Struct DistinctOnResult 

pub struct DistinctOnResult { /* private fields */ }

DISTINCT ON result — keeps only the first row per unique combination of the specified key columns. Uses hash-based deduplication so the input does not need to be sorted by the key columns (ORDER BY controls which row is “first” because the input stream preserves ORDER BY order). Memory usage is O(groups) where groups is the number of unique key combinations, not total rows.

Implementations

impl DistinctOnResult

pub fn new(inner: Box<dyn QueryResult>, key_indices: Vec<usize>) -> Self

Trait Implementations

impl QueryResult for DistinctOnResult

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

Returns the column names in the result

fn next(&mut self) -> bool

Moves the cursor to the next row

fn scan(&self, dest: &mut [Value]) -> Result<()>

Scans the current row into the provided values

fn row(&self) -> &Row

Returns the current row directly without copying

fn take_row(&mut self) -> Row

Takes ownership of the current row (avoids clone)

fn close(&mut self) -> Result<()>

Closes the result set and releases resources

fn rows_affected(&self) -> i64

Returns the number of rows affected by an INSERT, UPDATE, or DELETE

fn last_insert_id(&self) -> i64

Returns the last inserted ID for an INSERT operation

fn last_error(&mut self) -> Option<Error>

Returns a pending error from the last next() call, if any.

fn with_aliases( self: Box<Self>, aliases: FxHashMap<String, String>, ) -> Box<dyn QueryResult>

Sets column aliases for this result

fn columns_arc(&self) -> Option<CompactArc<Vec<String>>>

Returns column names as Arc for zero-copy sharing

fn try_into_arc_rows(&mut self) -> Option<CompactArc<Vec<Row>>>

Try to extract all rows as CompactArc<Vec<Row>> for zero-copy joins

fn estimated_count(&self) -> Option<usize>

Returns an estimate of the total number of rows in the result.

fn supports_typed_batches(&self) -> bool

Whether the result can yield decoded typed column batches without constructing a row/value object for every result record.

fn typed_batch_fallback_reason(&self) -> Option<TypedBatchFallbackReason>

If supports_typed_batches() is false, return the best semantic reason.

fn next_typed_batch(&mut self) -> Result<Option<TypedColumnBatch>, Error>

Advance to the next typed column batch.