graphrecords-query 0.5.0

use crate::{
    Explain, IndexDomain, Indexed, Operand, QueryResult, Unit, ValueDomain,
    element::{Pipeline, Preserving},
    execution::EvaluationCache,
    operations::{Apply, ElementKernel, ElementPipeline, Operation, OperationContext, Prepare},
    optimizer::{OperationInputs, OptimizerHints, PlanIdentity, PlanInputs},
    registry::operation_manifest,
    traits::DiscardValue,
};
use graphrecords_core::GraphRecord;

#[derive(Clone, Explain, Operation, OperationInputs, OptimizerHints, PlanIdentity, PlanInputs)]
#[operation(scope = Element)]
#[explain(label = "DiscardValue")]
#[plan(optimizer_hints(
    commutes_with_filter,
    allows_limit_pushdown,
    empty = if_any
))]
pub struct DiscardValueOperation;

impl Prepare for DiscardValueOperation {
    type Prepared<'a> = ();

    fn prepare<'a>(
        &'a self,
        _graphrecord: &'a GraphRecord,
        _cache: &'a EvaluationCache<'a>,
    ) -> QueryResult<Self::Prepared<'a>> {
        Ok(())
    }
}

impl<I: IndexDomain, V: ValueDomain> ElementKernel<Indexed<I, V>> for DiscardValueOperation {
    type Emission = Preserving;
    type OutShape = Indexed<I, Unit>;

    fn pipeline<'a>(
        _graphrecord: &'a GraphRecord,
        _prepared: Self::Prepared<'a>,
    ) -> QueryResult<ElementPipeline<'a, Indexed<I, V>, Self>> {
        Ok(Pipeline::unkeyed(|outcome: QueryResult<_>| {
            outcome.map(|_| ())
        }))
    }
}

impl<O: Apply<DiscardValueOperation>> DiscardValue for O {
    type ReturnOperand = O::Output;

    fn discard_value(&self) -> Self::ReturnOperand {
        Self::ReturnOperand::new(OperationContext::new(self.clone(), DiscardValueOperation))
    }
}

operation_manifest! {
    DiscardValueOperation {
        method: DiscardValue::discard_value;
        scope: element;

        kernel {
            parameters: <I: IndexDomain, V: ValueDomain>;
            input: Indexed<I, V>;
            output: Indexed<I, Unit>;
            emission: Preserving;
        }
    }
}