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  • Inherit all methods of object (including "constructor"), but modify some of them.

    - by Kirzilla
    Hello, Let's imagine that we have object Animal $.Animal = function(options) { this.defaults = { name : null } this.options = $.extend(this.defaults, options); } $.Animal.prototype.saySomething = function() { alert("I'm animal!"); } Now I'd like to create Cat object. It is absolutely similar to $.Annimal, but method saySomething() will look like this one... $.Cat.prototype.saySomething = function() { alert("I'm cat!"); } How can I inherit from Animal to create new object Cat and redefine saySomething() method? Thank you.

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  • How to call constructor of the current class and parent class at the same time?

    - by Siegfried
    public class A{ public A(int a, int b) {...} } public class B : A{ List a; List b; public B(){...} //constructor1 public B(int a, int b) : base(a,b){...} //constructor2 } My question is I need to initialize both list a and b in class B. If I put them in the constructor1, how can I call constructor1 in constructor2? I don't want to rewrite the initialization statements in constructor2 again. Thanks!

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  • Removing empty space with jQuery after deleting Selectable item

    - by Tx3
    I have two ordered lists and user can move items between them. I am using jQuery UI's Selectable for both of them. Problem is that when I move item from the middle of the list it leaves an empty space behind. How can I make list shrink according to the how many items is actually in the list? HTML <ol id="allUnits"> <li class="ui-state-default">Item 1</li> <li class="ui-state-default">Item 2</li> <li class="ui-state-default">Item 3</li> <li class="ui-state-default">Item 4</li> <li class="ui-state-default">Item 5</li> </ol> <input id="arrowRight" type="image" alt="Move item to right" src="<%= Url.Content("~/Content/Images/arrowRight.png")%>" /> <input id="arrowLeft" type="image" alt="Move item to left" src="<%= Url.Content("~/Content/Images/arrowLeft.png")%>" /> <ol id="productUnits"> <li class="ui-state-default">Item 1</li> <li class="ui-state-default">Item 2</li> <li class="ui-state-default">Item 3</li> <li class="ui-state-default">Item 4</li> <li class="ui-state-default">Item 5</li> </ol> jQuery $().ready(function () { $("#allUnits").selectable(); $("#productUnits").selectable(); $('#arrowRight').click(function () { return !$('#allUnits .ui-selected').remove().appendTo('#productUnits').removeClass(".ui-selected"); }); $('#arrowLeft').click(function () { return !$('#productUnits .ui-selected').remove().appendTo('#allUnits').removeClass(".ui-selected"); }); });

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  • C# Virtual method call in constructor - how to refactor?

    - by Cristi Diaconescu
    I have an abstract class for database-agnostic cursor actions. Derived from that, there are classes that implement the abstract methods for handling database-specific stuff. The problem is, the base class ctor needs to call an abstract method - when the ctor is called, it needs to initialize the database-specific cursor. I know why this shouldn't be done, I don't need that explanation! This is my first implementation, that obviously doesn't work - it's the textbook "wrong way" of doing it. The overridden method accesses a field from the derived class, which is not yet instantiated: public abstract class CursorReader { private readonly int m_rowCount; protected CursorReader() { m_rowCount = CreateCursor(sqlCmd); //virtual call ! } protected abstract int CreateCursor(string sqlCmd); } public class SqlCursorReader : CursorReader { private SqlConnection m_sqlConnection; public SqlCursorReader(string sqlCmd, SqlConnection sqlConnection) { m_sqlConnection = sqlConnection; //field initialized here } protected override int CreateCursor(string sqlCmd) { //uses not-yet-initialized member *m_sqlConnection* //so this throws a NullReferenceException var cursor = new CustomCursor(sqlCmd, m_sqlConnection); return cursor.Count(); } } I will follow up with an answer on my attempts to fix this...

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  • How to expose a constructor variable(sic!) as read-only?

