Senior Query Optimization

Test your Senior-level Caching Performance Query Optimization skills in Database Data Management. This timed assessment evaluates your expertise in Information Technology.

Duration: 5 minutes

•40 questions

Time Remaining: 05:00

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40 questions remaining

Question 1 of 40Assessment

What is the primary reason an optimizer prefers a 'Sequential Scan' over an 'Index Scan' for a query that returns 90% of a table's rows?

A. Sequential I/O is faster than the random I/O required to bounce between index and heap.

B. Index scans require exclusive locks on the table, which prevents concurrent reads.

C. The B-Tree structure becomes unstable when more than 50% of the entries are accessed.

D. Modern disk controllers can only perform sequential reads for large-scale data transfers.

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