Proper indexing can make your database queries 100x faster. Poor indexing wastes storage and slows down writes. Here's how to get it right.
Understanding Query Plans
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Index Selection Guidelines
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Composite Index Ordering
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Covering Indexes
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Partial Indexes
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Expression Indexes
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Index Maintenance
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Index for Sorting
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Monitoring Index Usage
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Best Practices
Creating Indexes:
✓ Index columns in WHERE clauses
✓ Index foreign keys
✓ Use composite indexes for multi-column queries
✓ Order: equality columns, then range, then sort
Avoiding Problems:
✗ Don't index low-cardinality columns alone
✗ Don't create redundant indexes
✗ Don't ignore write performance impact
✗ Don't forget to ANALYZE after bulk changes
Maintenance:
✓ Monitor index usage regularly
✓ Remove unused indexes
✓ Reindex periodically
✓ Update statistics
Conclusion
Effective indexing requires understanding your query patterns. Use EXPLAIN ANALYZE to verify index usage, create targeted indexes, and regularly audit for unused or duplicate indexes. The right indexes can transform query performance from seconds to milliseconds.