    - by Malax
    Hi StackOverflow! I have this rather simple question about Scala. Given that i have to following class definition: class Foo(var bar: Int) The code which is able to construct an instance of Foo must be able to pass the initial value for bar. But if I define bar as var the User is also able to change its value at runtime which is not what I want. The User should only be able to read bar. bar itself is modified internally so a val is not an option. I think I might be getting an answer very soon as this question is so simple. :-) Cheers, Malax

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  • Error No 150 mySQL

    - by buddhamagnet
    Hi all. This is making me sweat - I am getting error 150 when I try and create a table in mySQL. I've scoured the forums to no avail. The statement uses foreign key constraints - both tables are InnoDB, all relevant columns have the same data type and both tables have the same charset and collation. Here's the CREATE TABLE and the original CREATE TABLE statement for the table that's being referenced. Any ideas? New table: CREATE TABLE `approval` ( `rev_id` int(10) UNSIGNED NOT NULL, `rev_page` int(10) UNSIGNED NOT NULL, `user_id` int(10) UNSIGNED NOT NULL, `date` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, PRIMARY KEY (`rev_id`,`rev_page`,`user_id`), KEY `FK_approval_user` (`user_id`), CONSTRAINT `FK_approval_revision` FOREIGN KEY (`rev_id`, `rev_page`) REFERENCES `revision` (`rev_id`, `rev_page`), CONSTRAINT `FK_approval_user` FOREIGN KEY (`user_id`) REFERENCES `user` (`user_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; Referenced table: CREATE TABLE `revision` ( `rev_id` int(10) unsigned NOT NULL auto_increment, `rev_page` int(10) unsigned NOT NULL, `rev_text_id` int(10) unsigned NOT NULL, `rev_comment` tinyblob NOT NULL, `rev_user` int(10) unsigned NOT NULL default '0', `rev_user_text` varbinary(255) NOT NULL default '', `rev_timestamp` binary(14) NOT NULL default '\0\0\0\0\0\0\0\0\0\0\0\0\0\0', `rev_minor_edit` tinyint(3) unsigned NOT NULL default '0', `rev_deleted` tinyint(3) unsigned NOT NULL default '0', `rev_len` int(10) unsigned default NULL, `rev_parent_id` int(10) unsigned default NULL, PRIMARY KEY (`rev_id`), UNIQUE KEY `rev_page_id` (`rev_page`,`rev_id`), KEY `rev_timestamp` (`rev_timestamp`), KEY `page_timestamp` (`rev_page`,`rev_timestamp`), KEY `user_timestamp` (`rev_user`,`rev_timestamp`), KEY `usertext_timestamp` (`rev_user_text`,`rev_timestamp`) ) ENGINE=InnoDB AUTO_INCREMENT=4904 DEFAULT CHARSET=binary MAX_ROWS=10000000 AVG_ROW_LENGTH=1024;

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  • What happens if a bean attempts to load the Spring application context in its constructor?

    - by Derek Mahar
    Given the following Spring application context and class A, what happens when you run class A? applicationContext.xml (in classpath): <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"> <bean name="a" class="A"/> </beans> A.java: class A { private ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); public static void main(String[] args) { A a = new A(); } }

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  • Is is possible to intercept a constructor on a class you do not own?

    - by code poet
    Referring to my possible answer to this question: http://stackoverflow.com/questions/2907535/how-would-you-audit-asp-net-membership-tables-while-recording-what-user-made-the/2911616#2911616 Is it possible to intercept a call, coming from code you do not own, to a ctor on a sealed internal class that you do not own with the intention of manipulating the object before returning? Concrete example: SqlMembershipProvider, for all of it's data access, instantiates a connection helper class, System.Web.DataAccess.SqlConnectionHolder. The desired result is to intercept this instantiation and perform an operation on the public connection that is opened in the ctor of System.Web.DataAccess.SqlConnectionHolder before letting execution continue. Is this possible. If so, an brief example would be appreciated.

