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?_labels= and ?_label=COL to expand foreign keys in JSON/CSV

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These new querystring arguments can be used to request expanded foreign keys
in both JSON and CSV formats.

?_labels=on turns on expansions for ALL foreign key columns

?_label=COLUMN1&_label=COLUMN2 can be used to pick specific columns to expand

e.g. `Street_Tree_List.json?_label=qSpecies&_label=qLegalStatus`

    {
        "rowid": 233,
        "TreeID": 121240,
        "qLegalStatus": {
            "value" 2,
            "label": "Private"
        }
        "qSpecies": {
            "value": 16,
            "label": "Sycamore"
        }
        "qAddress": "91 Commonwealth Ave",
        ...
    }

The labels option also works for the HTML and CSV views.

HTML defaults to `?_labels=on`, so if you pass `?_labels=off` you can disable
foreign key expansion entirely - or you can use `?_label=COLUMN` to request
just specific columns.

If you expand labels on CSV you get additional columns in the output:

`/Street_Tree_List.csv?_label=qLegalStatus`

    rowid,TreeID,qLegalStatus,qLegalStatus_label...
    1,141565,1,Permitted Site...
    2,232565,2,Undocumented...

I also refactored the existing foreign key expansion code.

Closes #233. Refs #266.
This commit is contained in:
Simon Willison 2018-06-16 15:18:57 -07:00
commit ed631e690b
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9 changed files with 276 additions and 69 deletions
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30
datasette/views/base.py
View file

@ -168,11 +168,33 @@ class BaseView(RenderMixin):
except DatasetteError:
raise
# Convert rows and columns to CSV
headings = data["columns"]
# if there are columns_expanded we need to add additional headings
columns_expanded = set(data.get("columns_expanded") or [])
if columns_expanded:
headings = []
for column in data["columns"]:
headings.append(column)
if column in columns_expanded:
headings.append("{}_label".format(column))
async def stream_fn(r):
writer = csv.writer(r)
writer.writerow(data["columns"])
writer.writerow(headings)
for row in data["rows"]:
writer.writerow(row)
if not columns_expanded:
# Simple path
writer.writerow(row)
else:
# Look for {"value": "label": } dicts and expand
new_row = []
for cell in row:
if isinstance(cell, dict):
new_row.append(cell["value"])
new_row.append(cell["label"])
else:
new_row.append(cell)
writer.writerow(new_row)
content_type = "text/plain; charset=utf-8"
headers = {}
@ -208,6 +230,10 @@ class BaseView(RenderMixin):
if _format == "csv":
return await self.as_csv(request, name, hash, **kwargs)
if _format is None:
# HTML views default to expanding all forign key labels
kwargs['default_labels'] = True
extra_template_data = {}
start = time.time()
status_code = 200