datafusion_ffi/
arrow_wrappers.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
3// distributed with this work for additional information
4// regarding copyright ownership.  The ASF licenses this file
5// to you under the Apache License, Version 2.0 (the
6// "License"); you may not use this file except in compliance
7// with the License.  You may obtain a copy of the License at
8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing,
12// software distributed under the License is distributed on an
13// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14// KIND, either express or implied.  See the License for the
15// specific language governing permissions and limitations
16// under the License.
17
18use std::sync::Arc;
19
20use arrow::array::{ArrayRef, make_array};
21use arrow::datatypes::{Schema, SchemaRef};
22use arrow::error::ArrowError;
23use arrow::ffi::{FFI_ArrowArray, FFI_ArrowSchema, from_ffi, to_ffi};
24use datafusion_common::{DataFusionError, ScalarValue};
25use log::error;
26
27/// This is a wrapper struct around FFI_ArrowSchema simply to indicate
28/// that the underlying struct is FFI safe.
29#[repr(C)]
30#[derive(Debug)]
31pub struct WrappedSchema(pub FFI_ArrowSchema);
32
33impl From<SchemaRef> for WrappedSchema {
34    fn from(value: SchemaRef) -> Self {
35        let ffi_schema = match FFI_ArrowSchema::try_from(value.as_ref()) {
36            Ok(s) => s,
37            Err(e) => {
38                error!(
39                    "Unable to convert DataFusion Schema to FFI_ArrowSchema in FFI_PlanProperties. {e}"
40                );
41                FFI_ArrowSchema::empty()
42            }
43        };
44
45        WrappedSchema(ffi_schema)
46    }
47}
48/// Some functions are expected to always succeed, like getting the schema from a TableProvider.
49/// Since going through the FFI always has the potential to fail, we need to catch these errors,
50/// give the user a warning, and return some kind of result. In this case we default to an
51/// empty schema.
52fn catch_df_schema_error(e: &ArrowError) -> Schema {
53    error!(
54        "Unable to convert from FFI_ArrowSchema to DataFusion Schema in FFI_PlanProperties. {e}"
55    );
56    Schema::empty()
57}
58
59impl From<WrappedSchema> for SchemaRef {
60    fn from(value: WrappedSchema) -> Self {
61        let schema =
62            Schema::try_from(&value.0).unwrap_or_else(|e| catch_df_schema_error(&e));
63        Arc::new(schema)
64    }
65}
66
67/// This is a wrapper struct for FFI_ArrowArray to indicate
68/// that the struct is FFI Safe. For convenience, we also include the
69/// schema needed to create a record batch from the array.
70#[repr(C)]
71#[derive(Debug)]
72pub struct WrappedArray {
73    pub array: FFI_ArrowArray,
74    pub schema: WrappedSchema,
75}
76
77impl TryFrom<WrappedArray> for ArrayRef {
78    type Error = ArrowError;
79
80    fn try_from(value: WrappedArray) -> Result<Self, Self::Error> {
81        let data = unsafe { from_ffi(value.array, &value.schema.0)? };
82
83        Ok(make_array(data))
84    }
85}
86
87impl TryFrom<&ArrayRef> for WrappedArray {
88    type Error = ArrowError;
89
90    fn try_from(array: &ArrayRef) -> Result<Self, Self::Error> {
91        let (array, schema) = to_ffi(&array.to_data())?;
92        let schema = WrappedSchema(schema);
93
94        Ok(WrappedArray { array, schema })
95    }
96}
97
98impl TryFrom<&ScalarValue> for WrappedArray {
99    type Error = DataFusionError;
100
101    fn try_from(value: &ScalarValue) -> Result<Self, Self::Error> {
102        let array = value.to_array()?;
103        WrappedArray::try_from(&array).map_err(Into::into)
104    }
105}
106
107impl TryFrom<WrappedArray> for ScalarValue {
108    type Error = DataFusionError;
109
110    fn try_from(value: WrappedArray) -> Result<Self, Self::Error> {
111        let array: ArrayRef = value.try_into()?;
112        ScalarValue::try_from_array(array.as_ref(), 0)
113    }
114}
datafusion_ffi/arrow_wrappers.rs

datafusion_ffi/
arrow_wrappers.rs
