Table locks and row locks in MySQL: What types of locks are there in MySQL and what are their advantages and disadvantages?

Table locks and row locks in MySql: What types of locks are there in MySQL and what are their advantages and disadvantages

MySQL is an open source database software that provides support for many applications, including a large number of Management components and tools such as MySQL Workbench, etc. Locks in MySQL are crucial to ensuring system concurrency and data consistency. In MySQL, there are two types of locks: table locks and row locks. In this article, we will explore the lock types in MySQL, their respective advantages and disadvantages, and how they should be used to improve system performance.

1. Table lock

Table lock refers to locking the entire table and preventing other transactions from making changes to the table until the current transaction is completed. Table locks can be divided into shared locks and exclusive locks.

(1) Shared lock

Shared lock (also called read lock) refers to the locking of the table during read operations. After a transaction obtains a shared lock on a table, other transactions can still read the table, but cannot perform modification operations on the table until the transaction releases the lock. The counterpart to shared locks is exclusive locks.

The advantage of shared locks is that other transactions can still read the table without causing blocking. However, the disadvantage is that during the life cycle of the transaction holding the shared lock, other transactions cannot perform modification operations on the table, which may cause performance problems.

(2) Exclusive lock

Exclusive lock (also called write lock) refers to the locking of the table during write operations. When a transaction obtains an exclusive lock on a table, other transactions cannot read or write to the table until the transaction releases the lock. The counterpart to the exclusive lock is the shared lock.

The advantage of exclusive lock is that it can ensure the data consistency of write operations. However, the disadvantage is that when a transaction holds an exclusive lock, other transactions cannot read or write operations on the table, which will cause blocking.

2. Row lock

Row lock refers to the locking of a row when operating on it. Row locks can be divided into shared row locks and exclusive row locks.

(1) Shared row lock

Shared row lock (also called shared read lock) refers to the locking of a certain row during a read operation. When a transaction obtains a shared row lock on a row, other transactions can still read the row, but cannot write to the row until the transaction releases the lock.

The advantage of shared row locks is that the locking scope is reduced to the row level, and only the rows involved are restricted without affecting access to other rows. However, there is also the problem of blocking.

(2) Exclusive row lock

Exclusive row lock (also called exclusive write lock) refers to the locking of a certain row during a write operation. When a transaction obtains an exclusive row lock on a row, other transactions cannot read or write the row until the transaction releases the lock.

The advantage of exclusive row lock is that it can ensure the data consistency of write operations, but it also has the problem of blocking.

3. Selection of lock type

For different situations, different lock types should be selected.

(1) If the application has more read operations than write operations, shared locks should be used, because shared locks will not prevent other transactions from reading the table or rows.

(2) If the application has more write operations than read operations, exclusive locks should be used, because exclusive locks can ensure data consistency for write operations.

(3) If you only need to access tables or rows, you can use table locks, because table locks have smaller restrictions on operations than row locks.

(4) If you need to operate on a certain row, you can use row locks, because row locks have smaller restrictions on operations than table locks, and they will only restrict the rows involved and will not affect other OK.

To sum up, for the lock types in MySQL, you should choose the appropriate lock type according to the actual application scenario, and use locks reasonably to improve system performance and maintain data consistency.

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