vortex-layout 0.68.0

Vortex layouts provide a way to perform lazy push-down scans over abstract storage
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

// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: Copyright the Vortex contributors

mod reader;
pub mod writer;

use std::sync::Arc;

use vortex_array::DeserializeMetadata;
use vortex_array::EmptyMetadata;
use vortex_array::dtype::DType;
use vortex_error::VortexResult;
use vortex_session::VortexSession;
use vortex_session::registry::ReadContext;

use crate::LayoutChildType;
use crate::LayoutEncodingRef;
use crate::LayoutId;
use crate::LayoutReaderRef;
use crate::LayoutRef;
use crate::VTable;
use crate::children::LayoutChildren;
use crate::children::OwnedLayoutChildren;
use crate::layouts::chunked::reader::ChunkedReader;
use crate::segments::SegmentId;
use crate::segments::SegmentSource;
use crate::vtable;

vtable!(Chunked);

impl VTable for Chunked {
    type Layout = ChunkedLayout;
    type Encoding = ChunkedLayoutEncoding;
    type Metadata = EmptyMetadata;

    fn id(_encoding: &Self::Encoding) -> LayoutId {
        LayoutId::new_ref("vortex.chunked")
    }

    fn encoding(_layout: &Self::Layout) -> LayoutEncodingRef {
        LayoutEncodingRef::new_ref(ChunkedLayoutEncoding.as_ref())
    }

    fn row_count(layout: &Self::Layout) -> u64 {
        layout.row_count
    }

    fn dtype(layout: &Self::Layout) -> &DType {
        &layout.dtype
    }

    fn metadata(_layout: &Self::Layout) -> Self::Metadata {
        EmptyMetadata
    }

    fn segment_ids(_layout: &Self::Layout) -> Vec<SegmentId> {
        vec![]
    }

    fn nchildren(layout: &Self::Layout) -> usize {
        layout.children.nchildren()
    }

    fn child(layout: &Self::Layout, idx: usize) -> VortexResult<LayoutRef> {
        layout.children.child(idx, Self::dtype(layout))
    }

    fn child_type(layout: &Self::Layout, idx: usize) -> LayoutChildType {
        LayoutChildType::Chunk((idx, layout.chunk_offsets[idx]))
    }

    fn new_reader(
        layout: &Self::Layout,
        name: Arc<str>,
        segment_source: Arc<dyn SegmentSource>,
        session: &VortexSession,
    ) -> VortexResult<LayoutReaderRef> {
        Ok(Arc::new(ChunkedReader::new(
            layout.clone(),
            name,
            segment_source,
            session,
        )))
    }

    fn build(
        _encoding: &Self::Encoding,
        dtype: &DType,
        row_count: u64,
        _metadata: &<Self::Metadata as DeserializeMetadata>::Output,
        _segment_ids: Vec<SegmentId>,
        children: &dyn LayoutChildren,
        _ctx: &ReadContext,
    ) -> VortexResult<Self::Layout> {
        Ok(ChunkedLayout::new(
            row_count,
            dtype.clone(),
            children.to_arc(),
        ))
    }

    fn with_children(layout: &mut Self::Layout, children: Vec<LayoutRef>) -> VortexResult<()> {
        let new_children = OwnedLayoutChildren::layout_children(children);

        // Recalculate chunk offsets based on new children
        let mut chunk_offsets = Vec::with_capacity(new_children.nchildren() + 1);
        chunk_offsets.push(0);
        for i in 0..new_children.nchildren() {
            chunk_offsets.push(chunk_offsets[i] + new_children.child_row_count(i));
        }

        layout.children = new_children;
        layout.chunk_offsets = chunk_offsets;
        Ok(())
    }
}

#[derive(Debug)]
pub struct ChunkedLayoutEncoding;

/// Partitions a column into row-based chunks so that each chunk can be read independently.
///
/// Used to break large columns into smaller pieces for parallel I/O and to limit memory
/// usage when scanning.
#[derive(Clone, Debug)]
pub struct ChunkedLayout {
    row_count: u64,
    dtype: DType,
    children: Arc<dyn LayoutChildren>,
    chunk_offsets: Vec<u64>,
}

impl ChunkedLayout {
    pub fn new(row_count: u64, dtype: DType, children: Arc<dyn LayoutChildren>) -> Self {
        let mut chunk_offsets = Vec::with_capacity(children.nchildren() + 1);

        chunk_offsets.push(0);
        for i in 0..children.nchildren() {
            chunk_offsets.push(chunk_offsets[i] + children.child_row_count(i));
        }
        assert_eq!(
            chunk_offsets[children.nchildren()],
            row_count,
            "Row count mismatch"
        );
        Self {
            row_count,
            dtype,
            children,
            chunk_offsets,
        }
    }

    pub fn children(&self) -> &Arc<dyn LayoutChildren> {
        &self.children
    }
}