## TL;DR

To force a specific index, specify USE INDEX with the key name; if the index is missing the query errors instead of silently scanning. If INTERNAL_VECTOR_SEARCH is not in the ColumnStoreFilter line of EXPLAIN, the vector index is not being used.

## The error

```text
EXPLAIN check
```

## Fix

1. To force a specific index, specify USE INDEX with the key name; if the index is missing the query errors instead of silently scanning.
   Expected: You get the expected result; the problem is gone.
2. Re-run the original operation and confirm the error is gone.
   Expected: no error, normal output.

## When to use

- You hit this exact error with SingleStore Vector.
- The symptom matches: query not using the ANN index - EXPLAIN check.

## When NOT to use

- A different error message from SingleStore Vector; the cause here is specific to this error.
- Unrelated SingleStore Vector issues (different feature, different failure).
- You need general documentation for the tool; check the official docs instead.

## Compatibility

Reported against SingleStore Vector. Source: https://docs.singlestore.com/db/v8.7/reference/sql-reference/vector-functions/vector-indexing/.

## Variant phrasings

### query not using the ANN index - EXPLAIN check
### EXPLAIN check

## Why it happens

A vector query runs slowly as if the vector index does not exist. Check EXPLAIN to see whether the index is used at all.

## Edge cases

- If your error message differs even slightly, this is probably a different issue; search the exact text.
- If the fix does not help, capture the full error output and check the source link for updates.

## Source

https://docs.singlestore.com/db/v8.7/reference/sql-reference/vector-functions/vector-indexing/

---

## Vectle citations

- Exact version: <https://vectle.com/skills/skl_waeQ7pes0sYDKTR6a9Hwzw/versions/skv_sDq9Lz3d1nk7tm-2G763Nw>
- Canonical HTML skill page: <https://vectle.com/skills/skl_waeQ7pes0sYDKTR6a9Hwzw>
- Current Markdown URL: <https://vectle.com/skills/skl_waeQ7pes0sYDKTR6a9Hwzw/markdown>

## Selected public attribution and original notices/references

```json
{
  "author": "issueatlas",
  "client": null,
  "notices_and_references": [
    "https://docs.singlestore.com/db/v8.7/reference/sql-reference/vector-functions/vector-indexing/"
  ]
}
```