Struct ReaderBuilder

pub struct ReaderBuilder { /* private fields */ }

A builder for Reader and Decoder

Implementations

impl ReaderBuilder

pub fn new(schema: SchemaRef) -> Self

Create a new ReaderBuilder with the provided SchemaRef

This could be obtained using infer_json_schema if not known

Any columns not present in schema will be ignored, unless strict_mode is set to true. In this case, an error is returned when a column is missing from schema.

pub fn new_with_field(field: impl Into<FieldRef>) -> Self

Create a new ReaderBuilder that will parse JSON values of field.data_type()

Unlike ReaderBuilder::new this does not require the root of the JSON data to be an object, i.e. {..}, allowing for parsing of any valid JSON value(s)

// Root of JSON schema is a numeric type
let data = "1\n2\n3\n";
let field = Arc::new(Field::new("int", DataType::Int32, true));
let mut reader = ReaderBuilder::new_with_field(field.clone()).build(data.as_bytes()).unwrap();
let b = reader.next().unwrap().unwrap();
let values = b.column(0).as_primitive::<Int32Type>().values();
assert_eq!(values, &[1, 2, 3]);

// Root of JSON schema is a list type
let data = "[1, 2, 3, 4, 5, 6, 7]\n[1, 2, 3]";
let field = Field::new_list("int", field.clone(), true);
let mut reader = ReaderBuilder::new_with_field(field).build(data.as_bytes()).unwrap();
let b = reader.next().unwrap().unwrap();
let list = b.column(0).as_list::<i32>();

assert_eq!(list.offsets().as_ref(), &[0, 7, 10]);
let list_values = list.values().as_primitive::<Int32Type>();
assert_eq!(list_values.values(), &[1, 2, 3, 4, 5, 6, 7, 1, 2, 3]);

pub fn with_batch_size(self, batch_size: usize) -> Self

Sets the batch size in rows to read

pub fn coerce_primitive(self, coerce_primitive: bool) -> Self

👎Deprecated: Use with_coerce_primitive

Sets if the decoder should coerce primitive values (bool and number) into string when the Schema’s column is Utf8 or LargeUtf8.

pub fn with_coerce_primitive(self, coerce_primitive: bool) -> Self

Sets if the decoder should coerce primitive values (bool and number) into string when the Schema’s column is Utf8 or LargeUtf8.

pub fn with_strict_mode(self, strict_mode: bool) -> Self

Sets if the decoder should return an error if it encounters a column not present in schema

pub fn build<R: BufRead>(self, reader: R) -> Result<Reader<R>, ArrowError>

Create a Reader with the provided BufRead

pub fn build_decoder(self) -> Result<Decoder, ArrowError>

Create a Decoder