ledger locks

About innodb locks (record, gap, Next-Key lock) and innodbnext-key Record lock locks a single index record. Record lock always locks the index instead of the record itself, even if the table does not have any indexes, then innodb will create a hidden clustered primary key index in the background, and the lock is the hidden clustered primary key index. Therefore,

Why you need to use locks, of course, familiar with multi-threaded you, nature will not feel strange.Did you use the lock mechanism well in the code? Do you know several ways to implement locks?main.m 1 int main (int argc, const char * argv[]) {2 @autoreleasepool {3//common usage; you will see thread 1 lock, thread 2 waits until thread 1 executes, and thread 2 executes 4 NSLog (@ "Use Nslock (normal lock; i

Concurrent (thread-safe) issues arise when multiple processes or threads access the same resource at the same time (or in the same period). A lock can be used to resolve concurrency problems.Built-in lock for Java:Each Java object can be used as a lock that implements synchronization, which is called a built-in lock. When a thread enters a synchronous code block or method, the lock is automatically acquired, and the lock is freed when the synchronization code block or method exits. The only way

1.Lock interface locks are used to control how multiple threads access shared resources, in general, a lock prevents multiple threads from accessing shared resources concurrently (but some locks allow multiple threads to concurrently access shared resources, such as read-write locks). Before the lock interface appears, the Java program implements the lock functio

Label:1 years ago, I wrote an article in SQL Server why we need to update the lock. Today I want to continue this discussion, talk about intent locks in SQL Server, and why they are needed. lock hierarchy in SQL Server When I talk about lock escalation in SQL Server, I start with the lock level that SQL Server uses, when you read or modify your data. When you read a record, SQL Server requests a shared lock (S)by default, and when you modify a record

1. When manipulating DML (create,insert,update) statements, Oracle automatically adds row-level locks when the select * from table for update "of column" "Nowait|wait 3" Oracle also locks automaticallyRecommendation (1) nowait is generally added to the for update so that no other transaction is executed, and a transaction is determined and an error is thrown immediately.Recommendation (2) The general of col

: adaptive spin lock. That is, the first set up to spin 10 times, the result of the spin process successfully acquired the lock, then the next time can be set to the maximum spin 20 times. The truth is that if a lock can be released during spin, it is likely that this will happen the next time. Then it is more to give this lock some kind of "convenience" convenient it does not block lock (after all, a lot faster). Similarly, if the result of multiple attempts is completely unable to spin until t

); potential conflicts may occur between tables with few rows (although the fill factor [fillfactors] and the maximum number of rows per page [max_rows_per_page] can be used for specific addresses ); locks on both sides of each page are often separated. If a table is very small and resident on a single page, therefore, accessing a single row will actually destroy the locking mechanism for the entire table.Lock data onlyThe data locking mechanism is u

, clusters, tables, and databases.The lock types mainly include shared locks and exclusive locks.Special types of locks include intent locks, modification locks, and mode locks.The shared lock allows other transactions to continue to use the locked resources.The exclusive lock allows only one transaction to access data

SQL Server query performance optimization analysis transactions and locks (2 ). Step 1: Execute Example 2 and Example 3 code in the query analyzer. (This is the example in the previous article SQLSERVER query performance optimization analysis transactions and locks (2) -- Example 2 6 is locked by 53 SQL SERVER query performance optimization analysis transactions and lo