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
162
use std::path::{Path, PathBuf};

use polars_core::prelude::*;
use polars_io::cloud::CloudOptions;
use polars_io::parquet::ParallelStrategy;
use polars_io::{HiveOptions, RowIndex};

use crate::prelude::*;

#[derive(Clone)]
pub struct ScanArgsParquet {
    pub n_rows: Option<usize>,
    pub cache: bool,
    pub parallel: ParallelStrategy,
    pub rechunk: bool,
    pub row_index: Option<RowIndex>,
    pub low_memory: bool,
    pub cloud_options: Option<CloudOptions>,
    pub use_statistics: bool,
    pub hive_options: HiveOptions,
}

impl Default for ScanArgsParquet {
    fn default() -> Self {
        Self {
            n_rows: None,
            cache: true,
            parallel: Default::default(),
            rechunk: false,
            row_index: None,
            low_memory: false,
            cloud_options: None,
            use_statistics: true,
            hive_options: Default::default(),
        }
    }
}

#[derive(Clone)]
struct LazyParquetReader {
    args: ScanArgsParquet,
    path: PathBuf,
    paths: Arc<[PathBuf]>,
}

impl LazyParquetReader {
    fn new(path: PathBuf, args: ScanArgsParquet) -> Self {
        Self {
            args,
            path,
            paths: Arc::new([]),
        }
    }
}

impl LazyFileListReader for LazyParquetReader {
    /// Get the final [LazyFrame].
    fn finish(mut self) -> PolarsResult<LazyFrame> {
        if let Some(paths) = self.iter_paths()? {
            let paths = paths
                .into_iter()
                .collect::<PolarsResult<Arc<[PathBuf]>>>()?;
            self.paths = paths;
        }
        self.finish_no_glob()
    }

    fn finish_no_glob(self) -> PolarsResult<LazyFrame> {
        let row_index = self.args.row_index;

        let paths = if self.paths.is_empty() {
            Arc::new([self.path]) as Arc<[PathBuf]>
        } else {
            self.paths
        };
        let mut lf: LazyFrame = LogicalPlanBuilder::scan_parquet(
            paths,
            self.args.n_rows,
            self.args.cache,
            self.args.parallel,
            None,
            self.args.rechunk,
            self.args.low_memory,
            self.args.cloud_options,
            self.args.use_statistics,
            self.args.hive_options,
        )?
        .build()
        .into();

        // it is a bit hacky, but this row_index function updates the schema
        if let Some(row_index) = row_index {
            lf = lf.with_row_index(&row_index.name, Some(row_index.offset))
        }

        lf.opt_state.file_caching = true;
        Ok(lf)
    }

    fn path(&self) -> &Path {
        self.path.as_path()
    }

    fn paths(&self) -> &[PathBuf] {
        &self.paths
    }

    fn with_path(mut self, path: PathBuf) -> Self {
        self.path = path;
        self
    }

    fn with_paths(mut self, paths: Arc<[PathBuf]>) -> Self {
        self.paths = paths;
        self
    }

    fn with_n_rows(mut self, n_rows: impl Into<Option<usize>>) -> Self {
        self.args.n_rows = n_rows.into();
        self
    }

    fn with_row_index(mut self, row_index: impl Into<Option<RowIndex>>) -> Self {
        self.args.row_index = row_index.into();
        self
    }

    fn rechunk(&self) -> bool {
        self.args.rechunk
    }

    fn with_rechunk(mut self, toggle: bool) -> Self {
        self.args.rechunk = toggle;
        self
    }

    fn cloud_options(&self) -> Option<&CloudOptions> {
        self.args.cloud_options.as_ref()
    }

    fn n_rows(&self) -> Option<usize> {
        self.args.n_rows
    }

    fn row_index(&self) -> Option<&RowIndex> {
        self.args.row_index.as_ref()
    }
}

impl LazyFrame {
    /// Create a LazyFrame directly from a parquet scan.
    pub fn scan_parquet(path: impl AsRef<Path>, args: ScanArgsParquet) -> PolarsResult<Self> {
        LazyParquetReader::new(path.as_ref().to_owned(), args).finish()
    }

    /// Create a LazyFrame directly from a parquet scan.
    pub fn scan_parquet_files(paths: Arc<[PathBuf]>, args: ScanArgsParquet) -> PolarsResult<Self> {
        LazyParquetReader::new(PathBuf::new(), args)
            .with_paths(paths)
            .finish()
    }
}