Enum Expr 

pub enum Expr {
    Star,
    Named(String),
    Aliased {
        name: String,
        alias: String,
    },
    Aggregate {
        col: String,
        func: AggregateFunc,
        distinct: bool,
        filter: Option<Vec<Condition>>,
        alias: Option<String>,
    },
    Cast {
        expr: Box<Expr>,
        target_type: String,
        alias: Option<String>,
    },
    Def {
        name: String,
        data_type: String,
        constraints: Vec<Constraint>,
    },
    Mod {
        kind: ModKind,
        col: Box<Expr>,
    },
    Window {
        name: String,
        func: String,
        params: Vec<Expr>,
        partition: Vec<String>,
        order: Vec<Cage>,
        frame: Option<WindowFrame>,
    },
    Case {
        when_clauses: Vec<(Condition, Box<Expr>)>,
        else_value: Option<Box<Expr>>,
        alias: Option<String>,
    },
    JsonAccess {
        column: String,
        path_segments: Vec<(String, bool)>,
        alias: Option<String>,
    },
    FunctionCall {
        name: String,
        args: Vec<Expr>,
        alias: Option<String>,
    },
    SpecialFunction {
        name: String,
        args: Vec<(Option<String>, Box<Expr>)>,
        alias: Option<String>,
    },
    Binary {
        left: Box<Expr>,
        op: BinaryOp,
        right: Box<Expr>,
        alias: Option<String>,
    },
    Literal(Value),
    ArrayConstructor {
        elements: Vec<Expr>,
        alias: Option<String>,
    },
    RowConstructor {
        elements: Vec<Expr>,
        alias: Option<String>,
    },
    Subscript {
        expr: Box<Expr>,
        index: Box<Expr>,
        alias: Option<String>,
    },
    Collate {
        expr: Box<Expr>,
        collation: String,
        alias: Option<String>,
    },
    FieldAccess {
        expr: Box<Expr>,
        field: String,
        alias: Option<String>,
    },
    Subquery {
        query: Box<Qail>,
        alias: Option<String>,
    },
    Exists {
        query: Box<Qail>,
        negated: bool,
        alias: Option<String>,
    },
}

An expression node in the AST.

Variants

Star

All columns (*)

Named(String)

A named column or identifier.

Aliased

An aliased expression (expr AS alias)

Fields

name: String

Expression name.

alias: String

Alias.

Aggregate

An aggregate function (COUNT(col)) with optional FILTER and DISTINCT

Fields

col: String

Column to aggregate.

func: AggregateFunc

Aggregate function.

distinct: bool

Whether DISTINCT is applied.

filter: Option<Vec<Condition>>

PostgreSQL FILTER (WHERE …) clause for aggregates

alias: Option<String>

Optional alias.

Cast

Type cast expression (expr::type)

Fields

expr: Box<Expr>

Expression to cast.

target_type: String

Target SQL type.

alias: Option<String>

Optional alias.

Def

Column definition (name, type, constraints).

Fields

name: String

Column name.

data_type: String

SQL data type.

constraints: Vec<Constraint>

Column constraints.

Mod

ALTER TABLE modify (ADD/DROP column).

Fields

kind: ModKind

Modification kind.

col: Box<Expr>

Column expression.

Window

Window Function Definition

Fields

name: String

Window name/alias.

func: String

Window function name.

params: Vec<Expr>

Function arguments as expressions (e.g., for SUM(amount), use Expr::Named(“amount”))

partition: Vec<String>

PARTITION BY columns.

order: Vec<Cage>

ORDER BY clauses.

frame: Option<WindowFrame>

Frame specification.

Case

CASE WHEN expression

Fields

when_clauses: Vec<(Condition, Box<Expr>)>

WHEN condition THEN expr pairs (Expr allows functions, values, identifiers)

else_value: Option<Box<Expr>>

ELSE expr (optional)

alias: Option<String>

Optional alias

JsonAccess

JSON accessor (data->>‘key’ or data->‘key’ or chained data->‘a’->0->>‘b’)

Fields

column: String

Base column name

path_segments: Vec<(String, bool)>

JSON path segments: (key, as_text) as_text: true for ->> (extract as text), false for -> (extract as JSON) For chained access like x->‘a’->0->>‘b’, this is [(“a”, false), (“0”, false), (“b”, true)]

alias: Option<String>

Optional alias

FunctionCall

Function call expression (COALESCE, NULLIF, etc.)

