How to Create a Case-Insensitive Unique Compound Index in MongoDB?

Question Body: I'm trying to create a compound unique text index in MongoDB with the following fields:

tenant_id: 1 seller_id: 1 seller_sku_code: text. However, I'm encountering an error when trying to create the index:

Index build failed: 4df81a22-042f-4e51-bbec-b0f8a7dafe2e:
Collection product_db.skus ( 83cc8978-b0fe-4c4b-ae58-691e32db7f95 )
:: caused by :: E11000 duplicate key error
collection: product_db.skus index: tenant_id_1_seller_id_1_seller_sku_code_text dup key: { tenant_id: "1", seller_id: "113", _fts: "acc", _ftsx: 0.75 }

I need to ensure that the seller_sku_code is unique within the database and is case-insensitive. For example:

"ABC" and "abc" should not be allowed simultaneously. "ACC-2001" and "ACC-2000" should be allowed to coexist.

How can I create this unique, case-insensitive index on seller_sku_code while still ensuring the uniqueness of the tenant_id and seller_id fields?

  • Specify collation locale and strength refer to mongodb.com/docs/v5.0/core/index-case-insensitive. If you are using an old MongoDB version you might want to check if these are supported. Commented May 15 at 22:32
  • In a compound index uniqueness is applied on a combination of all fields in the index. If you need uniqueness on a specific field create a unique index on that field. Note that a field can be specified in more than one index. Can you include the MongoDB version, the code you are using to create the index and sample documents in your question.
    – prasad_
    Commented May 16 at 3:42

1 Answer 1


If I am understanding your situation correctly, you are actually trying to achieve 2 individual requirements:

  1. seller_sku_code: unique and case insensitive
  2. tenant_id and seller_id: unique

If it is true, it could be easier to just set up 2 separate indices for them:

"indexes": [
        "name": "tenant_id_seller_id_idx",
        "key": {
          "tenant_id": 1,
          "seller_id": 1
        "unique": true
        "name": "seller_sku_code_idx",
        "key": {
          "seller_sku_code": 1
        "unique": true,
        "collation": {
          "locale": "en",
          "strength": 2

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