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Snowflake

DEA-C02 · Question #102

A Data Engineer is trying to improve the performance of a long-running query by clustering the base table. What information from the output of the system function will verify CLUSTERING_INFORMATION…

The correct answer is D. The total number of constant micro-partitions in the table is low. Option D is correct because in Snowflake's SYSTEM$CLUSTERING_INFORMATION, a low count of constant micro-partitions - partitions where the clustering key's min and max values are identical - indicates the clustering process has successfully redistributed data so that partitions…

Performance Optimization

Question

A Data Engineer is trying to improve the performance of a long-running query by clustering the base table. What information from the output of the system function will verify CLUSTERING_INFORMATION that the clustering improved query performance?

Options

  • AThe average number of overlapping micro-partitions in the table is high.
  • BThe total number of constant micro-partitions in the table is high.
  • CThe average overlap depth of each micro-partition in the table is high.
  • DThe total number of constant micro-partitions in the table is low.

How the community answered

(56 responses)
  • A
    9% (5)
  • B
    4% (2)
  • C
    16% (9)
  • D
    71% (40)

Explanation

Option D is correct because in Snowflake's SYSTEM$CLUSTERING_INFORMATION, a low count of constant micro-partitions - partitions where the clustering key's min and max values are identical - indicates the clustering process has successfully redistributed data so that partitions span meaningful, non-overlapping ranges of the clustering key rather than being fragmented into single-value chunks, which optimizes range-based query pruning.

Options A and C are both wrong for the same reason: high average overlapping micro-partitions (A) and high average overlap depth (C) are both symptoms of poor clustering, meaning Snowflake must scan more micro-partitions per query - exactly what clustering is meant to fix. You want these values low after clustering.

Option B is wrong because a high constant micro-partition count would signal excessive fragmentation - each partition holds only one distinct clustering key value - which means clustering reorganized the data too granularly rather than optimally grouping rows into prunable, range-bounded partitions.

Memory tip: Think of overlap as the enemy. After clustering, you want depth and overlaps to be LOW (like a neat stack of sorted cards with no interleaving). Constant partitions being LOW means the data is spread efficiently across ranges, not broken into countless single-value silos. When in doubt: low overlap + low constant = clustering success.

Topics

#Table Clustering#Performance Tuning#System Functions#Micro-partitions

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