drizzle_core/expr/

agg.rs

//! Type-safe aggregate functions.
//!
//! These functions return expressions marked as aggregates, which can be used
//! to enforce GROUP BY rules at compile time.
//!
//! # Type Safety
//!
//! - `sum`, `avg`: Require `Numeric` types (Int, `BigInt`, Float, Double)
//! - `count`: Works with any type
//! - `min`, `max`: Work with any type (ordered types in SQL)

use crate::dialect::DialectTypes;
use crate::sql::SQL;
use crate::traits::SQLParam;
use crate::types::{Array, Numeric};
use crate::{PostgresDialect, SQLiteDialect};
use drizzle_types::postgres::types::{
    Boolean as PgBoolean, Float4, Float8, Int2, Int4, Int8, Numeric as PgNumeric,
};
use drizzle_types::sqlite::types::{
    Integer as SqliteInteger, Numeric as SqliteNumeric, Real as SqliteReal,
};

use super::{Agg, Expr, NonNull, Null, SQLExpr, Scalar};

// =============================================================================
// Dialect Aggregate Policy
// =============================================================================

/// Dialect-specific aggregate output mapping.
///
/// Keeps aggregate output typing in one place so all aggregate functions
/// follow the same per-dialect policy.
#[diagnostic::on_unimplemented(
    message = "no aggregate policy for `{Self}` on this dialect",
    label = "aggregate result type is not defined for this SQL type/dialect"
)]
pub trait AggregatePolicy<D>: Numeric {
    type Sum: crate::types::DataType;
    type Avg: crate::types::DataType;
}

#[diagnostic::on_unimplemented(
    message = "no statistical aggregate policy for `{Self}` on this dialect",
    label = "stddev/variance result type is not defined for this SQL type/dialect"
)]
pub trait StatisticalAggregatePolicy<D>: Numeric {
    type StddevPop: crate::types::DataType;
    type StddevSamp: crate::types::DataType;
    type VarPop: crate::types::DataType;
    type VarSamp: crate::types::DataType;
}

#[diagnostic::on_unimplemented(
    message = "boolean aggregates are not supported for `{Self}` on this dialect",
    label = "use a boolean expression with a dialect that supports BOOL_AND/BOOL_OR"
)]
pub trait BooleanAggregatePolicy<D>: crate::types::DataType {}

#[diagnostic::on_unimplemented(
    message = "this aggregate is not available for this dialect",
    label = "use a dialect-specific alternative"
)]
pub trait PostgresAggregateSupport {}

#[diagnostic::on_unimplemented(
    message = "this aggregate is not available for this dialect",
    label = "use a dialect-specific alternative"
)]
pub trait SQLiteAggregateSupport {}

#[diagnostic::on_unimplemented(
    message = "no COUNT return type defined for this dialect",
    label = "COUNT result type is not configured for this dialect marker"
)]
pub trait CountPolicy {
    /// The integer type returned by COUNT (e.g. Integer on `SQLite`, Int8 on `PostgreSQL`).
    type Count: crate::types::DataType;
}

impl CountPolicy for SQLiteDialect {
    type Count = drizzle_types::sqlite::types::Integer;
}

impl CountPolicy for PostgresDialect {
    type Count = drizzle_types::postgres::types::Int8;
}

#[diagnostic::on_unimplemented(
    message = "no floating-point return type defined for this dialect",
    label = "PERCENT_RANK/CUME_DIST result type is not configured for this dialect marker"
)]
pub trait FloatPolicy {
    /// The floating-point type returned by distribution window functions
    /// like `PERCENT_RANK` and `CUME_DIST` (Real on `SQLite`, Float8 on `PostgreSQL`).
    type Float: crate::types::DataType;
}

impl FloatPolicy for SQLiteDialect {
    type Float = drizzle_types::sqlite::types::Real;
}

impl FloatPolicy for PostgresDialect {
    type Float = drizzle_types::postgres::types::Float8;
}

impl AggregatePolicy<SQLiteDialect> for SqliteInteger {
    type Sum = Self;
    type Avg = SqliteReal;
}
impl AggregatePolicy<SQLiteDialect> for SqliteReal {
    type Sum = Self;
    type Avg = Self;
}
impl AggregatePolicy<SQLiteDialect> for SqliteNumeric {
    type Sum = Self;
    type Avg = SqliteReal;
}
impl AggregatePolicy<SQLiteDialect> for drizzle_types::sqlite::types::Any {
    type Sum = Self;
    type Avg = SqliteReal;
}

