in the home directory (recommended)log in to your user (non-root) and enter in the terminal:$ sudo gedit ~/.profile (or. bashrc)the following settings can be added to the path at the end of this file:export path= "$PATH: Your path1:your path2 ..."Save the file, log off and log in, and the variable takes effect. variables added in this way are valid only for the current user. method Two: The profile file under the system directory (caution)in the system's etc directory, there is a profile file t
A friend wants to introduce the filter vanishing point. Vanishing point Baidu has a lot of tutorials. The vanishing point filter is a feature that allows you to perform perspective correction edits in an image that contains a perspective plane (for example, the side of a building or any rectangular object). By using vanishing points, you can specify a plane in the image, and then apply edits such as paintin
changes made by the first editor. This problem can be avoided if the second editor is able to make changes after the first editor finishes.
2. Dirty reading means that when a transaction is accessing the data and the data has been modified and the modification has not been submitted to the database, another transaction accesses the data and then uses the data. Because this data is not yet submitted data, then another transaction read the data is dirty data, the operation based on dirty data ma
use of macros is very convenient:
: QX
Start recording macros and save results to register X
Q
Exit record mode
@x
Play macro commands that are recorded in the X register
To give a little explanation, when you enter in normal mode: After QX, all your edits to the text will be recorded, re-enter Q to exit the recording mode, and then enter @x to repeat the command you just recorded, which can
Advanced Editor, will contain macro features, Vim is certainly not missing, in Vim, the use of macros is very convenient:
: QX starts recording macros and stores the results in register X
Q Exit Record mode
@x play the Macro command recorded in the X register
To explain a little bit, when you enter in normal mode: QX, all your edits to the text will be recorded, then enter Q again to exit the recording mode.
Type, and then enter @x to repeat the com
Vs2008 can ctrl+alt+m+ (1/2/3/4) Memory window, ctrl+alt+r Register window, ctrl+alt+d assembly window,
can also debug--"Window--> memory to choose
View----Other windows----Command WindowStart debugging first, then enter memoryFor more commands:Command name alias full namePrint? Debug printingFast surveillance?? Debugging. Rapid MonitoringAdd new project Addproj file. Add New ProjectAliases alias Tool. AliasThe Auto window Autos debugging. Automatic window"Breakpoints" window BL debugging
HDFS Distributed Storage systems (delivers high reliability, high scalability and high throughput data storage services) HDFS Advantages: High fault tolerant data automatically save multiple copies, after the loss of replicas, automatic recovery for batch processing mobile computing rather than data, data location exposed to the computing framework for large data processing can be built on the cheap machine HDFS Disadvantage: Low latency data access such as millisecond, low latency and high thro
provider. (This type of cursor is powerful and also consumes the most system resources.) Dynamic cursors can see all the changes they have saved the collection of records. Users with dynamic cursors can see edits, additions, and deletions made by other users. If the data provider allows this type of cursor, it supports this visibility by fetching data from the data source every once in a while. There is no doubt that this will require a lot of resour
This article is partially transferred from Hadoop 2.0 NameNode HA and Federation practicesThis article is part of a tutorial on automatic ha+federation+yarn configuration in detail hadoop2
A Hadoop 20 HA implementation 1 uses shared storage to synchronize the edits information between two NN 2 Datanode hereinafter referred to as DN simultaneously to two NN reporting block information 3 Failovercontroller process for monitoring and controlling the NN p
. Profile or. bashrc file in the home directory (recommended)
Log in to your user (non-root) and enter in the terminal:
$ sudo gedit ~/.profile (or. bashrc)
The following settings can be added to the path at the end of this file:
Export path= "$PATH: Your path1:your path2 ..."
Save the file, log off and log in, and the variable takes effect.
Variables added in this way are valid only for the current user.
Method Two: The profile file under the system directory (caution)
In the system's etc
the best query evaluation scheme in detail. The general idea is that the fewer scenarios the optimizer investigates, the less time it takes to compile a query. On the other hand, because the optimizer skipped some scenarios, it might miss the best scenario.The optimizer's behavior with regard to the evaluation of the number of scenarios can be controlled by two system variables:· The Optimizer_prune_level variable tells the optimizer to skip some scenarios based on an estimate of the number of
Distributed File System HDFS-namenode architecture namenode
Is the management node of the entire file system.
