Method collect_index_reqs_inner

src/transform/src/dataflow.rs:930–1206

(
        &mut self,
        expr: &mut MirRelationExpr,
        contexts: &Vec<IndexUsageContext>,
    )

    }

    fn collect_index_reqs_inner(
        &mut self,
        expr: &mut MirRelationExpr,
        contexts: &Vec<IndexUsageContext>,
    ) -> Result<(), RecursionLimitError> {
        self.checked_recur_mut(|this| {
            // If an index exists on `on_id`, this function picks an index to be fully scanned.
            let pick_index_for_full_scan = |on_id: &GlobalId| {
                // Note that the choice we make here might be modified later at the
                // "Adjust FullScans to not introduce a new index dependency".
                choose_index(
                    this.source_keys,
                    on_id,
                    &this
                        .indexes_available
                        .indexes_on(*on_id)
                        .map(|(idx_id, key)| (idx_id, key.iter().cloned().collect_vec()))
                        .collect_vec(),
                )
            };

            // See comment on `IndexUsageContext`.
            Ok(match expr {
                MirRelationExpr::Join {
                    inputs,
                    implementation,
                    ..
                } => {
                    match implementation {
                        JoinImplementation::Differential(..) => {
                            for input in inputs {
                                this.collect_index_reqs_inner(
                                    input,
                                    &IndexUsageContext::from_usage_type(
                                        IndexUsageType::DifferentialJoin,
                                    ),
                                )?;
                            }
                        }
                        JoinImplementation::DeltaQuery(..) => {
                            // For Delta joins, the first input is special, see
                            // https://github.com/MaterializeInc/database-issues/issues/2115
                            this.collect_index_reqs_inner(
                                &mut inputs[0],
                                &IndexUsageContext::from_usage_type(IndexUsageType::DeltaJoin(
                                    DeltaJoinIndexUsageType::Unknown,
                                )),
                            )?;
                            for input in &mut inputs[1..] {
                                this.collect_index_reqs_inner(
                                    input,
                                    &IndexUsageContext::from_usage_type(IndexUsageType::DeltaJoin(
                                        DeltaJoinIndexUsageType::Lookup,
                                    )),
                                )?;
                            }
                        }
                        JoinImplementation::IndexedFilter(_coll_id, idx_id, ..) => {