[FEA] is_monotonic* properties are erroneously cached

[shwina]

The is_monotonic* properties of Column are cached. But because Columns are not immutable, this can lead to bugs like the following:

In [5]: s
Out[5]:
0    1
1    2
2    3
3    4
4    5
dtype: int64

In [6]: s.is_monotonic_increasing
Out[6]: True

In [7]: s[2:5] = [3, 2, 1]

In [8]: s.is_monotonic_increasing
Out[8]: True

In [9]: s
Out[9]:
0    1
1    2
2    3
3    2
4    1
dtype: int64

Some discussion here.

[vyasr]

I will remove caching entirely in #8130, but once that PR is merged we should consider if it is possible to invalidate the cache in all cases that should, which would make caching feasible.

[shwina]

@vyasr can this issue be closed out now that #8130 is merged?

[vyasr]

Yes I think so. We can revisit better caching in the future.