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MySQL InnoDB Transaction isolation level dirty read, Repeatable read, phantom read MySQL InnoDB transactions are isolated at four levels. The default value is repeatable read ). · READUNCOMMITTED ). Another transaction modifies the data but has not yet committed it, And the SELECT statement in this transaction reads th

　　Main content:1. Initial file operation2. Read-only (R,RB)3. Write only (W,WB)4. Append (A, AB)5. Read and write (r+)6. Write-read (w+)7. Additional write read (A +)8. Other methods of operation9. File modification and another way to open a file handleA. Operation of the initial fileusing Python to

I. DATABASE TRANSACTION ISOLATION LEVELThere are 4 isolation levels for database transactions, from low to high, READ UNCOMMITTED,Read Committed,Repeatable read, andSerializable, which can be resolved individually by each of the four levels Problems such as dirty reading, non-repetition reading, and Phantom reading. √: May appear x: does not appear

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

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

Ext: http://blog.csdn.net/fatherican/article/details/44966921 1, Dirty Read One transaction reads another transaction, and the pending modification is dirty read. Here's the so-called modification, in addition to the update operation, do not forget, but also includeInsert and delete operations. Consequences of dirty reading: If the latter transaction is rolled back, all changes made to it will be revoked.

4 attributes of a database transaction:Atomicity (atomic): both succeed or fail;Consistency (consistency): After a transaction operation, the database is in the same state as the business rules; for example, after the A,b account transfers, the total amount remains unchanged;Isolation (Isolation): transactions in operations do not affect each other;Persistence (Durability): After a transaction is committed, it is persisted to the database. Dirty read,

Issues arising from transaction concurrency:Dirty reads: One transaction reads data that is not committed by another transactionTransaction 1: Updating a single piece of dataTransaction 2: Read record of transaction 1 updateTransaction 1: Commit commits are calledAt this point, the data read by transaction 2 is data stored in database memory, called dirty reads.The data

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. 2. Non-repeatable reads : Refers to the same data that is read multiple times within a transaction. When this transact