impl StatisticalAggregatePolicy<PostgresDialect> for Int2 {
    type StddevPop = Float8;
    type StddevSamp = Float8;
    type VarPop = Float8;
    type VarSamp = Float8;
}
impl StatisticalAggregatePolicy<PostgresDialect> for Int4 {
    type StddevPop = Float8;
    type StddevSamp = Float8;
    type VarPop = Float8;
    type VarSamp = Float8;
}
impl StatisticalAggregatePolicy<PostgresDialect> for Int8 {
    type StddevPop = Float8;
    type StddevSamp = Float8;
    type VarPop = Float8;
    type VarSamp = Float8;
}
impl StatisticalAggregatePolicy<PostgresDialect> for Float4 {
    type StddevPop = Float8;
    type StddevSamp = Float8;
    type VarPop = Float8;
    type VarSamp = Float8;
}
impl StatisticalAggregatePolicy<PostgresDialect> for Float8 {
    type StddevPop = Self;
    type StddevSamp = Self;
    type VarPop = Self;
    type VarSamp = Self;
}
impl StatisticalAggregatePolicy<PostgresDialect> for PgNumeric {
    type StddevPop = Float8;
    type StddevSamp = Float8;
    type VarPop = Float8;
    type VarSamp = Float8;
}

impl BooleanAggregatePolicy<PostgresDialect> for PgBoolean {}

impl PostgresAggregateSupport for PostgresDialect {}
impl SQLiteAggregateSupport for SQLiteDialect {}

impl AggregatePolicy<PostgresDialect> for Int2 {
    type Sum = Int8;
    type Avg = Float8;
}
impl AggregatePolicy<PostgresDialect> for Int4 {
    type Sum = Int8;
    type Avg = Float8;
}
impl AggregatePolicy<PostgresDialect> for Int8 {
    type Sum = Self;
    type Avg = Float8;
}
impl AggregatePolicy<PostgresDialect> for Float4 {
    type Sum = Float8;
    type Avg = Float8;
}
impl AggregatePolicy<PostgresDialect> for Float8 {
    type Sum = Self;
    type Avg = Self;
}
impl AggregatePolicy<PostgresDialect> for PgNumeric {
    type Sum = Self;
    type Avg = Self;
}

// =============================================================================
// COUNT
// =============================================================================

/// COUNT(*) - counts all rows.
///
/// Returns a `BigInt`, `NonNull` (count is never NULL), Aggregate expression.
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::count_all;
///
/// let total = count_all();
/// // Generates: COUNT(*)
/// # "####;
/// ```
#[must_use]
pub fn count_all<'a, V>() -> SQLExpr<'a, V, <V::DialectMarker as CountPolicy>::Count, NonNull, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: CountPolicy,
{
    SQLExpr::new(SQL::raw("COUNT(*)"))
}

/// COUNT(expr) - counts non-null values.
///
/// Returns a `BigInt`, `NonNull` (count is never NULL), Aggregate expression.
/// Works with any expression type.
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::count;
///
/// let count = count(users.email);
/// // Generates: COUNT("users"."email")
/// # "####;
/// ```
pub fn count<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <V::DialectMarker as CountPolicy>::Count, NonNull, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: CountPolicy,
    E: Expr<'a, V>,
{
    SQLExpr::new(SQL::func("COUNT", expr.into_sql()))
}

/// COUNT(DISTINCT expr) - counts distinct non-null values.
///
/// Returns a `BigInt`, `NonNull`, Aggregate expression.
/// Works with any expression type.
pub fn count_distinct<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <V::DialectMarker as CountPolicy>::Count, NonNull, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: CountPolicy,
    E: Expr<'a, V>,
{
    SQLExpr::new(SQL::func(
        "COUNT",
        SQL::raw("DISTINCT").append(expr.into_sql()),
    ))
}

// =============================================================================
// SUM
// =============================================================================

/// SUM(expr) - sums numeric values.
///
/// Requires the expression to be `Numeric` (Int, `BigInt`, Float, Double).
/// Result type is dialect-aware.
/// Returns a nullable expression (empty set returns NULL).
///
/// # Type Safety
///
/// ```rust
/// # let _ = r####"
/// // ✅ OK: Numeric column
/// sum(orders.amount);
/// // SQLite: same width for integer sums
/// // PostgreSQL: Int/SmallInt promote to BigInt
///
/// // ❌ Compile error: Text is not Numeric
/// sum(users.name);
/// # "####;
/// ```
pub fn sum<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <E::SQLType as AggregatePolicy<V::DialectMarker>>::Sum, Null, Agg>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: AggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func("SUM", expr.into_sql()))
}

