mongoDB array pagination

Question

I have a comment collection with Comment Text in array with its Metadata. I like to the pagination in the Comment Text Array. The pagination should allow me to get the "previous 5" or "next 5". What is the best way to do this in mongoDB with good performance.

   { "_id" : ObjectId( "502c706ac2e6777781a593f6" ),
      "commentType":"loc",
      "commentList" : [ 
{ "commentText" : "HelloComment",
  "commentTS" : Date( 1345165636344 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fd182d92b2a87f780c6bbe8" ) } }, 
{ "commentText" : "2222222",
  "commentTS" : Date( 1345165636344 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fd182d92b2a87f780c6bbe8" ) } }, 
{ "commentText" : "3333333",
  "commentTS" : Date( 1345165636344 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fd182d92b2a87f780c6bbe8" ) } }, 
{ "commentText" : "44444444",
  "commentTS" : Date( 1345165636344 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fd182d92b2a87f780c6bbe8" ) } }, 
{ "commentText" : "5555555",
  "commentTS" : Date( 1345165636344 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fd182d92b2a87f780c6bbe8" ) } }, 
{ "commentText" : "6666666",
  "commentTS" : Date( 1345165636344 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fd182d92b2a87f780c6bbe8" ) } }, 
    { "commentText" : "777777",
  "commentTS" : Date( 1345165636344 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fd182d92b2a87f780c6bbe8" ) } }, 
    { "commentText" : "888888",
  "commentTS" : Date( 1345165636344 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fd182d92b2a87f780c6bbe8" ) } }, 
    { "commentText" : "6666666",
  "commentTS" : Date( 1345165636344 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fd182d92b2a87f780c6bbe8" ) } }, 
{ "commentText" : "999999",
  "commentTS" : Date( 1345165668809 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fdeb271de26fd298262bb84" ) } }, 
{ "commentText" : "HelloComment",
  "commentTS" : Date( 1345749858601 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fdeb271de26fd298262bb84" ) } }, 
{ "commentText" : "NewTestforcomments",
  "commentTS" : Date( 1345750020526 ),
  "commentLoc" : { "commentlat" : 0,
    "commentlong" : 0 },
  "userInfo" : { "$ref" : "userProfile",
    "$id" : ObjectId( "4fdeb271de26fd298262bb84" ) } } ],
   } }

Thanks for your help.

Sga · Accepted Answer · 2021-03-22 14:05:39Z

4

You can do this with $slice:

http://www.mongodb.org/display/DOCS/Retrieving+a+Subset+of+Fields#RetrievingaSubsetofFields-RetrievingaSubrangeofArrayElements

There's also a JS test example of slice here.

So, findOne, combined with $slice, is probably the way to go.

Without more info about the language you're using, I think that's the deepest I can go.

edited Mar 22, 2021 at 14:05

Sga

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answered Sep 20, 2012 at 17:51

Eve Freeman

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1 Comment

GusSL Over a year ago

The link to MongoDB is broken. Use this for info about $slice in projection: docs.mongodb.com/manual/reference/operator/projection/slice

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