InnoDB实现序列化隔离级别的方法

ha_innobase::external_lock(...){... if (lock_type != F_UNLCK) { /* MySQL is setting a new table lock */... if (trx->isolation_level == TRX_ISO_SERIALIZABLE //序列化隔离级别  && m_prebuilt->select_lock_type == LOCK_NONE  && thd_test_options(thd, OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN)) { //且在一个显式事务块内部   /* To get serializable execution, we let InnoDB conceptually add 'LOCK IN SHARE MODE' to all SELECTs  which otherwise would have been consistent reads. An exception is consistent reads in the AUTOCOMMIT=1 mode:  we know that they are read-only transactions, and they can be serialized also if performed as consistent reads. */  m_prebuilt->select_lock_type = LOCK_S; //加读锁，即 'LOCK IN SHARE MODE'  m_prebuilt->stored_select_lock_type = LOCK_S; } //否则，不加锁（这一点也很重要）... } else { TrxInInnoDB::end_stmt(trx); DEBUG_SYNC_C("ha_innobase_end_statement"); }...}

ha_innobase::store_lock(... /* Check for FLUSH TABLES ... WITH READ LOCK */ if (trx->isolation_level == TRX_ISO_SERIALIZABLE) {  m_prebuilt->select_lock_type = LOCK_S;  m_prebuilt->stored_select_lock_type = LOCK_S; } else {  m_prebuilt->select_lock_type = LOCK_NONE;  m_prebuilt->stored_select_lock_type = LOCK_NONE; } ...}