/// SUM(DISTINCT expr) - sums distinct numeric values.
///
/// Requires the expression to be `Numeric`.
/// Result type is dialect-aware.
pub fn sum_distinct<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <E::SQLType as AggregatePolicy<V::DialectMarker>>::Sum, Null, Agg>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: AggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func(
        "SUM",
        SQL::raw("DISTINCT").append(expr.into_sql()),
    ))
}

// =============================================================================
// AVG
// =============================================================================

/// AVG(expr) - calculates average of numeric values.
///
/// Requires the expression to be `Numeric`.
/// Always returns Double (SQL standard behavior), nullable.
///
/// # Type Safety
///
/// ```rust
/// # let _ = r####"
/// // ✅ OK: Numeric column
/// avg(products.price);
///
/// // ❌ Compile error: Text is not Numeric
/// avg(users.name);
/// # "####;
/// ```
pub fn avg<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <E::SQLType as AggregatePolicy<V::DialectMarker>>::Avg, Null, Agg>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: AggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func("AVG", expr.into_sql()))
}

/// AVG(DISTINCT expr) - calculates average of distinct numeric values.
///
/// Requires the expression to be `Numeric`.
pub fn avg_distinct<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <E::SQLType as AggregatePolicy<V::DialectMarker>>::Avg, Null, Agg>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: AggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func(
        "AVG",
        SQL::raw("DISTINCT").append(expr.into_sql()),
    ))
}

// =============================================================================
// MIN / MAX
// =============================================================================

/// MIN(expr) - finds minimum value.
///
/// Works with any expression type (ordered types in SQL).
/// Preserves the input expression's SQL type.
/// Result is nullable (empty set returns NULL).
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::min;
///
/// let cheapest = min(products.price);
/// // Generates: MIN("products"."price")
/// // Returns the same SQL type as products.price
/// # "####;
/// ```
pub fn min<'a, V, E>(expr: E) -> SQLExpr<'a, V, E::SQLType, Null, Agg>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
{
    SQLExpr::new(SQL::func("MIN", expr.into_sql()))
}

/// MAX(expr) - finds maximum value.
///
/// Works with any expression type (ordered types in SQL).
/// Preserves the input expression's SQL type.
/// Result is nullable (empty set returns NULL).
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::max;
///
/// let most_expensive = max(products.price);
/// // Generates: MAX("products"."price")
/// // Returns the same SQL type as products.price
/// # "####;
/// ```
pub fn max<'a, V, E>(expr: E) -> SQLExpr<'a, V, E::SQLType, Null, Agg>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
{
    SQLExpr::new(SQL::func("MAX", expr.into_sql()))
}

// =============================================================================
// STATISTICAL FUNCTIONS
// =============================================================================

/// `STDDEV_POP` - population standard deviation.
///
/// Calculates the population standard deviation of numeric values.
/// Requires the expression to be `Numeric`.
/// Returns Double, nullable (empty set returns NULL).
///
/// Note: This function is available in `PostgreSQL`. `SQLite` does not have it built-in.
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::stddev_pop;
///
/// let deviation = stddev_pop(measurements.value);
/// // Generates: STDDEV_POP("measurements"."value")
/// # "####;
/// ```
pub fn stddev_pop<'a, V, E>(
    expr: E,
) -> SQLExpr<
    'a,
    V,
    <E::SQLType as StatisticalAggregatePolicy<V::DialectMarker>>::StddevPop,
    Null,
    Agg,
>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: StatisticalAggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func("STDDEV_POP", expr.into_sql()))
}

/// `STDDEV_SAMP` / STDDEV - sample standard deviation.
///
/// Calculates the sample standard deviation of numeric values.
/// Requires the expression to be `Numeric`.
/// Returns Double, nullable (empty set returns NULL).
///
/// Note: This function is available in `PostgreSQL`. `SQLite` does not have it built-in.
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::stddev_samp;
///
/// let deviation = stddev_samp(measurements.value);
/// // Generates: STDDEV_SAMP("measurements"."value")
/// # "####;
/// ```
pub fn stddev_samp<'a, V, E>(
    expr: E,
) -> SQLExpr<
    'a,
    V,
    <E::SQLType as StatisticalAggregatePolicy<V::DialectMarker>>::StddevSamp,
    Null,
    Agg,
>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: StatisticalAggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func("STDDEV_SAMP", expr.into_sql()))
}

