Trait ColumnStatsReader

Source

pub trait ColumnStatsReader: Send + Sync {
    // Provided methods
    fn vertex_column_stats(
        &self,
        _space: &str,
        _tag: &str,
        _column: &str,
    ) -> Option<Arc<ColumnStatsSnapshot>> { ... }
    fn edge_column_stats(
        &self,
        _space: &str,
        _edge_type: &str,
        _column: &str,
    ) -> Option<Arc<ColumnStatsSnapshot>> { ... }
    fn vertex_table_stats(
        &self,
        _space: &str,
        _tag: &str,
    ) -> Option<Arc<TableCardinalitySnapshot>> { ... }
    fn edge_table_stats(
        &self,
        _space: &str,
        _edge_type: &str,
    ) -> Option<Arc<TableCardinalitySnapshot>> { ... }
    fn stats_epoch(&self) -> u64 { ... }
}

Expand description

Reader capability for optimizer-facing column statistics snapshots.

relation addressing follows the catalog naming: a tag name for vertex columns and an edge type name for edge columns.

Provided Methods§

Source

fn vertex_column_stats( &self, _space: &str, _tag: &str, _column: &str, ) -> Option<Arc<ColumnStatsSnapshot>>

Snapshot of one property column of tag inside space.

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fn edge_column_stats( &self, _space: &str, _edge_type: &str, _column: &str, ) -> Option<Arc<ColumnStatsSnapshot>>

Snapshot of one property column of edge_type inside space.

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fn vertex_table_stats( &self, _space: &str, _tag: &str, ) -> Option<Arc<TableCardinalitySnapshot>>

Table-level cardinality of vertex tag tag inside space.

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fn edge_table_stats( &self, _space: &str, _edge_type: &str, ) -> Option<Arc<TableCardinalitySnapshot>>

Table-level cardinality of edge type edge_type inside space.

Served by the engine from per-partition snapshot counts merged with TableCardinalitySnapshot::absorb; absent only when the edge type has no partitions. Costing falls back to live edge counts when unavailable.

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fn stats_epoch(&self) -> u64

Monotonic data-version stamp: changes whenever data has been written, independent of schema changes. Used by the optimizer’s statistics cache to detect stale estimates after DML.

Contract: 0 means “no writes observed / unknown” and is reserved; engines backed by real data must return values that strictly increase across DML (they may start at any value > 0). Consumers must treat a return value of 0 as “cacheability unknown” rather than as a valid epoch. Returns 0 when unknown.