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  • No "redefinition of default parameter error" for class template member function?

    - by STingRaySC
    Why does the following give no compilation error?: // T.h template<class T> class X { public: void foo(int a = 42); }; // Main.cpp #include "T.h" #include <iostream> template<class T> void X<T>::foo(int a = 13) { std::cout << a << std::endl; } int main() { X<int> x; x.foo(); // prints 42 } It seems as though the 13 is just silently ignored by the compiler. Why is this? The cooky thing is that if the template declaration is in Main.cpp instead of a header file, I do indeed get the default parameter redefinition error. Now I know the compiler will complain about this if it were just an ordinary (non-template) function. What does the standard have to say about default parameters in class template member functions or function templates?

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  • Problem with number/type of arguments passed to an overloaded c++ constructor wrapped with swig.

    - by MiKo
    I am trying to wrap a c++ class (let's call it "Spam") written by someone else with swig to expose it to Python. After solving several problems, I am able to import the module in python, but when I try to create an object of such class I obtain the following error: foo = Spam.Spam('abc',3) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "Spam.py", line 96, in __init__ this = _Spam.new_Spam(*args) NotImplementedError: Wrong number of arguments for overloaded function 'new_Spam'. Possible C/C++ prototypes are: Spam(unsigned char *,unsigned long,bool,unsigned int,SSTree::io_action,char const *) Spam(unsigned char *,unsigned long,bool,unsigned int,SSTree::io_action) Spam(unsigned char *,unsigned long,bool,unsigned int) Spam(unsigned char *,unsigned long,bool) Spam(unsigned char *,unsigned long) Googling around, I realized that the error is probably caused by the type of the arguments and not by the number (which is quite confusing), but I still cannot identify. I suspect the problem lies in passing a string as the first argument, but have no idea on how to fix it (keep in mind that I know almost no c/c++).

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  • How to ensure that a member variable is initialized before calling a class method

    - by Omkar Ekbote
    There's a class with a parametrized constructor that initializes a member variable. All public methods of the class then use this member variable to do something. I want to ensure that the caller always creates an object using the parametrized constructor (there is also a setter for this member variable) and then call that object's methods. In essence, it should be impossible for the caller to call any method without setting a value to the member variable (either by using the parametrized constructor or the setter). Currently, a caller can simply make an object using the default constructor and then call that object's method - I want to avoid checking whether or not the member variable is set in each and every one of the 20-odd methods of the class (and throw an exception if it is not). Though a runtime solution is acceptable (better than the one I mentioned above); a compile-time solution is preferable so that any developer will not be allowed to make that mistake and then waste hours debuggging it!

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  • How can one enforce calling a base class function after derived class constructor?

    - by Mike Elkins
    I'm looking for a clean C++ idiom for the following situation: class SomeLibraryClass { public: SomeLibraryClass() { /* start initialization */ } void addFoo() { /* we are a collection of foos */ } void funcToCallAfterAllAddFoos() { /* Making sure this is called is the issue */ } }; class SomeUserClass : public SomeLibraryClass { public: SomeUserClass() { addFoo(); addFoo(); addFoo(); // SomeUserClass has three foos. } }; class SomeUserDerrivedClass : public SomeUserClass { public: SomeUserDerrivedClass() { addFoo(); // This one has four foos. } }; So, what I really want is for SomeLibraryClass to enforce the calling of funcToCallAfterAllAddFoos at the end of the construction process. The user can't put it at the end of SomeUserClass::SomeUserClass(), that would mess up SomeUserDerrivedClass. If he puts it at the end of SomeUserDerrivedClass, then it never gets called for SomeUserClass. To further clarify what I need, imagine that /* start initialization */ acquires a lock, and funcToCallAfterAllAddFoos() releases a lock. The compiler knows when all the initializations for an object are done, but can I get at that information by some nice trick?

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  • Can I set NHibernate's default "OrderBy" to be "CreatedDate" not "Id"?

