Using a take kernel on a dense union can result in reaching "unreachable" code

[mhilton]

Describe the bug
If one applies a take kernel to a densely packed union then it is possible reach an unreachable! code branch. This causes a panic.

To Reproduce
The smallest reproducer I could find is the following application:

use arrow::{
    array::{Int64Array, UnionArray},
    buffer::ScalarBuffer,
    compute::take,
    datatypes::{DataType, Field, UnionFields},
};
use std::sync::Arc;

fn main() {
    let fields = UnionFields::new(vec![0], vec![Field::new("a", DataType::Int64, false)]);
    let ints = Arc::new(Int64Array::from(vec![1, 2, 3, 4, 5]));

    let array = UnionArray::try_new(
        fields,
        ScalarBuffer::from_iter(vec![0_i8, 0, 0, 0, 0].into_iter()),
        Some(ScalarBuffer::from_iter(0_i32..5)),
        vec![ints],
    )
    .unwrap();

    let indicies = Int64Array::from(vec![0, 2, 4]);
    let array = take(&array, &indicies, None).unwrap();
    assert_eq!(array.len(), 3);
}

Expected behavior
The take kernel should take the requested values from the UnionArray.

Additional context
Here's the full backtrace of the panic:

thread 'main' panicked at /Users/mhilton/.cargo/registry/src/index.crates.io-6f17d22bba15001f/arrow-select-52.2.0/src/filter.rs:548:61:
internal error: entered unreachable code
stack backtrace:
   0:        0x102282d38 - std::backtrace_rs::backtrace::libunwind::trace::h6196ef3b0a4e77ef
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/../../backtrace/src/backtrace/libunwind.rs:116:5
   1:        0x102282d38 - std::backtrace_rs::backtrace::trace_unsynchronized::hac375eab426f00dd
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:        0x102282d38 - std::sys_common::backtrace::_print_fmt::h2a4f1f15852b7d46
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:68:5
   3:        0x102282d38 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h205eab4daa59a56a
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:44:22
   4:        0x10229c2d8 - core::fmt::rt::Argument::fmt::h391b30ab7a26d7be
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/fmt/rt.rs:165:63
   5:        0x10229c2d8 - core::fmt::write::ha28d0fbf1a1eeba9
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/fmt/mod.rs:1168:21
   6:        0x102281078 - std::io::Write::write_fmt::h54f6960924d6c6c0
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/io/mod.rs:1835:15
   7:        0x102282b90 - std::sys_common::backtrace::_print::hfe43851cb14e36df
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:47:5
   8:        0x102282b90 - std::sys_common::backtrace::print::hb748761a345859f9
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:34:9
   9:        0x102283d68 - std::panicking::default_hook::{{closure}}::h6cb9ca91838de054
  10:        0x102283a34 - std::panicking::default_hook::h83345dc5126de57b
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:298:9
  11:        0x102284614 - std::panicking::rust_panic_with_hook::h9305dc63490c537b
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:795:13
  12:        0x102284024 - std::panicking::begin_panic_handler::{{closure}}::h0d6c6c01f5801c1a
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:656:13
  13:        0x1022831bc - std::sys_common::backtrace::__rust_end_short_backtrace::h2ace9f7ada66a76a
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:171:18
  14:        0x102283dc0 - rust_begin_unwind
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:652:5
  15:        0x1022a8188 - core::panicking::panic_fmt::hf3031f82c202a80d
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/panicking.rs:72:14
  16:        0x1022a8208 - core::panicking::panic::hfb97fcfe2d432218
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/panicking.rs:146:5
  17:        0x102169458 - arrow_select::filter::filter_native::h9f28851713a0b08f
                               at /Users/mhilton/.cargo/registry/src/index.crates.io-6f17d22bba15001f/arrow-select-52.2.0/src/filter.rs:548:61
  18:        0x102169930 - arrow_select::filter::filter_primitive::hcdf550095906b537
                               at /Users/mhilton/.cargo/registry/src/index.crates.io-6f17d22bba15001f/arrow-select-52.2.0/src/filter.rs:563:18
  19:        0x102112f88 - arrow_select::take::take_impl::{{closure}}::h239177a4c6a8bec8
                               at /Users/mhilton/.cargo/registry/src/index.crates.io-6f17d22bba15001f/arrow-select-52.2.0/src/take.rs:256:35
  20:        0x102121220 - core::iter::adapters::map::map_try_fold::{{closure}}::hab6993c506059229
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/iter/adapters/map.rs:96:28
  21:        0x102120e40 - core::iter::adapters::map::map_try_fold::{{closure}}::h3d41d09047cc2b32
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/iter/adapters/map.rs:96:21
  22:        0x10206995c - core::iter::traits::iterator::Iterator::try_fold::h72e753c0a4af1044
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/iter/traits/iterator.rs:2411:21
  23:        0x10211aef4 - <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::try_fold::h75e4ab88b8caf0c6
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/iter/adapters/map.rs:122:9
  24:        0x10211ae00 - <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::try_fold::h3043137ca45b49b3
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/iter/adapters/map.rs:122:9
  25:        0x10214eb84 - <core::iter::adapters::GenericShunt<I,R> as core::iter::traits::iterator::Iterator>::try_fold::h5e2f7ab5cb4ee7b9
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/iter/adapters/mod.rs:204:9
  26:        0x10214e530 - core::iter::traits::iterator::Iterator::try_for_each::h597277cdd977e2d5
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/iter/traits/iterator.rs:2473:9
  27:        0x10214e530 - <core::iter::adapters::GenericShunt<I,R> as core::iter::traits::iterator::Iterator>::next::h8aa312b9f15e2e1c
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/iter/adapters/mod.rs:187:14
  28:        0x102083ea0 - <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iter::h3cd7e10537f2b4ae
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/alloc/src/vec/spec_from_iter_nested.rs:26:32
  29:        0x1020a7598 - <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter::h7b756cb59644d8d3
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/alloc/src/vec/spec_from_iter.rs:33:9
  30:        0x1020a4320 - <alloc::vec::Vec<T> as core::iter::traits::collect::FromIterator<T>>::from_iter::h41de20caa2f31fb6
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/alloc/src/vec/mod.rs:2970:9
  31:        0x10215c8c0 - core::iter::traits::iterator::Iterator::collect::h0512061a5d22f37a
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/iter/traits/iterator.rs:2005:9
  32:        0x10215c8c0 - <core::result::Result<V,E> as core::iter::traits::collect::FromIterator<core::result::Result<A,E>>>::from_iter::{{closure}}::ha43fd813a35c4443
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/result.rs:1960:51
  33:        0x1021589a8 - core::iter::adapters::try_process::h9354d10d3933a934
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/iter/adapters/mod.rs:173:17
  34:        0x10215c5fc - <core::result::Result<V,E> as core::iter::traits::collect::FromIterator<core::result::Result<A,E>>>::from_iter::h20cdeefd686d375a
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/result.rs:1960:9
  35:        0x10211dc18 - core::iter::traits::iterator::Iterator::collect::h5c9250783e455d9f
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/iter/traits/iterator.rs:2005:9
  36:        0x1020d98dc - arrow_select::take::take_impl::hba5b9c3fe0878180
                               at /Users/mhilton/.cargo/registry/src/index.crates.io-6f17d22bba15001f/arrow-select-52.2.0/src/take.rs:251:28
  37:        0x1020c7d1c - arrow_select::take::take::h3cb3133ebe3f2b5b
                               at /Users/mhilton/.cargo/registry/src/index.crates.io-6f17d22bba15001f/arrow-select-52.2.0/src/take.rs:93:5
  38:        0x102063a2c - arrow_dense_array_unreachable::main::h12476859da44638b
                               at /Users/mhilton/src/arrow-dense-array-unreachable/src/main.rs:22:17
  39:        0x102063dd0 - core::ops::function::FnOnce::call_once::ha22a648cd6586e3f
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/ops/function.rs:250:5
  40:        0x102064850 - std::sys_common::backtrace::__rust_begin_short_backtrace::hcd25cd6cbcb964af
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:155:18
  41:        0x1020648e4 - std::rt::lang_start::{{closure}}::he4496dc4748c591b
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/rt.rs:159:18
  42:        0x10227f740 - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::h9ac6e053b27a4e69
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/ops/function.rs:284:13
  43:        0x10227f740 - std::panicking::try::do_call::h09e23e6341cf3ffa
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:559:40
  44:        0x10227f740 - std::panicking::try::hecb687885b834f0b
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:523:19
  45:        0x10227f740 - std::panic::catch_unwind::hf02037d5d7fd99df
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panic.rs:149:14
  46:        0x10227f740 - std::rt::lang_start_internal::{{closure}}::h2cb5afb5064cd3ee
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/rt.rs:141:48
  47:        0x10227f740 - std::panicking::try::do_call::h15529d58e6f83876
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:559:40
  48:        0x10227f740 - std::panicking::try::h393140c707be8ad0
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:523:19
  49:        0x10227f740 - std::panic::catch_unwind::h344c598b74f77cdb
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panic.rs:149:14
  50:        0x10227f740 - std::rt::lang_start_internal::hd3ad173a069f2ae5
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/rt.rs:141:20
  51:        0x1020648b0 - std::rt::lang_start::h6054b03865accfe8
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/rt.rs:158:17
  52:        0x102063c78 - _main

[gstvg]

Thanks for your report @mhilton, i will investigate

[alamb]

label_issue.py automatically added labels {'arrow'} from #6209