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RowSource

uqa_execution::scan

Trait RowSource 

Source 
pub trait RowSource: Send {
    // Required methods
    fn schema(&self) -> &[String];
    fn next_row(&mut self) -> ExecResult<Option<ResultRow>>;

    // Provided methods
    fn physical_schema(&self) -> Option<&RowSchema> { ... }
    fn estimated_cardinality(&self) -> Option<u64> { ... }
    fn output_ordering(&self) -> &[PhysicalOrder] { ... }
    fn next_batch(&mut self, max_rows: usize) -> ExecResult<Vec<ResultRow>> { ... }
    fn next_physical_batch(
        &mut self,
        max_rows: usize,
    ) -> ExecResult<Vec<PhysicalRow>> { ... }
    fn consume_into_aggregate(
        &mut self,
        _executor: &mut dyn AggregateExecutor,
    ) -> ExecResult<bool> { ... }
}
Expand description

Source of rows feeding a TableScan. Implementors typically own a snapshot of the underlying table or external relation; the scan operator holds the source as a boxed trait object so callers can mix and match implementations across one query.

Required Methods§

Source

fn schema(&self) -> &[String]

Stable column order for the rows produced by Self::next_row.

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fn next_row(&mut self) -> ExecResult<Option<ResultRow>>

Pull the next row. Returns None when the source is exhausted.

Provided Methods§

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fn physical_schema(&self) -> Option<&RowSchema>

Optional non-identity schema used by positional sources. This carries hidden lookup aliases and slot remaps that cannot be represented by the legacy column-name slice.

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fn estimated_cardinality(&self) -> Option<u64>

Estimated total rows available from this source.

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fn output_ordering(&self) -> &[PhysicalOrder]

Leading row order guaranteed by the source.

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fn next_batch(&mut self, max_rows: usize) -> ExecResult<Vec<ResultRow>>

Pull up to max_rows without forcing batch-capable sources through a row-at-a-time lock or backend call. The default preserves compatibility for iterator-like sources.

Source

fn next_physical_batch( &mut self, max_rows: usize, ) -> ExecResult<Vec<PhysicalRow>>

Pull a positional batch directly. Backend-native sources override this to avoid constructing named maps at the scan boundary; compatibility sources are converted exactly once here.

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fn consume_into_aggregate( &mut self, _executor: &mut dyn AggregateExecutor, ) -> ExecResult<bool>

Feed backend-native projected rows directly to an aggregate. Sources that cannot preserve their normal filter and virtual-column semantics return false without advancing their cursor.

Dyn Compatibility§

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors§