[C++/Python] Implement Array.isvalid/notnull/isnull as scalar functions

[asfimport]

For arrays with nulls, this amounts to returning the validity bitmap. Without nulls, an array of all 1 bits must be constructed. For isnull, the bits must be flipped (in this case, the un-set part of the new bitmap must stay 0, though).

Reporter: Wes McKinney / @wesm
Assignee: Ben Kietzman / @bkietz

Related issues:

• [C++] C++ array kernels framework and execution buildout (umbrella issue) (is a child of)

PRs and other links:

• GitHub Pull Request #1378
• GitHub Pull Request #7410

_{Note: This issue was originally created as ARROW-971. Please see the migration documentation for further details.}

[asfimport]

Licht Takeuchi / @Licht-T:
@wesm Is this already implemented in C++?

arrow/cpp/src/arrow/array.h

Line 185 in e8331f4

bool IsNull(int64_t i) const {

[asfimport]

Wes McKinney / @wesm:
The desired scope for this JIRA was to be like pandas.isnull or pandas.notnull, so returning a pyarrow.BooleanArray result

[asfimport]

Wes McKinney / @wesm:
The correct way to implement is now as arrow::compute::ScalarFunction

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 7410
#7410