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My goal is to add a comment to my CommentFeed and while doing that I want to push that comment into my topComments field and also update the 'numOfComments' . I want to limit the topComments to only 3 comments (How would I even set that up?). And how do I take the previous value of numOfComments and add one to it?

 CommentFeed.findOneAndUpdate(
 _id: commentId ,
 
 $push: 
 comments: 
 text: req.body.text
 ,
 $push: topComments:text: req.body.text, <--- Limit this somehow to only allow an array length of 3?
 $set: numOfComments: ? , <---What kind of logic is used here?
 
 ,
 new: true 
 )

CommentFeed Schema

 const CommentFeedSchema = new Schema(
 topComments:[text:type:String],
 numOfComments:type:Number,
 comments: [
 text: type: String, required: true 
 ]);

mongodb

share|improve this question

asked Mar 26 at 21:25

user10204157user10204157

19111 silver badge1313 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Possible duplicate of How to limit an array size in MongoDB?
  
  – OzW
  Mar 27 at 11:10
  

  
  
  
  

add a comment | 

0

My goal is to add a comment to my CommentFeed and while doing that I want to push that comment into my topComments field and also update the 'numOfComments' . I want to limit the topComments to only 3 comments (How would I even set that up?). And how do I take the previous value of numOfComments and add one to it?

 CommentFeed.findOneAndUpdate(
 _id: commentId ,
 
 $push: 
 comments: 
 text: req.body.text
 ,
 $push: topComments:text: req.body.text, <--- Limit this somehow to only allow an array length of 3?
 $set: numOfComments: ? , <---What kind of logic is used here?
 
 ,
 new: true 
 )

CommentFeed Schema

 const CommentFeedSchema = new Schema(
 topComments:[text:type:String],
 numOfComments:type:Number,
 comments: [
 text: type: String, required: true 
 ]);

mongodb

share|improve this question

asked Mar 26 at 21:25

user10204157user10204157

19111 silver badge1313 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Possible duplicate of How to limit an array size in MongoDB?
  
  – OzW
  Mar 27 at 11:10
  

  
  
  
  

add a comment | 

My goal is to add a comment to my CommentFeed and while doing that I want to push that comment into my topComments field and also update the 'numOfComments' . I want to limit the topComments to only 3 comments (How would I even set that up?). And how do I take the previous value of numOfComments and add one to it?

 CommentFeed.findOneAndUpdate(
 _id: commentId ,
 
 $push: 
 comments: 
 text: req.body.text
 ,
 $push: topComments:text: req.body.text, <--- Limit this somehow to only allow an array length of 3?
 $set: numOfComments: ? , <---What kind of logic is used here?
 
 ,
 new: true 
 )

CommentFeed Schema

 const CommentFeedSchema = new Schema(
 topComments:[text:type:String],
 numOfComments:type:Number,
 comments: [
 text: type: String, required: true 
 ]);

mongodb

share|improve this question

asked Mar 26 at 21:25

user10204157user10204157

19111 silver badge1313 bronze badges

 CommentFeed.findOneAndUpdate(
 _id: commentId ,
 
 $push: 
 comments: 
 text: req.body.text
 ,
 $push: topComments:text: req.body.text, <--- Limit this somehow to only allow an array length of 3?
 $set: numOfComments: ? , <---What kind of logic is used here?
 
 ,
 new: true 
 )

 const CommentFeedSchema = new Schema(
 topComments:[text:type:String],
 numOfComments:type:Number,
 comments: [
 text: type: String, required: true 
 ]);

share|improve this question

asked Mar 26 at 21:25

user10204157user10204157

19111 silver badge1313 bronze badges

share|improve this question

asked Mar 26 at 21:25

user10204157user10204157

19111 silver badge1313 bronze badges

asked Mar 26 at 21:25

user10204157user10204157

19111 silver badge1313 bronze badges

asked Mar 26 at 21:25

user10204157user10204157

19111 silver badge1313 bronze badges

1 Answer
1

active

oldest

votes

0

For the first issue (limiting the topComments array size) you can use the $slice operator. This has already been answered in other questions. But you might consider computing topComments from comments using the$slice operator in the projection argument:

CommentFeed.find( , comments: $slice: -3 )

For the second issue (updating a document using existing fields from that document), it is not something you can do in a simple findOneAndUpdate call. This was also discussed in other questions.
But you might consider computing numOfComments instead of updating it every time. You can do that with the $size operator of the aggregation framework:

CommentFeed.aggregate($project: numOfComments: $size:"$comments" )

share|improve this answer

edited Mar 27 at 11:24

answered Mar 27 at 11:13

OzWOzW

59811 gold badge77 silver badges2222 bronze badges

add a comment | 

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0

For the first issue (limiting the topComments array size) you can use the $slice operator. This has already been answered in other questions. But you might consider computing topComments from comments using the$slice operator in the projection argument:

CommentFeed.find( , comments: $slice: -3 )

For the second issue (updating a document using existing fields from that document), it is not something you can do in a simple findOneAndUpdate call. This was also discussed in other questions.
But you might consider computing numOfComments instead of updating it every time. You can do that with the $size operator of the aggregation framework:

CommentFeed.aggregate($project: numOfComments: $size:"$comments" )

share|improve this answer

edited Mar 27 at 11:24

answered Mar 27 at 11:13

OzWOzW

59811 gold badge77 silver badges2222 bronze badges

add a comment | 

0

For the first issue (limiting the topComments array size) you can use the $slice operator. This has already been answered in other questions. But you might consider computing topComments from comments using the$slice operator in the projection argument:

CommentFeed.find( , comments: $slice: -3 )

For the second issue (updating a document using existing fields from that document), it is not something you can do in a simple findOneAndUpdate call. This was also discussed in other questions.
But you might consider computing numOfComments instead of updating it every time. You can do that with the $size operator of the aggregation framework:

CommentFeed.aggregate($project: numOfComments: $size:"$comments" )

share|improve this answer

edited Mar 27 at 11:24

answered Mar 27 at 11:13

OzWOzW

59811 gold badge77 silver badges2222 bronze badges

add a comment | 

For the first issue (limiting the topComments array size) you can use the $slice operator. This has already been answered in other questions. But you might consider computing topComments from comments using the$slice operator in the projection argument:

CommentFeed.find( , comments: $slice: -3 )

For the second issue (updating a document using existing fields from that document), it is not something you can do in a simple findOneAndUpdate call. This was also discussed in other questions.
But you might consider computing numOfComments instead of updating it every time. You can do that with the $size operator of the aggregation framework:

CommentFeed.aggregate($project: numOfComments: $size:"$comments" )

share|improve this answer

edited Mar 27 at 11:24

answered Mar 27 at 11:13

OzWOzW

59811 gold badge77 silver badges2222 bronze badges

CommentFeed.find( , comments: $slice: -3 )

CommentFeed.aggregate($project: numOfComments: $size:"$comments" )

share|improve this answer

edited Mar 27 at 11:24

answered Mar 27 at 11:13

OzWOzW

59811 gold badge77 silver badges2222 bronze badges

answered Mar 27 at 11:13

OzWOzW

59811 gold badge77 silver badges2222 bronze badges

answered Mar 27 at 11:13

OzWOzW

59811 gold badge77 silver badges2222 bronze badges