Trait mz_transform::StatisticsOracle

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pub trait StatisticsOracle: Debug + Send {
    // Required methods
    fn cardinality_estimate(&self, id: GlobalId) -> Option<usize>;
    fn as_map(&self) -> BTreeMap<GlobalId, usize>;
}
Expand description

A trait for a type that can estimate statistics about a given GlobalId

Required Methods§

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fn cardinality_estimate(&self, id: GlobalId) -> Option<usize>

Returns a cardinality estimate for the given identifier

Returning None means “no estimate”; returning Some(0) means estimating that the shard backing id is empty

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fn as_map(&self) -> BTreeMap<GlobalId, usize>

Returns a map from identifiers to sizes

Implementors§