PostgreSQL: Vacuum Estimates and Semaphore Cleanup
Two unrelated changes landed, with no single pattern. Vacuum now excludes brand-new pages from row-count estimates to fix planner skew, backpatched through version 19, while support for named POSIX semaphores was removed as untested legacy code.
Duration: PT2M12S
Episode overview
This episode is a short developer briefing from PostgreSQL.
It explains recent repository work in plain language.
- Show: PostgreSQL
- Published: 2026-11-14T14:03:20Z
- Audio duration: PT2M12S
Transcript excerpt
This excerpt keeps the crawler page concise. Listen to the episode or use the RSS feed for the full update.
Hello, it's Saturday, November 14th, 2026, and this is your PostgreSQL developer briefing.
There is no single sweeping theme today — just two focused changes, with the most user-visible being a fix for how vacuum estimates table size.
First, vacuum accuracy. In commit 206e719, Melanie Plageman changed vacuum to exclude brand-new, never-written pages from its row-count estimates. The problem: vacuum always scans those new pages because they have no visibility map bits set, while it can skip pages already marked all-visible — especially now with…
Second, code simplification and maintainability. In commit 70c4a57, Tom Lane dropped support for named POSIX semaphores, the sem-open kind. That path dates to an older flexibility experiment and was once needed because it was the only standardized semaphore interface on macOS. But macOS has supported System V…
What's next: expect more stable planner statistics on backpatched branches without operational changes, and a slightly leaner, easier-to-test semaphore layer going forward.
That's your PostgreSQL update for today.
Nearby episodes from PostgreSQL
- Silent Correctness and Upgrade Reliability Fixes
- Stats, Planner and Replication Crash Fixes
- Silent Wrong-Result Fixes and Worker Reliability
- Composite Type Security Hardening
- Standby Inspection Guards and psql Interrupt Fix
- Weekly Recap - Reverts, Query Fixes, and Standby Safety
- JSON Revert and CI Overhaul
- Window Hangs, Planner Crashes and Replication Hardening