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Update read parquet example in parquet/arrow home #2730

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merged 2 commits into from Sep 15, 2022
Merged

Update read parquet example in parquet/arrow home #2730

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2c35104
Update example to read parquet
datapythonista Sep 15, 2022
c2cc78f
Remove outdated comment
datapythonista Sep 15, 2022
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34 changes: 10 additions & 24 deletions parquet/src/arrow/mod.rs
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Expand Up @@ -66,26 +66,24 @@
//! # Example of reading parquet file into arrow record batch
//!
//! ```rust
//! use arrow::record_batch::RecordBatchReader;
//! use parquet::file::reader::{FileReader, SerializedFileReader};
//! use parquet::arrow::{ParquetFileArrowReader, ArrowReader, ProjectionMask};
//! use std::sync::Arc;
//! use std::fs::File;
//! use parquet::arrow::arrow_reader::ParquetRecordBatchReaderBuilder;
//!
//! # use std::sync::Arc;
//! # use arrow::array::Int32Array;
//! # use arrow::datatypes::{DataType, Field, Schema};
//! # use arrow::record_batch::RecordBatch;
//! # use parquet::arrow::arrow_writer::ArrowWriter;
//! #
//! # let ids = Int32Array::from(vec![1, 2, 3, 4]);
//! # let schema = Arc::new(Schema::new(vec![
//! # Field::new("id", DataType::Int32, false),
//! # Field::new("id", DataType::Int32, false),
//! # ]));
//! #
//! # // Write to a memory buffer (can also write to a File)
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This comment isn't actually correct, although I appreciate it was incorrect before

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Thanks for the heads up, I didn't realize. I just removed it, I don't think it adds much value to say we're writing to the file here. But let me know if you've got a better idea.

//! # let file = File::create("data.parquet").unwrap();
//! #
//! # let batch =
//! # RecordBatch::try_new(Arc::clone(&schema), vec![Arc::new(ids)]).unwrap();
//! # let batch = RecordBatch::try_new(Arc::clone(&schema), vec![Arc::new(ids)]).unwrap();
//! # let batches = vec![batch];
//! #
//! # let mut writer = ArrowWriter::try_new(file, Arc::clone(&schema), None).unwrap();
Expand All @@ -97,26 +95,14 @@
//!
//! let file = File::open("data.parquet").unwrap();
//!
//! let mut arrow_reader = ParquetFileArrowReader::try_new(file).unwrap();
//! let mask = ProjectionMask::leaves(arrow_reader.parquet_schema(), [0]);
//!
//! println!("Converted arrow schema is: {}", arrow_reader.get_schema().unwrap());
//! println!("Arrow schema after projection is: {}",
//! arrow_reader.get_schema_by_columns(mask.clone()).unwrap());
//! let builder = ParquetRecordBatchReaderBuilder::try_new(file).unwrap();
//! println!("Converted arrow schema is: {}", builder.schema());
//!
//! let mut unprojected = arrow_reader.get_record_reader(2048).unwrap();
//! println!("Unprojected reader schema: {}", unprojected.schema());
//! let mut reader = builder.build().unwrap();
//!
//! let mut record_batch_reader = arrow_reader.get_record_reader_by_columns(mask, 2048).unwrap();
//! let record_batch = reader.next().unwrap().unwrap();
//!
//! for maybe_record_batch in record_batch_reader {
//! let record_batch = maybe_record_batch.unwrap();
//! if record_batch.num_rows() > 0 {
//! println!("Read {} records.", record_batch.num_rows());
//! } else {
//! println!("End of file!");
//! }
//!}
//! println!("Read {} records.", record_batch.num_rows());
//! ```

experimental!(mod array_reader);
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