oxirs-arq 0.3.1

Jena-style SPARQL algebra with extension points and query optimization
Documentation 
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//! Maintenance scheduling and view recommendation for materialized views.
//!
//! This sibling module provides:
//! - [`MaintenanceScheduler`] — a queue of view-maintenance tasks (full
//!   refresh, incremental update, statistics refresh, integrity check, …).
//! - [`ViewRecommendationEngine`] — proposes new views based on observed
//!   query patterns, cost, and benefit estimation.
//! - Supporting analyzers ([`QueryPatternAnalyzer`], [`CostAnalyzer`],
//!   [`BenefitEstimator`]).

use std::collections::{HashMap, VecDeque};
use std::sync::{Arc, RwLock};
use std::time::{Duration, SystemTime};

use anyhow::Result;

use crate::algebra::Algebra;
use crate::materialized_views_types::{
    BenefitEstimator, CostAnalyzer, MaintenanceScheduler, MaintenanceStrategy, MaintenanceTask,
    MaintenanceTaskType, QueryPatternAnalyzer, ResourceRequirements, SchedulerConfig,
    ViewRecommendation, ViewRecommendationEngine,
};

// ---------------------------------------------------------------------------
// MaintenanceScheduler impl
// ---------------------------------------------------------------------------

impl MaintenanceScheduler {
    pub(crate) fn new(config: SchedulerConfig) -> Result<Self> {
        Ok(Self {
            scheduled_tasks: Arc::new(RwLock::new(VecDeque::new())),
            active_tasks: Arc::new(RwLock::new(HashMap::new())),
            config,
        })
    }

    pub(crate) fn schedule_maintenance(
        &self,
        view_id: String,
        task_type: MaintenanceTaskType,
        scheduled_time: SystemTime,
        priority: u8,
    ) -> Result<()> {
        let task = MaintenanceTask {
            view_id,
            task_type,
            priority,
            scheduled_time,
            estimated_duration: Duration::from_secs(60), // Default 1 minute
            resource_requirements: ResourceRequirements {
                cpu_usage: 0.1,
                memory_usage: 64 * 1024 * 1024, // 64MB
                io_operations: 1000,
                network_bandwidth: 0,
            },
        };

        let mut scheduled = self.scheduled_tasks.write().expect("lock poisoned");
        scheduled.push_back(task);

        Ok(())
    }
}

// ---------------------------------------------------------------------------
// ViewRecommendationEngine impl
// ---------------------------------------------------------------------------

impl ViewRecommendationEngine {
    pub(crate) fn new() -> Result<Self> {
        Ok(Self {
            query_patterns: Arc::new(RwLock::new(QueryPatternAnalyzer::new())),
            cost_analyzer: CostAnalyzer::new(),
            benefit_estimator: BenefitEstimator::new(),
            recommendation_cache: Arc::new(RwLock::new(HashMap::new())),
        })
    }

    pub(crate) fn get_recommendations(&self) -> Result<Vec<ViewRecommendation>> {
        // Simplified recommendation logic
        let recommendations = vec![ViewRecommendation {
            view_definition: Algebra::Bgp(vec![]), // Placeholder
            estimated_benefit: 0.5,
            confidence: 0.7,
            creation_cost: 100.0,
            maintenance_cost: 10.0,
            maintenance_strategy: MaintenanceStrategy::Lazy,
            supporting_patterns: vec!["common_pattern_1".to_string()],
            justification: "Frequently accessed pattern with high cost".to_string(),
        }];

        Ok(recommendations)
    }
}

// ---------------------------------------------------------------------------
// Supporting analyzer constructors
// ---------------------------------------------------------------------------

impl QueryPatternAnalyzer {
    fn new() -> Self {
        Self {
            patterns: HashMap::new(),
            pattern_frequency: HashMap::new(),
            pattern_costs: HashMap::new(),
        }
    }
}

impl CostAnalyzer {
    fn new() -> Self {
        Self {
            historical_costs: HashMap::new(),
            cost_models: HashMap::new(),
        }
    }
}

impl BenefitEstimator {
    fn new() -> Self {
        Self {
            benefit_history: HashMap::new(),
            prediction_models: HashMap::new(),
        }
    }
}