Struct AggregateOperation 

pub struct AggregateOperation<M: Model, E: QueryEngine> { /* private fields */ }

Aggregate operation builder.

Engine ownership

The builder stores an Option<E> rather than the engine directly so existing unit tests that construct an AggregateOperation just to exercise SQL emission (AggregateOperation::<Model, MockEngine>::new()) keep working without a real engine. Production code always goes through AggregateOperation::with_engine (what the generated Client<E>::aggregate() accessor calls), and Self::exec refuses to run when the engine slot is empty.

Implementations

impl<M: Model, E: QueryEngine> AggregateOperation<M, E>

pub fn new() -> Self

Create a new aggregate operation without an engine.

Useful for unit tests that only exercise Self::build_sql. Self::exec will refuse to run on a builder created this way.

pub fn with_engine(engine: E) -> Self

Create a new aggregate operation bound to a concrete engine.

This is what the generated Client<E>::aggregate() accessor calls.

pub fn count(self) -> Self

Add a count of all rows.

pub fn count_column(self, column: impl Into<String>) -> Self

Add a count of non-null values in a column.

pub fn count_distinct(self, column: impl Into<String>) -> Self

Add a count of distinct values in a column.

pub fn sum(self, column: impl Into<String>) -> Self

Add sum of a numeric column.

pub fn avg(self, column: impl Into<String>) -> Self

Add average of a numeric column.

pub fn min(self, column: impl Into<String>) -> Self

Add minimum of a column.

pub fn max(self, column: impl Into<String>) -> Self

Add maximum of a column.

pub fn where(self, filter: impl Into<Filter>) -> Self

Add a filter condition.

pub fn build_sql(&self, dialect: &dyn SqlDialect) -> (String, Vec<FilterValue>)

Build the SQL for this operation.

pub async fn exec(self) -> QueryResult<AggregateResult>

Execute the aggregate operation.

Routes the single-row aggregate result through crate::traits::QueryEngine::aggregate_query and folds the column→value map into an AggregateResult. Returns an empty result (all fields None/empty) if the query yields zero rows — aggregates on empty tables do this on Postgres/MySQL/SQLite.

Errors with QueryError::internal if the builder was constructed via Self::new without an engine.

Trait Implementations

impl<M: Debug + Model, E: Debug + QueryEngine> Debug for AggregateOperation<M, E>

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

Formats the value using the given formatter.

impl<M: Model, E: QueryEngine> Default for AggregateOperation<M, E>

fn default() -> Self

Returns the “default value” for a type.