Implement queries for cmr and hydrocron

[frankinspace]

• refine https://github.com/podaac/hydrocron/blob/feature/issue-71/hydrocron/db/track_status.py prototype for cmr query
• add new query to https://github.com/podaac/hydrocron/blob/develop/hydrocron/api/data_access/db.py for hydrocron query
• may need placeholder for start date

[nikki-t]

I was able to implement the CMR query which returns a list of granule URs present in CMR for a specified time range. I started to implement the Hydrocron query but ran into some confusion around DynamoDB queries.

I would like to query the hydrocron tables in a way that returns all granuleUR with a range_start_time between a specified range which I can determine from the CMR query. So something this:

items = hydrocron_table.query(
            IndexName="GranuleURIndex",
            KeyConditionExpression=(Key("range_start_time").between(start_time, end_time))
        )

But when I try to do this the query produces an error and complains that I have not included a "key schema element" in the query:

botocore.exceptions.ClientError: An error occurred (ValidationException) when calling the Query operation: Query condition missed key schema element

From my understanding you cannot query DynamoDB on a date range only and instead would need to perform a scan which is costly.

For now I am going to query Hydrocron by granuleUR which I can get by iterating over the CMR query results to perform the query. This will allow me to automatically see what is in CMR but not in Hydrocron.

I won't be able to easily determine what is in Hydrocron but not in CMR (or overlap between the two). I think we would to set up another global secondary index on the "range_start_time" with a range key of "granuleUR" if we want to facilitate a different query. Although I am not sure that quite fits with the DynamoDB use case.

@torimcd - Does this fit with your understanding of DynamoDB queries?

Any objections to de-prioritizing determining what is in Hydrocron but not CMR since we were only going to log those results for now?

[nikki-t]

We will de-scope determining overlap and what exists in Hydrocron but not CMR for now. Create #206 to track future work.