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Fix CursorPagination when objects get deleted between calls (#6504)

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Co-Authored-By: Tom Quinonero <tq@3yourmind.com>
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Joachim Jablon 2019-04-14 02:08:34 +02:00 committed by Joachim Jablon
parent fab3a9c8b3
commit 1cd4f9fec1
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1 changed files with 14 additions and 4 deletions
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18
rest_framework/pagination.py
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@ -589,7 +589,7 @@ class CursorPagination(BasePagination):
if not self.has_next: if not self.has_next:
return None return None
if self.cursor and self.cursor.reverse and self.cursor.offset != 0: if self.page and self.cursor and self.cursor.reverse and self.cursor.offset != 0:
# If we're reversing direction and we have an offset cursor # If we're reversing direction and we have an offset cursor
# then we cannot use the first position we find as a marker. # then we cannot use the first position we find as a marker.
compare = self._get_position_from_instance(self.page[-1], self.ordering) compare = self._get_position_from_instance(self.page[-1], self.ordering)
@ -597,12 +597,14 @@ class CursorPagination(BasePagination):
compare = self.next_position compare = self.next_position
offset = 0 offset = 0
has_item_with_unique_position = False
for item in reversed(self.page): for item in reversed(self.page):
position = self._get_position_from_instance(item, self.ordering) position = self._get_position_from_instance(item, self.ordering)
if position != compare: if position != compare:
# The item in this position and the item following it # The item in this position and the item following it
# have different positions. We can use this position as # have different positions. We can use this position as
# our marker. # our marker.
has_item_with_unique_position = True
break break
# The item in this position has the same position as the item # The item in this position has the same position as the item
@ -611,7 +613,7 @@ class CursorPagination(BasePagination):
compare = position compare = position
offset += 1 offset += 1
else: if self.page and not has_item_with_unique_position:
# There were no unique positions in the page. # There were no unique positions in the page.
if not self.has_previous: if not self.has_previous:
# We are on the first page. # We are on the first page.
@ -630,6 +632,9 @@ class CursorPagination(BasePagination):
offset = self.cursor.offset + self.page_size offset = self.cursor.offset + self.page_size
position = self.previous_position position = self.previous_position
if not self.page:
position = self.next_position
cursor = Cursor(offset=offset, reverse=False, position=position) cursor = Cursor(offset=offset, reverse=False, position=position)
return self.encode_cursor(cursor) return self.encode_cursor(cursor)
@ -637,7 +642,7 @@ class CursorPagination(BasePagination):
if not self.has_previous: if not self.has_previous:
return None return None
if self.cursor and not self.cursor.reverse and self.cursor.offset != 0: if self.page and self.cursor and not self.cursor.reverse and self.cursor.offset != 0:
# If we're reversing direction and we have an offset cursor # If we're reversing direction and we have an offset cursor
# then we cannot use the first position we find as a marker. # then we cannot use the first position we find as a marker.
compare = self._get_position_from_instance(self.page[0], self.ordering) compare = self._get_position_from_instance(self.page[0], self.ordering)
@ -645,12 +650,14 @@ class CursorPagination(BasePagination):
compare = self.previous_position compare = self.previous_position
offset = 0 offset = 0
has_item_with_unique_position = False
for item in self.page: for item in self.page:
position = self._get_position_from_instance(item, self.ordering) position = self._get_position_from_instance(item, self.ordering)
if position != compare: if position != compare:
# The item in this position and the item following it # The item in this position and the item following it
# have different positions. We can use this position as # have different positions. We can use this position as
# our marker. # our marker.
has_item_with_unique_position = True
break break
# The item in this position has the same position as the item # The item in this position has the same position as the item
@ -659,7 +666,7 @@ class CursorPagination(BasePagination):
compare = position compare = position
offset += 1 offset += 1
else: if self.page and not has_item_with_unique_position:
# There were no unique positions in the page. # There were no unique positions in the page.
if not self.has_next: if not self.has_next:
# We are on the final page. # We are on the final page.
@ -678,6 +685,9 @@ class CursorPagination(BasePagination):
offset = 0 offset = 0
position = self.next_position position = self.next_position
if not self.page:
position = self.previous_position
cursor = Cursor(offset=offset, reverse=True, position=position) cursor = Cursor(offset=offset, reverse=True, position=position)
return self.encode_cursor(cursor) return self.encode_cursor(cursor)