Method on_unique

src/expr/src/relation.rs:2571–3074

Returns an expression that computes `self` on a group that has exactly one row. Instead of performing a `Reduce` with `self`, one can perform a `Map` with the expression returned by `on_unique`, which is cheaper. (See `ReduceElision`.)

(&self, input_type: &[ReprColumnType])

    /// Instead of performing a `Reduce` with `self`, one can perform a `Map` with the expression
    /// returned by `on_unique`, which is cheaper. (See `ReduceElision`.)
    pub fn on_unique(&self, input_type: &[ReprColumnType]) -> MirScalarExpr {
        match &self.func {
            // Count is one if non-null, and zero if null.
            AggregateFunc::Count => self
                .expr
                .clone()
                .call_unary(UnaryFunc::IsNull(crate::func::IsNull))
                .if_then_else(
                    MirScalarExpr::literal_ok(Datum::Int64(0), ReprScalarType::Int64),
                    MirScalarExpr::literal_ok(Datum::Int64(1), ReprScalarType::Int64),
                ),

            // SumInt16 takes Int16s as input, but outputs Int64s.
            AggregateFunc::SumInt16 => self
                .expr
                .clone()
                .call_unary(UnaryFunc::CastInt16ToInt64(scalar_func::CastInt16ToInt64)),

            // SumInt32 takes Int32s as input, but outputs Int64s.
            AggregateFunc::SumInt32 => self
                .expr
                .clone()
                .call_unary(UnaryFunc::CastInt32ToInt64(scalar_func::CastInt32ToInt64)),

            // SumInt64 takes Int64s as input, but outputs numerics.
            AggregateFunc::SumInt64 => self.expr.clone().call_unary(UnaryFunc::CastInt64ToNumeric(
                scalar_func::CastInt64ToNumeric(Some(NumericMaxScale::ZERO)),
            )),

            // SumUInt16 takes UInt16s as input, but outputs UInt64s.
            AggregateFunc::SumUInt16 => self.expr.clone().call_unary(
                UnaryFunc::CastUint16ToUint64(scalar_func::CastUint16ToUint64),
            ),

            // SumUInt32 takes UInt32s as input, but outputs UInt64s.
            AggregateFunc::SumUInt32 => self.expr.clone().call_unary(
                UnaryFunc::CastUint32ToUint64(scalar_func::CastUint32ToUint64),
            ),

            // SumUInt64 takes UInt64s as input, but outputs numerics.
            AggregateFunc::SumUInt64 => {
                self.expr.clone().call_unary(UnaryFunc::CastUint64ToNumeric(
                    scalar_func::CastUint64ToNumeric(Some(NumericMaxScale::ZERO)),
                ))
            }

            // JsonbAgg takes _anything_ as input, but must output a Jsonb array.
            AggregateFunc::JsonbAgg { .. } => MirScalarExpr::call_variadic(
                JsonbBuildArray,
                vec![
                    self.expr
                        .clone()
                        .call_unary(UnaryFunc::RecordGet(scalar_func::RecordGet(0))),
                ],
            ),

            // JsonbAgg takes _anything_ as input, but must output a Jsonb object.
            AggregateFunc::JsonbObjectAgg { .. } => {