Stats V2: inconsistent return for varying intervals: empty groups

[constantinius]

Environment

SaaS (https://sentry.io/)

Steps to Reproduce

A search query for the outcomes dataset produces varying results depending on the granularity specified by the interval parameter. Here is a request with 1h granularity that has the expected groups property filled.

{
    "start": "2025-01-07T13:00:00Z",
    "end": "2025-01-07T15:00:00Z",
    "intervals": [
        "2025-01-07T13:00:00Z",
        "2025-01-07T14:00:00Z"
    ],
    "groups": [
        {
            "by": {
                "outcome": "accepted",
                "reason": "none"
            },
            "totals": {
                "sum(quantity)": 27231
            },
            "series": {
                "sum(quantity)": [
                    0,
                    27231
                ]
            }
        }
    ]
}

But with a granularity of 1m, the otherwise same request returns an empty groups property:

{
    "start": "2025-01-07T13:35:00Z",
    "end": "2025-01-07T14:01:00Z",
    "intervals": [
        "2025-01-07T13:35:00Z",
        "2025-01-07T13:36:00Z",
        "2025-01-07T13:37:00Z",
        "2025-01-07T13:38:00Z",
        "2025-01-07T13:39:00Z",
        ...
        "2025-01-07T14:00:00Z"
    ],
    "groups": []
}

Expected Result

Responses similar to this with groups:

{
    "start": "2025-01-07T13:00:00Z",
    "end": "2025-01-07T15:00:00Z",
    "intervals": [
        "2025-01-07T13:00:00Z",
        "2025-01-07T14:00:00Z"
    ],
    "groups": [
        {
            "by": {
                "outcome": "accepted",
                "reason": "none"
            },
            "totals": {
                "sum(quantity)": 27231
            },
            "series": {
                "sum(quantity)": [
                    0,
                    27231
                ]
            }
        }
    ]
}```

### Actual Result

Missing groups:

```json
{
    "start": "2025-01-07T13:35:00Z",
    "end": "2025-01-07T14:01:00Z",
    "intervals": [
        "2025-01-07T13:35:00Z",
        "2025-01-07T13:36:00Z",
        "2025-01-07T13:37:00Z",
        "2025-01-07T13:38:00Z",
        "2025-01-07T13:39:00Z",
        ...
        "2025-01-07T14:00:00Z"
    ],
    "groups": []
}

Product Area

Stats

Link

No response

DSN

No response

Version

No response

[getsantry]

Routing to @getsentry/product-owners-stats for triage ⏲️