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fix(allocation-policies): Stop BytesScannedRejectingPolicy throttling every query - #8624
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…an limit is above ~3 TB BytesScannedRejectingPolicy asked the rate limiter for a fixed 1e12 bytes to find out how much quota was left. The rate limiter grants min(requested, remaining), so granted could never exceed 1 TB and used_quota = scan_limit - granted was overstated by scan_limit - 1 TB. For any scan_limit above ~3 TB the throttle check (granted < scan_limit - scan_limit // 1.5) was always true, so those tenants ran at half threads even with zero usage. quota_used was also wrong for every limit above 1 TB. Request scan_limit instead. check_within_quotas does not consume quota, so asking for the full limit only changes the reported remaining amount.
dezzeddi
marked this pull request as draft
October 29, 2026 06:11
dezzeddi
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dezzeddi
marked this pull request as ready for review
October 29, 2026 06:21
dezzeddi
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pbhandari
approved these changes
Nov 2, 2026
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BytesScannedRejectingPolicyasked the rate limiter for a fixed 1e12 bytes (1 TB; the old constant namePETABYTEwas wrong). The limiter grantsmin(requested, remaining), sograntednever exceeded 1 TB.The policy computes
used = limit - granted, so usage looked far higher than it was. With a 20 TB limit and zero usage,used= 19 TB, which is over the throttle point (20 / 1.5 ≈ 13.3 TB), so every query is throttled. This happens for any limit above about 3 TB.Fix: request
scan_limit.check_within_quotasdoesn't consume quota, so only the reported remaining amount changes.