Question

Carefully review and complete the "Indexing Practice Lab" located in the Additional Resources section of this module. Based on the examples and observations from the lab, what happens when PostgreSQL determines that a relatively large number of records will be matching the criteria of a query with a defined index?

a. A bitmap scan will be used.
b. A sequential scan will be used.
c. An index scan will be used.
d. None of the above.

Answer 1

In PostgreSQL, when a relatively large number of records match the criteria of a query with a defined index, an index scan is the preferred method. (option c is the correct answer)

Step-by-step explanation:

An index scan involves accessing the index data structure to locate the specific rows that satisfy the query conditions. This is more efficient than a sequential scan, where the database reads every row sequentially, or a bitmap scan, which is typically used for multiple conditions.

PostgreSQL's query planner analyzes the query and the available indexes to determine the most efficient access method. If a significant number of records match the query conditions and an index is available, it selects an index scan for faster data retrieval. This optimization improves query performance, especially in scenarios where a sequential scan would be less efficient due to the large dataset.

PostgreSQL utilizes an index scan when there is a substantial number of records matching the query criteria, optimizing the query performance by efficiently accessing the required data through the index.