delta_kernel 0.25.0

Core crate providing a Delta/Deltalake implementation focused on interoperability with a wide range of query engines.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161

//! A [`ParquetHandler`] implementation backed by a [`PlanExecutor`].

use std::sync::Arc;

use url::Url;

use crate::plans::{IoOperation, Operation, PlanExecutor, QueryPlanBuilder};
use crate::schema::SchemaRef;
use crate::{
    DeltaResult, DeltaResultIteratorStatic, EngineData, Error, FileDataReadResultIterator,
    FileMeta, ParquetFooter, ParquetHandler, PredicateRef,
};

/// A [`ParquetHandler`] that delegates to a [`PlanExecutor`].
pub struct PlanBasedParquetHandler {
    executor: Arc<dyn PlanExecutor>,
}

impl PlanBasedParquetHandler {
    pub fn new(plan_executor: Arc<dyn PlanExecutor>) -> Self {
        Self {
            executor: plan_executor,
        }
    }
}

impl ParquetHandler for PlanBasedParquetHandler {
    fn read_parquet_files(
        &self,
        files: &[FileMeta],
        physical_schema: SchemaRef,
        _predicate: Option<PredicateRef>,
    ) -> DeltaResult<FileDataReadResultIterator> {
        // TODO: `_predicate` is dropped. Re-apply it as a Filter node over the scan; the
        // single-node executor can then match the filter -> scan shape.
        let query = QueryPlanBuilder::scan_parquet(files.to_vec(), physical_schema).build()?;
        self.executor
            .execute_op(Operation::QueryPlan(query))?
            .into_data()
    }

    fn write_parquet_file(
        &self,
        _location: Url,
        _data: DeltaResultIteratorStatic<Box<dyn EngineData>>,
    ) -> DeltaResult<()> {
        Err(Error::unsupported(
            "PlanBasedParquetHandler does not support write_parquet_file yet",
        ))
    }

    fn read_parquet_footer(&self, file: &FileMeta) -> DeltaResult<ParquetFooter> {
        let op = IoOperation::parquet_footer(file.clone());
        self.executor
            .execute_op(Operation::IoOperation(op))?
            .into_parquet_footer()
    }
}

#[cfg(test)]
mod tests {
    // TODO(#2618): Refactor and share a test suite with sync engine tests.

    use std::path::Path;
    use std::sync::Arc;

    use tempfile::tempdir;
    use url::Url;

    use super::PlanBasedParquetHandler;
    use crate::arrow::array::{Array, Int64Array, RecordBatch};
    use crate::engine::arrow_conversion::TryIntoKernel as _;
    use crate::engine::arrow_data::ArrowEngineData;
    use crate::engine::sync::plan::SyncPlanExecutor;
    use crate::parquet::arrow::arrow_writer::ArrowWriter;
    use crate::schema::SchemaRef;
    use crate::{FileMeta, ParquetHandler as _};

    fn make_handler() -> PlanBasedParquetHandler {
        PlanBasedParquetHandler::new(Arc::new(SyncPlanExecutor::new()))
    }

    fn file_meta_for(path: &Path) -> FileMeta {
        let url = Url::from_file_path(path).unwrap();
        let size = std::fs::metadata(path).unwrap().len();
        FileMeta {
            location: url,
            last_modified: 0,
            size,
        }
    }

    fn make_test_parquet_file(path: &Path, batch: &RecordBatch) -> (FileMeta, SchemaRef) {
        let mut writer =
            ArrowWriter::try_new(std::fs::File::create(path).unwrap(), batch.schema(), None)
                .unwrap();
        writer.write(batch).unwrap();
        writer.close().unwrap();

        let file_meta = file_meta_for(path);
        let schema = Arc::new(batch.schema().as_ref().try_into_kernel().unwrap());
        (file_meta, schema)
    }

    #[test]
    fn test_read_parquet_files() {
        let temp_dir = tempdir().unwrap();
        let file_path = temp_dir.path().join("data.parquet");
        let batch = RecordBatch::try_from_iter(vec![(
            "value",
            Arc::new(Int64Array::from(vec![10, 20, 30])) as Arc<dyn Array>,
        )])
        .unwrap();
        let (file_meta, schema) = make_test_parquet_file(&file_path, &batch);

        let batches: Vec<RecordBatch> = make_handler()
            .read_parquet_files(&[file_meta], schema, None)
            .unwrap()
            .map(|r| {
                ArrowEngineData::try_from_engine_data(r.unwrap())
                    .unwrap()
                    .into()
            })
            .collect();

        assert_eq!(batches.len(), 1);
        assert_eq!(batches[0].num_rows(), 3);
        assert_eq!(
            batches[0]
                .column(0)
                .as_any()
                .downcast_ref::<Int64Array>()
                .unwrap()
                .values(),
            &[10, 20, 30]
        );
    }

    // TODO(#2618): Restore once `PlanBasedParquetHandler` moves to delta_kernel_default_engine
    // and can use the test_utils::engine_contract helpers without the kernel-cfg-test cycle issue.
    //
    // #[test]
    // fn test_parquet_handler_reads_contract() {
    //     test_parquet_handler_reads_file_with_arrow_schema(&make_handler());
    // }
    //
    // #[test]
    // fn test_read_parquet_footer_contract() {
    //     test_parquet_handler_reads_footer(&make_handler());
    // }
    //
    // #[test]
    // fn test_read_parquet_footer_missing_file_contract() {
    //     test_parquet_handler_footer_errors_on_missing_file(&make_handler());
    // }
    //
    // #[test]
    // fn test_read_parquet_footer_preserves_field_ids_contract() {
    //     test_parquet_handler_footer_preserves_field_ids(&make_handler());
    // }
}