Examine the mysqldumpslow output: Count: 109 Time=66.73s (6183s) Lock-0.00s (0s) Rows=3990419.2 (434955691), appuser[appuser]@localhost SELECT id, firstname, surname, address, age, birthdate FROM…

Question

Options

• AThere is network congestion between client and server.
• BNo index has been defined on the filtered column.
• CThere are 109 queries still being executed.
• DA table lock is causing delays.
• EA full table scan is being used.

• A
  70% (35)
• B
  16% (8)
• C
  4% (2)
• D
  10% (5)

Explanation

Examining the Evidence in the Output

Options A and E are flagged as correct, though B deserves scrutiny. E (full table scan) is well-supported: the query filters on age with no evidence of index usage, and the staggering average of ~4 million rows returned per execution is a hallmark of scanning every row in the table rather than using a targeted index lookup. A (network congestion) is plausible because transferring ~4 million rows per query across a client-server connection creates significant data transfer overhead, contributing to the total 6,183 seconds logged.

Why the distractors are wrong:

• B is tempting - a missing index on age would cause the full table scan - but E describes the observable execution behavior, and exam questions at this level typically treat B as the root cause and E as the symptom; the output itself shows the symptom (massive row counts), not the schema definition.
• C is wrong because Count: 109 is a historical log count (the query ran 109 times), not concurrent active queries.
• D is definitively ruled out by Lock=0.00s (0s) - zero lock time is explicitly shown.

Memory tip: Read the numbers before picking answers. In mysqldumpslow, Lock=0.00s eliminates lock theories instantly, and a Rows value in the millions almost always points to a full scan and/or excessive data transfer - the two dimensions of "slow" are execution (scan) and transfer (network).

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