PasteThePlan has a new AI Suggestions tab, and it’s been really fun to watch the query plans come in and the advice go out. Here are some examples:

• Date “tables” – when I looked at the query, I glossed over the real problem. I thought arc_Calendar was a real date table, but AI figured out that it’s actually generated on the fly with spt_values, something that blows my mind at what an incredibly bad idea that is. It never crossed my mind that someone would even consider doing this in production, and AI tells them what to do instead.
• This is fine – someone asked for advice on a select from a 1-row temp table. AI said get outta here with that nonsense.
• One-table delete – but due to foreign keys, it’s actually touching multiple tables. The AI advice explains what’s going on and how to make it go faster, plus boils it down to “if you only do one thing” – I love that! I love prioritized advice.
• Reporting process – a kitchen-sink style query that at first glance should probably be rewritten to dynamic SQL, but they’ve already solved that to some extent by slapping an option recompile hint on it. The AI advice catches a scalar UDF causing problems, suggests a rewrite using a technique the company’s already using on another column, and suggests a slight rewrite to push filtering earlier. Again, I love its recap here, all for free, in less than 30 seconds.
• Lengthy paged dynamic SQL – ugh, even just glancing at this makes me look at the clock to think about how long it would take me to analyze. In seconds, AI reasoned over this monster to suggest indexes that would help the paging, plus raises some eyebrows at a weird not-exists-not-exists design.
• Meaningful function rewrites – advice to quickly and easily change non-sargable functions into index seeks, and remove a correlated subquery.

Advice I’m not as wild about, and I’m thinking about how to tune the AI prompt in order to improve it:

• 16,000 row export with no WHERE clause – my first reaction here is to say, “Whoa now, we don’t tune for 16,000-row XML export queries.” However, when it comes to tuning the prompt to deliver better advice, I think we need to push the user harder to copy/paste in actual execution plans that include timing information, and then evaluate whether we should bother making changes, or whether the query’s performing good enough based on the wild output we’re asking for. This Power BI query is a similar example – whenever I see scientific notation for the estimated number of rows, I wanna stop tuning there and go get the actual plan.
• Covering indexes galore – this is just one example, but my first iteration on my AI prompt didn’t discourage covering indexes, and AI seems to really wanna suggest ’em. I need to refine the prompt to suggest starting indexes with just the keys, and then only add includes for covering if the query’s still not fast enough after the initial indexes. There also seems to be a hesitance to recommend clustered indexes on heaps, even reporting heaps that were just created for the purpose of the query we’re looking at.
• Lose the cursor – I’m surprised at how often I’ve seen folks paste cursor plans in. I do love the advice – it’s always “hey lose the cursor” – but I think we could do better. I’d like to be able to proactively rewrite stuff for folks, but realistically, a web page isn’t the best UI for that, and it will probably need a better, slower model with a >30 second timeout. We need to tell people, “Here’s a link to a set of commands that will rewrite the query for you” – whether that’s Claude Code, ChatGPT Codex, the plain chat interface for those tools, or something else.

And some queries & advice are just making me think. For example, in this multi-step reporting query, the AI seemed to find a lot of advice, but to understand if the advice is any good, I kinda want a followup status report from the user. Did they implement any of these fixes? Which ones? What kinds of differences did they see? We probably need a feedback loop of some kind to help iterate over the AI prompt.

I’m not delusional enough to think PasteThePlan.com is the right long-term solution for getting plan advice! We only have about 50 people using it each weekday. However, if that helps 50 people per day avoid posting questions to forums, and get instant answers that solve their problems for free and make users happier, then I’m very happy with that result. I couldn’t possibly answer 50 peoples’ query questions per day for free in my spare time!