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Dirty read (dirty read) unrepeatable read (phantom problem) Parsing1. Dirty read First, distinguish between dirty pages and dirty data Dirty pages are modified pages in the memory buffer pool. They are not flushed to the hard disk in time, but are already written to the redo log. It is normal to

Label:form of SQL Server data store Pre-read: Use the estimated information to go to the hard disk to read the data to the cache. Pre-read 100 times, which is estimated to read 100 pages of data from the hard disk to the cache. Physical reads: After the query plan is generated, if the cache is missing the

SQL Server logical read-pre-read-physical readHow SQL Server stores data 1. The page is the smallest operating unit, that is, read the database from disk at least one page, each page size is 8kb,sql server read to the page is atomic, either read a page, or completely unread,

1. Dirty read: Dirty read means that when a transaction is accessing data and modifying the data has not been committed to the database, another transaction also accesses the data, then the data is used. 2. Repeated read is not allowed.: Refers to reading the same data multiple times in a transaction. When the transaction is not completed, another transaction als

I. file read/write As mentioned above, stream reads and writes mainly include C ++ code 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 # Include # Include #

One, dirty reading, non-repeatable reading, Phantom reading 1, dirty read: Dirty read refers to when a transaction is accessing the data, and the data has been modified, and this modification has not been committed to the database, then another transaction also accesses the data, and then used this data.For example:Zhang San's salary was 5000 and transaction a changed his salary to 8000, but transaction a

Import Java.io.FileInputStream; Import Java.io.FileOutputStream; Import Java.io.InputStream; Import Org.apache.http.util.EncodingUtils; Import android.app.Activity; public class FileAccess {/** *, file access under Private folder (/data/data/package name/files) * * @param fileName * @param mess Age */public void Writefiledata (string fileName, String message) {try {FileOutputStream fou t = openfileoutput (fileName, mode_private); byte[] bytes = Message.getbytes ();

Comparison of VaR read/write and function read/write, get/set read/write Efficiency VaR is about 4 times faster than function, GET/set is similar to function 95VaR read: 567VaR write: 563[SWF] D: \ flexproject \ testspeed \ bin-Debug \ testspeed.swf-2,091 bytes after decompressionFunction

Tags: style class blog Code color data　DBCC Dropcleanbuffers -- empty cache SETSTATISTICSon -- Turn on IO statistics SELECT* from person -- query statement　　　　 Pre-read: Use the estimated information to go to the hard disk to read the data to the cache. Pre-read 100 times, which is estimated to read 100

Read all F = open ("Xi Yang", mode = "r", encoding = "UTF-8 ") Method 1: Read all at onceF = open ("Xi Yang", mode = "r", encoding = "UTF-8 ") Print (F. Read ()) Method 2: Read data in one row (determine the quantity and use for in iteration) F = open ("Xi Yang", mode = "r", encoding = "UTF-8 ") For line in F

Java Algorithm interview questions: Read all names from text files similar to the following, print duplicate names and repeated times, and sort by repeated times; read docx and read doc. Use the poi jar package to provide download, Read all names from text files similar to the following, print duplicate names and repea

Read Web page source code$curl = Curl_init ();curl_setopt ($curl, Curlopt_url, $url);curl_setopt ($curl, Curlopt_header, 1);curl_setopt ($curl, Curlopt_returntransfer, 1);curl_setopt ($curl, Curlopt_ssl_verifypeer, false);//This is the point.$contents = curl_exec ($curl);Export as TXT file$str = "ABCD";$FP =fopen ("Pic.txt", "w");Fputs ($fp, $STR);Fclose ($FP);Read tableRequire_once ' excel_reader2.php ';$d

———————————————————————————————————————————Read and write a string from a file (read/write directly/through Nsurl)#import int main (int argc, const char * argv[]) {@autoreleasepool {Writes a string directly to a file ***************NSString *str1=[[nsstring Alloc]init];[Email protected] "Lalalalala";Not through Nsurl, and directly to the string str1 write to an address file, as long as the creation of the c

PHP read the picture, read the bytes more than the actual bytes of the picture, read carefully the PHP manual self-Thinking code is no problem My code is as follows: $filepath = "C:\123.jpg"; $filesize =filesize ($filepath); $fs =fopen ($filepath, "R"); $readlen =1024;//How many bytes per read How many bytes

Because the version number is inconsistentPrompt after opening PD file:Click "OK" to open, click "Cancel" can not openHowever, after opening the modified save prompt:Workaround:The PDM file is actually an XML file that is opened directly with a text editor to modify the version numberChange the last version number of the root node to your PD version number and save it to open the edit.PD version Number View method: Open Pd>> help >> about PowerDesignerPowerDesigner Low version Open high version

Database transaction isolation level-dirty read, phantom read, non-repeated read, transaction level I. database transaction isolation level There are four database transaction isolation levels, from low to high: Read uncommitted, Read committed, Repeatable

Database transaction isolation level and dirty read, phantom read, non-repeated read, transaction level I. database transaction isolation level There are four database transaction isolation levels, from low to high: Read uncommitted, Read committed, Repeatable

I. Database transaction ISOLATION LEVEL There are 4 isolation levels for database transactions, from low to high to read uncommitted, Read committed, Repeatable read, and Serializable, which can solve the problems of dirty reading, non-repeatable reading, and Phantom reading one by one. √: May appear x: does not appear Dirty

1. Some problematic reads in the transaction: dirty read, non-repeatable read, Phantom readThe dirty read (Dirty Read) transaction T1 updated the contents of a row of records, but did not commit the changes. The transaction T2 reads the updated row, and then T1 performs the rollback operation, canceling the modificatio

Read fixed XML files: Set myxml = server. Createobject ("Microsoft. xmldom ")Myxml. Load (server. mappath ("test. xml "))Set myroot=myxml.doc umentelement. selectsinglenode ("Ao ")Dim lenth: lenth = myroot. childnodes. Length 'node countFor I = 0 to lenth-1Response. Write (myroot. childnodes. Item (I). Text)Next Set myroot = nothingSet myxml = nothing%> Read the XML returned by the URL