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PostgreSQL中的咨询锁范围

[英]Advisory locks scope in postgresql

原文 2017-06-06 03:46:40 8 1 postgresql

I am new to postgresql and trying to understand advisory locks. 我是Postgresql的新手，并试图了解咨询锁。 I have the following two scenarios: 我有以下两种情况：

With different databases in two different sessions: (Works in expected manner) 在两个不同的会话中使用不同的数据库：（按预期方式工作）
Session 1: SELECT pg_advisory_lock(1); 会话1： SELECT pg_advisory_lock(1); Successfully acquires the lock 成功获得锁
Session 2 (note in different database): SELECT pg_advisory_lock(1); 会话2（在不同数据库中的注释）： SELECT pg_advisory_lock(1); Successfully acquires the lock 成功获得锁
With Different Schemas in same database: When I do the same operation, the second 'session' blocks. 在同一数据库中使用不同的架构：当我执行相同的操作时，第二个“会话”将阻塞。

It appears that advisory locks operate at database level rather than (database and schema) combination. 咨询锁似乎在数据库级别而不是（数据库和架构）组合上运行。 Is my assumption correct or is there anything I am missing? 我的假设是正确的还是我缺少什么？

1 个解决方案

In postgres schema is a namespace. 在postgres模式中是一个名称空间。 More than just a prefix, but less than another database. 不仅仅是前缀，但少于另一个数据库。 in your case two, second session not "blocks", but rather is waiting as per docs : 在您的情况下，第二个会话不是“阻塞”，而是按照docs等待：

If another session already holds a lock on the same resource identifier, this function will wait until the resource becomes available. 如果另一个会话已经在同一资源标识符上持有锁，则此功能将等待直到资源可用为止。

Regarding successful locking on different databases: After you run SELECT pg_advisory_lock(1); 关于成功锁定不同数据库：运行SELECT pg_advisory_lock(1); checkout pg_locks , column objid 检出pg_locks ，列objid

OID of the lock target within its system catalog, or null if the target is not a general database object 锁定目标在其系统目录中的OID；如果目标不是通用数据库对象，则为null

So this number is per database - you can reference same 1 for many databases - those will be different OIDs. 因此，此数字是每个数据库的-您可以为多个数据库引用相同的1-这些将是不同的OID。