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60 lines
2 KiB
Markdown
60 lines
2 KiB
Markdown
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This adapts one b+ tree implementation
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https://sourcegraph.com/github.com/timtadh/data-structures@master/-/tree/tree/bptree
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to persist changes to on disk.
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# When a node needs to persist itself?
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* A node changed its key or value
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* When an item is added.
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* When an item is updated.
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* When an item is deleted.
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* When a node is split.
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* 2 new nodes are created (they shoud persist themselves).
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* Parent node need to point to the new nodes.
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* When a node is merged.
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* delete one node
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* persist the merged node
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In general, if one node is returned from a function, the node should have already been persisted.
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The parent node may need to delete the old node.
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BpTree
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Add(key ItemKey, value ItemValue)
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new_root = self.getRoot().put(key,value)
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a, b, err := self.insert(key, value)
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self.internal_insert(key, value)
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self.internal_split(q.keys[0], q)
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persist(a,b)
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self.persist() // child add q node
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self.maybePersist(child == p)
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self.leaf_insert(key, value)
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self.persist() // if dedup
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self.leaf_split(key, value)
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self.pure_leaf_split(key, value)
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persist(a,b)
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a.persist()
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persist(a,b)
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self.put_kv(key, value)
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new_root.persist()
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self.setRoot(new_root)
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oldroot.destroy()
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// maybe persist BpTree new root
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Replace(key ItemKey, where WhereFunc, value ItemValue)
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leaf.persist()
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RemoveWhere(key ItemKey, where WhereFunc)
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self.getRoot().remove(key, where)
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self.internal_remove(key, nil, where)
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child.leaf_remove(key, nil, where)
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child.leaf_remove(key, sibling.keys[0], where)
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l.destroy() // when the node is empty
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a.maybePersist(hasChange)
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self.destroy() // when no keys left
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self.persist() // when some keys are left
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self.leaf_remove(key, self.keys[len(self.keys)-1], where)
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new_root.persist() // when new root is added
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// maybe persist BpTree new root
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