# How should I read a database query plan before tuning a query?

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HELP CENTER · FAQ Databases 2 min read
# How should I read a database query plan before tuning a query?
A query plan describes how the database expects to retrieve and combine rows for a particular query and data state. Use it to form a hypothesis about cost, then compare estimated behavior with runtime metrics and representative data rather than optimizing from one visual label alone.
IaGenify
Databases

## Read the plan in context
Check whether the plan uses scans, indexes, joins, sorts, or temporary operations and how many rows each step estimates. A scan is not automatically wrong; it may be efficient for a small table or a query that returns much of the data.
Compare estimated and actual row counts when the engine provides runtime analysis. Large differences can point to stale statistics, correlated data, or parameter-sensitive behavior; refresh or investigate statistics before forcing a specific access path.
## Change one factor and measure
Use representative parameters and data volume, and capture latency, rows processed, and resource use before and after a change. Indexes can reduce reads but increase write cost and storage, so assess the whole workload.
Confirm behavior under concurrency and across important parameter values. Preserve a way to compare plans after schema, statistics, or engine changes, since a plan that was efficient yesterday may not remain so. [← Back to Databases FAQs](https://help.iagenify.com/faqs/databases)