Question

我有一个数据集（例子）：

{u'geometry': {u'type': u'Point', u'coordinates': [151.5162, -9.44365]}, u'_id': ObjectId('5ad70f71f2119236741ffb39'), u'type': u'Feature', u'properties': {u'POS_ID': u'592795', u'STATUS': u'0', u'TIMESTAMP': u'2013-12-31 18:52:00.000', u'MMSI': u'636015725'}}

{u'geometry': {u'type': u'Point', u'coordinates': [119.0369, -0.3608933]}, u'_id': ObjectId('5ad70f71f2119236741ffb0d'), u'type': u'Feature', u'properties': {u'POS_ID': u'592557', u'STATUS': u'0', u'TIMESTAMP': u'2013-12-31 18:49:00.000', u'MMSI': u'636092156'}} 

{u'geometry': {u'type': u'Point', u'coordinates': [158.1707, -0.9142034]}, u'_id': ObjectId('5ad85e210b2d50e1174f5d29'), u'type': u'Feature', u'properties': {u'POS_ID': u'132856', u'STATUS': u'15',   u'TIMESTAMP': u'2013-12-31 17:04:00.000', u'MMSI': u'503551000'}} 

{u'geometry': {u'type': u'Point', u'coordinates': [158.2707, -0.8142034]}, u'_id': ObjectId('5ad85e2c0b2d50e1174f5d2a'), u'type': u'Feature', u'properties': {u'POS_ID': u'132856', u'STATUS': u'15', u'TIMESTAMP': u'2013-12-31 17:04:00.000',u'MMSI': u'503551000'}} 

{u'geometry': {u'type': u'Point', u'coordinates': [157.1707, -0.9142034]}, u'_id': ObjectId('5ad878c05b66f42caf578c45'), u'type': u'Feature', u'properties': {u'POS_ID': u'132856', u'STATUS': u'10', u'TIMESTAMP': u'2013-12-31 17:04:00.000', u'MMSI': u'503551000' }} 

{u'geometry': {u'type': u'Point', u'coordinates': [157.1707, -0.9142034]}, u'_id': ObjectId('5ad878c45b66f42caf578c46'), u'type': u'Feature', u'properties': {u'POS_ID': u'132856', u'STATUS': u'10',  u'TIMESTAMP': u'2013-12-31 17:04:00.000', u'MMSI': u'503551000'}}

我想获取2个随机记录，但保留具有相同MMSI的记录。更具体地说，正如您所看到的，最后四条记录具有相同的MMSI。如果我想获取2个我想要返回的随机记录：

{u'geometry': {u'type': u'Point', u'coordinates': [119.0369, -0.3608933]}, u'_id': ObjectId('5ad70f71f2119236741ffb0d'), u'type': u'Feature', u'properties': {u'POS_ID': u'592557', u'STATUS': u'0', u'TIMESTAMP': u'2013-12-31 18:49:00.000', u'MMSI': u'636092156'}} 

{u'geometry': {u'type': u'Point', u'coordinates': [158.1707, -0.9142034]}, u'_id': ObjectId('5ad85e210b2d50e1174f5d29'), u'type': u'Feature', u'properties': {u'POS_ID': u'132856', u'STATUS': u'15',   u'TIMESTAMP': u'2013-12-31 17:04:00.000', u'MMSI': u'503551000'}} 

{u'geometry': {u'type': u'Point', u'coordinates': [158.2707, -0.8142034]}, u'_id': ObjectId('5ad85e2c0b2d50e1174f5d2a'), u'type': u'Feature', u'properties': {u'POS_ID': u'132856', u'STATUS': u'15', u'TIMESTAMP': u'2013-12-31 17:04:00.000',MMSI': u'503551000'}} 

{u'geometry': {u'type': u'Point', u'coordinates': [157.1707, -0.9142034]}, u'_id': ObjectId('5ad878c05b66f42caf578c45'), u'type': u'Feature', u'properties': {u'POS_ID': u'132856', u'STATUS': u'10', u'TIMESTAMP': u'2013-12-31 17:04:00.000', u'MMSI': u'503551000' }} 

{u'geometry': {u'type': u'Point', u'coordinates': [157.1707, -0.9142034]}, u'_id': ObjectId('5ad878c45b66f42caf578c46'), u'type': u'Feature', u'properties': {u'POS_ID': u'132856', u'STATUS': u'10',  u'TIMESTAMP': u'2013-12-31 17:04:00.000', u'MMSI': u'503551000'}}

