idn locks

Shared lock (s lock ):If transaction t adds a shared lock to data a, other transactions can only add a shared lock to data a, but cannot apply an exclusive lock until all shared locks are released. Transactions authorized to share locks can only read data and cannot modify data.Exclusive lock (x lock ):If transaction t adds an exclusive lock to data a, other transactions cannot add any type of lock to aunti

Optimistic locks and pessimistic locks, optimistic locks pessimistic locks Locking) This concept has been touched upon when we learned multithreading. In fact, the lock here and the concurrent lock processing in multithreading are a truth. They all violently classify resources as their own. Here, we use

Update lost: New changes to overwrite first, the development of three ways to solve 1, raise the transaction level to the highest level transaction_serializable Both sides of the operation should raise the level; The query uses the shared lock; updates use the update lock; one query, one update, the shared lock and the update lock conflict; When both sides update the lock and a deadlock occurs, the program automatically rolls back one side of the operation to avoid the loss of the update 2, p

Page Level: Engine BDB.Table-level: Engine MyISAM, which is interpreted as locking the entire table and reading at the same time.Row-level: Engine INNODB, locking a single row of records At the table level, the entire table is locked directly. During the lock period, other processes cannot perform write operations on the table. If you are writing a lock, other processes are not allowed to read it.Row-level, which only locks specified records, so that

In computer science, a lock is a synchronization mechanism used to forcibly restrict access to resources in the execution of multiple threads, which is used to guarantee the satisfaction of mutex requirements in concurrency control. In the DBMS, database locks can be divided into row-level locks (InnoDB engines), table-level locks (MyISAM engines), and page-leve

MySQL row-level lock, table-level lock, page-level lock details page-level: engine BDB. Table-level: engine MyISAM, which is interpreted as locking the entire table and reading at the same time. Row-level: engine INNODB, locking a single row of records At the table level, the entire table is locked directly. during the lock period, other processes cannot perform write operations on the table. If you are writing a lock, other processes are not allowed to read it.Row-level, which only

MySQL row-level locks, table-level locks, page-level locks, mysql details Page Level: Engine BDB. Table-level: Engine MyISAM, which is interpreted as locking the entire table. It can be read at the same time but cannot be written at the row level. Engine INNODB locks a single row of records and directly

Page level: Engine BDB.Table level: Engine MyISAM, understood to lock the entire table, can be read at the same time, write notRow level: Engine INNODB, separate one-line record lock Table level, locking the entire table directly, and other processes cannot write to the table while you are locked out. If you are writing a lock, then the other processes are read and not allowedRow level, which locks only the specified record, so that other processes c

Overview of the LockWhy should I introduce a lock?Multiple users at the same timeThe concurrency of a database causes the following data inconsistencies:Missing updatesA,b two users read the same data and make changes, one of the user's changes to destroy the result of another change, such as booking systemDirty ReadA the user modified the data, then B users read out the data, but a user for some reason to cancel the modification of the data, data restore the original value, at this time the dat

　　In computer science, a lock is a synchronization mechanism used to forcibly restrict access to resources when executing multiple threads, which is used to guarantee the satisfaction of mutex requirements in concurrency control.In the DBMS, database locks can be divided into row-level locks (InnoDB engines), table-level locks (MyISAM engines), and page-level

operation by acquiring a lock to do the same data operation, which is similar to the Java synchronized, so pessimistic lock takes more time. In addition to the optimistic lock corresponding to the pessimistic lock is implemented by the database itself, to use, we directly call the database of related statements can be.Here, the two other lock concepts involved in the pessimistic lock come out, and they are shared locks and exclusive

In computer science, a lock is a synchronization mechanism used to forcibly restrict access to resources when executing multiple threads, which is used to guarantee the satisfaction of mutex requirements in concurrency control.As described in the lock mechanism of the database, the database locks can be divided into row-level locks (InnoDB engines), table-level locks