#62 Added cli tool to export data in a csv format (#85)

* #62 Added cli tool to export data in a csv format

* CR fixes

Cargo.toml

@@ -13,7 +13,7 @@ rust-version = "1.70"
 
 [dependencies]
 anyhow = { version = "1.0", optional = true }
-arrow = { version = "51", features = ["prettyprint"] }
+arrow = { version = "51", features = ["prettyprint", "chrono-tz"] }
 bytes = "1.4"
 chrono = { version = "0.4.37", default-features = false, features = ["std"] }
 chrono-tz = "0.8.6"
@@ -72,6 +72,10 @@ path = "./examples/datafusion_integration.rs"
 name = "orc-metadata"
 required-features = ["cli"]
 
+[[bin]]
+name = "orc-export"
+required-features = ["cli"]
+
 [[bin]]
 name = "orc-stats"
 required-features = ["cli"]

src/bin/orc-export.rs

@@ -0,0 +1,42 @@
+use std::{fs::File, io, path::PathBuf};
+
+use anyhow::Result;
+use arrow::csv;
+use clap::Parser;
+use orc_rust::ArrowReaderBuilder;
+
+#[derive(Parser)]
+#[command(name = "orc-export")]
+#[command(version, about = "Export data from orc file to csv", long_about = None)]
+struct Cli {
+    /// Path to the orc file
+    file: PathBuf,
+    /// Output file. If not provided output will be printed on console
+    #[arg(short, long)]
+    output: Option<PathBuf>,
+    // TODO: head=N
+    // TODO: convert_dates
+    // TODO: format=[csv|json]
+    // TODO: columns="col1,col2"
+}
+
+fn main() -> Result<()> {
+    let cli = Cli::parse();
+    let f = File::open(&cli.file)?;
+    let output_writer: Box<dyn io::Write> = if let Some(output) = cli.output {
+        Box::new(File::create(output)?)
+    } else {
+        Box::new(io::stdout())
+    };
+
+    let reader = ArrowReaderBuilder::try_new(f)?.build();
+    let mut writer = csv::WriterBuilder::new()
+        .with_header(true)
+        .build(output_writer);
+
+    for batch in reader.flatten() {
+        writer.write(&batch)?;
+    }
+
+    Ok(())
+}