我有这种格式的mongo数据。我每天15分钟收集数据。我想在Rate字段上计算基本统计数据，例如min，max和average，这是每15分钟一段时间的嵌套文档。我想将匹配汇总为 日期 - ＆gt; 配对 显示 配对，最小值，最大值和平均值的“20160108”和分组对不起，我对mongo有点新意，特别是它的聚合。如果你可以指导我，那将是件好事。
示例数据
> db.Currency.find({Date : "20160108"},{Pair : 1 ,Date: 1, Rate :1 , _id : 0})
{ "Pair" : "USDIDR", "Date" : "20160108", "Rate" : { "0000" : "13945.0000", "0015" : "13945.0000", "0030" : "13945.0000", "0045" : "13945.0000", "0100" : "13945.0000", "0115" : "13890.0000", "0130" : "13860.0000", "0145" : "13875.0000", "0200" : "13900.0000", "0215" : "13880.0000", "0230" : "13880.0000", "0245" : "13910.0000", "0300" : "13910.0000", "0315" : "13910.0000", "0330" : "13910.0000", "0345" : "13900.0000", "0400" : "13900.0000", "0415" : "13900.0000", "0430" : "13900.0000", "0445" : "13900.0000", "0500" : "13900.0000", "0515" : "13900.0000", "0530" : "13900.0000", "0545" : "13905.0000", "0600" : "13905.0000", "0615" : "13905.0000", "0630" : "13905.0000", "0645" : "13905.0000", "0700" : "13905.0000", "0715" : "13910.0000", "0730" : "13910.0000", "0745" : "13910.0000", "0800" : "13910.0000", "0815" : "13910.0000", "0830" : "13920.0000", "0845" : "13920.0000", "0900" : "13920.0000", "0915" : "13920.0000", "0930" : "13920.0000", "0945" : "13920.0000", "1000" : "13920.0000", "1015" : "13920.0000", "1030" : "13920.0000", "1045" : "13920.0000", "1100" : "13920.0000", "1115" : "13920.0000", "1130" : "13920.0000", "1145" : "13920.0000", "1200" : "13920.0000", "1215" : "13920.0000", "1230" : "13920.0000", "1245" : "13920.0000", "1300" : "13920.0000", "1315" : "13920.0000", "1330" : "13920.0000", "1345" : "13920.0000", "1400" : "13890.0000", "1415" : "13890.0000", "1430" : "13900.0000", "1445" : "13900.0000", "1500" : "13900.0000", "1515" : "13915.0000", "1530" : "13915.0000", "1545" : "13915.0000", "1600" : "13925.0000", "1615" : "13925.0000", "1630" : "13925.0000", "1645" : "13925.0000", "1700" : "13925.0000", "1715" : "13925.0000", "1730" : "13925.0000", "1745" : "13925.0000", "1800" : "13925.0000", "1815" : "13925.0000", "1830" : "13925.0000", "1845" : "13925.0000", "1900" : "13925.0000", "1915" : "13925.0000", "1930" : "13925.0000", "1945" : "13925.0000", "2000" : "13925.0000", "2015" : "13925.0000", "2030" : "13925.0000", "2045" : "13925.0000", "2100" : "13925.0000", "2115" : "13925.0000", "2130" : "13925.0000", "2145" : "13925.0000", "2200" : "13925.0000", "2215" : "13925.0000", "2230" : "13925.0000", "2245" : "13925.0000", "2300" : "13925.0000", "2315" : "13925.0000", "2330" : "13925.0000", "2345" : "13925.0000" } }
{ "Pair" : "USDKRW", "Date" : "20160108", "Rate" : { "0000" : "1197.5950", "0015" : "1196.8450", "0030" : "1197.0100", "0045" : "1197.8000", "0100" : "1198.5500", "0115" : "1197.6000", "0130" : "1192.1500", "0145" : "1194.2000", "0200" : "1195.7450", "0215" : "1195.4000", "0230" : "1195.4500", "0245" : "1195.9500", "0300" : "1197.0551", "0315" : "1196.6500", "0330" : "1195.6500", "0345" : "1197.6500", "0400" : "1197.7500", "0415" : "1196.5000", "0430" : "1196.6500", "0445" : "1197.3000", "0500" : "1196.9000", "0515" : "1196.7500", "0530" : "1197.2500", "0545" : "1197.1949", "0600" : "1197.9449", "0615" : "1198.1949", "0630" : "1198.3051", "0645" : "1198.6450", "0700" : "1197.5950", "0715" : "1198.0450", "0730" : "1198.2450", "0745" : "1199.7950", "0800" : "1201.0450", "0815" : "1200.8950", "0830" : "1199.9550", "0845" : "1199.9550", "0900" : "1199.8950", "0915" : "1201.1450", "0930" : "1201.8950", "0945" : "1201.4950", "1000" : "1201.6949", "1015" : "1202.0450", "1030" : "1202.2950", "1045" : "1201.7550", "1100" : "1201.3600", "1115" : "1202.1450", "1130" : "1202.0950", "1145" : "1202.3450", "1200" : "1201.4449", "1215" : "1201.3950", "1230" : "1200.3550", "1245" : "1199.9449", "1300" : "1200.8950", "1315" : "1201.3450", "1330" : "1201.2100", "1345" : "1202.1949", "1400" : "1203.3550", "1415" : "1204.1550", "1430" : "1204.3550", "1445" : "1205.1150", "1500" : "1206.2950", "1515" : "1207.1949", "1530" : "1207.1949", "1545" : "1208.1550", "1600" : "1207.4449", "1615" : "1207.1500", "1630" : "1207.6450", "1645" : "1208.2950", "1700" : "1207.8950", "1715" : "1207.9950", "1730" : "1207.9950", "1745" : "1207.9550", "1800" : "1208.0950", "1815" : "1207.9950", "1830" : "1208.4950", "1845" : "1208.2450", "1900" : "1214.0350", "1915" : "1210.8950", "1930" : "1210.6450", "1945" : "1210.3350", "2000" : "1209.2150", "2015" : "1209.0950", "2030" : "1207.6949", "2045" : "1207.7950", "2100" : "1207.7950", "2115" : "1207.9449", "2130" : "1207.7450", "2145" : "1208.0450", "2200" : "1206.9000", "2215" : "1208.3950", "2230" : "1208.3950", "2245" : "1208.3950", "2300" : "1208.3950", "2315" : "1208.3950", "2330" : "1208.3950", "2345" : "1208.3950" } }