There are cases where users sort a table using compound-values sort_key
and one of the key has nullable set to True. For example, sorting a
table using ['id', 'updated_at'] where 'updated_at' can be None.
When marker_value is None, we cannot do value comparison using '<' or
'>' operators. This patch adds a check if the value from the marker
corresponding to the nullable-key has None value. If that is the case,
we skip the comparison.
Back to the example above, instead of always getting the following
criteria (which doesn't work):
(id > MARKER_ID) or (id == MARKER_ID && updated_at > None) <-- failure
we will get the following criteria when 'updated_at' is None:
(id > MARKER_ID)
This is not hurting in any way to existing / legal use cases where
callers are expected to include a unique key in sort keys. If there are
such cases, this patch is not making things worse because the sorting
is already unpredictable.
Closes-Bug: #1615938
Change-Id: Iea2cd0bb2556b0b15a0baaa76ef522a3097f9928
(cherry picked from commit b3869d04cf)
3787363005