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Schema Changes in Source (New Column Addition) - Impact

SQLeasy0.4 min readPremium
Frequency
Low
Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Verizon
Key Concepts Tested
etlspark
Expert AnswerPremium
79 wordsInterview-ready
New column in source: impact on ETL—schema mismatch, pipeline failure if not handled. Solutions: schema evolution (add column with default), use schema-on-read (Spark, Parquet), dynamic schema detection, add column to target with default. Best: version schema, use flexible formats (Parquet), add columns as nullable initially, backfill if needed. **Why it matters**: Design choices compound at scale—wrong approach can cause 100× overhead....
The complete answer continues with detailed implementation patterns, architectural trade-offs, and production-grade considerations. It covers performance optimization strategies, common pitfalls to avoid, and real-world examples from companies like Verizon. The answer also includes follow-up discussion points that interviewers commonly explore.

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