Function mz_transform::dataflow::prune_and_annotate_dataflow_index_imports

fn prune_and_annotate_dataflow_index_imports(
    dataflow: &mut DataflowDesc,
    indexes: &dyn IndexOracle,
    dataflow_metainfo: &mut DataflowMetainfo,
) -> Result<(), TransformError>

Restricts the indexes imported by dataflow to only the ones it needs. It also adds to the DataflowMetainfo how each index will be used. It also annotates global Gets with whether they will be reads from Persist or an index, plus their index usage types.

The input dataflow should import all indexes belonging to all views/sources/tables it references.

The input plans should be normalized with NormalizeLets! Otherwise we might find dangling ArrangeBys at the top of unused Let bindings.