8000 上一级节点remove_from_index的疑问 · Issue #5 · enpeizhao/duck_db · GitHub
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上一级节点remove_from_index的疑问 #5

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liyishui2003 opened this issue Feb 22, 2025 · 0 comments
Open

上一级节点remove_from_index的疑问 #5

liyishui2003 opened this issue Feb 22, 2025 · 0 comments

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@liyishui2003
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作者您好！代码里写到：

if(where == end(parent) - 1){
                    // if leaf is last element then merge : | prev | leaf | -> | prev leaf |
                    assert(leaf.prev != 0);
                    leaf_node_t prev;
                    map(&prev,leaf.prev);

                    index_key = begin(prev)->key; //此处为什么是begin(prev)->key?

                    merge_leafs(&prev,&leaf);//数据结构层面合并
                    node_remove(&prev,&leaf);//物理层面合并(用到了map/unmap)
                    unmap(&prev,leaf.prev);//修改了prev，要回写
                }
                else {
                    assert(leaf.next!=0);
                    leaf_node_t next;
                    map(&next,leaf.next);
                    index_key = begin(leaf)->key; //此处为什么是begin(leaf)->key?
                    merge_leafs(&leaf,&next);
                    node_remove(&leaf,&next);
                    unmap(&leaf,offset);
                }

合并两个节点后，要删除原本分隔两个节点的键，而这个键应该是取右边节点的最小值或者其它合适的值？不太理解为什么反而取第一个节点最前面的键，还望指教。
谢谢
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