also supports the use of conditional logic and data can be rejected based on constraint violations. However, the best tip I can leave you with is to not constrain your solution design approach – expressor operators can be combined in many different ways to achieve the desired results.  For example, in the expressor Dataflow below, I can post-process the reject data from the Filter which did not meet my pre-defined criteria and, if successful, Funnel it back into the flow so that it gets written to the target table. I continue to be impressed that expressor offers all this functionality as part of their FREE expressor Studio desktop ETL tool, which you can download from here.  Their Studio ETL tool is absolutely free and they are very open about saying that if you want to deploy their software on a dedicated Windows Server, you need to purchase their server software, whose pricing is posted on their website. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• The SSIS tuning tip that everyone misses

  - by Rob Farley

  I know that everyone misses this, because I’m yet to find someone who doesn’t have a bit of an epiphany when I describe this. When tuning Data Flows in SQL Server Integration Services, people see the Data Flow as moving from the Source to the Destination, passing through a number of transformations. What people don’t consider is the Source, getting the data out of a database. Remember, the source of data for your Data Flow is not your Source Component. It’s wherever the data is, within your database, probably on a disk somewhere. You need to tune your query to optimise it for SSIS, and this is what most people fail to do. I’m not suggesting that people don’t tune their queries – there’s plenty of information out there about making sure that your queries run as fast as possible. But for SSIS, it’s not about how fast your query runs. Let me say that again, but in bolder text: The speed of an SSIS Source is not about how fast your query runs. If your query is used in a Source component for SSIS, the thing that matters is how fast it starts returning data. In particular, those first 10,000 rows to populate that first buffer, ready to pass down the rest of the transformations on its way to the Destination. Let’s look at a very simple query as an example, using the AdventureWorks database: We’re picking the different Weight values out of the Product table, and it’s doing this by scanning the table and doing a Sort. It’s a Distinct Sort, which means that the duplicates are discarded. It'll be no surprise to see that the data produced is sorted. Obvious, I know, but I'm making a comparison to what I'll do later. Before I explain the problem here, let me jump back into the SSIS world... If you’ve investigated how to tune an SSIS flow, then you’ll know that some SSIS Data Flow Transformations are known to be Blocking, some are Partially Blocking, and some are simply Row transformations. Take the SSIS Sort transformation, for example. I’m using a larger data set for this, because my small list of Weights won’t demonstrate it well enough. Seven buffers of data came out of the source, but none of them could be pushed past the Sort operator, just in case the last buffer contained the data that would be sorted into the first buffer. This is a blocking operation. Back in the land of T-SQL, we consider our Distinct Sort operator. It’s also blocking. It won’t let data through until it’s seen all of it. If you weren’t okay with blocking operations in SSIS, why would you be happy with them in an execution plan? The source of your data is not your OLE DB Source. Remember this. The source of your data is the NCIX/CIX/Heap from which it’s being pulled. Picture it like this... the data flowing from the Clustered Index, through the Distinct Sort operator, into the SELECT operator, where a series of SSIS Buffers are populated, flowing (as they get full) down through the SSIS transformations. Alright, I know that I’m taking some liberties here, because the two queries aren’t the same, but consider the visual. The data is flowing from your disk and through your execution plan before it reaches SSIS, so you could easily find that a blocking operation in your plan is just as painful as a blocking operation in your SSIS Data Flow. Luckily, T-SQL gives us a brilliant query hint to help avoid this. OPTION (FAST 10000) This hint means that it will choose a query which will optimise for the first 10,000 rows – the default SSIS buffer size. And the effect can be quite significant. First let’s consider a simple example, then we’ll look at a larger one. Consider our weights. We don’t have 10,000, so I’m going to use OPTION (FAST 1) instead. You’ll notice that the query is more expensive, using a Flow Distinct operator instead of the Distinct Sort. This operator is consuming 84% of the query, instead of the 59% we saw from the Distinct Sort. But the first row could be returned quicker – a Flow Distinct operator is non-blocking. The data here isn’t sorted, of course. It’s in the same order that it came out of the index, just with duplicates removed. As soon as a Flow Distinct sees a value that it hasn’t come across before, it pushes it out to the operator on its left. It still has to maintain the list of what it’s seen so far, but by handling it one row at a time, it can push rows through quicker. Overall, it’s a lot more work than the Distinct Sort, but if the priority is the first few rows, then perhaps that’s exactly what we want. The Query Optimizer seems to do this by optimising the query as if there were only one row coming through: This 1 row estimation is caused by the Query Optimizer imagining the SELECT operation saying “Give me one row” first, and this message being passed all the way along. The request might not make it all the way back to the source, but in my simple example, it does. I hope this simple example has helped you understand the significance of the blocking operator. Now I’m going to show you an example on a much larger data set. This data was fetching about 780,000 rows, and these are the Estimated Plans. The data needed to be Sorted, to support further SSIS operations that needed that. First, without the hint. ...and now with OPTION (FAST 10000): A very different plan, I’m sure you’ll agree. In case you’re curious, those arrows in the top one are 780,000 rows in size. In the second, they’re estimated to be 10,000, although the Actual figures end up being 780,000. The top one definitely runs faster. It finished several times faster than the second one. With the amount of data being considered, these numbers were in minutes. Look at the second one – it’s doing Nested Loops, across 780,000 rows! That’s not generally recommended at all. That’s “Go and make yourself a coffee” time. In this case, it was about six or seven minutes. The faster one finished in about a minute. But in SSIS-land, things are different. The particular data flow that was consuming this data was significant. It was being pumped into a Script Component to process each row based on previous rows, creating about a dozen different flows. The data flow would take roughly ten minutes to run – ten minutes from when the data first appeared. The query that completes faster – chosen by the Query Optimizer with no hints, based on accurate statistics (rather than pretending the numbers are smaller) – would take a minute to start getting the data into SSIS, at which point the ten-minute flow would start, taking eleven minutes to complete. The query that took longer – chosen by the Query Optimizer pretending it only wanted the first 10,000 rows – would take only ten seconds to fill the first buffer. Despite the fact that it might have taken the database another six or seven minutes to get the data out, SSIS didn’t care. Every time it wanted the next buffer of data, it was already available, and the whole process finished in about ten minutes and ten seconds. When debugging SSIS, you run the package, and sit there waiting to see the Debug information start appearing. You look for the numbers on the data flow, and seeing operators going Yellow and Green. Without the hint, I’d sit there for a minute. With the hint, just ten seconds. You can imagine which one I preferred. By adding this hint, it felt like a magic wand had been waved across the query, to make it run several times faster. It wasn’t the case at all – but it felt like it to SSIS.

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