(I) A table has many duplicate values in a column. The base is very small. What indexes should be created?
-- Create a bitmap index. For details, see the comparison of the lock costs between B-tree indexes and bitmap indexes.
For example:
Create bitmap index idx_bm_product on products (list_price) tablespace users;
(Ii) the value of a column in a table is increasing all the time. It is not a random number. What index should I create?
-- Reverse index, that is, reversed Index
For example:
Cre
to put; Delete: Deletes a resource from the server. * * (3) * *. **uri**: A URI can be used to point to a resource, that is, each URI corresponds to a specific resource. To access this URI, the URI becomes the geology or identifier of each step of the resource. In general, each resource has at least one URI corresponding to it, and the most typical URI is the URL. * * (4) * *. * * Stateless * *: so-called non-state, which means that all resources can be located by URI, and that this location is
In the previous article, I wrote my understanding of float (1), which mainly describes the initial intention of float and some actual problems brought about by float. Smart CSS developers use the placeholder feature of CSS for layout, which has indeed achieved some good results,
But it also brings some practical problems. For exampleThere is no height after float, and the height is 0. Please pay attention to this phenomenon by the majority of CSS de
Filter chain understanding and Filter chain understandingI. Filter chain
Web. the filter is configured in xml, the init () method is executed during container startup, and the destroy () method is executed to destroy the filter when the container is closed, each time the server receives a request, it will first pass through the filter. If there is a suitable filter, it will execute the doFilter method of the corresponding filter.
The doFilter method h
reference value should be placed in the heap, and the original value should be put on the stack:Remember a word: energy is to keep the balance, is nothing more than time to change space, space for the question of timeHeap is larger than the stack, the stack is faster than the operation of the heap, the object is a complex structure, and can be freely extended, such as: The array can be infinitely expanded, the object can freely add properties. Put them in the heap in order not to affect the eff
*)/rigidbody.mass,forcemode.acceleration);
Forcemode.impulse. The entirety of the force vector supplied to the addforce call would be applied all at once, IM mediately.
forcemode.velocitychange. Like Forcemode.impulse except the object's mass is ignored. So the following lines give the same result:Rigidbody. Addforce ((Vector3.forward *), forcemode.impulse); Rigidbody. Addforce ((Vector3.forward *)/rigidbody.mass,forcemode.velocitychange);
I made a little test to verify. The script demonst
******" = ProxyFactory pf = pf. setInterfaces (target. getClass (). getInterfaces (); pf. setOptimize (); pf. setProxyTargetClass (); = 2, 3Implement pre-enhancement through Spring
The above uses ProxyFactory to create a proxy. Next we declare the proxy through Spring configuration.
In addition to the pre-enhancement BeforeAdvice, the post-enhancement AfterReturningAdvice, surround enhancement MethodInterceptor, and exception throw enhancement are also available.
ThrowsAdvice and IntroductionI
Understanding of the stack, heap, value type, and reference type in C #
1. What is the full name of GC? garbage collection, Chinese name garbage collection, is a function of. net for memory management. The garbage collector tracks and recycles the objects allocated in the managed memory, and periodically recycles the memory allocated to objects not effectively referenced. GC is automatically executed when the available memory cannot meet the memory re
Lucene In Action 1.5, a vast majority of translation and understanding, bilingual comparison■ IndexWriter
IndexWriter is the central component of the indexing process. This class creates
A new index and adds documents ents to an existing index. You can think of Index-
Writer as an object that gives you write access to the index but doesn't let you read
Or search it. Despite its name, IndexWriter isn't the only class that's used to modify
An index; sec
Article turn from: Uncle Tom-in-depth understanding of JavaScript series articlesIn-depth understanding of the JavaScript series, including the original, translation, reprint, collation and other types of articles, if it is useful to you, please recommend supporting a, to the power of the uncle writing.In-depth understanding of the JavaScript series (1): Basic po
In-depth understanding of the JavaScript series, including the original, translation, reprint, collation and other types of articles, if it is useful to you, please recommend supporting a, to the power of the uncle writing.In-depth understanding of the JavaScript series (1): Basic points for writing high-quality JavaScript codeIn-depth understanding of JavaScript
DescriptionThis tutorial bypassed some basic JavaScript syntax, directly explaining the two most difficult parts of JavaScript, and the two most significant differences from other mainstream object-oriented languages- prototypes and closures, and of course, the prototype chain and the scope chain. Help you uncover the most mysterious veil of JavaScript. Why do we have to talk about these two points of knowledge?This is my experience in learning JavaScript for so many years, the most difficult to
reader's point of view.Starting from mid-August to start thinking, write notes, check the relevant information, until September 17 began to formally write, to now finish, all the way down is not easy. I am not a professional writer, but also a complete spare time to do, is completely squeezed out. (This piece of paper is written before work today, get up a while). It's not easy. Also hope that we recommend more, more reproduced. There is a lot of trouble to communicate.Thx!In-depth
Https://www.cnblogs.com/xdp-gacl/p/4249939.htmlAloof, pale wolfOnly to find a way to succeed, not to find excuses for failure!Talking about the understanding of spring IOCPeople who have studied the spring framework will surely hear the two concepts of Spring's IOC (inversion of Control) and DI (Dependency injection), which, for beginners of spring, always feel that the two concepts of IOC and DI are ambiguous and difficult to understand. Today, we sh
Language is an important symbol of human being different from other animals. Natural language is an oral language (voice) and written language (writing) that distinguishes interpersonal communication from formal or artificial languages such as logical and programming languages. 1. Language and language understanding
Language is the natural medium for human communication, which includes oral and written language as well as body language (such as bookke
ObjectiveToday's JavaScript is a great way to rely on a wide range of applications. Web programmers have become accustomed to using a variety of excellent JavaScript frameworks to quickly develop WEB applications, ignoring the learning and deep understanding of native JavaScript. So, often the case is that many of the programmers who have done it for many years are always unclear about closures, functional programming, and prototypes, even if the fram
In-depth understanding of the JavaScript series, including the original, translation, reprint, collation and other types of articles, if it is useful to you, please recommend supporting a, to the power of the uncle writing.Reprinted: Uncle Tom Http://www.cnblogs.com/TomXu/archive/2011/12/15/2288411.htmlIn-depth understanding of the JavaScript series (1): Basic points for writing high-quality JavaScript code
"In-depth understanding of JavaScript Series" series of technical Articles to organize collectionsIn-depth understanding of the JavaScript series from Uncle Tom's finishing paste, the original address http://www.cnblogs.com/TomXu/archive/2011/12/15/2288411.html here for JavaScript learning reference1 in-depth understanding of JavaScript Series (1): Basic points f
In-depth understanding of the JavaScript series, including the original, translation, reprint, collation and other types of articles, if it is useful to you, please recommend supporting a, to the power of the uncle writing.In-depth understanding of the JavaScript series (1): Basic points for writing high-quality JavaScript codeIn-depth understanding of JavaScript
the process of understanding process scheduling and process switching during the time-tracking analysis process20135111 Li Guangji Original works reproduced please specify the source + "Linux kernel analysis" MOOC course http://mooc.study.163.com/course/USTC-1000029000I. Experimental requirements :1, the topic self-proposed, the content revolves on the process scheduling time and the process switch carries on;
2, can combine the key code, experime
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