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What is the usage of Optimize and REORG commands in Databricks?

Spark/Big Datamedium0.5 min readPremium

**OPTIMIZE**: Compacts small files in Delta table. Merges files; improves read performance. No Z-order. Run: `OPTIMIZE table_name`. **REORG**: OPTIMIZE + Z-order. Compacts and clusters by columns. Better predicate pushdown for filtered columns. Run: `REORG TABLE table_name...

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Frequency
Low
Asked at 1 company
Category
452
questions in Spark/Big Data
Difficulty Split
88E|81M|283H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
PWC
Key Concepts Tested
partitionwindow

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Expert Answer
97 words

OPTIMIZE: Compacts small files in Delta table. Merges files; improves read performance. No Z-order. Run: OPTIMIZE table_name.

REORG: OPTIMIZE + Z-order. Compacts and clusters by columns. Better predicate pushdown for filtered columns. Run: REORG TABLE table_name APPLY (ZORDER BY (col1, col2)).

When: After many small writes. Before large reads. During maintenance window.

Trade-offs: REORG more expensive; Z-order helps reads on clustered columns. High cardinality column = low benefit.

Scalability Trade-offs: Both expensive on large tables. Run per partition or during low traffic.

Cost Implications: Run weekly or when small-file count exceeds threshold. Balance cost vs. read benefit.

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