feat: add GET /api/v1/chart/{chart_id}/data/?format{format} API

[betodealmeida]

SUMMARY

This PR adds a new API for retrieving data associated with a saved chart via a GET request.

The API uses the stored query_context (#15824) to run the query and fetch the data.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A

TESTING INSTRUCTIONS

I accessed the endpoint manually by hitting http://localhost:9000/api/v1/chart/56/data/:

{
  "result": [
    {
      "cache_key": "bf6383e65e2d57b646778b8b0bbb875b",
      "cached_dttm": null,
      "cache_timeout": 86400,
      "annotation_data": {},
      "error": null,
      "is_cached": false,
      "query": "SELECT gender AS gender,\n       SUM(num) AS sum__num\nFROM birth_names\nWHERE ds >= TO_TIMESTAMP('1900-01-01 00:00:00.000000', 'YYYY-MM-DD HH24:MI:SS.US')\n  AND ds < TO_TIMESTAMP('2000-01-01 00:00:00.000000', 'YYYY-MM-DD HH24:MI:SS.US')\nGROUP BY gender\nORDER BY sum__num DESC\nLIMIT 50000",
      "status": "success",
      "stacktrace": null,
      "rowcount": 2,
      "colnames": [
        "gender",
        "sum__num"
      ],
      "coltypes": [
        1,
        0
      ],
      "data": [
        {
          "gender": "boy",
          "sum__num": 40276116
        },
        {
          "gender": "girl",
          "sum__num": 28055783
        }
      ],
      "applied_filters": [],
      "rejected_filters": []
    }
  ]
}

And http://localhost:9000/api/v1/chart/56/data/?format=csv:

gender,sum__num
boy,40276116
girl,28055783

I also added unit tests covering the case where query_context is null, and the case where it's present and data is returned.

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[eschutho]

debug?

[betodealmeida]

Ugh, thanks! :)

[eschutho]

LGTM pending one small debug leftover

[codecov]

Codecov Report

Merging #15827 (22e1b3d) into master (9a79a57) will increase coverage by 0.00%.
The diff coverage is 81.39%.

@@           Coverage Diff           @@
##           master   #15827   +/-   ##
=======================================
  Coverage   76.90%   76.90%           
=======================================
  Files         984      984           
  Lines       51670    51698   +28     
  Branches     6991     6991           
=======================================
+ Hits        39736    39758   +22     
- Misses      11710    11716    +6     
  Partials      224      224           

Flag	Coverage Δ
mysql	81.53% <81.39%> (-0.01%)	⬇️
postgres	81.56% <81.39%> (-0.01%)	⬇️
python	81.65% <81.39%> (-0.01%)	⬇️
sqlite	81.19% <81.39%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
superset/charts/api.py	86.17% <81.39%> (-0.63%)	⬇️

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[santiblanko]

I need this data paginated. It's possible?