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How do these policies affect query performance?

SQLeasy0.2 min read

**RLS (Row-Level Security)**: Adds predicate to every query; can use index if predicate column indexed; complex predicates = slower. **Column masking**: Per-row computation; adds overhead. **Result caching**: Speeds repeat queries; invalidated on write. **Trade-off**: Security...

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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
TCS

Why This Question Matters

This easy-level SQL question appears frequently in data engineering interviews at companies like TCS. While less common, it tests deeper understanding that distinguishes strong candidates.

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Start by clearly defining the core concept being asked about. Interviewers want to see that you understand the fundamentals before diving into implementation details. Structure your answer with a definition, then explain the practical application with a concise example.

Expert Answer
47 words

RLS (Row-Level Security): Adds predicate to every query; can use index if predicate column indexed; complex predicates = slower. Column masking: Per-row computation; adds overhead. Result caching: Speeds repeat queries; invalidated on write. Trade-off: Security vs. latency. Design policies with indexed columns; test EXPLAIN with RLS enabled.

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