BEGIN语句开始一个新的事务,COMMIT语句提交当前事务,并将其更改持久保存到数据库中,ROLLBACK语句撤消当前事务中的所有更改。 以下是一个示例,展示如何使用事务来插入数据到数据库中: BEGIN;INSERTINTOusers (name, email)VALUES('John Doe','johndoe@example.com');INSERTINTOord
postgres=# begin; BEGIN 或者 postgres=# begin TRANSACTION ; BEGIN 也可以定义事务的级别。 postgres=# begin transaction isolation level read committed ; BEGIN 提交事务 进程#1访问。 postgres=# begin; BEGIN postgres=# delete from tdsql_pg where id=5; DELETE1 postgres=# postgres=# select * from ...
事务块流转状态变为TBLOCK_SUBBEGIN; 【CommitTransactionCommand】:完成收尾工作,在顶层内存事务内存上下文申请新的CurTransactionContext,记录在CurrentTransactionState->curTransactionContext和全局变量CurTransactionContext中。 1.2 执行ROLLBACK TO SAVEPOINT my_savepoint; 【DDL】:标记事务块状态。 【CommitTransactionComma...
postgresql transaction的rollback方法 PostgreSQL Transaction Rollback Method Introduction: In PostgreSQL, a transaction is a sequence of SQL statements that are executed as a single unit. It allows you to group multiple database operations together and treatthem as a single atomic operation. If any ...
The raw parsing stage is sufficient to identify the transaction control commands (BEGIN, ROLLBACK, etc), and these can then be correctly executed without any further analysis. Once we know that we are dealing with an actual query (such as SELECT or UPDATE), it is okay to start a ...
Rollback Prevention of XID As mentioned above, thelatest transaction number minuses oldest transaction numbermust be less than 2^31. Otherwise, rollback will occur, and the data generated by the old transaction will not be visible to the new transaction.How does the kernel avoid this problem?
The point of this example is to demonstrate the need for StartTransactionCommand and CommitTransactionCommand to be state smart – they should call CommandCounterIncrement between the calls to BeginTransactionBlock and EndTransactionBlock and outside these calls they need to do normal start, commit ...
SECURITY DEFINER specifies that the procedure is to be executed with the privileges of the user that owns it. A SECURITY DEFINER procedure cannot execute transaction control statements (for example, COMMIT and ROLLBACK, depending on the language). ...
A writer thread sets ExclusiveLock on its transactionid. All row level lock waiters set ShareLock. The lock manager resumes all previously locked backend locks as soon as the writer releases the lock. Lock release for transactionid occurs on commit or rollback. pg_stat_activity Another great ...
CREATE TRIGGER PreventTableDrop ON DATABASE FOR DROP_TABLE AS BEGIN RAISERROR ('Tables can't be dropped in this database', 16, 1) ROLLBACK TRANSACTION END; Test the trigger by attempting to drop a table. DROP TABLE [Invoices]; GO ...