[FEATURE] SQL functions in WHERE clause not evaluated for required parameters (start_time), and projected parameter/response columns return null #686

Summary

Two related issues observed querying openai_admin.usage.completions.

1. Function expressions in the WHERE clause are not evaluated for required parameters

When a required parameter is supplied via a function expression rather than a literal, the value is not resolved and the parameter is dropped from the request, producing a 400 from the provider.

SELECT
  json_extract(r.value, '$.project_id')    AS project_id,
  json_extract(r.value, '$.model')         AS model,
  date(u.start_time, 'unixepoch')          AS usage_date,
  json_extract(r.value, '$.input_tokens')  AS input_tokens,
  json_extract(r.value, '$.output_tokens') AS output_tokens
FROM openai_admin.usage.completions u, json_each(u.results) r
WHERE u.start_time = strftime('%s', date('now', '-30 days'))
  AND u.bucket_width = '1d'
  AND u.group_by = 'project_id'
ORDER BY usage_date, project_id;

Result:

http response status code: 400, response body: {
  "error": {
    "message": "Missing required parameter: 'start_time'.",
    "type": "invalid_request_error",
    "param": "start_time",
    "code": "missing_required_parameter"
  }
}

The expression itself evaluates fine standalone:

select strftime('%s', date('now', '-30 days'));
-- 1781481600

The same query with the literal substituted does dispatch the request:

WHERE u.start_time = 1781481600

Expected: scalar function expressions on the right hand side of a required parameter predicate are evaluated before request construction, and the resolved value is bound to the parameter.

2. Projected columns return null / zero when the request does succeed

With the literal form, the request succeeds but the projection is largely empty:

|-------------------------------|-------|------------|--------------|---------------|
|          project_id           | model | usage_date | input_tokens | output_tokens |
|-------------------------------|-------|------------|--------------|---------------|
| proj_RBWsjunhtdHqTO3MgxytkuB5 | null  |          0 | null         | null          |
|-------------------------------|-------|------------|--------------|---------------|

Observations:

• project_id resolves via json_extract(r.value, '$.project_id'), so json_each(u.results) is expanding correctly.
• input_tokens and output_tokens are null despite being siblings of project_id in the same result object.
• usage_date is 0, indicating u.start_time is not projectable in the response row even though it was supplied as a parameter. Parameter values should be echoed into the row so they can be projected and joined against.
• model may legitimately be null given group_by = 'project_id', but should be confirmed.

Environment

• Provider: openai_admin
• Resource: openai_admin.usage.completions
• stackql version:
• Provider version:

Suspected areas

• Parameter binding path: literal-only extraction from the WHERE clause, function expressions ignored rather than evaluated or rejected.
• Response projection: parameter columns not merged into the emitted row; possible schema mismatch on the nested results[].result[] shape for the usage endpoints.

Acceptance criteria

• WHERE start_time = strftime('%s', date('now', '-30 days')) dispatches a request with the resolved epoch value.
• If an expression cannot be evaluated at plan time, stackql returns a clear error rather than silently dropping the parameter.
• Projecting u.start_time returns the supplied parameter value.
• input_tokens and output_tokens return values from the response payload.