/// `VAR_POP` - population variance.
///
/// Calculates the population variance of numeric values.
/// Requires the expression to be `Numeric`.
/// Returns Double, nullable (empty set returns NULL).
///
/// Note: This function is available in `PostgreSQL`. `SQLite` does not have it built-in.
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::var_pop;
///
/// let variance = var_pop(measurements.value);
/// // Generates: VAR_POP("measurements"."value")
/// # "####;
/// ```
pub fn var_pop<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <E::SQLType as StatisticalAggregatePolicy<V::DialectMarker>>::VarPop, Null, Agg>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: StatisticalAggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func("VAR_POP", expr.into_sql()))
}

/// `VAR_SAMP` / VARIANCE - sample variance.
///
/// Calculates the sample variance of numeric values.
/// Requires the expression to be `Numeric`.
/// Returns Double, nullable (empty set returns NULL).
///
/// Note: This function is available in `PostgreSQL`. `SQLite` does not have it built-in.
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::var_samp;
///
/// let variance = var_samp(measurements.value);
/// // Generates: VAR_SAMP("measurements"."value")
/// # "####;
/// ```
pub fn var_samp<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <E::SQLType as StatisticalAggregatePolicy<V::DialectMarker>>::VarSamp, Null, Agg>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: StatisticalAggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func("VAR_SAMP", expr.into_sql()))
}

/// VARIANCE - `PostgreSQL` alias for sample variance (`VAR_SAMP`).
pub fn variance<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <E::SQLType as StatisticalAggregatePolicy<V::DialectMarker>>::VarSamp, Null, Agg>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: StatisticalAggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func("VARIANCE", expr.into_sql()))
}

/// `BOOL_AND` - true if all non-null inputs are true (`PostgreSQL`).
pub fn bool_and<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <V::DialectMarker as DialectTypes>::Bool, Null, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: PostgresAggregateSupport,
    E: Expr<'a, V>,
    E::SQLType: BooleanAggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func("BOOL_AND", expr.into_sql()))
}

/// `BOOL_OR` - true if any non-null input is true (`PostgreSQL`).
pub fn bool_or<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <V::DialectMarker as DialectTypes>::Bool, Null, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: PostgresAggregateSupport,
    E: Expr<'a, V>,
    E::SQLType: BooleanAggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func("BOOL_OR", expr.into_sql()))
}

/// `JSON_AGG` - aggregates values into a JSON array (`PostgreSQL`).
pub fn json_agg<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <V::DialectMarker as DialectTypes>::Json, Null, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: PostgresAggregateSupport,
    E: Expr<'a, V>,
{
    SQLExpr::new(SQL::func("JSON_AGG", expr.into_sql()))
}

/// `JSONB_AGG` - aggregates values into a JSONB array (`PostgreSQL`).
pub fn jsonb_agg<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <V::DialectMarker as DialectTypes>::Jsonb, Null, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: PostgresAggregateSupport,
    E: Expr<'a, V>,
{
    SQLExpr::new(SQL::func("JSONB_AGG", expr.into_sql()))
}

/// `ARRAY_AGG` - aggregates values into a SQL array (`PostgreSQL`).
pub fn array_agg<'a, V, E>(expr: E) -> SQLExpr<'a, V, Array<E::SQLType>, Null, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: PostgresAggregateSupport,
    E: Expr<'a, V>,
{
    SQLExpr::new(SQL::func("ARRAY_AGG", expr.into_sql()))
}

// =============================================================================
// TOTAL (SQLite)
// =============================================================================

/// TOTAL - sums numeric values, returning 0.0 for empty sets (`SQLite`).
///
/// Unlike `SUM`, which returns NULL for an empty result set,
/// `TOTAL` always returns a floating-point value (0.0 for empty sets).
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::total;
///
/// // SELECT TOTAL(orders.amount)
/// let total_amount = total(orders.amount);
/// # "####;
/// ```
pub fn total<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <V::DialectMarker as DialectTypes>::Double, NonNull, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: SQLiteAggregateSupport,
    E: Expr<'a, V>,
    E::SQLType: Numeric,
{
    SQLExpr::new(SQL::func("TOTAL", expr.into_sql()))
}

