node.js - Returning a subset of array items in MongoDB -


can offer advice on how return subset of array items? example, let's suppose have collection of documents (similar example below) contains simple _id key , key contains array of objects.

i find _id's , matching objects match simple criteria:

// campaigns {   "_id" : "fred's c25k",   "campaigndata" : [     {       "date" : "2015-06-17",       "source" : "nike"     },     {       "date" : "2015-06-17",       "source" : "reebok",     },     {       "date" : "2015-06-12",       "source" : "nike"     },     {       "date" : "2015-06-14",       "source" : "adidas"     },   ] }, {   "_id" : "mike's marathon",   "campaigndata" : [     {       "date" : "2015-06-17",       "source" : "nike"     }   ] }, {   "_id" : "jacob's jamboree",   "campaigndata" : [     {       "date" : "2015-06-17",       "source" : "keen"     }   ] }

i result contain _id , matching objects for, say, date value of "2015-06-17"

// goal => generate result set looks like: {   "_id" : "fred's c25k",   "campaigndata" : [     {       "date" : "2015-06-17",       "source" : "nike"     },     {       "date" : "2015-06-17",       "source" : "reebok",     }   ] }, {   "_id" : "mike's marathon",   "campaigndata" : [     {       "date" : "2015-06-17",       "source" : "nike"     }   ] }, {   "_id" : "jacob's jamboree",   "campaigndata" : [     {       "date" : "2015-06-17",       "source" : "keen"     }   ] }

use aggregation framework achieve desired result. following pipeline consists of $match operator stage first step filter documents should pass through pipeline. next stage $unwind operator deconstructs campaigndata array field input documents output document each element. each output document replaces array element value. need $match step subdocuments match given date criteria. matched documents used in next $group pipeline step preserve original array using $push group accumulator operator:

db.collection.aggregate([     {         "$match": {             "campaigndata.date" : "2015-06-17"         }     },     {         "$unwind": "$campaigndata"     },     {         "$match": {             "campaigndata.date" : "2015-06-17"         }     },     {         "$group": {             "_id": "$_id",             "campaigndata": {                 "$push": "$campaigndata"             }         }     } ])

result:

/* 0 */ {     "result" : [          {             "_id" : "mike's marathon",             "campaigndata" : [                  {                     "date" : "2015-06-17",                     "source" : "nike"                 }             ]         },          {             "_id" : "jacob's jamboree",             "campaigndata" : [                  {                     "date" : "2015-06-17",                     "source" : "keen"                 }             ]         },          {             "_id" : "fred's c25k",             "campaigndata" : [                  {                     "date" : "2015-06-17",                     "source" : "nike"                 },                  {                     "date" : "2015-06-17",                     "source" : "reebok"                 }             ]         }     ],     "ok" : 1 }

Comments

Post a Comment

Popular posts from this blog

powershell Start-Process exit code -1073741502 when used with Credential from a windows service environment -

i'm running strange behavior powershell start-process call. here call: $process = start-process ` "c:\somepath\mybinary.exe" ` -passthru ` -credential $defaultcredential ` -wait ` -workingdirectory "c:\somepath" ` -loaduserprofile if ($process.exitcode -ne 0) { #do } this call return exit code - 1073741502 . after quick search, exit code seems related generic error when program not load required dll (aka. status_dll_init_failed ). when run without -credential $credential program runs correctly. in order isolate problem, manually launched some.exe in prompt target credential , runs smoothly. so problem seems come way start-process cmdlet launch process. i found potential solutions problem tried apply no luck : link , link . would have idea of what's going on here ? edit 1: run proc mon monitoring program activities when launched directly or via powershell script. problem seems occur when loading kernelbase
Read more

twig - Using Twigbridge in a Laravel 5.1 Package -

i'm trying create laravel 5.1 package uses twigbridge instead of .php views. can normal .php views display fine, when try make use of .twig templates i'm met error. possible use twigbridge templates when creating views laravel package or pretty stuck blade , php ? edit 1: loading twig template without extending works. it's when start using {% extends 'file' %} error comes out. i error error loading /virtual/laravel/packages/username/mypackage/src/views/sample.twig: template "templates.master" not defined () in "/virtual/laravel/packages/username/mypackage/src/views/sample.twig" @ line 1. my folders username |_ mypackage |_ src |_ controllers - samplecontroller.php |_ views |_ templates - master.twig - sample.twig twig template sample.twig {% extends 'templates.master' %} {% block content %} {{ parent()
Read more

c# - LINQ join Entities from HashSet's, Join vs Dictionary vs HashSet performance -

i have hashset's each stores t, have written test application compares different relation algorithms can think of, i'm not pleased results getting. does there exist more efficient ways of achieving object relations, once testing? using system; using system.collections.generic; using system.linq; using system.text; using system.threading.tasks; using system.diagnostics; namespace linqtests { class program { static void main(string[] args) { hashset<user> usertable = new hashset<user>(); hashset<userproperty> userpropertytable = new hashset<userproperty>(); #region lets create dummy data. console.writeline("please wait while creating dummy data, can take while..."); console.writeline(""); int rows = 1000000; for(int x = 0; x < rows; x++) { random rnd = new random(); // ad
Read more