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What is Spark's Catalyst Optimizer? Explain its stages.

Spark/Big Datahard0.7 min readPremium
Frequency
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Asked at 2 companies
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questions in Spark/Big Data
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1,863
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Asked at these companies
DunnhumbyFragma Data Systems
Key Concepts Tested
joinoptimizationsparksql
Expert AnswerPremium
132 wordsInterview-ready
Catalyst is Spark SQL's extensible query optimizer—it converts logical plans to physical plans with rule-based and cost-based optimizations. **Stages**: (1) **Analysis**—resolve table/column references using Catalog; bind types. (2) **Logical optimization**—apply rules: predicate pushdown (filter at scan), projection pruning (drop unused columns), constant folding, join reordering. (3) **Physical planning**—generate candidate plans (e.g., broadcast vs. sort-merge join); select via cost model....
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