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Relax JSON schema inference generics #4063

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Apr 14, 2023
Merged

Relax JSON schema inference generics #4063

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Relax JSON schema inference generics
tustvold Apr 12, 2023
950205d
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tustvold Apr 12, 2023
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27 changes: 13 additions & 14 deletions arrow-json/src/reader/schema.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ use indexmap::map::IndexMap as HashMap;
use indexmap::set::IndexSet as HashSet;
use serde_json::Value;
use std::borrow::Borrow;
use std::io::{BufRead, BufReader, Read, Seek};
use std::io::{BufRead, Seek};
use std::sync::Arc;

#[derive(Debug, Clone)]
Expand Down Expand Up @@ -147,17 +147,17 @@ fn generate_schema(spec: HashMap<String, InferredType>) -> Result<Schema, ArrowE
/// }
/// ```
#[derive(Debug)]
pub struct ValueIter<'a, R: Read> {
reader: &'a mut BufReader<R>,
pub struct ValueIter<R: BufRead> {
reader: R,
max_read_records: Option<usize>,
record_count: usize,
// reuse line buffer to avoid allocation on each record
line_buf: String,
}

impl<'a, R: Read> ValueIter<'a, R> {
impl<R: BufRead> ValueIter<R> {
/// Creates a new `ValueIter`
pub fn new(reader: &'a mut BufReader<R>, max_read_records: Option<usize>) -> Self {
pub fn new(reader: R, max_read_records: Option<usize>) -> Self {
Self {
reader,
max_read_records,
Expand All @@ -167,7 +167,7 @@ impl<'a, R: Read> ValueIter<'a, R> {
}
}

impl<'a, R: Read> Iterator for ValueIter<'a, R> {
impl<R: BufRead> Iterator for ValueIter<R> {
type Item = Result<Value, ArrowError>;

fn next(&mut self) -> Option<Self::Item> {
Expand Down Expand Up @@ -228,11 +228,11 @@ impl<'a, R: Read> Iterator for ValueIter<'a, R> {
/// ```
///
/// [`Reader`]: super::Reader
pub fn infer_json_schema_from_seekable<R: Read + Seek>(
reader: &mut BufReader<R>,
pub fn infer_json_schema_from_seekable<R: BufRead + Seek>(
mut reader: R,
max_read_records: Option<usize>,
) -> Result<Schema, ArrowError> {
let schema = infer_json_schema(reader, max_read_records);
let schema = infer_json_schema(&mut reader, max_read_records);
// return the reader seek back to the start
reader.rewind()?;

Expand Down Expand Up @@ -265,8 +265,8 @@ pub fn infer_json_schema_from_seekable<R: Read + Seek>(
/// // seek back to start so that the original file is usable again
/// file.seek(SeekFrom::Start(0)).unwrap();
/// ```
pub fn infer_json_schema<R: Read>(
reader: &mut BufReader<R>,
pub fn infer_json_schema<R: BufRead>(
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The idea here is that any existing user of this API will be fine because a &mut BufReader<R> also implements BufRead?

https://doc.rust-lang.org/stable/std/io/trait.BufRead.html

reader: R,
max_read_records: Option<usize>,
) -> Result<Schema, ArrowError> {
infer_json_schema_from_iterator(ValueIter::new(reader, max_read_records))
Expand Down Expand Up @@ -515,7 +515,7 @@ mod tests {
use super::*;
use flate2::read::GzDecoder;
use std::fs::File;
use std::io::Cursor;
use std::io::{BufReader, Cursor};

#[test]
fn test_json_infer_schema() {
Expand Down Expand Up @@ -700,8 +700,7 @@ mod tests {

#[test]
fn test_invalid_json_infer_schema() {
let re =
infer_json_schema_from_seekable(&mut BufReader::new(Cursor::new(b"}")), None);
let re = infer_json_schema_from_seekable(Cursor::new(b"}"), None);
assert_eq!(
re.err().unwrap().to_string(),
"Json error: Not valid JSON: expected value at line 1 column 1",
Expand Down