Enum Expr 

pub enum Expr {
    Column {
        qual: Option<String>,
        name: String,
    },
    Literal(Value),
    Star,
    QualifiedStar(String),
    Func {
        name: String,
        args: Vec<Expr>,
    },
    Case {
        operand: Option<Box<Expr>>,
        whens: Vec<(Expr, Expr)>,
        else_: Option<Box<Expr>>,
    },
    Binary {
        op: String,
        left: Box<Expr>,
        right: Box<Expr>,
    },
    Unary {
        op: String,
        expr: Box<Expr>,
    },
    InList {
        expr: Box<Expr>,
        list: Vec<Expr>,
        negated: bool,
    },
    IsNull {
        expr: Box<Expr>,
        negated: bool,
    },
    Cast {
        expr: Box<Expr>,
        ty: String,
    },
    Subquery(Box<Select>),
    Exists {
        query: Box<Select>,
        negated: bool,
    },
    ArrayQuery(Box<Select>),
    InSubquery {
        expr: Box<Expr>,
        query: Box<Select>,
        negated: bool,
    },
    Quantified {
        op: String,
        left: Box<Expr>,
        all: bool,
        right: Box<Expr>,
    },
    Index {
        expr: Box<Expr>,
        index: Box<Expr>,
    },
    ArrayLit(Vec<Expr>),
    Agg {
        name: String,
        args: Vec<Expr>,
        order_by: Vec<OrderBy>,
        distinct: bool,
    },
}

Variants

Column

nspname or n.nspname. The qualifier is kept because a join makes bare names ambiguous, and resolving an ambiguous name by guessing is how a query silently reads the wrong table’s column.

Fields

qual: Option<String>

name: String

Literal(Value)

Star

* in count(*), and in a bare select list.

QualifiedStar(String)

alias.*

Func

Fields

name: String

args: Vec<Expr>

Case

Both SQL spellings: simple — CASE x WHEN 'r' THEN 'table' ... ELSE ... END searched — CASE WHEN x = 'r' THEN 'table' ... ELSE ... END psql’s \dt uses the simple form with nine branches.

Fields

operand: Option<Box<Expr>>

whens: Vec<(Expr, Expr)>

else_: Option<Box<Expr>>

Binary

Fields

op: String

left: Box<Expr>

right: Box<Expr>

Unary

Fields

op: String

expr: Box<Expr>

InList

x [NOT] IN (a, b, c)

Fields

expr: Box<Expr>

list: Vec<Expr>

negated: bool

IsNull

x IS [NOT] NULL

Fields

expr: Box<Expr>

negated: bool

Cast

x::type — the cast is PARSED and then ignored at evaluation, because this engine is dynamically typed. Ignoring it is safe for the shapes catalogue SQL uses (prattrs::int2[]), and the alternative — refusing every cast — would reject queries whose result the cast cannot change.

Fields

expr: Box<Expr>

ty: String

Subquery(Box<Select>)

(SELECT ...) used as a VALUE: one column, at most one row. Postgres’s \dT hinges on one ((SELECT c.relkind = 'c' FROM pg_class c WHERE c.oid = t.typrelid)), and \d <table> on three.

Exists

[NOT] EXISTS (SELECT ...) — never NULL, which is why it is its own variant rather than Subquery IS NOT NULL.

Fields

query: Box<Select>

negated: bool

ArrayQuery(Box<Select>)

ARRAY(SELECT ...) — the first column of every row, as one array. \dp, \dT+, \dD and \dy all build one and hand it to array_to_string.

InSubquery

x [NOT] IN (SELECT ...) — InList semantics over the first column.

Fields

expr: Box<Expr>

query: Box<Select>

negated: bool

Quantified

x op ANY (...) / x op SOME (...) / x op ALL (...). The right side evaluates to an array — an ArrayQuery when it was written as a subquery — and op is applied element by element.

Fields

op: String

left: Box<Expr>

all: bool

right: Box<Expr>

Index

arr[i] — one-based, as Postgres subscripts are.

Fields

expr: Box<Expr>

index: Box<Expr>

ArrayLit(Vec<Expr>)

ARRAY[a, b, c] — an array literal.

Agg

An aggregate call: count(*), array_agg(x ORDER BY y), string_agg(DISTINCT s, ',').

A variant of its own rather than a Func whose name happens to be in a list. “Is this an aggregate?” was a string comparison repeated at five sites — the select-list check, the pushdown walker, the join-key walker, the folder and the evaluator — and five copies of one rule is five chances to disagree about it. It is now a question about SHAPE.

It also carries the two modifiers only an aggregate has, and which SQLAlchemy’s primary-key reflection depends on: array_agg(CAST(attname AS TEXT) ORDER BY ord) is meaningless without the ordering — the array IS the column list, in key order.

Fields

name: String

args: Vec<Expr>

order_by: Vec<OrderBy>

Sorts the rows of the GROUP before the values are collected.

distinct: bool

Trait Implementations

impl Clone for Expr

fn clone(&self) -> Expr

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Expr

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

Formats the value using the given formatter.

impl PartialEq for Expr

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Expr