Macos querious 2 enum
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Only DML statements are transactional and can be rolled back. MariaDB will issue an error when trying to write data in the middle of a read-only transaction. This is a small performance optimization. Read-only transactions are also available using START TRANSACTION READ ONLY. Whether autocommit is enabled or not, we can start transactions explicitly, and they will not be automatically committed: START TRANSACTION īEGIN can also be used to start a transaction, but does not work in stored procedures. We can disable it, and manually commit transactions: SET SESSION autocommit = 0 No data access is possible outside a transaction.īy default autocommit is on, which means that the transaction is committed automatically after each SQL statement. The first read or write to an InnoDB table starts a transaction. It needs to perform a two-phase commit to be sure that changes to different tables are logged in the correct order. If the binary log is enabled, writing into different transactional storage engines in a single transaction, or writing into transactional and non-transactional engines inside the same transaction, implies some extra work for MariaDB.
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In case of a crash, committed data written into a transactional table can always be recovered, but this is not necessarily true for non-transactional tables.Data in transactional tables cannot be changed by other connections in the middle of a transaction, but data in non-transactional tables can.We will receive a warning `1196` which reminds us of this. In case of rollback, changes to non-transactional engines won't be undone.It is important to remember that non-transactional engines will have the following limitations: It is possible to write into transactional and non-transactional tables within a single transaction. The reason is that a metadata lock is acquired on the table for the duration of the transaction, so that ALTER TABLEs are queued. Writing into a non-transactional table in a transaction can still be useful. For MyRocks and TokuDB please check the proper KnowledgeBase sections. Most of the information in this page refers to generic MariaDB server behaviors or InnoDB. Most storage engines are not transactional, therefore they should not considered general purpose engines. Other transactional storage engines include MyRocks and TokuDB. The default storage engine, InnoDB, fully supports transactions. In MariaDB, transactions are optionally implemented by storage engines. Transactions, Storage Engines and the Binary Log These SQL Server features are not available in MariaDB: Note that XA transactions are handled in a completely different way and are not covered in this page.
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This page explains how transactions work in MariaDB, and highlights the main differences between MariaDB and SQL Server transactions.