PostgreSQL通常使用checkpoint进程来清理一些废弃的文件,对于wal文件来说,会在checkpoint时生成一些备用的wal文件或者清理旧的不使用的wal文件,且看相关配置[GUC2]。注意此处描述的为7.1版本的情况,一些参数已经不适用于最新的PostgreSQL版本。 WAL_FILES 在7.1版本的PostgreSQL中,wal_files参数如果大于0,在做检查点时会预先...
* If a WAL record modifies any relation files, in ways not covered by the * usual block references, this flag is set. This is not used for anything * by PostgreSQL itself, but it allows external tools that read WAL and keep * track of modified blocks to recognize such special record t...
postgresql中数据处理过程中的位置只有内存和WAL中,在内存中的整个page中己包含更新提交的也包含没有提交的,如果不将整个page写入WAL中,在介质恢复的时候WAL中记录的数据不足以实现完整的恢复(说白了就是无法实现介质恢复时事务的回滚),写入整个page。 说到这里似乎更明白了,postgresql中不存在类似oracle的undo文件,pos...
Transactions' commits and aborts — since a change of the status is done in XACT buffers and it also takes some time for the change to get to disk. File operations (creation and deletion of files and directories, such as creation of files during creation of a table) — since these operat...
PostgreSQL备机在回放主机的WAL日志过程中,由于回放较慢会导致pg_control文件中checkpoint timestamp远远小于备机自身时间(和checkpoint中的时间戳一致),PostgreSQL备机pg_control文件的checkpoint记录的位点是从主机传过来WAL里面的checkpoint记录位置,由此可见备机pg_control文件中checkpoint相关字段是来自于PostgreSQL主机的check...
postgresql 手动清理wal日志的101个坑 新年的第一天,总结下去年遇到的关于WAL日志清理的101个坑,以及如何相对安全地进行清理。前面是关于WAL日志堆积的原因分析,清理相关可以直接看第三部分。 首先说明,手动清理wal日志是一个高风险的操作,尤其对于带主从的生产大库,能不用尽量不要用。
认识PostgreSQL WAL(1) WAL is an acronym of Write Ahead Logging, which is a protocol or a rule to write both changes and actions into a transaction log, whereas in PostgreSQL, WAL is an acronym of Write Ahead Log. There the term is used as synonym of transaction log, and also used to...
PostgreSQL backup tool Usage:wal-g [command]Available Commands:backup-fetch Fetches a backup from ...
在PostgreSQL 12中,WAL归档是通过将WAL文件复制到归档目录中来实现的。WAL文件可以被恢复,使得在数据库损坏或故障时能够恢复至最新可恢复状态。以下是实现这项任务的代码示例: 在postgresql.conf中设置归档目录: archive_mode = on archive_command = 'cp %p /path/to/archive/%f' 创建归档目录: mkdir /path/to...
I have a PostgreSQL cluster binary backup and set of WAL files. I would like to perform PITR but first I need to find the point where I need to restore to. So I need to find a particular transaction LSN or XID number which later I'm goin to use as recovery_target. Could you...