Reviewed by Aditya Kumar · Last reviewed 2026-03-24
Manually created Hive partition directories (e.g., /table/country=US/date=2024-01-01/) are not visible to Hive until metadata is added. Hive uses the metastore to find partitions; manually created dirs are unknown. Fix: run MSCK REPAIR TABLE table_name to scan the table...
This medium-level SQL question appears frequently in data engineering interviews at companies like Dunnhumby. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (partition) will help you answer variations of this question confidently.
Break this problem into components. Identify the core trade-offs involved, then walk the interviewer through your reasoning step by step. Demonstrate awareness of edge cases and production considerations - this is what separates good answers from great ones.
Manually created Hive partition directories (e.g., /table/country=US/date=2024-01-01/) are not visible to Hive until metadata is added. Hive uses the metastore to find partitions; manually created dirs are unknown. Fix: run MSCK REPAIR TABLE table_name to scan the table directory and add partition metadata. Alternative: ALTER TABLE table_name ADD PARTITION (country='US', date='2024-01-01') LOCATION '/path/to/partition'. Best practice: use Hive's INSERT or ADD PARTITION; avoid manual directory creation. For external tables, ensure LOCATION is correct. MSCK REPAIR can be slow on large tables; for incremental adds use ADD PARTITION. Why it matters: Design choices compound at scale—wrong approach can cause 100× overhead. Scalability trade-offs: Profile before optimizing; validate on sample then full. Cost implications: Suboptimal choices multiply at billion-row scale.
Red Flag: Generic textbook answers. Pro-Move: 'At scale we measured X, implemented Y, achieved Z%—validated and iterated.'
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According to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 1 company. DataEngPrep.tech maintains an editor-reviewed database of 1,863 data engineering interview questions across 7 categories.