Struct FileMetadata 

pub struct FileMetadata {
    pub version: i32,
    pub num_rows: usize,
    pub max_row_group_height: usize,
    pub created_by: Option<String>,
    pub row_groups: Vec<RowGroupMetadata>,
    pub key_value_metadata: Option<Vec<KeyValue>>,
    pub schema_descr: SchemaDescriptor,
    pub column_orders: Option<Vec<ColumnOrder>>,
    pub footer_buf: Buffer<u8>,
    /* private fields */
}

Available on crate feature polars-io only.

Metadata for a Parquet file.

Fields

version: i32

version of this file.

num_rows: usize

number of rows in the file.

max_row_group_height: usize

Max row group height, useful for sharing column materializations.

created_by: Option<String>

String message for application that wrote this file.

This should have the following format: <application> version <application version> (build <application build hash>).

parquet-mr version 1.8.0 (build 0fda28af84b9746396014ad6a415b90592a98b3b)

row_groups: Vec<RowGroupMetadata>

The row groups of this file

key_value_metadata: Option<Vec<KeyValue>>

key_value_metadata of this file.

schema_descr: SchemaDescriptor

schema descriptor.

column_orders: Option<Vec<ColumnOrder>>

Column (sort) order used for min_value and max_value of each leaf column in this file, one per leaf of schema_descr in the same order.

None when the file has no column orders, or not one per leaf; each column then has the undefined (legacy) column order.

footer_buf: Buffer<u8>

Footer bytes that back this file’s column-chunk statistics. Stats min_value / max_value are stored as (offset, len) ranges into this buffer; pass &self.footer_buf to [super::ColumnChunkMetadata::statistics] to materialise them.

Implementations

impl FileMetadata

pub fn schema(&self) -> &SchemaDescriptor

Returns the [SchemaDescriptor] that describes the schema of this file.

pub fn key_value_metadata(&self) -> &Option<Vec<KeyValue>>

Returns the file-level key-value metadata, if present.

pub fn column_order(&self, i: usize) -> ColumnOrder

Returns column order for the ith leaf column in this file. If column orders are not available, returns undefined (legacy) column order.

pub fn pruned( &self, keep_top_level_names: &[PlSmallStr], predicate_top_level_names: &[PlSmallStr], ) -> Result<FileMetadata, ParquetError>

Prune to projected columns, keeping statistics only for predicate columns.

Returns a new FileMetadata containing only:

• top-level schema fields whose name is in keep_top_level_names,
• row-group chunks corresponding to those fields’ leaves,
• statistics on chunks whose column is in predicate_top_level_names.

predicate_top_level_names is treated as a subset of keep_top_level_names; pass &[] to drop all stats. created_by and key_value_metadata are also dropped (not needed by the read hot path); column_orders is kept for the remaining leaves.

Metadata for encrypted files is returned unpruned, as decrypting column chunks relies on each column’s position in the full file schema.

Returns Err only when [RowGroupMetadata::from_compact] rejects the rebuilt row group (chunks-vs-leaves desync). Callers can fall back to unpruned metadata; the unpruned form is always valid.

TODO: a planner-side pass could pre-evaluate static predicates against stats and drop fully-skipped row groups, removing stats from the wire for those cases.

Trait Implementations

impl Clone for FileMetadata

fn clone(&self) -> FileMetadata

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for FileMetadata

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for FileMetadata

fn deserialize<D>(d: D) -> Result<FileMetadata, <D as Deserializer<'de>>::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for FileMetadata

fn serialize<S>( &self, s: S, ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.