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Add logical_type() to vtab::Value #657

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Add logical_type() to vtab::Value #657

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23 changes: 21 additions & 2 deletions crates/duckdb/src/vtab/value.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
use crate::ffi::{duckdb_destroy_value, duckdb_free, duckdb_get_int64, duckdb_get_varchar, duckdb_value};
use crate::core::LogicalTypeHandle;
use crate::ffi::{duckdb_destroy_value, duckdb_free, duckdb_get_int64, duckdb_get_value_type, duckdb_get_varchar, duckdb_value};
use std::{ffi::CStr, fmt, os::raw::c_void};

/// The Value object holds a single arbitrary value of any type that can be
Expand Down Expand Up @@ -30,6 +31,15 @@ impl Value {
pub fn to_int64(&self) -> i64 {
unsafe { duckdb_get_int64(self.ptr) }
}

/// Returns a LogicalTypeHandle representing the type of this value.
pub fn logical_type(&self) -> LogicalTypeHandle {
// SAFETY: The returned LogicalTypeHandle frees allocated memory when dropped.
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@mlafeldt mlafeldt Jan 20, 2026

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Not true. duckdb_get_value_type returns a borrowed pointer to internal memory owned by the Value, not a new allocation. The C API docs say: "The type itself must not be destroyed". But LogicalTypeHandle::Drop calls duckdb_destroy_logical_type, causing double-free/corruption when dropped. I suggest returning an owned copy.

Alternatively, if sufficient, implement logical_type_id and return LogicalTypeId, which doesn't have this ownership problem.

unsafe {
let lt_handle = duckdb_get_value_type(self.ptr);
LogicalTypeHandle { ptr: lt_handle }
}
}
}

impl fmt::Display for Value {
Expand All @@ -47,7 +57,7 @@ impl fmt::Display for Value {
#[cfg(test)]
mod tests {
use super::*;
use crate::ffi::duckdb_create_varchar;
use crate::ffi::{duckdb_create_varchar, DUCKDB_TYPE_DUCKDB_TYPE_VARCHAR};
use std::ffi::CString;

#[test]
Expand All @@ -57,4 +67,13 @@ mod tests {
let val = Value::from(duckdb_val);
assert_eq!(val.to_string(), "some value");
}

#[test]
fn test_logical_type() {
let c_str = CString::new("some value").unwrap();
let duckdb_val = unsafe { duckdb_create_varchar(c_str.as_ptr()) };
let val = Value::from(duckdb_val);
let logical_type = val.logical_type();
assert_eq!(logical_type.raw_id(), DUCKDB_TYPE_DUCKDB_TYPE_VARCHAR);
}
}