How to get the last N records in mongodb

Question

I can t find anywhere it has been documented this  By default  the find   operation will get the records from beginning  How can I get the last N records in mongodb   Edit  also I want the returned result ordered from less recent to most recent  not the reverse

User · Answer

db collection find   hint     natural   -1     sort field  1 -1  limit n   according to mongoDB Documentation   You can specify    natural   1   to force the query to perform a forwards collection scan  You can also specify    natural   -1   to force the query to perform a reverse collection scan

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You can try this method   Get the total number of records in the collection with   db dbcollection count      Then use skip   db dbcollection find   skip db dbcollection count   - 1  pretty

User · Answer

use  slice operator to limit array elements GeoLocation find     name  1  geolocation   slice  -5         then  result    gt          res json result               catch  err    gt          res status 500  json   success  false  msg   Something went wrong    err            where geolocation is array of data  from that we get last 5 record

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Look under Querying  Sorting and Natural Order  http   www mongodb org display DOCS Sorting and Natural Order as well as sort   under Cursor Methods http   www mongodb org display DOCS Advanced Queries

User · Answer

db collection find   sort   natural  -1    limit 5

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If I understand your question  you need to sort in ascending order   Assuming you have some id or date field called  x  you would do       sort      db foo find   sort  x 1      The 1 will sort ascending  oldest to newest  and -1 will sort descending  newest to oldest    If you use the auto created  id field it has a date embedded in it     so you can use that to order by      db foo find   sort   id 1      That will return back all your documents sorted from oldest to newest   Natural Order    You can also use a Natural Order mentioned above      db foo find   sort   natural 1      Again  using 1 or -1 depending on the order you want   Use  limit      Lastly  it s good practice to add a limit when doing this sort of wide open query so you could do either      db foo find   sort   id 1   limit 50     or  db foo find   sort   natural 1   limit 50

User · Answer

If you use MongoDB compass  you can use sort filed to filter

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You may want to be using the find options   http   docs meteor com api collections html Mongo-Collection-find  db collection find      sort   createdAt  -1   skip 2  limit  18   fetch

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Sorting  skipping and so on can be pretty slow depending on the size of your collection   A better performance would be achieved if you have your collection indexed by some criteria  and then you could use min   cursor   First  index your collection with db collectionName setIndex  yourIndex   You can use ascending or descending order  which is cool  because you want always the  N last items     so if you index by descending order it is the same as getting the  first N items    Then you find the first item of your collection and use its index field values as the min criteria in a search like   db collectionName find   min minCriteria  hint yourIndex  limit N    Here s the reference for min   cursor  https   docs mongodb com manual reference method cursor min

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In order to get last N records you can execute below query  db yourcollectionname find   query       orderby    natural   -1    limit yournumber   if you want only one last record  db yourcollectionname findOne   query       orderby    natural   -1     Note  In place of  natural you can use one of the columns from your collection

User · Answer

You can t  skip  based on the size of the collection  because it will not take the query conditions into account   The correct solution is to sort from the desired end-point  limit the size of the result set  then adjust the order of the results if necessary    Here is an example  based on real-world code   var query   collection find    conditions     sort   natural   -1   limit N    query exec function err  results        if  err               else if  results length    0              else           results reverse       put the results into the desired order         results forEach function result                   do something with each result

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Last function should be sort  not limit   Example   db testcollection find   limit 3  sort  timestamp -1

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you can use sort     limit    skip   to get last N record start from any skipped  value   db collections find   sort key value  limit int value  skip some int value

User · Answer

The last N added records  from less recent to most recent  can be seen with this query   db collection find   skip db collection count   - N    If you want them in the reverse order   db collection find   sort    natural  -1    limit N    If you install Mongo-Hacker you can also use   db collection find   reverse   limit N    If you get tired of writing these commands all the time you can create custom functions in your    mongorc js  E g   function last N        return db collection find   skip db collection count   - N       then from a mongo shell just type last N

User · Answer

bin-chen   You can use an aggregation for the latest n entries of a subset of documents in a collection  Here s a simplified example without grouping  which you would be doing between stages 4 and 5 in this case    This returns the latest 20 entries  based on a field called  timestamp    sorted ascending  It then projects each documents  id  timestamp and whatever field you want to show into the results   var pipeline                             match       stage 1  filter out a subset                  first field    needs to have this value                    second field    needs to be this                                                   sort       stage 2  sort the remainder last-first                  timestamp   -1                                                  limit   20   stage 3  keep only 20 of the descending order subset                                    sort                      rt   1   stage 4  sort back to ascending order                                                  project       stage 5  add any fields you want to show in your results                   id   1                   timestamp    1                   whatever field you want to show   1                                yourcollection aggregate pipeline  function resultCallBack err  result         account for  err       do something with  result      so  result would look something like            id    ObjectId  5ac5b878a1deg18asdafb060         timestamp     2018-04-05T05 47 37 045Z        whatever field you want to show    -3 46000003814697            id    ObjectId  5ac5b878a1de1adsweafb05f         timestamp     2018-04-05T05 47 38 187Z        whatever field you want to show    -4 13000011444092     Hope this helps

[mongodb] How to get the last N records in mongodb?

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