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//! What a scan built for an open: a frame, or what the load turns into a file first.
use std::path::PathBuf;
use polars::prelude::LazyFrame;
use crate::{FileFormat, OpenOptions, cli};
/// What a scan built: the frame, or what the load has to turn into a file it can scan
/// first, since the copy has to outlive the scan.
pub(crate) enum Scan {
Frame(Box<LazyFrame>),
Decompress {
file: PathBuf,
format: FileFormat,
},
/// Arrow IPC streams, which the load converts to one IPC file before it scans.
Streams(Vec<PathBuf>),
/// A compressed file a format spec matched, to decompress and then read with it.
DecompressSpec {
file: PathBuf,
choice: crate::formats::Choice,
},
/// GPS logs, or a VCD dump, FIX log or SDF file, read into files of their own
/// before the frame over them is built (`Step::Convert`).
ReadInto {
files: Vec<PathBuf>,
format: FileFormat,
},
/// A file of several tables (a SQLite database, a NumPy archive), named, and no
/// `--table`: the home screen lists them.
Tables {
file: PathBuf,
tables: Vec<String>,
format: FileFormat,
},
/// A member compressed in an archive (a NumPy array), decompressed to a file before
/// it is read (`Step::Convert`).
Unpack {
file: PathBuf,
member: String,
format: FileFormat,
},
/// A local file to show as bytes: no reader and no spec takes it, or `--hex` asked.
Hex {
file: PathBuf,
asked: bool,
},
}
impl Scan {
/// The reader the scan chose: `found` (what the read reported, else what was
/// asked for) for a frame, else the format of what is to be converted.
pub(crate) fn format(&self, found: Option<FileFormat>) -> Option<FileFormat> {
match self {
Scan::Frame(_) => found,
Scan::Decompress { format, .. } | Scan::ReadInto { format, .. } => Some(*format),
Scan::Streams(_) => Some(FileFormat::Arrow),
Scan::DecompressSpec { .. } => None,
Scan::Tables { format, .. } => Some(*format),
Scan::Unpack { format, .. } => Some(*format),
Scan::Hex { .. } => None,
}
}
/// How the open reads what this scan found, as [`FileFormat::read_mode`] says for
/// its format and how it is stored. `format` is the reader the scan chose; a frame
/// with none is a Parquet scan of a directory, a glob or a bucket.
/// A frame of converted Arrow streams (`options.arrow_parts`) is the IPC file they
/// were converted to, scanned again.
pub(crate) fn read_mode(
&self,
format: Option<FileFormat>,
spec: bool,
options: &OpenOptions,
) -> Option<crate::ReadMode> {
use crate::{ReadMode, Stored};
let spec_read = |stored| cli::FormatChoice::Spec(String::new()).read_mode(stored);
let converted = options.arrow_parts.as_ref().is_some_and(|parts| {
parts
.iter()
.any(|part| matches!(part, crate::formats::ipc_stream::Part::Converted { .. }))
});
match self {
Scan::Frame(_) if spec => spec_read(Stored::Plain),
Scan::Frame(_) if converted => FileFormat::Arrow.read_mode(Stored::Stream),
Scan::Frame(_) => format.map_or(Some(ReadMode::Lazy), |f| f.read_mode(Stored::Plain)),
Scan::Decompress { format, .. } => format.read_mode(Stored::Compressed {
in_memory: options.decompress_in_memory,
}),
Scan::Streams(_) => FileFormat::Arrow.read_mode(Stored::Stream),
Scan::ReadInto { format, .. } => format.read_mode(Stored::Plain),
Scan::DecompressSpec { .. } => spec_read(Stored::Compressed { in_memory: false }),
Scan::Tables { format, .. } => format.read_mode(Stored::Plain),
Scan::Unpack { .. } => Some(crate::ReadMode::Decompressed),
Scan::Hex { .. } => None,
}
}
}
impl From<LazyFrame> for Scan {
fn from(lf: LazyFrame) -> Self {
Scan::Frame(Box::new(lf))
}
}