    - by Chris F
    This is an oddball question I figure. Can I get NHibernate to ask SQL to sort data by CreatedDate by default unless I set an OrderBy in my HQL or Criteria? I'm interested in knowing whether this sort can be accomplished at the DB level to avoid bringing in LINQ. The reason is that I use GUIDs for Ids and when I do something like this: Sheet sheet = sheetRepository.Get(_someGUID); IList<SheetLineItems> lineItems = sheet.LineItems; to fetch all of the lineItems, they come back in whatever arbitrary way that SQL sorts that fetch, which I figure is GUID. At some point I'll add ordinals to my line items, but for now, I just want to use CreatedDate as the sort criteria. I don't want to be forced to do: IList<SheetLineItem> lineItems = sheetLineItemRepository.GetAll(_sheetGUID); and then writing that method to sort by CreatedDate. I figure if everything is just sorted on CreatedDate by default, that would be fine, unless specifically requested otherwise.

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  • Why "constructor-way" of declaring variable in "for-loop" allowed but in "if-statement" not allowed?

    - by PiotrNycz
    Consider this simple example: /*1*/ int main() { /*2*/ for (int i(7); i;){break;} /*3*/ if (int i(7)) {} /*4*/ } Why line-2 compiles just fine, whilst line-3 gives the error? This is little strange to me why if-statement is in this aspect treated worse than for-loop? If this is compiler specific - I tested with gcc-4.5.1: prog.cpp: In function 'int main()': prog.cpp:3:7: error: expected primary-expression before 'int' prog.cpp:3:7: error: expected ')' before 'int' I was inspired by this question [UPDATE] I know this compiles just fine: /*1*/ int main() { /*2*/ for (int i = 7; i;){break;} /*3*/ if (int i = 7) {} /*4*/ }

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  • How to overwrite a convenience constructor the proper way?

    - by mystify
    For example I want to overwrite from UIButton: + (id)buttonWithType:(UIButtonType)buttonType So I would do: + (id)buttonWithType:(UIButtonType)buttonType { UIButton *button = [UIButton buttonWithType:buttonType]; if (button != nil) { // do own config stuff ... } return button; } is that the right way? Or did I miss something? (yeah, I have been overwriting thousands of instance methods, but never class methods ;) )

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  • C++ Pass a hidden arg to a class constructor?

    - by JP
    I would like to define a class that accept the pointer to it's parent class as an Argument, but would it be possible to somehow pass it without needing to pass it directly such as: class Child { public: Child(Parent* hiddenArg); }; class Parent { public: Child myChild; }; I know this is weird, but I am making my own Signal/Slot implementation and Child would be a signal defined, but I would like to get the parent so I can use it's Event Dispatcher...

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  • Retrieve nested list from XDocument with LINQ

    - by twreid
    Ok I want my link query to return a list of users. Below is the XML <section type="Users"> <User type="WorkerProcessUser"> <default property="UserName" value="Main"/> <default property="Password" value=""/> <default property="Description" value=""/> <default property="Group" value=""/> </User> <User type="AnonymousUser"> <default property="UserName" value="Second"/> <default property="Password" value=""/> <default property="Description" value=""/> <default property="Group" value=""/> </User> </section> And my current LINQ Query that doesn't work. doc is an XDocument var users = (from iis in doc.Descendants("section") where iis.Attribute("type").Value == "Users" from user in iis.Elements("User") from prop in user.Descendants("default") select new { Type = user.Attribute("type").Value, UserName = prop.Attribute("UserName").Value }); This does not work can anyone tell me what I need to fix? Here is my second attempt after fixing for the wrong property name. However this one does not seem to enumerate the UserName value for me when I try to use it or at least when I try to write it to the console. Also this returns 8 total results I should only have 2 results as I only have 2 users. (from iis in doc.Descendants("section") where iis.Attribute("type").Value == "Users" from user in iis.Elements("User") from prop in user.Descendants("default") select new { Type = user.Attribute("type").Value, UserName = (from name in prop.Attributes("property") where name.Value == "UserName" select name.NextAttribute.Value).ToString() });

