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partition.rs
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partition.rs
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static USAGE: &str = r#"
Partitions the given CSV data into chunks based on the value of a column.
See `split` command to split a CSV data by row count, by number of chunks or
by kb-size.
The files are written to the output directory with filenames based on the
values in the partition column and the `--filename` flag.
EXAMPLE:
Partition nyc311.csv file into separate files based on the value of the
"Borough" column in the current directory:
$ qsv partition Borough . --filename "nyc311-{}.csv" nyc311.csv
will create the following files, each containing the data for each borough:
nyc311-Bronx.csv
nyc311-Brooklyn.csv
nyc311-Manhattan.csv
nyc311-Queens.csv
nyc311-Staten_Island.csv
For more examples, see https://github.com/dathere/qsv/blob/master/tests/test_partition.rs.
Usage:
qsv partition [options] <column> <outdir> [<input>]
qsv partition --help
partition arguments:
<column> The column to use as a key for partitioning.
You can use the `--select` option to select
the column by name or index, but only one
column can be used for partitioning.
See `select` command for more details.
<outdir> The directory to write the output files to.
<input> The CSV file to read from. If not specified, then
the input will be read from stdin.
partition options:
--filename <filename> A filename template to use when constructing the
names of the output files. The string '{}' will
be replaced by a value based on the partition column,
but sanitized for shell safety.
[default: {}.csv]
-p, --prefix-length <n> Truncate the partition column after the
specified number of bytes when creating the
output file.
--drop Drop the partition column from results.
Common options:
-h, --help Display this message
-n, --no-headers When set, the first row will NOT be interpreted
as column names. Otherwise, the first row will
appear in all chunks as the header row.
-d, --delimiter <arg> The field delimiter for reading CSV data.
Must be a single character. (default: ,)
"#;
use std::{
collections::{hash_map::Entry, HashSet},
fs, io,
path::Path,
};
use ahash::AHashMap;
use regex::Regex;
use serde::Deserialize;
use crate::{
config::{Config, Delimiter},
select::SelectColumns,
util::{self, FilenameTemplate},
CliResult,
};
#[derive(Clone, Deserialize)]
struct Args {
arg_column: SelectColumns,
arg_input: Option<String>,
arg_outdir: String,
flag_filename: FilenameTemplate,
flag_prefix_length: Option<usize>,
flag_drop: bool,
flag_no_headers: bool,
flag_delimiter: Option<Delimiter>,
}
pub fn run(argv: &[&str]) -> CliResult<()> {
let args: Args = util::get_args(USAGE, argv)?;
fs::create_dir_all(&args.arg_outdir)?;
// It would be nice to support efficient parallel partitions, but doing
// so would involve more complicated inter-thread communication, with
// multiple readers and writers, and some way of passing buffers
// between them.
args.sequential_partition()
}
impl Args {
/// Configuration for our reader.
fn rconfig(&self) -> Config {
Config::new(self.arg_input.as_ref())
.delimiter(self.flag_delimiter)
.no_headers(self.flag_no_headers)
.select(self.arg_column.clone())
}
/// Get the column to use as a key.
#[allow(clippy::unused_self)]
fn key_column(&self, rconfig: &Config, headers: &csv::ByteRecord) -> CliResult<usize> {
let select_cols = rconfig.selection(headers)?;
if select_cols.len() == 1 {
Ok(select_cols[0])
} else {
fail!("can only partition on one column")
}
}
/// A basic sequential partition.
fn sequential_partition(&self) -> CliResult<()> {
let rconfig = self.rconfig();
let mut rdr = rconfig.reader()?;
let headers = rdr.byte_headers()?.clone();
let key_col = self.key_column(&rconfig, &headers)?;
let mut gen = WriterGenerator::new(self.flag_filename.clone());
let mut writers: AHashMap<Vec<u8>, BoxedWriter> = AHashMap::new();
let mut row = csv::ByteRecord::new();
while rdr.read_byte_record(&mut row)? {
// Decide what file to put this in.
let column = &row[key_col];
let key = match self.flag_prefix_length {
// We exceed --prefix-length, so ignore the extra bytes.
Some(len) if len < column.len() => &column[0..len],
_ => column,
};
let mut entry = writers.entry(key.to_vec());
let wtr =
match entry {
Entry::Occupied(ref mut occupied) => occupied.get_mut(),
Entry::Vacant(vacant) => {
// We have a new key, so make a new writer.
let mut wtr = gen.writer(&*self.arg_outdir, key)?;
if !rconfig.no_headers {
if self.flag_drop {
wtr.write_record(headers.iter().enumerate().filter_map(
|(i, e)| if i == key_col { None } else { Some(e) },
))?;
} else {
wtr.write_record(&headers)?;
}
}
vacant.insert(wtr)
},
};
if self.flag_drop {
wtr.write_record(row.iter().enumerate().filter_map(|(i, e)| {
if i == key_col {
None
} else {
Some(e)
}
}))?;
} else {
wtr.write_byte_record(&row)?;
}
wtr.flush()?;
}
Ok(())
}
}
type BoxedWriter = csv::Writer<Box<dyn io::Write + 'static>>;
/// Generates unique filenames based on CSV values.
struct WriterGenerator {
template: FilenameTemplate,
counter: usize,
used: HashSet<String>,
non_word_char: Regex,
}
impl WriterGenerator {
fn new(template: FilenameTemplate) -> WriterGenerator {
WriterGenerator {
template,
counter: 1,
used: HashSet::new(),
non_word_char: Regex::new(r"\W").unwrap(),
}
}
/// Create a CSV writer for `key`. Does not add headers.
fn writer<P>(&mut self, path: P, key: &[u8]) -> io::Result<BoxedWriter>
where
P: AsRef<Path>,
{
let unique_value = self.unique_value(key);
self.template.writer(path.as_ref(), &unique_value)
}
/// Generate a unique value for `key`, suitable for use in a
/// "shell-safe" filename. If you pass `key` twice, you'll get two
/// different values.
fn unique_value(&mut self, key: &[u8]) -> String {
// Sanitize our key.
let utf8 = String::from_utf8_lossy(key);
let safe = self.non_word_char.replace_all(&utf8, "").into_owned();
let base = if safe.is_empty() {
"empty".to_owned()
} else {
safe
};
// Now check for collisions.
if self.used.contains(&base) {
loop {
let candidate = format!("{}_{}", &base, self.counter);
self.counter = self.counter.checked_add(1).unwrap_or_else(|| {
// We'll run out of other things long before we ever
// reach this, but we'll check just for correctness and
// completeness.
panic!("Cannot generate unique value")
});
if !self.used.contains(&candidate) {
self.used.insert(candidate.clone());
return candidate;
}
}
} else {
self.used.insert(base.clone());
base
}
}
}