To Index or Not to Index: When Does Index Usage Really Matter?

Must-Follow Practices and Pitfalls to Avoid for Optimal Index Usage

DOs:

• Create indexes when facing performance bottlenecks: Indexes significantly improve query execution speed by allowing faster data retrieval.
• Index fields used in WHERE clauses: Indexes optimize queries where the field is used as a filter criterion, ensuring efficient data selection.
• Utilize indexes for foreign key references: Indexing the foreign key column in both the referencing and referenced tables enhances data integrity and performance.
• Employ multicolumn indexes for complex queries: When multiple fields are involved in WHERE clauses or sorting, creating multicolumn indexes provides a significant performance boost.
• Keep table statistics updated: Accurate statistics guide the optimizer in choosing the best execution plan, including optimal index usage.

DONTs:

• Avoid creating unnecessary indexes: Unnecessary indexes introduce overhead and slow down write operations without any performance benefits.
• Don't index fields used in range scans: Range scans (e.g., WHERE field BETWEEN start AND end) generally do not benefit from indexes.
• Consider data distribution when indexing: If the data is evenly distributed or sparsely populated, indexes may not be effective and can lead to performance degradation.
• Avoid partial indexes unless necessary: Partial indexes exclude specific values or ranges, resulting in smaller indexes but potentially sacrificing query performance for certain cases.

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