Module arrow

High-level API for reading/writing Arrow RecordBatches and Arrays to/from Parquet Files.

Apache Arrow is a cross-language development platform for in-memory data.

Example of writing Arrow record batch to Parquet file

 let ids = Int32Array::from(vec![1, 2, 3, 4]);
 let vals = Int32Array::from(vec![5, 6, 7, 8]);
 let batch = RecordBatch::try_from_iter(vec![
   ("id", Arc::new(ids) as ArrayRef),
   ("val", Arc::new(vals) as ArrayRef),
 ]).unwrap();

 let file = tempfile().unwrap();

 // WriterProperties can be used to set Parquet file options
 let props = WriterProperties::builder()
     .set_compression(Compression::SNAPPY)
     .build();

 let mut writer = ArrowWriter::try_new(file, batch.schema(), Some(props)).unwrap();

 writer.write(&batch).expect("Writing batch");

 // writer must be closed to write footer
 writer.close().unwrap();

Example of reading parquet file into arrow record batch

let file = File::open("data.parquet").unwrap();

let builder = ParquetRecordBatchReaderBuilder::try_new(file).unwrap();
println!("Converted arrow schema is: {}", builder.schema());

let mut reader = builder.build().unwrap();

let record_batch = reader.next().unwrap().unwrap();

println!("Read {} records.", record_batch.num_rows());

Re-exports

• pub use self::arrow_writer::ArrowWriter;

Modules

• arrow_reader
  Contains reader which reads parquet data into arrow RecordBatch
• arrow_writer
  Contains writer which writes arrow data into parquet data.

Structs

• FieldLevels
  Schema information necessary to decode a parquet file as arrow Fields
• ProjectionMask
  A ProjectionMask identifies a set of columns within a potentially nested schema to project

Constants

• ARROW_SCHEMA_META_KEY
  Schema metadata key used to store serialized Arrow IPC schema
• PARQUET_FIELD_ID_META_KEY
  The value of this metadata key, if present on Field::metadata, will be used to populate BasicTypeInfo::id

Functions

• arrow_to_parquet_schema
  Convert arrow schema to parquet schema
• parquet_to_arrow_field_levels
  Convert a parquet SchemaDescriptor to FieldLevels
• parquet_to_arrow_schema
  Convert Parquet schema to Arrow schema including optional metadata
• parquet_to_arrow_schema_by_columns
  Convert parquet schema to arrow schema including optional metadata, only preserving some leaf columns.