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HELP CENTER · FAQDatabases1 min read

When should I add an index to a database table?

Consider an index when a measured query repeatedly filters, joins, or orders by the same columns and scans too much data. Check the query plan and workload first: indexes improve some reads but consume storage and add work to writes.

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Use evidence from the query workload

Identify the slow query and inspect how many rows it reads versus returns. An index may help when selective predicates or join keys let the database locate a small portion of a large table.

Column order matters for composite indexes, and an index that does not match the query pattern may not be used. Confirm the database's guidance for the specific engine rather than adding an index to every filtered column.

Balance faster reads with write costs

Each relevant insert, update, or delete may need to maintain index entries. Too many indexes can slow writes, increase storage, and make schema changes more complex.

Measure query latency and resource use before and after adding an index with representative data. Keep the change only if the workload improves overall, and verify that the index is used by the intended query rather than merely existing.

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