Struct ApproxCountDistinctAnalyzer 

pub struct ApproxCountDistinctAnalyzer { /* private fields */ }

Analyzer that computes approximate count distinct using HyperLogLog.

This analyzer provides memory-efficient cardinality estimation for high-cardinality columns with configurable precision. It uses DataFusion’s built-in APPROX_DISTINCT function which implements the HyperLogLog algorithm.

Example

use term_guard::analyzers::advanced::ApproxCountDistinctAnalyzer;
use datafusion::prelude::*;

let ctx = SessionContext::new();
// Register your data table

let analyzer = ApproxCountDistinctAnalyzer::new("user_id");
let state = analyzer.compute_state_from_data(&ctx).await?;
let metric = analyzer.compute_metric_from_state(&state)?;

if let MetricValue::Long(approx_distinct) = metric {
    println!("Approximate distinct users: {}", approx_distinct);
}

Implementations

impl ApproxCountDistinctAnalyzer

pub fn new(column: impl Into<String>) -> Self

Creates a new approximate count distinct analyzer for the specified column.

pub fn column(&self) -> &str

Returns the column being analyzed.

Trait Implementations

impl Analyzer for ApproxCountDistinctAnalyzer

type State = ApproxCountDistinctState

The state type for incremental computation.

type Metric = MetricValue

The metric type produced by this analyzer.

fn compute_state_from_data<'life0, 'life1, 'async_trait>( &'life0 self, ctx: &'life1 SessionContext, ) -> Pin<Box<dyn Future<Output = AnalyzerResult<Self::State>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait,

Computes the state from the input data.

fn compute_metric_from_state( &self, state: &Self::State, ) -> AnalyzerResult<Self::Metric>

Computes the final metric from the accumulated state.

fn name(&self) -> &str

Returns the name of this analyzer.

fn description(&self) -> &str

Returns a description of what this analyzer computes.

fn metric_key(&self) -> String

Returns the metric key for storing results.

fn columns(&self) -> Vec<&str>

Returns the column(s) this analyzer operates on, if any.

fn merge_states(&self, states: Vec<Self::State>) -> AnalyzerResult<Self::State>

Merges multiple states into a single state.

fn is_combinable(&self) -> bool

Indicates whether this analyzer can be combined with others.

impl Clone for ApproxCountDistinctAnalyzer

fn clone(&self) -> ApproxCountDistinctAnalyzer

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ApproxCountDistinctAnalyzer

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

Formats the value using the given formatter.