I m 研究并需要了解某种交易计划是否具有序列性。 我理解确定这一方法的方法,即把交易作为节点和节点,如果图表不准确,则该办法不能序列。 但是,这究竟是什么意思,什么决定从一个交易到另一个交易在图表中是否有直接优势? 此处的序列化是否与纸质物体的序列化相同?
感谢任何见解
交易序列化与物体序列化无关。 在全面实施后,可序列交易的单独程度确保,任何一套同时发生的可系列交易的行为都与(<>~>>>>(一时)序列执行顺序一致,因为交易是在某一时间进行的。 这意味着,如果你能够证明,单单单管理一个数据库的交易就能够做正确的事,那么它将在任何可序列交易组合中做正确的事,或者将重开序列的故障,以便从一开始便可以重新进行。
可通过多种方式实施可扩展的交易隔离。 最常见的办法是严格分两个阶段(S2PL)。 这一点非常普遍,你常常看到答案,只有从这种技术的角度来讨论问题。 也有令人乐观的一致控制(OCC)、可序列的光线隔离(SSI)和其他。
PostgreSQL versions before 9.1, MS SQL Server in some configurations, and all versions of Oracle don t actually provide serializable transactions. They let you ask for them, but actually provide snapshot isolation. PostgreSQL versions starting with 9.1 use SSI when serializable transaction isolation is requested.
不可能在SO的答复中彻底讨论这些技术如何发挥作用,而是总结上述技术:
S2 在交易中,笔记每份书面材料都获得一锁,不能与任何东西分享,交易中的每一份都获得一锁,可以与其他文本共享,但不能与书面共享。 阅读的锁必须涵盖扫描指数中的“gps”。 闭关时间一直到交易结束,随着交易工作在其他交易中明显可见而原封不动。 如果封锁造成循环,则称为“解除锁定”,循环所涉交易之一将退回。
在管理协委会下,一项交易跟踪其使用的数据,而不锁定数据。 在要求进行交易时,交易会检查任何其他交易是否修改了任何数据并作出了承诺。 如果是,承诺的请求失败了,工作则退缩。
根据职业安全倡议,各组别各行各行各业,但行文不打字,书写字不行。 正在跟踪阅读标准的依赖情况,以寻找可见度模式,从而在明显的执行顺序中形成一个周期。 如果发现“危险结构”,这意味着有可能按明显的执行顺序进行周期,则可能周期所涉的交易之一将予撤销。 该公司比S2PL更喜欢,但在较大的争论中则有这么多的退步。
Full disclosure: I teamed with Dan R.K. Ports of MIT to implement the new SSI-based serializable transactions in PostgreSQL 9.1.
Serialization means that transaction can be executed in a serial way, one after the other (nothing to do with object serialization), basically a transaction its serializable if regardless of the order these are interleaved the result will be as if they were executed in a serial way, if the graph its cyclic then it is not serializable and there is some risk of conflict, here is where your isolation level will help to decide wheter the transaction should be executed in a serial way, meaning first one and then the other or wheter it should try to execute it in an interleaved way hoping there is no conflicts. Its not a complete answer but i hope this will help.
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