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  • phpMyAdmin "No database selected" MySQL

    - by user1751660
    I downloaded a MySQL backup file and promptly imported into MAMP's phpMyAdmin. I got this return: Error SQL query: -- -- Database: `mysql` -- -- -------------------------------------------------------- -- -- Table structure for table `columns_priv` -- CREATE TABLE IF NOT EXISTS `columns_priv` ( `Host` CHAR( 60 ) COLLATE utf8_bin NOT NULL DEFAULT '', `Db` CHAR( 64 ) COLLATE utf8_bin NOT NULL DEFAULT '', `User` CHAR( 16 ) COLLATE utf8_bin NOT NULL DEFAULT '', `Table_name` CHAR( 64 ) COLLATE utf8_bin NOT NULL DEFAULT '', `Column_name` CHAR( 64 ) COLLATE utf8_bin NOT NULL DEFAULT '', `Timestamp` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP , `Column_priv` SET( 'Select', 'Insert', 'Update', 'References' ) CHARACTER SET utf8 NOT NULL DEFAULT '', PRIMARY KEY ( `Host` , `Db` , `User` , `Table_name` , `Column_name` ) ) ENGINE = MYISAM DEFAULT CHARSET = utf8 COLLATE = utf8_bin COMMENT = 'Column privileges'; MySQL said: #1046 - No database selected I did not alter the .sql file at all. Any hints on how i can get this puppy going locally? Thanks!

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  • How to change class name of a button

    - by stackOver Flow
    I have four buttons like this <div class="btn-group"> <button id="btn-men" class="btn btn-default active" i18n:translate="men">Men</button> <button id="btn-women" class="btn btn-default" i18n:translate="women">Women</button> <button id="btn-kids" class="btn btn-default" i18n:translate="kids">Kids</button> </div> And I have different css styles for the class "btn btn-default active" and "btn btn-default". what I want to know is if there is any way of changing the class name of the clicked button as btn btn-default active from btn btn-default and also change the unclicked button as btn btn-default during run time. I also use i18n for mulitilingual purpose.

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  • How to check whether a default browser is opened in the operating system (Java)?

    - by stempel1984
    Hi, I am newbie here. During my work, I faced an interesting problem. I need to: check whether a default html browser is opened; check whether the browser is minimized/maximized (simply, a window's state); get an url address typed in the browser. If any of these conditions is not met, I have to open the browser in a maximized view with a desired url address. I primarily wanted to do all this in Java, but it came to my mind that I should employ many techniques/technologies and combine them appropriately to complete the functionality. But, which ones? That's the problem. I just recalled Windows API, but I'm not sure if it is of any help... Some users on another forum suggested that I should consider JNI (no experience at all)... I only know how to open a default browser (e.g. with use of the 'browse(URI uri)' method of the 'java.awt.Desktop' class) - that's too little to be proud of. Please give me some hints, maybe links to reasonable discussions, I would greatly appreciate any suggestions how to approach the problem.

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  • Auto DOP and Concurrency

