CODEWITHSUNDEEP
mongodbindexing
WHITECOLOR
WHITECOLOR

Reputation: 26142

mongodb Index to find empty values

Let's say I have a emails collection with fields and records like:

{
  sendAt: "",
  to: "[email protected]",
  from: "[email protected]"
}

If I need to to query only records with empty sendAt field. Considering this requirement how should I index this collection field? I don't actually need to query any specific dates in sendAt field so full index will be redundant in my view. Is it possible to do with mondogb?

Upvotes: 0

Views: 609

Answers (1)

Evgeny S.
Evgeny S.

Reputation: 858

Starting from MongoDb 3.2 you can use partial indexes: https://docs.mongodb.org/manual/core/index-partial.

For example, in your case:

db.emails.createIndex(
   { sendAt: 1 },
   { partialFilterExpression: { sendAt: "" } }
)

Another approach is to add extra field to documents where sendAt is empty and create a sparse index on that field: https://docs.mongodb.org/manual/core/index-sparse/

{
  sendAt: "",
  to: "[email protected]",
  from: "[email protected]",
  sendAtEmpty: true
}

{
  sendAt: "1/1/1980",
  to: "[email protected]",
  from: "[email protected]",
}

db.emails.createIndex( { "sendAtEmpty": 1 }, { sparse: true } )

Upvotes: 2

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