add test for reading strings from parquet

rust/datafusion/src/datasource/parquet.rs

@@ -348,17 +348,12 @@ impl RecordBatchIterator for ParquetFile {
 #[cfg(test)]
 mod tests {
  use super::*;
- use arrow::array::Int32Array;
+ use arrow::array::{BinaryArray, Int32Array};
  use std::env;
 
  #[test]
  fn read_read_i32_column() {
- let testdata = env::var("PARQUET_TEST_DATA").unwrap();
- let filename = format!("{}/alltypes_plain.parquet", testdata);
-
- let table = ParquetTable::new(&filename);
-
- println!("{:?}", table.schema());
+ let table = load_table("alltypes_plain.parquet");
 
  let projection = Some(vec![0]);
  let scan = table.scan(&projection, 1024).unwrap();
@@ -383,4 +378,41 @@ mod tests {
  format!("{:?}", values)
  );
  }
+
+ #[test]
+ fn read_read_string_column() {
+ let table = load_table("alltypes_plain.parquet");
+
+ let projection = Some(vec![9]);
+ let scan = table.scan(&projection, 1024).unwrap();
+ let mut it = scan.borrow_mut();
+ let batch = it.next().unwrap().unwrap();
+
+ assert_eq!(1, batch.num_columns());
+ assert_eq!(8, batch.num_rows());
+
+ let array = batch
+ .column(0)
+ .as_any()
+ .downcast_ref::<BinaryArray>()
+ .unwrap();
+ let mut values: Vec<String> = vec![];
+ for i in 0..8 {
+ let str: String = String::from_utf8(array.value(i).to_vec()).unwrap();
+ values.push(str);
+ }
+
+ assert_eq!(
+ "[\"0\", \"1\", \"0\", \"1\", \"0\", \"1\", \"0\", \"1\"]",
+ format!("{:?}", values)
+ );
+ }
+
+ fn load_table(name: &str) -> Box<Table> {
+ let testdata = env::var("PARQUET_TEST_DATA").unwrap();
+ let filename = format!("{}/{}", testdata, name);
+ let table = ParquetTable::new(&filename);
+ println!("{:?}", table.schema());
+ Box::new(table)
+ }
 }