Struct CteCycle 

pub struct CteCycle {
    pub columns: Vec<Cow<'static, str>>,
    pub set: Cow<'static, str>,
    pub using: Cow<'static, str>,
    pub to: Option<Expr>,
    pub default_val: Option<Expr>,
}

CYCLE <cols> SET <col> [TO <value> DEFAULT <value>] USING <col>

Stops a recursive CTE from looping forever over cyclic data by marking the row that closes a cycle.

The mark values must be constants

PostgreSQL’s grammar spells the optional group TO AexprConst DEFAULT AexprConst — a literal constant, not an expression, so a bound argument in either slot is rejected by the server with a syntax error at the placeholder. libpg_query confirms it. The fields are Exprs because everything else in this module is, and because a constant is written expr::literal or expr::raw; a dialect’s cycle mod is where the narrowing belongs.

Fields

columns: Vec<Cow<'static, str>>

The columns that identify a row, quoted.

set: Cow<'static, str>

The name of the cycle-mark column to add, quoted.

using: Cow<'static, str>

The name of the path column to add, quoted.

to: Option<Expr>

The constant the mark column takes on a cycle. The grammar pairs this with default_val: both or neither.

default_val: Option<Expr>

The constant the mark column takes otherwise.

Implementations

impl CteCycle

pub fn new( columns: impl IntoIterator<Item = impl Into<Cow<'static, str>>>, set: impl Into<Cow<'static, str>>, using: impl Into<Cow<'static, str>>, ) -> Self

A cycle clause over columns, adding the mark column set and the path column using.

pub fn is_empty(&self) -> bool

Whether the clause is absent.

Trait Implementations

impl Clone for CteCycle

fn clone(&self) -> CteCycle

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for CteCycle

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

Formats the value using the given formatter.

impl Default for CteCycle

fn default() -> CteCycle

Returns the “default value” for a type.

impl Expression for CteCycle

fn write_sql(&self, w: &mut SqlWriter<'_>)

Append this fragment to w.