Struct Relation 

pub struct Relation<'a> {
    pub name: Cow<'a, str>,
    pub arguments: Option<Arguments<'a>>,
    pub columns: Vec<Value<'a>>,
    pub emit: Option<&'a EmitKind>,
    pub advanced_extension: Option<&'a AdvancedExtension>,
    pub children: Vec<Option<Relation<'a>>>,
}

Fields

name: Cow<'a, str>

arguments: Option<Arguments<'a>>

Arguments to the relation, if any.

• None means this relation does not take arguments, and the argument section is omitted entirely.
• Some(args) with both vectors empty means the relation takes arguments, but none are provided; this will print as _ => ....
• Some(args) with non-empty vectors will print as usual, with positional arguments first, then named arguments, separated by commas.

columns: Vec<Value<'a>>

The columns emitted by this relation, pre-emit - the ‘direct’ column output.

emit: Option<&'a EmitKind>

The emit kind, if any. If none, use the columns directly.

advanced_extension: Option<&'a AdvancedExtension>

The advanced extension (enhancement and/or optimizations) attached to this relation, if any. Mirrors the advanced_extension field carried by standard relation types in the protobuf (Read, Filter, Project, etc…) Extension relations (ExtensionLeaf, ExtensionSingle, ExtensionMulti) do not carry this field and always set it to None.

children: Vec<Option<Relation<'a>>>

The input relations.

Implementations

impl Relation<'_>

pub fn write_header<S: Scope, W: Write>(&self, ctx: &S, w: &mut W) -> Result

Write the single header line for this relation, e.g. Filter[$0 => $0]. Does not write a trailing newline; callers are responsible for any newline that follows (either from adv_ext or from the next child).

pub fn write_children<S: Scope, W: Write>(&self, ctx: &S, w: &mut W) -> Result

Write each child relation at one indent level deeper than ctx. Each child is preceded by a newline.

impl<'a> Relation<'a>

pub fn emitted(&self) -> usize

impl<'a> Relation<'a>

pub fn input_refs(&self) -> Vec<Value<'a>>

Create a vector of values that are references to the emitted outputs of this relation. “Emitted” here meaning the outputs of this relation after the emit kind has been applied.

This is useful for relations like Filter and Limit whose direct outputs are primarily those of its children (direct here meaning before the emit has been applied).

pub fn convert_children<S: Scope>( refs: Vec<Option<&'a Rel>>, ctx: &S, ) -> (Vec<Option<Relation<'a>>>, usize)

Convert a vector of relation references into their structured form.

Returns a list of children (with None for ones missing), and a count of input columns.

impl<'a> Relation<'a>

pub fn from_rel<S: Scope>(rel: &'a Rel, ctx: &S) -> Self

Trait Implementations

impl Textify for Relation<'_>

fn name() -> &'static str

fn textify<S: Scope, W: Write>(&self, ctx: &S, w: &mut W) -> Result