bug fix: stop all kinds of expressions from cnf-exploding

[systay]

Description

In a recent change (#14560) we fixed a bug in the CNF rewriter that stopped it from rewriting a lot of cases.
Unfortunately, we succeeded too well, and the newly rewritten expressions are timing out in expression fuzzing on CI. This is because CNF rewriting in some situations result in huge outputs (see Wikipedia)

This PR stops the rewriting once the produced expression has grown to 10 times the size of the original expression.

Related Issue(s)

Fixes #14569

Checklist

• "Backport to:" labels have been added if this change should be back-ported
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on the CI
• Documentation was added or is not required

[vitess-bot]

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[vmg]

I think we need to look at benchmarks for this @systay, the O complexity of this new code is pathological because after each rewrite, you need to walk the whole AST to count the nodes.

Since we control the rewrite patterns, I think it would be much more efficient to keep track of the amount of added & removed nodes during the rewrite. The tracking doesn't need to be fully accurate, just enough to detect unbounded growth, so it should be very easy to implement!

[systay]

I think we need to look at benchmarks for this @systay, the O complexity of this new code is pathological

Yeah, you are right. This was sloppy. I'll work on it

[vmg]

aaaah linear time

[vitess-bot]

Hello! 👋

This Pull Request is now handled by arewefastyet. The current HEAD and future commits will be benchmarked.

You can find the performance comparison on the arewefastyet website.