使用Redis解决“树”形数据的复杂查询

最近因业务需要，研究了一下树数据结果的存储及查询解决方案。 最初的想法是使用neo4j,可是在网上看了一下开源的不支持集群，感觉用的人不多。

网上也查了一些 树形结构数据存储方案 但每种实现方案都有它的一定局限性。

想了一短时间后，想出了下面的方案：

一、 因为复杂的查询都由Redis来处理，所以数据库表的设计就变得非常简单：tree 表

二、Redis的数据存储方案：

把表的数据存储到一个Hash表中，使用表中的id值做为此hash表的key, value值为：

{
   id: 10,
   parentId: 9,
   childIds: [11]
}

代码实现

为了简化测试，这里只演示Redis相关的操作

1. Tree 类定义

    public class Tree {
        private Integer id;
        private String name;
        private Integer parentId;
        private List<Integer> childIds;
    }
   

2. 往Redis中添加测试数据：

    [@Test](https://my.oschina.net/azibug)
    public void addTestData() throws Exception {
        String key = "tree-test-key";
        Tree tree = new Tree();
        List<Integer> childIds = new ArrayList<>();
        int max = 100000
        tree.setChildIds(childIds);
        for (int i = 0; i < max; i++) {
            tree.setId(i);
            tree.setName("tree" + i);
            if (i > 0) {
                tree.setParentId(i - 1);
            }
            childIds.clear();
            if(i < (max - 1)){
                childIds.add(i + 1);
            }
            redis.setHash(key, "" + i, JsonUtil.toJson(tree));
        }
    }
   

3. Lua 代码的实现

在Lua中使用递归时，需要使用“尾调用”来优化代码。关于尾调用的知识，大家可以上网去搜索。

获取所有子节点 get-tree-childs.lua

local treeKey = KEYS[1]
local fnodeId  = ARGV[1]

local function getTreeChild(currentnode, t, res)
  if currentnode == nil or t == nil  then
    return res
  end

  local nextNode = nil
  local nextType = nil
  if t == "id" and (type(currentnode) == "number" or type(currentnode) == "string") then
    local treeNode = redis.call("HGET", treeKey, currentnode)
    if treeNode then
      local node = cjson.decode(treeNode)
      table.insert(res, treeNode)
      if node and node.childIds then
        nextNode = node.childIds
        nextType = "childIds"
      end
    end
  elseif t == "childIds" then
    nextNode = {}
    nextType = "childIds"
    local treeNode  = nil
    local node = nil
    local cnt = 0
    for _, val in ipairs(currentnode) do
      treeNode = redis.call("HGET", treeKey, tostring(val))
      if treeNode then
        node = cjson.decode(treeNode)
        table.insert(res, treeNode)
        if node and node.childIds then
          for _, val2 in ipairs(node.childIds) do
            table.insert(nextNode, val2)
            cnt = cnt + 1
          end
        end
      end
    end
    if cnt == 0 then
      nextNode = nil
      nextType = nil
    end
  end
  return getTreeChild(nextNode, nextType, res)
end


if treeKey and fnodeId then
  return getTreeChild(fnodeId, "id", {})
end

return {}

获取所有子节点数目 get-tree-childs-cnt.lua

local treeKey = KEYS[1]
local fnodeId  = ARGV[1]

local function getTreeChildCnt(currentnode, t, res)
  if currentnode == nil or t == nil  then
    return res
  end

  local nextNode = nil
  local nextType = nil
  if t == "id" and (type(currentnode) == "number" or type(currentnode) == "string") then
    local treeNode = redis.call("HGET", treeKey, currentnode)
    if treeNode then
      local node = cjson.decode(treeNode)
      res = res + 1
      if node and node.childIds then
        nextNode = node.childIds
        nextType = "childIds"
      end
    end
  elseif t == "childIds" then
    nextNode = {}
    nextType = "childIds"
    local treeNode  = nil
    local cnt = 0
    for _, val in ipairs(currentnode) do
      treeNode = redis.call("HGET", treeKey, tostring(val))
      if treeNode then
        local node = cjson.decode(treeNode)
        res = res + 1
        if node and node.childIds then
          for _, val2 in ipairs(node.childIds) do
            table.insert(nextNode, val2)
            cnt = cnt + 1
          end
        end
      end
    end
    if cnt == 0 then
      nextNode = nil
      nextType = nil
    end
  end
  return getTreeChildCnt(nextNode, nextType, res)
end


if treeKey and fnodeId then
  return getTreeChildCnt(fnodeId, "id", 0)
end

return 0

获取所有子节点数目 get-tree-parent.lua

local treeKey = KEYS[1]
local nodeId  = ARGV[1]

local function getTreeParent(treeKey, res, nodeId)
  if nodeId == nil or not (type(nodeId) == "number" or type(nodeId) == "string") then
    return res
  end
  local treeNode = redis.call("HGET", treeKey, nodeId)
  local nextNodeId = nil
  if treeNode then
    local node = cjson.decode(treeNode)
    table.insert(res, treeNode)
    if node then
      nextNodeId = node.parentId
    end
  end
  return getTreeParent(treeKey, res, nextNodeId)
end


if treeKey and nodeId then
  return getTreeParent(treeKey, {}, nodeId)
end

return {}

获取所有子节点数目 get-tree-parent-cnt.lua

local treeKey = KEYS[1]
local nodeId  = ARGV[1]

local function getTreeParentCnt(treeKey, nodeId, res)
  if nodeId == nil or not (type(nodeId) == "number" or type(nodeId) == "string") then
    return res
  end
  local treeNode = redis.call("HGET", treeKey, nodeId)
  local nextNodeId = nil
  if treeNode then
    local node = cjson.decode(treeNode)
    res = res + 1
    if node then
      nextNodeId = node.parentId
    end
  end
  return getTreeParentCnt(treeKey, nextNodeId, res)
end


if treeKey and nodeId then
  return getTreeParentCnt(treeKey, nodeId, 0)
end

return 0

以上代码因为使用了“尾调用”，所以变得相对比较复杂

总结

此方案相对比较灵活，能支持相对比较大量的数据。

缺点：过于依赖Redis。数据同步会麻烦些，好在操作不是很复杂。