[MASSMAIL]Parallel Recovery in PostgreSQL

Hi, Hackers

I have observed that there has been a paucity of discussion concerning the parallel replay of WAL logs. 

The most recent discourse on this subject was during the PGCon event in 2023, where it was noted that PostgreSQL utilizes a single process for WAL replay. 

However, when configuring primary-secondary replication, there exists a tangible scenario where the primary accumulates an excessive backlog that the secondary cannot replay promptly.

This situation prompts me to question whether it is pertinent to consider integrating a parallel replay feature. 

Such a functionality could potentially mitigate the risk of delayed WAL application on replicas and enhance overall system resilience and performance.

I am keen to hear your thoughts on this issue and whether you share the view that parallel WAL replay is a necessity that we should collaboratively explore further.

Thank you for your attention to this matter.

Best regards,

David Fan