graphrecords-query 0.5.0

use crate::{
    EvaluateOperand, Explain, IndexDomain, Indexed, Multiple, Operand, Ordered, QueryResult,
    capabilities::ValueEquivalence,
    execution::EvaluationCache,
    operands::OperandHandle,
    operations::{Apply, KeyedStream, LaneKernel, Operation, OperationContext, Prepare},
    optimizer::{Estimate, OperationInputs, OptimizerHints, PlanIdentity, PlanInputs, Stats},
    registry::operation_manifest,
    traits::DropDuplicates,
};
use graphrecords_core::GraphRecord;
use graphrecords_utils::aliases::GrHashSet;

#[derive(Clone, Explain, Operation, OperationInputs, OptimizerHints, PlanIdentity, PlanInputs)]
#[operation(scope = Lane)]
#[explain(label = "DropDuplicates")]
#[plan(optimizer_hints(empty = if_any))]
pub struct DropDuplicatesOperation;

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

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

impl<I: IndexDomain, V: ValueEquivalence> LaneKernel<Indexed<I, V>, Multiple<Ordered>>
    for DropDuplicatesOperation
{
    type Output = OperandHandle<Indexed<I, V>, Multiple<Ordered>>;

    fn execute<'a>(
        _graphrecord: &'a GraphRecord,
        values: KeyedStream<'a, I, V, Multiple<Ordered>>,
        _prepared: Self::Prepared<'a>,
    ) -> QueryResult<<Self::Output as EvaluateOperand>::ReturnValue<'a>> {
        let mut seen = GrHashSet::default();

        Ok(Box::new(values.filter_map(
            move |(index, outcome)| match outcome {
                Ok(value) if seen.insert(V::equivalence_key(&value)) => Some((index, Ok(value))),
                Ok(_) => None,
                Err(failure) => Some((index, Err(failure))),
            },
        )))
    }

    fn estimate(&self, input: Estimate, _stats: &Stats) -> Estimate {
        Estimate {
            elements: None,
            distinct: input.distinct,
            selectivity: None,
            per_group: None,
        }
    }
}

impl<O: Apply<DropDuplicatesOperation>> DropDuplicates for O {
    type ReturnOperand = O::Output;

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

operation_manifest! {
    DropDuplicatesOperation {
        method: DropDuplicates::drop_duplicates;
        scope: lane;

        kernel {
            parameters: <
                I: IndexDomain,
                V: ValueEquivalence,
            >;
            input: (Indexed<I, V>, Multiple<Ordered>);
            output: OperandHandle<Indexed<I, V>, Multiple<Ordered>>;
        }
    }
}