How Can I Monitor the Performance Impact of MySQL Indexing?

How to Monitor the Impact of MySQL Indexing on Query Performance

Q: How can I assess the performance improvements resulting from applying indexes to MySQL tables?

A:

To evaluate the efficacy of indexing, utilize the EXPLAIN EXTENDED query:

EXPLAIN EXTENDED SELECT col1, col2, col3, COUNT(1) 
FROM table_name 
WHERE col1 = val 
GROUP BY col1 
ORDER BY col2;

Followed by SHOW WARNINGS;. This provides insight into query performance and index usage.

Additional Tips:

• Implement "covering indexes" by prioritizing columns from the WHERE clause, GROUP BY, ORDER BY, and SELECT clauses when creating an index.
• For instance, with the provided query, a covering index would resemble KEY(col1, col2, col3) to optimize performance.

Caution:

• Keep in mind that excessive indexing can hinder insert query execution speed.

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