EXPLAIN

MongoDB Explain – Using PMM-QAN for MongoDB Query Analytics

MongoDB 4.0 Features Webinar

In this blog post, we will walk through PMM-Query Analytics for MongoDB. We will see how to analyze MongoDB query performance; review the initial parameters that we need to check; and find out how to compare MongoDB query performance with and without indexes with the help of EXPLAIN plan.
The Percona Monitoring and Management QAN (PMM-QAN) dashboard […]

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Webinar Thu 6/21: How to Analyze and Tune MySQL Queries for Better Performance

database query tuning

Please join Percona’s MySQL Database Administrator, Brad Mickel as he presents How to Analyze and Tune MySQL Queries for Better Performance on Thursday, June 21st, 2018, at 10:00 AM PDT (UTC-7) / 1:00 PM EDT (UTC-4).
Register Now
 
Query performance is essential in making any application successful. In order to finely tune your queries you first […]

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Understanding PMM QAN – Graphs & Metrics

understanding PMM QAN

In this blog post, I will share with you how to set up the PMM QAN for MongoDB and the formulas behind the metrics and graphs that you see on the QAN dashboard.
When one of my customers wanted to load test and understand the behavior of the queries in their MongoDB instance through a […]

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This Week in Data with Colin Charles 18: Percona Live Call For Papers and a MongoDB 3.6 Overview

Colin Charles

Join Percona Chief Evangelist Colin Charles as he covers happenings, gives pointers and provides musings on the open source database community.
I highly recommend submitting to the CFP for Percona Live Santa Clara 2018 even though it only closes December 22 2017. By the 3rd week of December, i.e. before the CfP closes, it is very […]

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Introduction to Troubleshooting Performance – Troubleshooting Slow Queries webinar: Q & A

InnoDB Troubleshooting

In this blog, I will provide answers to the Q & A for the Troubleshooting Slow Queries webinar.
First, I want to thank you for attending the April 28 webinar. The recording and slides for the webinar are available here. Below is the list of your questions that I wasn’t able to answer during the webinar, with […]

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EXPLAIN FORMAT=JSON wrap-up

EXPLAIN FORMAT=JSON

This blog is an EXPLAIN FORMAT=JSON wrap-up for the series of posts I’ve done in the last few months.
In this series, we’ve discussed everything unique to
EXPLAIN FORMAT=JSON. I intentionally skipped a description of members such as
table_name,
access_type  or
select_id, which are not unique.
In this series, I only mentioned in passing members that […]

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EXPLAIN FORMAT=JSON: nested_loop makes JOIN hierarchy transparent

EXPLAIN FORMAT=JSON

Once again it’s time for another EXPLAIN FORMAT=JSON is cool! post. This post will discuss how EXPLAIN FORMAT=JSON allows the nested_loop command to make the JOIN operation hierarchy transparent.
The regular
EXPLAIN  command lists each table that participates in a 
JOIN  operation on a single row. This works perfectly for simple queries:

MySQL

mysql> explain select * from […]

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EXPLAIN FORMAT=JSON: cost_info knows why optimizer prefers one index to another

Percona Server 5.7 performance improvements

Time for another entry in the EXPLAIN FORMAT=JSON is cool! series of blog posts. This time we’ll discuss how using EXPLAIN FORMAT=JSON allows you to see that
cost_info  knows why the optimizer prefers one index to another.
Tables often have more than one index. Any of these indexes can be used to resolve query. The optimizer has […]

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EXPLAIN FORMAT=JSON: buffer_result is not hidden!

MongoDB System Tuning

Time for another entry in the EXPLAIN FORMAT=JSON is cool! series. Today we’re going to look at how you can view the buffer result using JSON (instead of the regular
EXPLAIN command.
Regular
EXPLAIN does not identify if
SQL_BUFFER_RESULT was used at all. To demonstrate, let’s run this query:

MySQL

mysql> explain select * from salariesG
*************************** 1. row ***************************
[…]

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EXPLAIN FORMAT=JSON knows everything about UNIONs: union_result and query_specifications

Ready for another post in the EXPLAIN FORMAT=JSON is Cool series! Great! This post will discuss how to see all the information that is contained in optimized queries with
UNION using the
union_result and
query_specifications commands.
 
When optimizing complicated queries with
UNION, it is easy to get lost in the regular
EXPLAIN  output trying to identify which part of […]

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