feat: Allow selectors.of_type("array<struct>")

[Riezebos]

Is your feature request related to a problem?

t = ibis.memtable([{
    "id": "1",
    "array_struct_col": [{"a": "b"}],
    "array_int_col": [1,2,3]
}])
t.mutate(s.across(s.of_type("array<struct>"), _.cast("array<json>")))

ParseError: expected '<' at 0:12

What is the motivation behind your request?

I am trying to mutate all columns that are an array with a struct in them but I don't want to mutate array columns with any other datatype in them

Describe the solution you'd like

From my perspective as a user the logical solution would be the on in my example code. It's already possible to do s.of_type("array") and s.of_type("struct"). But a different solution is also fine by me.

I found a workaround for now but that seems a but ineffecient:

t = t.mutate(s.across(s.of_type("array"), lambda col: col.cast("array<json>") if col.unnest().type().is_struct() else col))

What version of ibis are you running?

9.5.0

What backend(s) are you using, if any?

Duckdb

Code of Conduct

• I agree to follow this project's Code of Conduct

[cpcloud]

You can do this with the where selector, which should be a bit more concise:

In [18]: from ibis.interactive import *

In [19]: t = ibis.memtable([{
    ...:     "id": "1",
    ...:     "array_struct_col": [{"a": "b"}],
    ...:     "array_int_col": [1,2,3]
    ...: }])

In [20]: t.select(s.where(lambda c: c.type().is_array() and c.type().value_type.is_struct()))
Out[20]:
┏━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃ array_struct_col         ┃
┡━━━━━━━━━━━━━━━━━━━━━━━━━━┩
│ array<struct<a: string>> │
├──────────────────────────┤
│ [{...}]                  │
└──────────────────────────┘

In [21]: t.mutate(s.across(s.where(lambda c: c.type().is_array() and c.type().value_type.is_struct()), _.length()))
Out[21]:
┏━━━━━━━━┳━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━┓
┃ id     ┃ array_struct_col ┃ array_int_col        ┃
┡━━━━━━━━╇━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━┩
│ string │ int64            │ array<int64>         │
├────────┼──────────────────┼──────────────────────┤
│ 1      │                1 │ [1, 2, ... +1]       │
└────────┴──────────────────┴──────────────────────┘

[Riezebos]

Thanks!

TIL Array.value_type exists, good to know!