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Working with JSON Indexes in SQL Server 2025

Koen Verbeeck tries out a new index type:

We’re trying the new JSON data type in SQL Server for data stored as JSON in a table. When we query it using functions such as JSON_VALUE, we see a full table scan is performed for each query. Is there a way we can index the JSON to improve performance?

The JSON index has a somewhat different definition of its structure and there are some limitations to how it works, but for specific JSON-related queries, you can see the improvement.

3 Comments

  1. George Walkey
    George Walkey 2025-11-05

    Im seeing only 1.8x speedups using the JSON DataType and JSON Indexes vs ye old VCMax. Will continue testing on RTM+

    • Kevin Feasel
      Kevin Feasel 2025-11-05

      Thanks for the concrete numbers. I’m not sure what to expect with JSON indexing, so it’s good to get some specific examples of how it’s faring in real-world scenarios.

  2. George Walkey
    George Walkey 2025-11-06

    Yes Indeed!
    I need more data to test with too
    TBH, was looking forward to this feature probably more than others in the box
    AKA Cosmos paltry 2MB JSON document limit vs 2GB for SQL Server etc

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