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What are common failure modes of Query Execution Plans?
What are common failure modes of Query Execution Plans?
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Audio N/AQuick interview answer
Common failures around Query Execution Plans: blocking the hot path, ignoring backpressure, and weak timeout/retry design. Tuning without measuring; ignoring rows mismatch (estimate 10, actual 1M).
Detailed answer
Failure modes for Query Execution Plans: Known pitfalls: Tuning without measuring; ignoring rows mismatch (estimate 10, actual 1M). • Missing timeouts / unbounded retries • No backpressure when downstream slows • Assuming ordering/guarantees the runtime does not provide How seniors prevent them: ANALYZE/UPDATE STATISTICS after bulk changes; compare before/after cost. Parent context: Baseline: Optimizer chooses join order, access paths (seek vs scan), and algorithms (hash vs merge join). EXPLAIN/EXPLAIN ANALYZE shows estimated vs actual rows — key for tuning.
Full explanation
Name concrete failure modes and the mitigation for each — that scores higher than a vague “it can fail.” Optimizer chooses join order, access paths (seek vs scan), and algorithms (hash vs merge join). EXPLAIN/EXPLAIN ANALYZE shows estimated vs actual rows — key for tuning.
Follow-up questions
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Parent context — Query Execution Plans
Baseline: Optimizer chooses join order, access paths (seek vs scan), and algorithms (hash vs merge join). EXPLAIN/EXPLAIN ANALYZE shows estimated vs actual rows — key for tuning.
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