https://www.percona.com/blog/explain-extended-can-tell-you-all-kinds-of-interesting-things/
EXPLAIN EXTENDED shows what MySQL optimizer does to your query - Percona
May 15, 2026 - While many people are familiar with the MySQL EXPLAIN command, fewer people are familiar with "explain extended" which was added in MySQL 4.1
mysql optimizerexplainextendedshows
https://www.percona.com/resource/mysql-query-optimizer-explained-through-optimizer-trace-percona/
The MySQL Query Optimizer Explained Through Optimizer Trace - Percona
Apr 6, 2026 - All major considerations and decisions made by the MySQL Query Optimizer may be recorded in an Optimizer Trace. While EXPLAIN will show the query execution...
mysql queryoptimizerexplainedtracepercona