Enum ScanOrdering 

pub enum ScanOrdering {
    Unordered,
    Concatenated {
        columns: Vec<ScanSortColumn>,
        bounds: OrderingBounds,
    },
    PerFile {
        columns: Vec<ScanSortColumn>,
    },
}

How a partition scan’s declared output ordering is realized.

Two scan shapes exist: a single sequential file group spanning every input partition (Unordered, Concatenated) and one file group per input partition (PerFile, scanned by k readers for a downstream SortPreservingMergeExec). Unordered and Concatenated build and execute the identical single-file-group scan – they differ only in whether the resulting order is declared to DataFusion, not in scan shape or execution strategy (see ScanOrdering::declares_concatenated_ordering).

Variants

Unordered

No declared ordering (today’s default).

Concatenated

All files form one sequential file group that concatenates in globally-sorted order. Requires non-overlapping leading-column bounds (checked against bounds).

Fields

columns: Vec<ScanSortColumn>

bounds: OrderingBounds

PerFile

Each file is internally sorted by columns; files may overlap arbitrarily. The scan yields one ordered plan partition per file, for a downstream SortPreservingMergeExec. columns should be non-empty – SqlBatchView::with_merge_sort_order rejects an empty list at construction, but this enum and View::get_scan_output_ordering are public, so that is not the only construction path. An empty columns is still safe: it never certifies (see Partition::certifies_sort_order), so make_partitioned_execution_plan degrades it to Unordered for any non-empty partition rather than planning and recording a vacuous ordering.

Fields

columns: Vec<ScanSortColumn>

Implementations

impl ScanOrdering

pub fn declares_concatenated_ordering(&self) -> bool

True when this ordering declares a concatenating scan’s global order (Concatenated). PerFile returns false because a per-file ordering only becomes a global one through a downstream merge – it is the other strategy, not an undeclared version of this one. A bool, not the columns themselves: nothing on the concatenating path inspects the declared columns, only whether an ordering was declared at all (see QueryMerger::execute_concatenated_merge in merge.rs).

Trait Implementations

impl Clone for ScanOrdering

fn clone(&self) -> ScanOrdering

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ScanOrdering

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.