Postgresql 中文操作指南

77.3. Backup Manifest WAL Range Object #

描述 WAL 范围的对象始终具有三个键：

The object which describes a WAL range always has three keys:

  • Timeline

    • The timeline for this range of WAL records, as an integer.

  • Start-LSN

    • The LSN at which replay must begin on the indicated timeline in order to make use of this backup. The LSN is stored in the format normally used by PostgreSQL; that is, it is a string consisting of two strings of hexadecimal characters, each with a length of between 1 and 8, separated by a slash.

  • End-LSN

    • The earliest LSN at which replay on the indicated timeline may end when making use of this backup. This is stored in the same format as Start-LSN.

通常，只有一个 WAL 范围。但是，如果备份是从备用数据库获取的，该备份在备份期间由于上游晋升而切换时间线，则可能存在多个范围，每个范围具有不同的时间线。同一时间线永远不会有多个 WAL 范围。

Ordinarily, there will be only a single WAL range. However, if a backup is taken from a standby which switches timelines during the backup due to an upstream promotion, it is possible for multiple ranges to be present, each with a different timeline. There will never be multiple WAL ranges present for the same timeline.