脏写:基于某个未提交的数据进行写。 解决方法:与脏读一样,read committed以上,可见性判断要求xmin必须提交。 丢失更新:事务1,事务2同时修改某个元组。事务1先提交,事务2未基于事务1的提交进行修改,而是直接覆盖了。 解决方法:因为是多版本,所以一个事务只能更新一个版本的元组。对相同版本的元组进行更改,pg使用了...
PGPROC*proc=&allProcs[wakeidx]; wakeidx=pg_atomic_read_u32(&proc->procArrayGroupNext); pg_atomic_write_u32(&proc->procArrayGroupNext,INVALID_PGPROCNO); /* ensure all previous writes are visible before follower continues. */ pg_write_barrier(); proc->procArrayGroupMember=false; if(...
A friend recommended PGResource to us and we had our first meeting with the PGResource team online due to distance barrier, and I must say it was excellent because that barrier was broken and our three websites were delivered in a timely manner. We are very happy and satisfied with your ...
PG_THREAD_WAIT_STATUS allows you to test the block waiting status about the backend thread and auxiliary thread of the current instance.The waiting statuses in the wait_s
通过PG_THREAD_WAIT_STATUS视图可以检测当前实例中工作线程(backend thread)以及辅助线程(auxiliary thread)的阻塞等待情况。wait_status列的等待状态有以下状态。当wait_status为acquire lwlock、acquire lock或者wait io时,表示有等待事件。正在
=INVALID_PGPROCNO){intextraWaits=0;/* Sleep until the leader clears our XID. */for(;;){/* acts as a read barrier */PGSemaphoreLock(&proc->sem);if(!proc->procArrayGroupMember)break;extraWaits++;}Assert(pg_atomic_read_u32(&proc->procArrayGroupNext)==INVALID_PGPROCNO);/* Fix ...
今天我们来谈谈数据库的等待事件问题。等待事件是做性能优化、故障诊断的利器。Oracle数据库在7.3开始通过OWI提供了等待事件接口,自此开始,等待事件已经成为DBA分析数据库的最为重要的手段之一。 最近我一直在梳理PG及其相近与相兼容的数据库的等待事件,用于D-SMART的运维知识图谱之中。前阵子去阿布吉徒步,这个工作被耽搁...
pthread_barrier_t barrier; pthread_mutex_t sync_mutex; atomic_long nsSum; int sync_count; struct CacheLine { atomic_char atomics[CL_SIZE]; }; // this function used to get cache line size from runtime /* * unsigned int get_cache_line_size_x86() { ...
最近发现PG的等待事件的名称发生了一些变化,因此需要重新对相关的知识图谱进行更新。我们的知识图谱中,把PG以及衍生的数据库产品中的等待事件是作为相同的一类知识梳理的,因此在梳理过程中,合并了PG及其衍生数据库产品的等待事件,包括了近期大热的Gaussdb。Gaussdb对PG的等待事件扩展了很多,不过因为缺少实际案例和文档,很多...
Plant cell walls are the main physical barrier encountered by pathogens colonizing plant tissues. Alteration of cell wall integrity (CWI) can activate specific defenses by impairing proteins involved in cell wall biosynthesis, degradation and remodeling,