Struct RelationDesc

pub struct RelationDesc {
    pub typ: RelationType,
    pub names: Vec<Option<String>>,
}

A description of the shape of a relation.

It bundles a RelationType with the name of each column in the relation. Individual column names are optional.

Fields

typ: RelationType

names: Vec<Option<String>>

Implementations

impl RelationDesc

pub fn len(&self) -> Result<usize>

pub fn to_df_schema(&self) -> Result<DFSchema>

pub fn apply_mfp(&self, mfp: &SafeMfpPlan) -> Result<Self>

apply mfp, and also project col names for the projected columns

impl RelationDesc

pub fn empty() -> Self

Constructs a new RelationDesc that represents the empty relation with no columns and no keys.

pub fn try_new<I, N>(typ: RelationType, names: I) -> Result<Self>

where I: IntoIterator<Item = N>, N: Into<Option<String>>,

Constructs a new RelationDesc from a RelationType and an iterator over column names.

pub fn new_unchecked<I, N>(typ: RelationType, names: I) -> Self

where I: IntoIterator<Item = N>, N: Into<Option<String>>,

Constructs a new RelationDesc from a RelationType and an iterator over column names.

Panics

Panics if the arity of the RelationType is not equal to the number of items in names.

pub fn from_names_and_types<I, T, N>(iter: I) -> Self

where I: IntoIterator<Item = (N, T)>, T: Into<ColumnType>, N: Into<Option<String>>,

pub fn concat(self, other: Self) -> Self

Concatenates a RelationDesc onto the end of this RelationDesc.

pub fn with_column<N>(self, name: N, column_type: ColumnType) -> Self

where N: Into<Option<String>>,

Appends a column with the specified name and type.

pub fn with_key(self, indices: Vec<usize>) -> Self

Adds a new key for the relation.

pub fn try_with_names<I, N>(self, names: I) -> Result<Self>

where I: IntoIterator<Item = N>, N: Into<Option<String>>,

Builds a new relation description with the column names replaced with new names.

pub fn arity(&self) -> usize

Computes the number of columns in the relation.

pub fn typ(&self) -> &RelationType

Returns the relation type underlying this relation description.

pub fn iter(&self) -> impl Iterator<Item = (&Option<String>, &ColumnType)>

Returns an iterator over the columns in this relation.

pub fn iter_types(&self) -> impl Iterator<Item = &ColumnType>

Returns an iterator over the types of the columns in this relation.

pub fn iter_names(&self) -> impl Iterator<Item = &Option<String>>

Returns an iterator over the names of the columns in this relation.

pub fn get_by_name(&self, name: &String) -> Option<(usize, &ColumnType)>

Finds a column by name.

Returns the index and type of the column named name. If no column with the specified name exists, returns None. If multiple columns have the specified name, the leftmost column is returned.

pub fn get_name(&self, i: usize) -> &Option<String>

Gets the name of the ith column.

Panics

Panics if i is not a valid column index.

Trait Implementations

impl Clone for RelationDesc

fn clone(&self) -> RelationDesc

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for RelationDesc

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for RelationDesc

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Hash for RelationDesc

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for RelationDesc

fn cmp(&self, other: &RelationDesc) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for RelationDesc

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

Tests for self and other values to be equal, and is used by ==.

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

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

impl PartialOrd for RelationDesc

fn partial_cmp(&self, other: &RelationDesc) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Serialize for RelationDesc

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for RelationDesc

impl StructuralPartialEq for RelationDesc