QueryPerformancePolicy.ts•2.26 kB
import { QueryExecutedEvent } from '../events/QueryExecutedEvent.js';
/**
* QueryPerformancePolicy
*
* Policy for evaluating query performance and providing recommendations.
* Implements the policy pattern from DDD.
*/
export class QueryPerformancePolicy {
constructor(
private readonly slowQueryThreshold: number = 1000,
private readonly criticalQueryThreshold: number = 5000
) {}
/**
* Evaluates a query execution event and determines if it requires attention.
* @param event The query executed event
* @returns boolean indicating if the query performance is concerning
*/
evaluate(event: QueryExecutedEvent): boolean {
return event.executionTime > this.slowQueryThreshold;
}
/**
* Gets the severity level of a query execution event.
* @param event The query executed event
* @returns Severity level as string
*/
getSeverity(event: QueryExecutedEvent): 'normal' | 'slow' | 'critical' {
if (event.executionTime > this.criticalQueryThreshold) {
return 'critical';
} else if (event.executionTime > this.slowQueryThreshold) {
return 'slow';
}
return 'normal';
}
/**
* Provides recommendations for improving query performance.
* @param event The query executed event
* @returns Array of recommendation strings
*/
getRecommendations(event: QueryExecutedEvent): string[] {
const recommendations: string[] = [];
const sql = event.sql.toLowerCase();
// Basic recommendations based on query analysis
if (event.executionTime > this.slowQueryThreshold) {
recommendations.push('Consider adding appropriate indexes for this query');
if (sql.includes('select *')) {
recommendations.push('Avoid using SELECT * and specify only needed columns');
}
if (!sql.includes('where') && (sql.includes('update') || sql.includes('delete'))) {
recommendations.push('Add WHERE clause to limit the scope of data modification');
}
if (sql.includes("like '%")) {
recommendations.push('Leading wildcards in LIKE clauses prevent index usage');
}
if (event.rowCount > 1000) {
recommendations.push('Consider pagination for large result sets');
}
}
return recommendations;
}
}