[ARROW-15054] Attribute nbytes of slice will return the value corresponding to the whole structure

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Duplicate
• Component/s: Python
• External issue URL: https://github.com/apache/arrow/issues/30570
• Assignee: Unassigned
• Reporter: Adrien Hoarau
• Created: 10/Dec/21 12:42
• Updated: 11/Jan/23 08:44
• Resolved: 10/Dec/21 12:46

Description

Whether for tables/arrays, slicing and then calling `nbytes` will return the value for the whole struct. I don't know if this is a bug or the desired behaviour (and if it is I would argue that it should return a result relative to the slice, and also ask if there is any way to get the memory size of my slice?).

 

```

import pyarrow

pyarrow._version_

>>> 6.0.0

table = pyarrow.Table.from_arrays([pyarrow.array(['foo', 'bar', 'qux'], type=pyarrow.string())], names=["a"])

table.num_rows

>>> 3

table.nbytes

>>> 25

table.slice(0, 2).num_rows

>>> 2

table.slice(0, 2).nbytes

>>> 25

```