Home / Companies / ClickHouse / Blog / Post Details
Content Deep Dive

Read your writes: WAIT FOR in PostgreSQL 19

Blog post from ClickHouse

Post Details
Company
Date Published
Author
-
Word Count
1,395
Company Posts That Month
27
Language
English
Hacker News Points
-
Post removed?
No
Summary

PostgreSQL 19, currently in beta, adds the `WAIT FOR LSN` command to let sessions wait until write-ahead log progress reaches a specified location, enabling read-your-writes consistency on asynchronous replicas without requiring every primary commit to wait for replica replay. After a write, an application or intermediary can obtain the primary’s current WAL insert LSN and issue `WAIT FOR` on a standby before reading, ensuring the relevant changes have been replayed while avoiding application-side polling. The command supports replay, flush, and write wait modes, optional timeouts, and a `NO_THROW` option that returns statuses such as success, timeout, or not in recovery. It must be executed as a top-level, snapshot-free utility command because holding a snapshot while waiting could block WAL replay and create a self-deadlock. The feature preserves asynchronous write performance by imposing delay only on reads that require freshness, and it may be especially useful for connection poolers or protocol-aware proxies that can automatically track LSNs and route consistent reads to replicas.

Trends Found in this Post

No tracked trend matches for this post yet.

Use This Data

Use this post, company, and trend context to find content marketing opportunities, perform competitive analysis, or address product feature gaps via the Plushcap MCP server or the Plushcap API.