Struct datafusion::prelude::Column

pub struct Column {
    pub relation: Option<String>,
    pub name: String,
}

A named reference to a qualified field in a schema.

Fields

relation: Option<String>

relation/table name.

name: String

field/column name.

Implementations

impl Column

pub fn new( relation: Option<impl Into<String>>, name: impl Into<String> ) -> Column

Create Column from optional qualifier and name

pub fn from_name(name: impl Into<String>) -> Column

Create Column from unqualified name.

pub fn from_qualified_name(flat_name: impl Into<String>) -> Column

Deserialize a fully qualified name string into a column

pub fn flat_name(&self) -> String

Serialize column into a flat name string

pub fn normalize_with_schemas( self, schemas: &[&Arc<DFSchema>], using_columns: &[HashSet<Column, RandomState>] ) -> Result<Column, DataFusionError>

Qualify column if not done yet.

If this column already has a relation, it will be returned as is and the given parameters are ignored. Otherwise this will search through the given schemas to find the column. This will use the first schema that matches.

A schema matches if there is a single column that – when unqualified – matches this column. There is an exception for USING statements, see below.

Using columns

Take the following SQL statement:

SELECT id FROM t1 JOIN t2 USING(id)

In this case, both t1.id and t2.id will match unqualified column id. To express this possibility, use using_columns. Each entry in this array is a set of columns that are bound together via a USING clause. So in this example this would be [{t1.id, t2.id}].

Trait Implementations

impl Clone for Column

fn clone(&self) -> Column

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Column

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

Formats the value using the given formatter.

impl Display for Column

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

Formats the value using the given formatter.

impl From<&String> for Column

Create a column, cloning the string

fn from(c: &String) -> Column

Converts to this type from the input type.

impl From<&str> for Column

fn from(c: &str) -> Column

Converts to this type from the input type.

impl From<String> for Column

Create a column, reusing the existing string

fn from(c: String) -> Column

Converts to this type from the input type.

impl FromStr for Column

type Err = Infallible

The associated error which can be returned from parsing.

fn from_str(s: &str) -> Result<Column, <Column as FromStr>::Err>

Parses a string s to return a value of this type.

impl Hash for Column

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

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 Column

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

This method returns an Ordering between self and other.

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

Compares and returns the maximum of two values.

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

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Selfwhere Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval.

impl PartialEq<Column> for Column

fn eq(&self, other: &Column) -> 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 PartialOrd<Column> for Column

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

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

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

This method tests less than (for self and other) and is used by the < operator.

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

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

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

This method tests greater than (for self and other) and is used by the > operator.

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

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

impl Eq for Column

impl StructuralEq for Column

impl StructuralPartialEq for Column