Fields

name: String

Function name (coalesce, nullif, etc.)

args: Vec<Expr>

Arguments to the function (now supports nested expressions)

alias: Option<String>

Optional alias

SpecialFunction

Special SQL function with keyword arguments (SUBSTRING, EXTRACT, TRIM, etc.) e.g., SUBSTRING(expr FROM pos [FOR len]), EXTRACT(YEAR FROM date)

Fields

name: String

Function name (SUBSTRING, EXTRACT, TRIM, etc.)

args: Vec<(Option<String>, Box<Expr>)>

Arguments as (optional_keyword, expr) pairs e.g., [(None, col), (Some(“FROM”), 2), (Some(“FOR”), 5)]

alias: Option<String>

Optional alias

Binary

Binary expression (left op right)

Fields

left: Box<Expr>

Left operand.

op: BinaryOp

Binary operator.

right: Box<Expr>

Right operand.

alias: Option<String>

Optional alias.

Literal(Value)

Literal value (string, number) for use in expressions e.g., ‘62’, 0, ‘active’

ArrayConstructor

Array constructor: ARRAY[expr1, expr2, …]

Fields

elements: Vec<Expr>

Array elements.

alias: Option<String>

Optional alias.

RowConstructor

Row constructor: ROW(expr1, expr2, …) or (expr1, expr2, …)

Fields

elements: Vec<Expr>

Row elements.

alias: Option<String>

Optional alias.

Subscript

Array/string subscript: arr[index].

Fields

expr: Box<Expr>

Base expression.

index: Box<Expr>

Index expression.

alias: Option<String>

Optional alias.

Collate

Collation: expr COLLATE “collation_name”

Fields

expr: Box<Expr>

Expression.

collation: String

Collation name.

alias: Option<String>

Optional alias.

FieldAccess

Field selection from composite: (row).field

Fields

expr: Box<Expr>

Composite expression.

field: String

Field name.

alias: Option<String>

Optional alias.

Subquery

Scalar subquery: (SELECT … LIMIT 1) Used in COALESCE, comparisons, etc.

Fields

query: Box<Qail>

Inner query.

alias: Option<String>

Optional alias.

Exists

EXISTS subquery: EXISTS(SELECT …)

Fields

query: Box<Qail>

Inner query.

negated: bool

Whether this is NOT EXISTS.

alias: Option<String>

Optional alias.

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

Formats the value using the given formatter.

impl Display for Expr

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

Formats the value using the given formatter.

impl ExprExt for Expr

fn with_alias(self, alias: &str) -> Expr

Add an alias to this expression.

fn or_default(self, default: impl Into<Expr>) -> Expr

COALESCE with a default value.

fn json(self, key: &str) -> JsonBuilder

JSON text extraction (column->>‘key’).

fn path(self, dotted_path: &str) -> JsonBuilder

JSON path extraction with dot notation.

fn cast(self, target_type: &str) -> Expr

Cast to a type: CAST(expr AS type)

fn upper(self) -> Expr

UPPER(expr)

fn lower(self) -> Expr

LOWER(expr)

fn trim(self) -> Expr

TRIM(expr)

fn length(self) -> Expr

LENGTH(expr)

fn abs(self) -> Expr

ABS(expr)

impl From<&String> for Expr

fn from(s: &String) -> Self

Converts to this type from the input type.

impl From<&str> for Expr

fn from(s: &str) -> Self

Convert a string reference to a Named expression. Enables: .select(["id", "name"]) instead of .select([col("id"), col("name")])

impl From<AggregateBuilder> for Expr

fn from(builder: AggregateBuilder) -> Self

Converts to this type from the input type.

impl From<BinaryBuilder> for Expr

fn from(builder: BinaryBuilder) -> Self

Converts to this type from the input type.

impl From<CaseBuilder> for Expr

fn from(builder: CaseBuilder) -> Self

Converts to this type from the input type.

impl From<CastBuilder> for Expr

fn from(builder: CastBuilder) -> Self

Converts to this type from the input type.

impl From<ConcatBuilder> for Expr

fn from(builder: ConcatBuilder) -> Self

Converts to this type from the input type.

impl From<Expr> for Value

Convert an Expr into a Value for use in correlated subquery filters.

Example

use qail_core::ast::builders::col;

// WHERE session_id = parent_table.id
.eq("session_id", col("parent_table.id"))

fn from(expr: Expr) -> Self

Converts to this type from the input type.

impl From<FunctionBuilder> for Expr

fn from(builder: FunctionBuilder) -> Self

Converts to this type from the input type.

impl From<JsonBuilder> for Expr

fn from(builder: JsonBuilder) -> Self

Converts to this type from the input type.

impl From<String> for Expr

fn from(s: String) -> Self

Converts to this type from the input type.

impl PartialEq for Expr

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