sqlite - WAL 同步正常与关闭

Question

在 WAL 的原始文档中，清楚地说明了 FULL 和 NORMAL 同步之间的区别 ¹ :

Write transactions are very fast since they only involve writing the content once (versus twice for rollback-journal transactions) and because the writes are all sequential. Further, syncing the content to the disk is not required, as long as the application is willing to sacrifice durability following a power loss or hard reboot. (Writers sync the WAL on every transaction commit if PRAGMA synchronous is set to FULL but omit this sync if PRAGMA synchronous is set to NORMAL.)

但是我在任何地方都找不到 WAL 模式下 PRAGMA synchronous = OFF 的效果。我怀疑它与NORMAL相同。有人有知情答案吗？

Answer 1

documentation还说:

In WAL mode when synchronous is NORMAL (1), the WAL file is synchronized before each checkpoint and the database file is synchronized after each completed checkpoint and the WAL file header is synchronized when a WAL file begins to be reused after a checkpoint.

所以使用OFF，对于正常交易没有区别，但是任何checkpoint会不安全。