Execution plans have a significant impact on performance.
How does the system come up with an execution plan? It depends on accurate statistics. With accurate statistics, execution statements are highly reusable and frequent compilation is avoided, which also helps improve performance.
However, if you suspect that the statistics are not accurate enough, you can force the SQL statement to be compiled. The main methods are to clear the execution plan in memory and use compiled statements.
Why is the query speed faster after index reconstruction?
1. Data fragmentation is eliminated
2. Updated statistical information.