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Add support for offsets and limits in wheres #230

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Add support for offsets and limits in wheres #230

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44 changes: 43 additions & 1 deletion binder/views.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1051,6 +1051,38 @@ def _follow_related(self, fieldspec):
return (RelatedModel(fieldname, related_model, related_field),) + view._follow_related(fieldspec)


# This will pop the *limit* and *offset* parameters from the *where* clauses of requests.
# These parameters allow the frontend to limit the amount of data it gets from big relations.
# The usage is illustrated by the following fragment of one of our unit tests:
# `res = self.client.get('/zoo/', data={'with': 'animals.caretaker', 'where': 'animals(name:contains=lion),animals(#offset=1),animals(#limit=1)'})`
#
# In our frontend, it can be used by overriding `getDefaultParams` in a class extending `AdminOverview`:
# `getDefaultParams() { return { where: 'campaigns(#limit=25)' }; }`
def _pop_limit_and_offset(self, field_where_map) -> (int, int):
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if not field_where_map or 'filters' not in field_where_map:
return (None, None)
filters = field_where_map['filters']

limit = None
offset = None
raw_limit = None
raw_offset = None
for filter in filters:
key, value = filter.split('=')
if key == '#limit':
limit = int(value)
raw_limit = filter
if key == '#offset':
offset = int(value)
raw_offset = filter

if raw_limit:
filters.remove(raw_limit)
if raw_offset:
filters.remove(raw_offset)

return (limit, offset)

# This will return a dictionary of dotted "with string" keys and
# tuple values of (view_class, id_dict). These ids do not require
# permission scoping. This will be done when fetching the actual
Expand All @@ -1067,7 +1099,10 @@ def _get_with_ids(self, pks, request, include_annotations, with_map, where_map):

next_relation = self._follow_related(field)[0]
view = self.get_model_view(next_relation.model)
q, _ = view._filter_relation(None if vr else next_relation.fieldname, where_map.get(field, None), request, {
field_where_map = where_map.get(field, None)
limit, offset = self._pop_limit_and_offset(field_where_map)

q, _ = view._filter_relation(None if vr else next_relation.fieldname, field_where_map, request, {
rel[len(field) + 1:]: annotations
for rel, annotations in include_annotations.items()
if rel == field or rel.startswith(field + '.')
Expand Down Expand Up @@ -1123,6 +1158,13 @@ def _get_with_ids(self, pks, request, include_annotations, with_map, where_map):
.distinct()
)

if limit is not None and offset is not None:
query = query[offset:offset + limit]
if limit is not None and offset is None:
query = query[0:limit]
if limit is None and offset is not None:
query = query[offset:]

for pk, rel_pk in query:
rel_ids_by_field_by_id[field][pk].append(rel_pk)

Expand Down
105 changes: 79 additions & 26 deletions tests/test_filterable_relations.py
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Original file line number Diff line number Diff line change
Expand Up @@ -43,37 +43,90 @@ def test_where(self):

# Filter the animal relations on animals with lion in the name
# This means we don't expect the goat and its caretaker in the with response

def test_response(res, expected_animals, expected_with):
self.assertEqual(res.status_code, 200)
res = jsonloads(res.content)

assert_json(res, {
'data': [
{
'id': zoo.id,
'animals': expected_animals,
EXTRA(): None,
}
],
'with': expected_with,
EXTRA(): None,
})

# Test without offset or limit
res = self.client.get('/zoo/', data={'with': 'animals.caretaker', 'where': 'animals(name:contains=lion)'})
self.assertEqual(res.status_code, 200)
res = jsonloads(res.content)
test_response(res, [antlion.id, sealion.id], {
'animal': [
{
'id': antlion.id,
EXTRA(): None,
},
{
'id': sealion.id,
EXTRA(): None,
},
],
'caretaker': [
{
'id': freeman.id,
EXTRA(): None,
},
]
})

assert_json(res, {
'data': [
# Test with limit
res = self.client.get('/zoo/', data={'with': 'animals.caretaker', 'where': 'animals(name:contains=lion),animals(#limit=1)'})
test_response(res, [antlion.id], {
'animal': [
{
'id': zoo.id,
'animals': [antlion.id, sealion.id],
'id': antlion.id,
EXTRA(): None,
}
},
],
'with': {
'animal': [
{
'id': antlion.id,
EXTRA(): None,
},
{
'id': sealion.id,
EXTRA(): None,
},
],
'caretaker': [
{
'id': freeman.id,
EXTRA(): None,
},
]
},
EXTRA(): None,
'caretaker': [
{
'id': freeman.id,
EXTRA(): None,
},
]
})

# Test with offset
res = self.client.get('/zoo/', data={'with': 'animals.caretaker', 'where': 'animals(name:contains=lion),animals(#offset=1)'})
test_response(res, [sealion.id], {
'animal': [
{
'id': sealion.id,
EXTRA(): None,
},
],
'caretaker': []
})

# Test with offset and limit
res = self.client.get('/zoo/', data={'with': 'animals.caretaker', 'where': 'animals(name:contains=lion),animals(#offset=1),animals(#limit=1)'})
test_response(res, [sealion.id], {
'animal': [
{
'id': sealion.id,
EXTRA(): None,
},
],
'caretaker': []
})

# Test with offset and 0 limit
res = self.client.get('/zoo/', data={'with': 'animals.caretaker', 'where': 'animals(name:contains=lion),animals(#offset=1),animals(#limit=0)'})
test_response(res, [], {
'animal': [],
'caretaker': []
})


Expand Down