Inefficient Query

Issue Type

Operational

Problem

An inefficient query is a query that takes significantly longer than it could with some optimizations.

It could be inefficient because it:

• Examines a large number of rows to return quite a small set
• Does a full table scan rather than using an index
• Doesn't pick an index
• Picks a Low Cardinality index
• Does a full scan sort
• Creates a temporary table

Remediation

The way to fix this depends very much on your data set and how you're querying it.

In most cases creating, combining or changing an INDEX can solve the problem.

If in doubt, consult a Data Engineer or Database Administrator would be a good start.

External Resources

• Percona: FULL TABLE SCAN vs FULL INDEX SCAN
• MySQL ORDER BY optimizations
• MySQL GROUP BY optimizations