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The update_tip_num SQL used GREATEST(current, new) which prevented tip_num from ever decreasing. During a reorg, handle_reorg needs to roll tip_num back to the fork point so the sync engine re-fetches the canonical chain. Added rollback_tip_num() that uses a direct SET instead of GREATEST, and updated handle_reorg to use it. The normal forward-sync path still uses update_tip_num with GREATEST for monotonic advancement. Tests verify: - tip_num decreases during reorg via rollback_tip_num - tip_num still advances monotonically via update_tip_num (GREATEST) - After rollback, forward sync resumes and advances past old tip Amp-Thread-ID: https://ampcode.com/threads/T-019d458d-01b9-76ca-9fb1-bfbd3729d359 Co-authored-by: Amp <amp@ampcode.com>
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Problem
update_tip_numusesGREATEST(sync_state.tip_num, EXCLUDED.tip_num)which makes tip_num monotonically increasing. During a chain reorganization,handle_reorgneeds to roll tip_num back to the fork point so the sync engine re-fetches the canonical chain — but GREATEST prevents any decrease.Severity: High — reorgs silently fail to update tip_num, causing the sync engine to skip re-syncing orphaned blocks with their canonical replacements.
Fix
Added
rollback_tip_num()which uses a directSET tip_num = $1instead ofGREATEST. Updatedhandle_reorgto use this new function. The normal forward-sync path still usesupdate_tip_numwithGREATESTfor safe monotonic advancement.Changes
src/sync/writer.rs: Addedrollback_tip_num()— unconditionally sets tip_num and head_num to the fork pointsrc/sync/engine.rs:handle_reorg()now callsrollback_tip_numinstead ofupdate_tip_numtests/smoke_test.rs: 3 new tests:test_rollback_tip_num_decreases_during_reorg— verifies tip_num can decreasetest_update_tip_num_still_monotonic_forward— verifies GREATEST still works for forward synctest_rollback_then_forward_sync_resumes— verifies full rollback→resume cycleTesting