【数据存储】大数据报表分页导出：大结果集的分批落盘设计

local PAGE_SIZE = 5000
local function exportPage()
    local lastId = tonumber(getsysvar("EXPORT_CURSOR") or "0")
    local rows, cursor = fetchRows(lastId, PAGE_SIZE)
    if #rows == 0 then
        setsysvar("EXPORT_DONE", 1)
        return false
    end
    local fileNo = tonumber(getsysvar("EXPORT_FILE_NO") or "0") + 1
    setsysvarex("EXPORT_FILE_NO", fileNo, 1)
    setsysvarex("EXPORT_CURSOR", cursor, 1)
    return true
end

local function mergeChunks(totalExpect)
    local total, no = 0, 0
    while true do
        no = no + 1
        local cnt = tonumber(getsysvar("EXPORT_CHUNK_CNT_" .. no) or "0")
        if cnt == 0 then break end
        total = total + cnt
    end
    setsysvar("EXPORT_CHECK", total .. "/" .. totalExpect)
    return total == totalExpect
end