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Correct the interaction between overheating and offset-based paging

Authored by epriestley on Aug 22 2019, 3:16 AM.



Ref T13386. If you issue differential.query with a large offset (like 3000), it can overheat regardless of policy filtering and fail with a nonsensical error message.

This is because the overheating limit is based only on the query limit, not on the offset.

For example, querying for "limit = 100" will never examine more than 1,100 rows, so a query with "limit = 100, offset = 3000" will always fail (provided there are at least that many revisions).

Not all numbers work like you might expect them to becuase there's also a 1024-row fetch window, but basically small limits plus big offsets always fail.

Test Plan

Artificially reduced the internal window size from 1024 to 5, then ran differential.query with offset=50 and limit=3. Before: overheated with weird error message. After: clean result.

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Event Timeline

epriestley created this revision.Aug 22 2019, 3:16 AM
epriestley requested review of this revision.Aug 22 2019, 3:18 AM
This revision was not accepted when it landed; it landed in state Needs Review.Aug 22 2019, 3:27 AM
This revision was automatically updated to reflect the committed changes.