MariaDB Index Maintenance & Performance Cheatsheet

mariadb-index-maintenance.md

MariaDB Index Maintenance & Performance Cheatsheet 🛠️🚀

1️⃣ Check for Long-Running Queries

SHOW FULL PROCESSLIST;

• Look for queries with high Time values (e.g., >5s).
• Identify queries stuck in "Sending data", "Copying to tmp table", or "Waiting for table lock".

SELECT * FROM information_schema.PROCESSLIST WHERE TIME > 5;

• Shows queries running for longer than 5 seconds.

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2️⃣ Check for Index Fragmentation

SELECT table_name, data_length, index_length, data_free
FROM information_schema.tables
WHERE table_schema = 'your_database_name';

• If data_free is large, the table may be fragmented.

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3️⃣ Rebuild & Optimize Indexes

OPTIMIZE TABLE tbl_entries, tbl_entries_data_411, tbl_entries_data_409, tbl_entries_data_412;

• Reclaims unused space & defragments indexes.
• Run periodically if tables experience frequent updates/deletes.

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4️⃣ Update Query Optimizer Statistics

ANALYZE TABLE tbl_entries, tbl_entries_data_411, tbl_entries_data_409, tbl_entries_data_412;

• Ensures MariaDB selects the best index for queries.

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5️⃣ Automate Index Optimization (Optional)

📌 Run weekly via cron job

crontab -e

Add:

0 0 * * 0 mysql -u root -p'password' -e "OPTIMIZE TABLE tbl_entries, tbl_entries_data_411, tbl_entries_data_409, tbl_entries_data_412;"

• Runs every Sunday at midnight.
• Only enable if tables change frequently.

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6️⃣ Find the Most Expensive Queries

SELECT query, total_latency, exec_count 
FROM sys.statement_analysis 
ORDER BY total_latency DESC 
LIMIT 5;

• Shows queries consuming the most resources.

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7️⃣ Check for Locking Issues

SHOW ENGINE INNODB STATUS;

• Look for "Waiting for table lock" or "Pending writes".

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8️⃣ Kill a Stuck Query

KILL <ID>;

• Get the query ID from SHOW FULL PROCESSLIST; and terminate it.

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🛠️ Best Practices

✅ Run SHOW FULL PROCESSLIST; to monitor live queries.
✅ Use OPTIMIZE TABLE if performance degrades.
✅ Don't overuse OPTIMIZE TABLE—only when necessary.
✅ Consider Redis caching for frequently run queries.
✅ Monitor data_free to check if indexes need rebuilding.

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🚀 TL;DR

1. Queries slow? → SHOW FULL PROCESSLIST;
2. Index fragmentation? → SELECT table_name, data_free FROM information_schema.tables;
3. Fix fragmentation? → OPTIMIZE TABLE tbl_name;
4. MariaDB picking wrong indexes? → ANALYZE TABLE tbl_name;
5. Recurring optimization? → Use a cron job if needed.