Why I don't trust AI with my query plans

Ashraf — Sat, 14 Feb 2026 10:26:55 +0000

I got tired of EXPLAIN tools that sent my query plans to AI services or hallucinated index suggestions. So I built something different.

The problem

Last month I was debugging a slow query at work. The EXPLAIN output was 400 lines of JSON. I tried three different "AI-powered" analyzers:

Two suggested adding an index that already existed
One hallucinated a table name that wasn't in my database

I just wanted to know: where did the time actually go?

The realization

Current tools fall into two camps:

AI wrappers – Send your plan to OpenAI, get generic advice.
Visualizers – Pretty graphs, but you still interpret them.

Neither tells you "4.5 seconds were spent in triggers, 0.03ms in the scan."

What I built

PlanCheck is a client-side PostgreSQL EXPLAIN analyzer with one rule: truth only.

No AI. No API calls. No "smart" suggestions.
100% client-side. Your query plans never leave the browser.
Hardcoded rules based on actual PostgreSQL behavior.

18 edge cases I tested

Issue	What it looks like
Trigger amplification	4.5s in triggers, 0.03ms in scan
JIT overhead	700ms compilation to save 100ms
Bitmap recheck failure	Index returns 15K rows, all discarded
Recursive CTE runaway	100K iterations with 99.9% filter rejection
Partition pruning failure	53M rows scanned, 1 returned
... plus 13 more	(too many to list, but you get the idea)

The technical challenge

Parsing EXPLAIN output in the browser sounds easy. It's not.

PostgreSQL has 40+ node types. Each has different fields, metrics, and edge cases. I had to handle:

TEXT format (messy indentation, inconsistent fields)
JSON with null values (missing timing data)
"Never executed" nodes that shouldn't be flagged
Deep nesting (4+ levels of nested loops)

All while keeping the bundle under 200KB.

What "truth only" actually means

When a tool suggests "add an index," it's guessing your intent. Maybe you want that full table scan for analytics. Maybe the index exists but PostgreSQL chose not to use it.

So PlanCheck only reports measurable facts:

"Scanned 1M rows sequentially"
"Trigger took 4.5s, scan took 0.03ms"
"Index returned 15k rows, recheck discarded all"

You decide what to fix.

Try it

plancheck.dev

Paste your EXPLAIN (ANALYZE, BUFFERS, FORMAT JSON) output. No signup. No data collection.

What should I add next?

I'm looking for edge cases I haven't tested yet. If you have a query plan that breaks it, I want to see it. Drop a comment or reach out!

DEV Community: Ashraf