问题描述
XID和TX列中的分数代表什么.这是postgres的pgadmin工具的屏幕截图.
What does the fractions in column XID and TX stand for. This is a screenshot of the postgres's pgadmin tool.
我知道TX和XID分别表示事务和事务ID，但是我不明白分数符号的含义.
I understand that TX and XID mean transaction and transaction ID respectively, however I don't understand what the fraction notation means.
推荐答案
虚拟事务ID为"n/nnnn"格式.实际的XID只是整数.虚拟xid的第一部分是每个连接唯一的后端标识符.第二部分是该连接的后端为其交易分配的临时交易ID.
Virtual transaction IDs have the "n/nnnn" format. Real XIDs are just integers. The first part of the virtual xid is a backend identifier that's unique to each connection; the second part is a temporary transaction id assigned by that connection's backend for its transactions.
有关详细信息，请参见src/include/storage/lock.h中VirtualTransactionId的定义.
See the definition of VirtualTransactionId in src/include/storage/lock.h for details.
这些列似乎与pg_locks中的virtualxid和/或transactionid和virtualtransaction列相对应.参见文档.
Those columns appear to correspond to the virtualxid and/or transactionid and virtualtransaction columns in pg_locks. See the docs.
如果我说的没错，那么:
If I'm correct in that then:
- "TX"是持有或等待锁定的交易的虚拟交易ID.
- "XID"是等待交易所针对的交易的虚拟交易ID(如果目标是虚拟xid).在PgAdmin中，如果它是正常的xid，它也可能会显示目标的xid.
虚拟事务ID是PostgreSQL在事务开始时分配给每个事务的临时瞬态事务ID.它们没有记录在磁盘上.仅当事务执行需要对磁盘进行事务性写入的操作时，才分配实际xid.
Virtual transaction IDs are temporary, transient transaction IDs that PostgreSQL allocates to every transaction at transaction start. They aren't recorded on disk. A real xid is only allocated when the transaction does something that requires a transactional write to disk.
根据链接的手册:
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