Enum ScanMode 

pub enum ScanMode {
    Unknown,
    CountMetadata,
    CountSurvivors,
    ArrowShadow,
    NativePageCursor,
    MultiRunCursor,
    NativePushdown,
    Materialized,
    DirectDispatch,
    ExternalModule,
}

Which physical scan path served a query. Recorded by the SQL scan ([crate::scan]) and the native query entry points. Used in benchmarks and path-sensitive tests to assert that the expected path was taken.

Variants

Unknown

The trace was never filled (no recording site ran). Indicates a path that has not yet been instrumented.

CountMetadata

COUNT(*) / empty projection answered from the maintained live_count metadata in O(1) — no run read, no index resolve.

CountSurvivors

COUNT(*) with a pushed WHERE answered from survivor set cardinality via crate::engine::Table::count_conditions — index resolve only, no column decode.

ArrowShadow

Zero-copy Arrow IPC shadow read — no per-column decode at all (clean single-run unfiltered table).

NativePageCursor

Single-run lazy page cursor: fused predicate + page skip + late materialization (crate::cursor::NativePageCursor).

MultiRunCursor

Multi-run k-way merge cursor (crate::cursor::MultiRunCursor).

NativePushdown

Index pushdown fast path: survivors resolved then gathered column-wise from a single reader (crate::engine::Table::query_columns_native fast path — no cursor streaming, but no row materialization either).

Materialized

Full materialization fallback: visible_columns_native or rows_for_rids — rows go through the Row { HashMap } shape. This is the path optimizations try to avoid.

DirectDispatch

§5.3 direct SQL dispatch: a simple single-table SELECT recognized from the raw SQL (sqlparser AST) and served straight from the native column cursor, bypassing DataFusion parse+plan+optimize entirely.

ExternalModule

DataFusion scan served by an external table module / virtual table provider rather than a native MongrelDB storage table.

Trait Implementations

impl Clone for ScanMode

fn clone(&self) -> ScanMode

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ScanMode

impl Debug for ScanMode

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

Formats the value using the given formatter.

impl Default for ScanMode

fn default() -> ScanMode

Returns the “default value” for a type.

impl Display for ScanMode

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

Formats the value using the given formatter.

impl Eq for ScanMode

impl PartialEq for ScanMode

fn eq(&self, other: &ScanMode) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for ScanMode