understanding subnetting

(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

Understanding and simple implementation of Spring Aop, springaop understanding1. The Aspect-Oriented Programming mentioned in the AOP concept is actually a set of actions when processing a series of business logic. For example, to connect to the database: load the driver ----- get class -------- get the connection object ------- access the database ------ query --------- operation results for the above series of actions we regard the dotted line as a

Format:(function () {//code}) ();The first pair of parentheses of the enclosing function (function () {}) returns an unnamed function to the script, followed by a pair of empty parentheses that immediately execute the returned unnamed function, which is the parameter of the anonymous function in parentheses.(function (ARG) {alert (arg+100);}) (20);This example returns 120.Come back to see jquery plugin writing(function ($) { //Code Goes here}) (JQuery);This code is equivalent tovar A=functon ($

Recently, some good articles have been found on overseas websites, collected and sorted for your own understanding, recorded as notes, so that you can have memories in the future.ASP. NET is a very powerful platform for building Web applications. It provides great flexibility and capabilities so that it can be used to build all types of Web applications. most people are only familiar with high-level frameworks such as WebForms and WebServices. the. NE

, single-case1. Instance variable: the instance variable belongs to the class object, that is, the object instance is private and is allocated in the heap of the virtual machine.2. Verify thread security for instance variables:(1) From the program, we can see that when the singleton mode, there is a resource conflict, when not a singleton mode, there will not be a thread conflict.(2) Program operation result diagram:Figure 1:Figure 2:3, the conclusion: the instance variable is the instance objec

Last time is a note on a chat item, inside the socket is also involved in a lot. So what is a socket?The two programs on the network realize the exchange of data through a two-way communication connection, one end of this connection is called a socket.In layman's terms, I think it is a connector that connects the two. The English meaning of the socket is "hole" or "socket". He's the equivalent of that socket, connected to the communication between different virtual machines or different computer

(pSpatialFilter, True) Use Cursor to access records Now you have a good understanding of the general mechanism for generating cursor. Let's see how to use a cursor to access the returned records. Remember, cursor is a set of records from only one table or element class in memory. When a cursor is generated for the first time, an associated pointer is also generated. You can use a cursor to access a row of records at a time. This pointer helps you tra

The following things are not what I have created. They are the essence of some books I think. After learning about JavaScript, I feel that my understanding of JavaScript has been further improved, find out something that is also known as a trick or a trick. I will apply this knowledge to a new framework. The goal of the new framework is to use js to display various charts. Although there are already many frameworks with this function, however, I think

Understanding the emulator's limitations Although the new simulator keeps up with the development of devices and ensures high-fidelity simulation of devices and the convenience of developers, each simulator has some limitations when simulating real devices. The smartphone code run by the simulator in the smartphone SDK is compiled for the x86 CPU. In most major application development scenarios, this is enough to meet the requirements. However, this t

Coredata first class understanding coredata, coredata first class understandingProblem There are many ways to persistently store data in iOS/Mac: NSUserDefault, Key chain, C language file interface, NSFileHandle, write method in basic framework, archive, and so on. In practical applications, we often need to convert the data into objects in a certain format, and perform certain filtering and other operations before using them, which is not very conven

forced conversion operation to convert it to object. Forced conversion does not change B object, but your B object view limits the data and behavior to. After B is forcibly converted to a, the can be forcibly converted to B. If Class B is used as Class B, data and behavior of Class A and Class B can be obtained at the same time. Objects can represent multiple types of capabilities called polymorphism. by understanding these concepts, you can define

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