使用 mysqldump 选项 --single-transaction

Question

在 InnoDB、MyISAM 等引擎的表格中。当我们将 mysqldump 与选项 --single-transaction 等一起使用时，该选项有什么用？即在这里查看代码。

/usr/bin/mysqldump -h ${HOST} -u${SOURCEUSER}  -p${SOURCEPASS} \
    --skip-add-drop-table -t --skip-lock-tables --single-transaction --skip-add-locks --complete-insert -q -e --skip-disable-keys \
    --where="ID=${ID}" \
    ${SOURCEDB} ${SOURCETABLE} | sed -e "s/INSERT INTO/REPLACE INTO/" | sed -e "s/${SOURCETABLE}/${TARGETTABLE}/g" |  /usr/bin/mysql -u${TARGETUSER} -p${TARGETPASS} ${TARGETDB} ;

求解释！谢谢！

Answer 1

直接引用自dev.mysql.com

This option sets the transaction isolation mode to REPEATABLE READ and sends a START TRANSACTION SQL statement to the server before dumping data. It is useful only with transactional tables such as InnoDB, because then it dumps the consistent state of the database at the time when START TRANSACTION was issued without blocking any applications.

如果您需要阅读更多：

When using this option, you should keep in mind that only InnoDB tables are dumped in a consistent state. For example, any MyISAM or MEMORY tables dumped while using this option may still change state.

While a --single-transaction dump is in process, to ensure a valid dump file (correct table contents and binary log coordinates), no other connection should use the following statements: ALTER TABLE, CREATE TABLE, DROP TABLE, RENAME TABLE, TRUNCATE TABLE. A consistent read is not isolated from those statements, so use of them on a table to be dumped can cause the SELECT that is performed by mysqldump to retrieve the table contents to obtain incorrect contents or fail.

The --single-transaction option and the --lock-tables option are mutually exclusive because LOCK TABLES causes any pending transactions to be committed implicitly.

To dump large tables, combine the --single-transaction option with the --quick option.

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使用 mysqldump 选项 --single-transaction

Use of mysqldump option --single-transaction

mysqldump