Struct JsonSchemaAligner 

pub struct JsonSchemaAligner<S> {
    inner: S,
    output_schema: SchemaRef,
    projected_root_presence: Vec<bool>,
    expected_input_col_num: usize,
    all_roots_present: bool,
    mode: ResolvedAlignMode,
    is_schema_matched: Option<bool>,
}

Adapts Parquet record batches to the output schema expected by the reader.

Nested projection can return only part of a JSON2 column, or omit its root entirely when no requested leaves are read. This stream restores missing roots with null arrays of the expected types.

Existing JSON2 columns are aligned to the logical schema inferred from type hints or rewritten to the specified JSON2 physical layout, as selected by AlignMode.

Fields

inner: S

output_schema: SchemaRef

Output schema expected by the upper reader.

projected_root_presence: Vec<bool>

Whether each projected root exists in the physical batch returned by parquet.

expected_input_col_num: usize

Number of columns expected from the physical batch returned by parquet.

all_roots_present: bool

Whether all projected roots are present and the stream can pass batches through.

mode: ResolvedAlignMode

Alignment mode with parsed and validated rewrite settings.

is_schema_matched: Option<bool>

The cache for whether incoming batches already match output schema.

Implementations

impl<S> JsonSchemaAligner<S>

where S: Stream<Item = Result<RecordBatch>>,

pub(crate) fn new( inner: S, projected_root_presence: Vec<bool>, output_schema: SchemaRef, mode: AlignMode, ) -> Result<JsonSchemaAligner<S>>

Creates an aligner with a shared output schema and an explicit operation. Parses rewrite metadata once and validates layouts against output field types.

Trait Implementations

impl<S> Debug for JsonSchemaAligner<S>

fn fmt(&self, __derive_more_f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<S> Stream for JsonSchemaAligner<S>

where S: Stream<Item = Result<RecordBatch>> + Unpin,

type Item = Result<RecordBatch, Error>

Values yielded by the stream.

fn poll_next( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Option<Self::Item>>

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.