tl;dr Idea: use parameters of content-type response header, e.g.:

content-type: application/octet-stream; total_volume=FLOAT; year=INT;
...
{"total_volume":78.0,"year":2018}

If implementing this feature, remember to also make sure the header is included in Access-Control-Expose-Headers (not to be confused with Access-Control-Allow-Headers, which is about which headers are allowed in the request) so that cross-origin client code can read it from the response.

This is not necessary for CORS-safelisted response headers, which include only Cache-Control, Content-Language, Content-Length, Content-Type, Expires, Last-Modified, and Pragma (deprecated).

Perhaps it would be appropriate to use the "parameters" of the Content-Type response header, which is actually kind of intended for this purpose (but could have unknown effects on proxies like Cloudflare):

The indicated media type defines both the data format and how that data is intended to be processed by a recipient

The type/subtype MAY be followed by semicolon-delimited parameters (Section 5.6.6) in the form of name/value pairs. The presence or absence of a parameter might be significant to the processing of a media type, depending on its definition within the media type registry. Parameter values might or might not be case-sensitive, depending on the semantics of the parameter name.

For example, for this request:

curl 'https://demo.seafowl.io/q/4be9110c4fe720dae8310fde08f028b49d01a5c41b70df21668a143265f6a4bc.csv' \
  -H $'x-seafowl-query: SELECT%20year%3A%3Ainteger%20AS%20year%2C%0ASUM(volume)%20AS%20total_volume%0AFROM%20supply_chains%0AWHERE%20country_of_production%20%3D%20\'ARGENTINA\'%0AAND%20country_of_import%20%3D%20\'AFGHANISTAN\'%0AAND%20commodity%20%3D%20\'CORN\'%0AGROUP%20BY%201%20ORDER%20BY%201%20ASC'

which outputs:

{"total_volume":78.0,"year":2018}

maybe we could return the content-type header like:

content-type: application/octet-stream; total_volume=FLOAT; year=INT;

Return result set type information in the HTTP response #356

Description

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions