ArrowNotImplementedError: Function 'equal' has no kernel matching input types (string_view, string)

[danking]

What happens?

I can't seem to compare a string_view Arrow column (via the pyarrow Dataset API) to a literal. Is there anyway to force the literal to be a string_view instead of a string?

I originally reported this in duckdb/duckdb#19861 and was instructed to refile here.

To Reproduce

Install the latest versions of: duckdb, vortex-data, and typing-extensions (due to a missing dependency in vortex).

uv add duckdb vortex-data typing-extensions

Python code:

import vortex as vx
import duckdb
vx.io.write(vx.array([{"column": "a string"}]), 'foo.vortex')
x = vx.open('foo.vortex').to_dataset()
duckdb.execute("select * from x where \"column\" == 'hello world'").to_arrow_table()

Python output:

Traceback (most recent call last):
  File "<python-input-0>", line 5, in <module>
    duckdb.execute("select * from x where \"column\" == 'hello world'").to_arrow_table()
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
_duckdb.Error: ArrowNotImplementedError: Function 'equal' has no kernel matching input types (string_view, string)

At:
  pyarrow/error.pxi(92): pyarrow.lib.check_status

---

I can't replicate with the DuckDB CLI. Whatever path that takes must avoid a string_view?

install vortex; load vortex; select * from read_vortex('foo.vortex') where "column" == 'hello world';
┌─────────┐
│ column  │
│ varchar │
├─────────┤
│ 0 rows  │
└─────────┘

---

The full transcript of what I did:

# mkdir bar
# cd bar
# uv init
Initialized project `bar`
# uv add duckdb vortex-data typing-extensions
Using CPython 3.14.0
Creating virtual environment at: .venv
Resolved 7 packages in 58ms
Installed 6 packages in 15ms
 + duckdb==1.4.2
 + protobuf==5.29.5
 + pyarrow==22.0.0
 + substrait==0.25.0
 + typing-extensions==4.15.0
 + vortex-data==0.56.0
# uv run python
Python 3.14.0 (main, Oct 31 2025, 23:20:55) [Clang 21.1.4 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import vortex as vx
... import duckdb
... vx.io.write(vx.array([{"column": "a string"}]), 'foo.vortex')
... x = vx.open('foo.vortex').to_dataset()
... duckdb.execute("select * from x where \"column\" == 'hello world'").to_arrow_table()
... 
Traceback (most recent call last):
  File "<python-input-0>", line 5, in <module>
    duckdb.execute("select * from x where \"column\" == 'hello world'").to_arrow_table()
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
_duckdb.Error: ArrowNotImplementedError: Function 'equal' has no kernel matching input types (string_view, string)

At:
  pyarrow/error.pxi(92): pyarrow.lib.check_status

>>> 

OS:

macOS

DuckDB Package Version:

1.4.2

Python Version:

1.4.2

Full Name:

Daniel King

Affiliation:

SpiralDB, Inc.

What is the latest build you tested with? If possible, we recommend testing with the latest nightly build.

I have tested with a stable release

Did you include all relevant data sets for reproducing the issue?

Yes

Did you include all code required to reproduce the issue?

• Yes, I have

Did you include all relevant configuration to reproduce the issue?

• Yes, I have

[paultiq]

Reproduced with just pyarrow.

import pyarrow as pa
import duckdb 

mytable = pa.table({'col1': pa.array(['foo', 'bar'] * 50, type=pa.string_view())})
duckdb.sql("select * from mytable where col1='a string' ")

Looks like root cause is here in the push down, not also checking for a ArrowVariableSizeType::VIEW:

duckdb-python/src/duckdb_py/arrow/pyarrow_filter_pushdown.cpp

Lines 122 to 130 in 4ebe06f

	case LogicalTypeId::VARCHAR:
	return dataset_scalar(constant.ToString());
	case LogicalTypeId::BLOB: {
	if (type.GetTypeInfo<ArrowStringInfo>().GetSizeType() == ArrowVariableSizeType::VIEW) {
	py::handle binary_view_type = import_cache.pyarrow.binary_view();
	return dataset_scalar(scalar(py::bytes(constant.GetValueUnsafe<string>()), binary_view_type()));
	}
	return dataset_scalar(py::bytes(constant.GetValueUnsafe<string>()));
	}

* trying to query a scanner here will cause a duckdb segfault: x = vx.open('foo.vortex').to_dataset().scanner()

[danking]

Yeah, I also noticed the segfault. I’m not sure what’s wrong with the Scanner. It could be our (Vortex’s) fault.

[paultiq]

The segfault seems to be inside pyarrow, not duckdb:

(I'll file in Vortex)

0x00007fff96ab2d3c in __pyx_getprop_7pyarrow_8_dataset_7Scanner_projected_schema(_object*, void*) [clone .lto_priv.0] () from >/home/extra/git/goodenv/.venv/lib/python3.13/site-pack
ages/pyarrow/_dataset.cpython-313-x86_64-linux-gnu.so

MRE of the segfault:

import vortex as vx

vx.io.write(vx.array([{"col1": "a string"}]), 'foo.vortex')
x = vx.open('foo.vortex').to_dataset().scanner().projected_schema()