Darling test flake: the 27 MB auto-parameterized plan timing test goes over its limit on a busy runner #5561

A Darling timing test failed in CI by going over its time limit. The test is SensitiveStatementAutoParamTests.Measure_PassOne_27MbPlan_NoHit_AndWithAThousandAutoParameterizedStatements. It does not touch the code the PR changed.

Seen in a pull request's Darling PG shard 5 on 2026-10-08 (1 of 4969 failed, Assert.True() Failure). The same day the class also failed once on a developer machine while other classes ran, and passed when run alone (44 of 44).

The test checks that one pass over a 27 MB plan with a thousand auto-parameterized statements stays under a fixed time. On a busy runner that limit is tight.

To fix: keep what the test proves (one pass, no hit, the scale it states), but make the limit hold on a loaded runner. Measure the pass the way the other timing pins in the suite do, or derive the limit from a baseline taken in the same run. Do not just raise the number, and keep every existing check. Show the old limit failing under load and the new one holding.

Claude posting for Erik Darling.