Mvcc Memes

Posts tagged with Mvcc

Why Does Count (*) Take So Long When The Database Already Knows How Many Rows It Has? 🤔
Databases Backend Programming
2 months ago 60.7M views 0 shares
Why Does Count (*) Take So Long When The Database Already Knows How Many Rows It Has? 🤔
You'd think the database would just... know, right? Like it's literally keeping track of everything. But nope, your innocent COUNT(*) on a million-row table just triggered a full table scan that took 45 seconds. The database is out here counting every single row like a kindergartener learning numbers for the first time. Here's the kicker: most databases don't maintain an exact row count because of MVCC (Multi-Version Concurrency Control) and transaction isolation. Different transactions might see different row counts at the same time, so the database can't just keep one magical number. Instead, it has to actually count them all, respecting your WHERE clauses, deleted rows, and whatever chaos your concurrent transactions are causing. Fun times. Pro tip: If you need fast counts, either use approximations, maintain your own counter table, or just accept that coffee breaks are now a legitimate part of your query execution strategy. ☕

A Short Horror Story
Rust Databases Backend Programming
2 months ago 9.0M views 0 shares
A Short Horror Story
The absolute whiplash from "we're rewriting Postgres in Rust!" to "I look forward to death" in the span of 4 hours is peak developer energy. Rewriting one of the most battle-tested, production-critical databases in existence? Sure, sounds fun! Then reality hits: maintaining backward compatibility with decades of SQL quirks, implementing MVCC (Multi-Version Concurrency Control) from scratch, handling type systems, and oh yeah, making it live . That's when the existential dread kicks in. The "LLVM of databases" comment is particularly spicy—basically promising to create the foundational compiler infrastructure equivalent for databases. No pressure, just casually revolutionizing an entire industry while dealing with edge cases that have been accumulating since the 90s. Rust devs really do be announcing world-changing projects and then immediately regretting every life choice that led them there. The borrow checker can't save you from this one, buddy.