It maintains the file directory tree of the entire file system [to make retrieval faster, this directory tree is stored in memory],
The metadata of the file/directory and the data block list corresponding to each file.
Receives user operation requests.
Hadoop ensures the robustness of namenode and is not prone to death. the file directory tree and the metadata of the file/directory are s
the Django model, you can directly manipulate the database table structure, etc.Open account/models.py, create an account modelaccount = models.CharField(max_length=64, blank=True, verbose_name=‘用户名‘)Account: Field nameModels. Charfield: Specifies that the field type is char, corresponding to the database is varcharMax_length: is the field lengthBlank: Whether it can be emptyVerbose_name: Control is the display of the background listIn addition, the common field options areNull: If the value of
SublimeText shortcut keys
1. Editing)
Basic Editing)
Paste into sequence →, not KJHL, (yes, I am talking about Vim, Nima is also better than WSAD), paste cut copy are consistent with the system.
Ctrl + Enter Add a row under the current row and then jump to the row; Ctrl + Shift + Enter Add a row above the current row and jump to the row.
Ctrl + ←/→ move words by word. Ctrl + Shift + ←/→ select words by word.
Ctrl + ↑/↓ Move the current display area, Ctrl + Shift + ↑/↓ Move the current row.
Se
After one week of recruitment and a trial release of the topic, the working framework of the blog Park journal team has been basically set up. During this period, I received high support from enthusiastic netizens and would like to express my gratitude to you. Through the trial of the first topic, we have received a lot of enthusiastic feedback on the number of pages of journals, the layout of articles, and the difficulty of selecting materials. I sincerely accept your criticism. After several
namenode, a cold backup of NameNode, and merges fsimage and fsedits and sends them to namenode.
DataNode: Slave node, Slave, working. Stores block data sent from the client and reads and writes data blocks.
Hot Backup: B is a hot backup, if a is broken. Then B immediately runs the work that replaces.
Cold backup: B is a cold backup, if a breaks down. B cannot replace a immediately. However, B stores some information about a to reduce the loss after a is broken.
Fsimage: Metadata image file (dir
Sed command details,1. Introduction
Sed is a non-interactive editor. It does not modify the file unless you use shell redirection to save the results. By default, all output rows are printed to the screen.
Sed editor processes files (or inputs) row by row and sends the results to the screen. The specific process is as follows: first, sed stores the currently being processed rows in a temporary cache (also known as the mode space), and then processes the rows in the temporary buffer, then, send t
(M_hookhelper = = null)M_hookhelper = new Hookhelperclass ();M_hookhelper.hook = Hook;}Occurs when the this command is clickedpublic override void OnClick (){IMapControl3 Mapcontrol = null;Get the Mapcontrol from the hook with the container is a Toolbarcontrolif (M_hookhelper.hook is Itoolbarcontrol){Mapcontrol = (IMapControl3) ((Itoolbarcontrol) m_hookhelper.hook). Buddy;}In case the container is Mapcontrolelse if (M_hookhelper.hook is IMapControl3){Mapcontrol = (IMapControl3) M_hookhelper.hoo
Sed command learning Notes 1. sed introduction sed is a non-interactive editor. It does not modify the file unless you use shell redirection to save the results. By default, all output rows are printed to the screen. Sed editor processes files (or inputs) row by row and sends the results to the screen. Detailed process... sed command learning Notes 1. sed introduction sed is a non-interactive editor. It does not modify the file unless you use shell redirection to save the results. By default, al
In an HA cluster, two separate machines are configured to become a namenode. At any moment, only one namenode is active and the other is standby state. The active Namenode is responsible for all request operations from the client, while standby is ready to become active namenode on standby.To maintain synchronization between Namenode active and Namenode standby, two namenode are synchronized through a daemon called journalnodes. When Namenode active namespace has been modified, Namenode active l
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