how to troubleshoot & optimize database query performance for your application

Confidential, Dynatrace, LLC

Asad AliDirector, Product Specialist@AsadThoughtsDynatrace

How to Troubleshoot & Optimize Database Query Performance for Your Application

Let the blame game start!

Web Server Application Server Database

DEV Team DBA Team

Blame the database for all performance issues

Blame the SW/HW or system administrators

Network?

Database Heavy: 66.51% (40.27s)

Time Spent in SQL Execs

Excessive SQL: 24889! Calls to Database

Database Heavy: 66.51% (40.27s)

Time Spent in SQL Execs

DatabasePerformance

hotspots

Application Design

DB Design DB Queries

Server/Infrastructure

Database Performance Hotspots

Application Design Database Infrastructure

Application

of databaseperformance issuescan be solved by developers70

%

Database Performance Hotspots

• Lack of use of bind values• Too many SQL statements per user action• Database server overloaded• DB connection pool monitoring

Example 1:performance tuning by using bind variables

Oracle SQL Cache<?php

$db = new PDO('oci:dbname=sid', 'username', 'password');

$data = Array();$data[] = $db->query("select * from country where code = 'AT'");$data[] = $db->query("select * from country where code = 'AU'");$data[] = $db->query("select * from country where code = 'NZ'");$data[] = $db->query("select * from country where code = 'ES'");

?>

?>

Query Plan Evaluation

MSSQL Cache

MSSQL Cache

Little Bobby TablesaddStudentInfo(String lname, String fname) {

String query = “insert into Student(last_name, first_name)values (‘”+lname + ”’, ‘” + fname + “’)”;

}Normal Operation:

First Name: AsadLast Name : Aliinsert into Student (‘Ali’, ‘Asad’)

Malicious Operation:First Name: Asad’); Drop table Student;Last Name : Aliinsert into Student (‘Ali’, ‘Asad’); Drop table

Student

Little Bobby Tables

Oracle SQL Cache<?php

$db = new PDO('oci:dbname=sid', 'username', 'password');

$data = Array();$ps = $db->prepare("select * from country where code = :code");$data[] = $ps->execute(array("code" => "AT"));$data[] = $ps->execute(array("code" => "AU"));$data[] = $ps->execute(array("code" => "NZ"));$data[] = $ps->execute(array("code" => "ES"));

?>

?>

Example 2:application performing

too many SQL statements

Excessive SQL: 24889! Calls to Database

Database Heavy: 66.51% (40.27s)

Time Spent in SQL Execs

Why are there so many SQL statements?$schools = new SchoolEntities();

foreach ($schools as $school) { foreach ($school->departments as $department) { foreach ($department->courses as $course) { echo $department->name . ": " . $course->title); } }}

N+1 problem• 10 schools• 20 departments per school• 50 courses per department

=> 10 x 20 x 50 = 10001 single database statements !!!

Retrieving too many records$schools = new SchoolEntities();

foreach ($schools->departments as $department) { foreach ($department->courses as $course) { if ($course->category == "SQL" && $course->level == "expert")) { echo $department->name . ": " . $course->title); } }}

=> 3 records, still 10001 queries

Solution: use a JOIN query with a WHERE clause$rows = $db->query ("select department.name as department, course.title as course from school join department on school_id = school.id join course on department_id = department.id where course.category = 'SQL' and course.level = 'expert'");

foreach ($rows as $row) { echo $department . ": " . $course);}

=> ONE database statement !!!

Example 3:overloaded database server

Major database performance problem

Example 4: database connection pool settings

Database Connection Pool

Database Connection Pool

Database Connection Pool

Auto DB Pattern Detection

Live Demo

Q & A@AsadThoughts

Performance Tuning – best practices• Use bind variables to leverage SQL caching• Use join queries to avoid N+1 problems• Avoid index killers in queries• Use stored procedures for complex functionality• Leverage connection pooling• Watch for other processes / application on your database

http://apmblog.dynatrace.com/2016/05/23/improve-oracle-database-performance-using-bind-variables/

https://www.infoq.com/articles/Diagnose-Microservice-Performance-Anti-Patterns