CODEWITHSUNDEEP
mongodbaggregation-framework
Mihai
Mihai

Reputation: 229

Assure order when using $skip and $limit in MongoDB

I have data like this in my collection:

...
{ name: 'ad1cvbc', price: 300 },
{ name: 'tbcvbc3', price: 500 },
{ name: 'yjc5vbc', price: 500 },
{ name: 'at7vvbc', price: 500 },
{ name: 'a86v5bc', price: 500 },
{ name: 'a23dvbc', price: 500 },
{ name: 'adth4bc', price: 500 },
{ name: 'e34bc', price: 700 },
...

And I have an aggregate like this:

[
    { $match: { ... } },
    { $sort: { price: -1 } },
    { $skip: x },
    { $limit: 20 }
]

Where x is increased with 20 every single time I wants more data, but the problem is that, because I have multiple price with same value( and I have more than 20) sometimes I get the same document. How cand I assure that the order is the same and I don't get duplicates when I have many rows with the field for the sort having the same value.

Edit: So if I want to get 3 items each time I may have the following results:

1st call result:

{ name: 'ad1cvbc', price: 300 },
{ name: 'tbcvbc3', price: 500 },
{ name: 'yjc5vbc', price: 500 }  // <- this

2st call result:

{ name: 'a23dvbc', price: 500 },
{ name: 'yjc5vbc', price: 500 }, // <- this
{ name: 'at7vvbc', price: 500 }

1 document is repeated because MongoDB doesn't get each time the items in order when the documents has the same value for the sort field.

Upvotes: 1

Views: 270

Answers (1)

s7vr
s7vr

Reputation: 75914

Something like

[
    { $match: { ... } },
    { $sort: { name:-1, price: -1 } },
    { $skip: x },
    { $limit: x + 20 }
]

Upvotes: 1

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