graphrecords_query/operations/conversion/
discard_value.rs

1use crate::{
2    Explain, IndexDomain, Indexed, Operand, QueryResult, Unit, ValueDomain,
3    element::{Pipeline, Preserving},
4    execution::EvaluationCache,
5    operations::{Apply, ElementKernel, ElementPipeline, Operation, OperationContext, Prepare},
6    optimizer::{OperationInputs, OptimizerHints, PlanIdentity, PlanInputs},
7    registry::operation_manifest,
8    traits::DiscardValue,
9};
10use graphrecords_core::GraphRecord;
11
12#[derive(Clone, Explain, Operation, OperationInputs, OptimizerHints, PlanIdentity, PlanInputs)]
13#[operation(scope = Element)]
14#[explain(label = "DiscardValue")]
15#[plan(optimizer_hints(
16    commutes_with_filter,
17    allows_limit_pushdown,
18    empty = if_any
19))]
20pub struct DiscardValueOperation;
21
22impl Prepare for DiscardValueOperation {
23    type Prepared<'a> = ();
24
25    fn prepare<'a>(
26        &'a self,
27        _graphrecord: &'a GraphRecord,
28        _cache: &'a EvaluationCache<'a>,
29    ) -> QueryResult<Self::Prepared<'a>> {
30        Ok(())
31    }
32}
33
34impl<I: IndexDomain, V: ValueDomain> ElementKernel<Indexed<I, V>> for DiscardValueOperation {
35    type Emission = Preserving;
36    type OutShape = Indexed<I, Unit>;
37
38    fn pipeline<'a>(
39        _graphrecord: &'a GraphRecord,
40        _prepared: Self::Prepared<'a>,
41    ) -> QueryResult<ElementPipeline<'a, Indexed<I, V>, Self>> {
42        Ok(Pipeline::unkeyed(|outcome: QueryResult<_>| {
43            outcome.map(|_| ())
44        }))
45    }
46}
47
48impl<O: Apply<DiscardValueOperation>> DiscardValue for O {
49    type ReturnOperand = O::Output;
50
51    fn discard_value(&self) -> Self::ReturnOperand {
52        Self::ReturnOperand::new(OperationContext::new(self.clone(), DiscardValueOperation))
53    }
54}
55
56operation_manifest! {
57    DiscardValueOperation {
58        method: DiscardValue::discard_value;
59        scope: element;
60
61        kernel {
62            parameters: <I: IndexDomain, V: ValueDomain>;
63            input: Indexed<I, V>;
64            output: Indexed<I, Unit>;
65            emission: Preserving;
66        }
67    }
68}
graphrecords_query/operations/conversion/discard_value.rs

graphrecords_query/operations/conversion/
discard_value.rs
