-
aggregate(pipeline,options)指定 group 的 keys, 通过操作符$push/$addToSet/$sum等实现简单的 reduce, 不支持函数/自定义变量 -
group({ key, reduce, initial [, keyf] [, cond] [, finalize] })支持函数(keyf)mapReduce的阉割版本 -
mapReduce终极大杀器 -
count(query)too young too simple distinct(field,query)
最后两个操作很简单, 这里主要比较前面 3 个操作
样本数据
- created 时间戳(ms)
- group 组别 [A-Z]
- category 目录 C[1-10]
- count
- title 26 个字母随机组成
{'group': 'E', 'created': 1402764223433, 'count': 63, 'datetime': datetime.datetime(2014, 6, 15, 0, 43, 43, 433000), 'title': 'KNBVHICLGOUESDFYTJWRXMPZQA', 'category': 'C8'}
{'group': 'I', 'created': 1413086660063, 'count': 93, 'datetime': datetime.datetime(2014, 10, 12, 12, 4, 20, 62000), 'title': 'UJZXCIHBFKELPYVWGAQRMNOSDT', 'category': 'C10'}
{'group': 'H', 'created': 1440750343730, 'count': 41, 'datetime': datetime.datetime(2015, 8, 28, 16, 25, 43, 730000), 'title': 'HSDKQPFMNBJEGXYZARITCVOWLU', 'category': 'C1'}
{'group': 'S', 'created': 1437710373637, 'count': 14, 'datetime': datetime.datetime(2015, 7, 24, 11, 59, 33, 637000), 'title': 'ZFJITUDHMBRLGKNEWSCPXVOYQA', 'category': 'C10'}
{'group': 'Z', 'created': 1428307315436, 'count': 78, 'datetime': datetime.datetime(2015, 4, 6, 16, 1, 55, 436000), 'title': 'FUYXWOQZPTKMSCNGDHEJVBILAR', 'category': 'C5'}
{'group': 'R', 'created': 1402809274964, 'count': 74, 'datetime': datetime.datetime(2014, 6, 15, 13, 14, 34, 963000), 'title': 'JKZCMPIAONDTWRQLHGUEVSFXYB', 'category'