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ZSPREAD.lua
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ZSPREAD.lua
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-- @desc: Spread members between two ZSETs so they are even size
-- @usage: redis-cli eval "$(cat ZSPREAD.lua)" 2 <zset1> <zset2>
-- @return: list of spread members
local function round(num)
if num >= 0 then return math.floor(num+.5)
else return math.ceil(num-.5) end
end
local function randomFromTo(from, to)
local diff = to - from
return round((math.random() * diff) + from)
end
local function ZSPREAD(zset1, zset2)
local zset1size = redis.call("ZCARD", zset1)
if zset1size == 0 then return {} end
local zset2size = redis.call("ZCARD", zset2)
if zset2size == 0 then return {} end
local fromZset, fromZsetSize = zset1, zset1size
local toZsetSize, toZsetSize = zset2, zset2size
if zset1size > zset2size then
fromZset, fromZsetSize = toZset, toZsetSize
elseif zset1size == zset2size then
return {}
end
local spreadCount = round(((fromZsetSize - toZsetSize) / 2))
if spreadCount == 0 then return {} end
local members = redis.call("ZREVRANGEBYSCORE", zset1, "+INF", "-INF", "WITHSCORES")
local tmpMembers = {}
for i=1,spreadCount do
local randIdx = randomFromTo(0, (fromZsetSize - 1))
local tmpMember = redis.call("ZREVRANGE", fromZset, randIdx, randIdx, "WITHSCORES")
for idx,val in ipairs(tmpMember) do
if idx % 2 == 0 then
redis.call("ZADD", toZset, tonumber(val), tmpMembers[#tmpMembers])
else
table.insert(tmpMembers, val)
redis.call("ZREM", fromZset, val)
end
end
end
return tmpMembers
end
return ZSPREAD(KEYS[1], KEYS[2])