COF-C03 - Snowflake AI Data Cloud Features and Architecture - Section 1.6

Explain micro-partitions, data clustering, and how Snowflake stores and prunes table data.

Explain that Snowflake stores table data in immutable, compressed, columnar micro-partitions that carry metadata about the values they hold. Describe how the natural clustering of data and partition pruning let Snowflake skip micro-partitions that cannot match a query, and what clustering depth indicates about a large table.

micro-partitionscolumnar storagepartition pruningnatural clusteringclustering depth

Practice question for this objective

Free sampleSnowflake AI Data Cloud Features and Architecturemedium

An engineer runs SYSTEM$CLUSTERING_INFORMATION on a fact table and sees an average clustering depth close to 1 for the clustering column. They must explain to the team what that low depth indicates about how the data is organised on that column. Which interpretation is correct?

  • AFew micro-partitions overlap on that column's value ranges, so the data is well clustered and queries on it prune effectively. Correct
  • BThe clustering key was rejected, so Snowflake silently stopped maintaining any physical ordering and reverted the table to fully unordered load order.
  • COnly one micro-partition exists for the whole table, so clustering depth cannot grow above 1 regardless of how much data is loaded.
  • DAlmost every micro-partition overlaps on that column's value ranges, so the table is badly clustered and most partitions must be scanned.
Interpret an average clustering depth near 1 as minimal micro-partition overlap on the clustering column, meaning the table is well clustered for pruning. Clustering depth measures the average number of micro-partitions whose value ranges overlap at any point along the clustering column. A depth close to 1 means almost no overlap, so for a given predicate Snowflake can isolate a small set of partitions and skip the rest, which is exactly the pruning behaviour clustering is meant to deliver.

Why A is correct: A clustering depth approaching 1 means very few micro-partitions share overlapping value ranges for that column, which is the ideal state for pruning and confirms strong clustering.

Why B is wrong: Snowflake does not silently reject a clustering key, and a depth near 1 reflects good organisation rather than abandoned maintenance, so this misreads the metric.

Why C is wrong: Depth near 1 measures overlap across many partitions, not a single-partition table, and large tables hold many micro-partitions, so this confuses depth with partition count.

Why D is wrong: Heavy overlap and poor pruning correspond to a high clustering depth, not a depth near 1, so this inverts the meaning of the metric the engineer is reading.

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