本文介绍Arrow生态持久化存储文件的读取方式之一，使用Rust parquet库读取parquet文件。
Cargo.toml中依赖库如下
[package]
name = "parquet_rs_read_parquet"
version = "0.1.0"
edition = "2021"
[dependencies]
anyhow = "1.0.86"
arrow = { version = "52.1.0", features = ["prettyprint"] }
parquet = "52.1.0"
代码如下
use anyhow::Result;
use arrow::array::AsArray;
use parquet::arrow::arrow_reader::ParquetRecordBatchReaderBuilder;
use std::fs::File;
const PQ_FILE: &str = "../assets/sample.parquet";
fn main() -> Result<()> {
read_with_parquet(PQ_FILE)?;
Ok(())
}
fn read_with_parquet(file: &str) -> Result<()> {
let file = File::open(file)?;
let reader = ParquetRecordBatchReaderBuilder::try_new(file)?
.with_batch_size(8192)
.with_limit(3)
.build()?;
for record_batch in reader {
let record_batch = record_batch?;
let emails = record_batch.column(0).as_binary::<i32>();
for email in emails {
let email = email.unwrap();
println!("{:?}", String::from_utf8_lossy(email));
}
}
Ok(())
}
PQ_FILE: 表示parquet文件的路径，当前我们使用的相对目录，这个目录是运行时的相 对目录，即cargo run命令运行 时的目录即为当前目录record_batch.column(0).as_binary::<i32>(): 这里需要用到arrow::array::AsArrayTraitParquetRecordBatchReaderBuilder:build()函数返回一个ParquetRecordBatchReaderString::from_utf8_lossy(): 将二进制转换为字符串
运行
# `cd parquet_rs_read_parquet`, otherwise, the `sample.parquet` file cannot be found.
cargo run
- 执行结果