第一个MMSI = 636092156，第二个MMSI = 503551000（4个记录）。

在SQL中我想要类似的东西：

select from table where MMSI in (select distinct(MMSI) from table limit 2));

到目前为止，我有查询：

getlimitShips = db.samplecol.aggregate([{"$lookup":{"from":"samplecol", "localField":"properties.MMSI", "foreignField":"properties.MMSI", "as":"ff"}},{ "$limit" : 97},{ "$project": {"_id":0, "ff.properties.POS_ID":0,"ff.properties.STATUS":0, "ff.properties.TIMESTAMP":0])

count_lim = 0
for limS in getlimitShips:
    print "SHIP:", limS["properties"]["MMSI"],"\n"
    count_lim = count_lim +1
    print "Record",count_lim,": ", limS,"\n"

返回：

...

...

SHIP：503551000

记录97：{u'geometry'：{u'type'：u'Point'，u'coordinates'：   [157.1707，-0.9142034]}，u'type'：u'Feature'，u'properties'：   {u'POS_ID'：u'132856'，u'STATUS'：u'10'，u'MMSI'：u'503551000'，   u'COURSE'：u'12'，u'TIMESTAMP'：u'2013-12-31 17：04：00.000'}，   u'ff'：[{u'geometry'：{u'coordinates'：[141.8705，-12.67311]}，   u'properties'：{u'MMSI'：u'503551000'}}，{u'geometry'：   {u'coordinates'：[158.1707，-0.9142034]}，u'properties'：{u'MMSI'：   u'503551000'}}，{u'geometry'：{u'coordinates'：[158.2707，   -0.8142034]}，u'properties'：{u'MMSI'：u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，-0.9142034]}，u'properties'：{u 'MMSI'：   u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，   -0.9142034]}，u'properties'：{u'MMSI'：u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，-0.9142034]}，u'properties'：{u 'MMSI'：   u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，   -0.9142034]}，u'properties'：{u'MMSI'：u'503551000'}}]}

SHIP：503551000

记录104：{u'geometry'：{u'type'：u'Point'，u'coordinates'：   [157.1707，-0.9142034]}，u'type'：u'Feature'，u'properties'：   {u'POS_ID'：u'132856'，u'STATUS'：u'10'，u'MMSI'：u'503551000'，   u'COURSE'：u'10'，u'TIMESTAMP'：u'2013-12-31 17：04：00.000'}，u'ff'：   [{u'geometry'：{u'coordinates'：[141.8705，-12.67311]}，u'properties'：   {u'MMSI'：u'503551000'}}，{u'geometry'：{u'coordinates'：[158.1707，   -0.9142034]}，u'properties'：{u'MMSI'：u'503551000'}}，{u'geometry'：{u'coordinates'：[158.2707，-0.8142034]}，u'properties'：{u 'MMSI'：   u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，   -0.9142034]}，u'properties'：{u'MMSI'：u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，-0.9142034]}，u'properties'：{u 'MMSI'：   u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，   -0.9142034]}，u'properties'：{u'MMSI'：u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，-0.9142034]}，u'properties'：{u 'MMSI'：   u'503551000'}}]}

SHIP：503551000

记录105：{u'geometry'：{u'type'：u'Point'，u'coordinates'：   [157.1707，-0.9142034]}，u'type'：u'Feature'，u'properties'：   {u'POS_ID'：u'132856'，u'STATUS'：u'10'，u'MMSI'：u'503551000'，   u'COURSE'：u'4'，u'TIMESTAMP'：u'2013-12-31 17：04：00.000'}，u'ff'：   [{u'geometry'：{u'coordinates'：[141.8705，-12.67311]}，u'properties'：   {u'MMSI'：u'503551000'}}，{u'geometry'：{u'coordinates'：[158.1707，   -0.9142034]}，u'properties'：{u'MMSI'：u'503551000'}}，{u'geometry'：{u'coordinates'：[158.2707，-0.8142034]}，u'properties'：{u 'MMSI'：   u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，   -0.9142034]}，u'properties'：{u'MMSI'：u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，-0.9142034]}，u'properties'：{u 'MMSI'：   u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，   -0.9142034]}，u'properties'：{u'MMSI'：u'503551000'}}，{u'geometry'：{u'coordinates'：[157.1707，-0.9142034]}，u'properties'：{u 'MMSI'：   u'503551000' }}]}

正如您所看到的，查询返回与聚合结果相同的船舶，其次数与记录在mongo中的次数相同。有人如何删除查询中的重复项并返回聚合结果一次？

使用Mongo

0 个答案: