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87 lines
2.4 KiB
87 lines
2.4 KiB
use polars::prelude::*;
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use std::fs;
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use std::io;
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use std::io::Read;
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/// Read CSV file
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pub fn read_csv(path: String) -> LazyFrame {
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LazyCsvReader::new(path)
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.finish()
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.expect("Could not load file")
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}
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/// Read parquet and return a Polars LazyFrame
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pub fn read_parquet(path: String) -> LazyFrame {
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LazyFrame::scan_parquet(path, ScanArgsParquet::default()).expect("Could not read parquet file")
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}
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/// Read IPC setream
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pub fn read_ipc() -> LazyFrame {
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let mut buffer = Vec::new();
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let _res: () = match io::stdin().lock().read_to_end(&mut buffer) {
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Ok(_ok) => (),
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Err(_e) => (),
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};
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let cursor = io::Cursor::new(buffer);
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match IpcStreamReader::new(cursor).finish() {
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Ok(df) => df.lazy(),
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Err(_e) => LazyFrame::default(),
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}
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}
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/// Read CSV format from stdin and return a Polars DataFrame
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pub fn load_csv_from_stdin() -> LazyFrame {
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let mut buffer = Vec::new();
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let _res: () = match io::stdin().lock().read_to_end(&mut buffer) {
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Ok(_ok) => (),
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Err(_e) => (),
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};
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let cursor = io::Cursor::new(buffer);
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match CsvReader::new(cursor).finish() {
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Ok(df) => df.lazy(),
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Err(_e) => LazyFrame::default(),
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}
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}
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/// Write to IPC steram
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pub fn write_ipc(df: LazyFrame) {
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IpcStreamWriter::new(io::stdout().lock())
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.finish(&mut df.collect().expect("Could not collect dataframe"))
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.expect("Could not write to stream");
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}
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/// Take a Polars Dataframe and write it as CSV to stdout
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pub fn dump_csv_to_stdout(df: &mut DataFrame) {
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let _res: () = match CsvWriter::new(io::stdout().lock()).finish(df) {
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Ok(_ok) => (),
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Err(_e) => (),
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};
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}
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/// Write a Polars DataFrame to Parquet
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pub fn write_parquet(
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mut df: DataFrame,
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path: String,
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compression: String,
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statistics: bool,
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chunksize: Option<usize>,
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) {
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// Selected compression not implemented yet
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let mut _file = match fs::File::create(path) {
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Ok(mut file) => {
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let mut w = ParquetWriter::new(&mut file);
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if statistics {
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w = w.with_statistics(statistics);
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}
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if chunksize.unwrap_or(0) > 0 {
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w = w.with_row_group_size(chunksize);
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}
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let _r = match w.finish(&mut df) {
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Ok(_r) => (),
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Err(e) => eprintln!("{e}"),
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};
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}
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Err(e) => eprintln!("{e}"),
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};
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}
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