CQL Support

[jisantuc]

Overview

This PR holds the attempted implementation in Franklin of CQL filters as described in radiantearth/stac-api-spec#128. The culmination of the PR was filter extension feedback in that PR and the related OGC CQL PR.

Checklist

• New tests have been added or existing tests have been modified

Notes

This will stay a draft until there's more work to do with the filter extension -- it removes the query extension implementation which is not quite dead yet, so it's a little stuck.

Testing Instructions

• tests

[kthyng]

Hi @jisantuc! I'm working with STAC and franklin and needing to be able to filter, hence finding this issue. Any idea of the time frame on this? Would you expect this PR to work in the meantime if I were to use it? Thanks for your effort!

[pomadchin]

Hey @kthyng 👋 I'm afraid there is no definite answer to your question, in the meantime you may try to use the implemented query extension and mb it will be good enough for your purposes.

[kthyng]

@pomadchin Thanks for your response! I had tried to use the query extension in the past and thought I couldn't get it to work, but I will try again. Should it work as described in the STAC query readme? Or any examples you could point me to?

[pomadchin]

@kthyng yes! that is exactly it. just add an extra query field into the JSON body of the POST request to the /search endpoint and it should work. Let me know if you have any problems with it, I'll try to assist!

[jisantuc]

@kthyng a little more background -- you can see over in the API spec repo that the filter extension is still evolving. This is in part due to ongoing work in the OGC group around conformance class organization and what functionality lives where. This PR implemented a very early version of the filter extension as a test of how easy / difficult that would be -- support of the current form of the filter extension would require new work I believe.

[kthyng]

Thanks @jisantuc, that makes sense. I asked about timing in the STAC gitter and heard the following for what it's worth!

now that 1.0.0-beta.5 of the spec is out, Filter Extension is stable enough to actually implement (it depends on the CQL2 spec, which has been changing significantly over the last few months, but has stabilized now)