Tag - EXPLAIN FORMAT=JSON is Cool!

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 […]

Read more

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 […]

Read more

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 […]

Read more

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 ***************************
[…]

Read more

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 […]

Read more