    - by jean-pierre.dijcks
    After spending some time in the cloud, I figured it is time to come down to earth and start discussing some of the new Auto DOP features some more. As Database Machines (the v2 machine runs Oracle Database 11.2) are effectively selling like hotcakes, it makes some sense to talk about the new parallel features in more detail. For basic understanding make sure you have read the initial post. The focus there is on Auto DOP and queuing, which is to some extend the focus here. But now I want to discuss the concurrency a little and explain some of the relevant parameters and their impact, specifically in a situation with concurrency on the system. The goal of Auto DOP The idea behind calculating the Automatic Degree of Parallelism is to find the highest possible DOP (ideal DOP) that still scales. In other words, if we were to increase the DOP even more  above a certain DOP we would see a tailing off of the performance curve and the resource cost / performance would become less optimal. Therefore the ideal DOP is the best resource/performance point for that statement. The goal of Queuing On a normal production system we should see statements running concurrently. On a Database Machine we typically see high concurrency rates, so we need to find a way to deal with both high DOP’s and high concurrency. Queuing is intended to make sure we Don’t throttle down a DOP because other statements are running on the system Stay within the physical limits of a system’s processing power Instead of making statements go at a lower DOP we queue them to make sure they will get all the resources they want to run efficiently without trashing the system. The theory – and hopefully – practice is that by giving a statement the optimal DOP the sum of all statements runs faster with queuing than without queuing. Increasing the Number of Potential Parallel Statements To determine how many statements we will consider running in parallel a single parameter should be looked at. That parameter is called PARALLEL_MIN_TIME_THRESHOLD. The default value is set to 10 seconds. So far there is nothing new here…, but do realize that anything serial (e.g. that stays under the threshold) goes straight into processing as is not considered in the rest of this post. Now, if you have a system where you have two groups of queries, serial short running and potentially parallel long running ones, you may want to worry only about the long running ones with this parallel statement threshold. As an example, lets assume the short running stuff runs on average between 1 and 15 seconds in serial (and the business is quite happy with that). The long running stuff is in the realm of 1 – 5 minutes. It might be a good choice to set the threshold to somewhere north of 30 seconds. That way the short running queries all run serial as they do today (if it ain’t broken, don’t fix it) and allows the long running ones to be evaluated for (higher degrees of) parallelism. This makes sense because the longer running ones are (at least in theory) more interesting to unleash a parallel processing model on and the benefits of running these in parallel are much more significant (again, that is mostly the case). Setting a Maximum DOP for a Statement Now that you know how to control how many of your statements are considered to run in parallel, lets talk about the specific degree of any given statement that will be evaluated. As the initial post describes this is controlled by PARALLEL_DEGREE_LIMIT. This parameter controls the degree on the entire cluster and by default it is CPU (meaning it equals Default DOP). For the sake of an example, let’s say our Default DOP is 32. Looking at our 5 minute queries from the previous paragraph, the limit to 32 means that none of the statements that are evaluated for Auto DOP ever runs at more than DOP of 32. Concurrently Running a High DOP A basic assumption about running high DOP statements at high concurrency is that you at some point in time (and this is true on any parallel processing platform!) will run into a resource limitation. And yes, you can then buy more hardware (e.g. expand the Database Machine in Oracle’s case), but that is not the point of this post… The goal is to find a balance between the highest possible DOP for each statement and the number of statements running concurrently, but with an emphasis on running each statement at that highest efficiency DOP. The PARALLEL_SERVER_TARGET parameter is the all important concurrency slider here. Setting this parameter to a higher number means more statements get to run at their maximum parallel degree before queuing kicks in.  PARALLEL_SERVER_TARGET is set per instance (so needs to be set to the same value on all 8 nodes in a full rack Database Machine). Just as a side note, this parameter is set in processes, not in DOP, which equates to 4* Default DOP (2 processes for a DOP, default value is 2 * Default DOP, hence a default of 4 * Default DOP). Let’s say we have PARALLEL_SERVER_TARGET set to 128. With our limit set to 32 (the default) we are able to run 4 statements concurrently at the highest DOP possible on this system before we start queuing. If these 4 statements are running, any next statement will be queued. To run a system at high concurrency the PARALLEL_SERVER_TARGET should be raised from its default to be much closer (start with 60% or so) to PARALLEL_MAX_SERVERS. By using both PARALLEL_SERVER_TARGET and PARALLEL_DEGREE_LIMIT you can control easily how many statements run concurrently at good DOPs without excessive queuing. Because each workload is a little different, it makes sense to plan ahead and look at these parameters and set these based on your requirements.

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