Struct lance::datatypes::Schema

pub struct Schema {
    pub fields: Vec<Field>,
    pub metadata: HashMap<String, String>,
}

Lance Schema.

Fields

fields: Vec<Field>

Top-level fields in the dataset.

metadata: HashMap<String, String>

Metadata of the schema

Implementations

impl Schema

pub fn project<T: AsRef<str>>(&self, columns: &[T]) -> Result<Self>

Project the columns over the schema.

let schema = Schema::from(...);
let projected = schema.project(&["col1", "col2.sub_col3.field4"])?;

pub fn intersection(&self, other: &Self) -> Result<Self>

Intersection between two Schema.

pub fn project_by_ids(&self, column_ids: &[i32]) -> Self

Returns a new schema that only contains the fields in column_ids.

This projection can filter out both top-level and nested fields

pub fn project_by_schema<S: TryInto<Self, Error = Error>>( &self, projection: S ) -> Result<Self>

Project the schema by another schema, and preserves field metadata, i.e., Field IDs.

Parameters

• projection: The schema to project by. Can be arrow_schema::Schema or Schema.

pub fn exclude<T: TryInto<Self> + Debug>(&self, schema: T) -> Result<Self>

Exclude the fields from other Schema, and returns a new Schema.

pub fn field(&self, name: &str) -> Option<&Field>

Get a field by name. Return None if the field does not exist.

pub fn merge<S: TryInto<Self, Error = Error>>(&self, other: S) -> Result<Self>

Merge this schema from the other schema.

After merging, the field IDs from other schema will be reassigned, following the fields in self.

Trait Implementations

impl Clone for Schema

fn clone(&self) -> Schema

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Schema

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

Formats the value using the given formatter.

impl Default for Schema

fn default() -> Schema

Returns the “default value” for a type.

impl Display for Schema

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

Formats the value using the given formatter.

impl From<&Schema> for (Vec<Field>, HashMap<String, Vec<u8>>)

Convert a Schema to a list of protobuf Field and Metadata

fn from(schema: &Schema) -> Self

Converts to this type from the input type.

impl From<&Schema> for Schema

Convert Lance Schema to Arrow Schema

fn from(schema: &Schema) -> Self

Converts to this type from the input type.

impl From<&Schema> for Vec<Field>

Convert a Schema to a list of protobuf Field.

fn from(schema: &Schema) -> Self

Converts to this type from the input type.

impl From<&Vec<Field>> for Schema

Convert list of protobuf Field to a Schema.

fn from(fields: &Vec<Field>) -> Self

Converts to this type from the input type.

impl From<(&Vec<Field>, HashMap<String, Vec<u8>>)> for Schema

Convert list of protobuf Field and Metadata to a Schema.

fn from((fields, metadata): (&Vec<Field>, HashMap<String, Vec<u8>>)) -> Self

Converts to this type from the input type.

impl PartialEq for Schema

fn eq(&self, other: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl TryFrom<&Schema> for Schema

Make API cleaner to accept both Schema and Arrow Schema.

type Error = Error

The type returned in the event of a conversion error.

fn try_from(schema: &Self) -> Result<Self>

Performs the conversion.

impl TryFrom<&Schema> for Schema

Convert arrow2::datatype::Schema to Lance

type Error = Error

The type returned in the event of a conversion error.

fn try_from(schema: &ArrowSchema) -> Result<Self>

Performs the conversion.