// =============================================================================
// GROUP_CONCAT / STRING_AGG
// =============================================================================

/// `GROUP_CONCAT` - concatenates values into a string (`SQLite`).
///
/// Returns Text type, nullable.
pub fn group_concat<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <V::DialectMarker as DialectTypes>::Text, Null, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: SQLiteAggregateSupport,
    E: Expr<'a, V>,
    E::SQLType: crate::types::Textual,
{
    SQLExpr::new(SQL::func("GROUP_CONCAT", expr.into_sql()))
}

/// `STRING_AGG` - concatenates text values using a delimiter (`PostgreSQL`).
pub fn string_agg<'a, V, E, D>(
    expr: E,
    delimiter: D,
) -> SQLExpr<'a, V, <V::DialectMarker as DialectTypes>::Text, Null, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: PostgresAggregateSupport,
    E: Expr<'a, V>,
    E::SQLType: crate::types::Textual,
    D: Expr<'a, V>,
    D::SQLType: crate::types::Textual,
{
    SQLExpr::new(SQL::func(
        "STRING_AGG",
        expr.into_sql()
            .push(crate::Token::COMMA)
            .append(delimiter.into_sql()),
    ))
}

// =============================================================================
// PostgreSQL Aggregate Functions
// =============================================================================

/// EVERY - true if all non-null inputs are true (`PostgreSQL`).
///
/// SQL standard alias for `BOOL_AND`.
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::every;
///
/// // SELECT EVERY(orders.is_paid)
/// let all_paid = every(orders.is_paid);
/// # "####;
/// ```
pub fn every<'a, V, E>(
    expr: E,
) -> SQLExpr<'a, V, <V::DialectMarker as DialectTypes>::Bool, Null, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: PostgresAggregateSupport,
    E: Expr<'a, V>,
    E::SQLType: BooleanAggregatePolicy<V::DialectMarker>,
{
    SQLExpr::new(SQL::func("EVERY", expr.into_sql()))
}

/// `JSON_OBJECT_AGG` - aggregates key/value pairs into a JSON object (`PostgreSQL`).
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::json_object_agg;
///
/// // SELECT JSON_OBJECT_AGG(settings.key, settings.value)
/// let obj = json_object_agg(settings.key, settings.value);
/// # "####;
/// ```
pub fn json_object_agg<'a, V, K, Val>(
    key: K,
    value: Val,
) -> SQLExpr<'a, V, <V::DialectMarker as DialectTypes>::Json, Null, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: PostgresAggregateSupport,
    K: Expr<'a, V>,
    Val: Expr<'a, V>,
{
    SQLExpr::new(SQL::func(
        "JSON_OBJECT_AGG",
        key.into_sql()
            .push(crate::Token::COMMA)
            .append(value.into_sql()),
    ))
}

/// `JSONB_OBJECT_AGG` - aggregates key/value pairs into a JSONB object (`PostgreSQL`).
///
/// # Example
///
/// ```rust
/// # let _ = r####"
/// use drizzle_core::expr::jsonb_object_agg;
///
/// // SELECT JSONB_OBJECT_AGG(settings.key, settings.value)
/// let obj = jsonb_object_agg(settings.key, settings.value);
/// # "####;
/// ```
pub fn jsonb_object_agg<'a, V, K, Val>(
    key: K,
    value: Val,
) -> SQLExpr<'a, V, <V::DialectMarker as DialectTypes>::Jsonb, Null, Agg>
where
    V: SQLParam + 'a,
    V::DialectMarker: PostgresAggregateSupport,
    K: Expr<'a, V>,
    Val: Expr<'a, V>,
{
    SQLExpr::new(SQL::func(
        "JSONB_OBJECT_AGG",
        key.into_sql()
            .push(crate::Token::COMMA)
            .append(value.into_sql()),
    ))
}

// =============================================================================
// Distinct Wrapper
// =============================================================================

/// DISTINCT - marks an expression as DISTINCT.
///
/// Typically used inside aggregate functions.
pub fn distinct<'a, V, E>(expr: E) -> SQLExpr<'a, V, E::SQLType, E::Nullable, Scalar>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
{
    SQLExpr::new(SQL::raw("DISTINCT").append(expr.into_sql()))
}