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Guard B-tree splits against node exhaustion - #238
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Signed-off-by: Qian-Cheng-nju <Qian-Cheng-nju@users.noreply.github.com>
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With
MaxOccupancy = 2, two nodes and keys{1,2,3}, inserting two keys fills the root. The next insertion needs a root split, but only one free node remains.SplitRootLeafstill tries to choose two distinct free nodes, and TLC stops at the secondCHOOSE.FreeNodesRemaindoes not catch this case: one node is still free. The same issue applies toSplitRootInner; an ordinarySplitLeafneeds one free node.This adds guards for the number of nodes each split needs. If the pool is too small, the split blocks. Would that be the right allocation policy here, or would you prefer to make sufficient space an explicit assumption?
The new
MCbtreeExhaustion.cfgchecks all five safety invariants with a two-node pool. It completes with 202 distinct states. The existingMCbtree.cfgalso passes with the same 374,727 distinct states; its generated-state count is updated for the new existential guards.This leaves the missing
SplitInneraction in #234 as a separate issue.