Snowpro Core · Free Practice Question Medium
Question 14
When defining a clustering key which type of columns should be considered?
- A Columns with extremely low cardinality
- B Columns with extremely high cardinality
- C Columns with high enough cardinality to enable efficient partition pruning
Reveal correct answer
Correct answer: C
Explanation
When defining clustering keys, the initial candidate clustering columns are those columns that are frequently used in the WHERE clause or other selective filters. Additionally, columns that are used for joining can also be considered. Furthermore, the columns' cardinality (number of distinct values) is also important. It is crucial to choose a column with a high enough cardinality to allow effective partition pruning while having a low enough cardinality for Snowflake to group data into micro-partitions efficiently. A column with too few distinct values (e.g., gender) will result in minimal partition pruning. On the other hand, a column that has too many distinct values (e.g., customer id) will result in too much overhead when maintaining the partitions. When creating a multi-column cluster key, order the columns from the lowest cardinality to the higher cardinality; otherwise, the effectiveness of clustering will be reduced. https://docs.snowflake.com/en/user-guide/tables-clustering-keysDiscussion
Think the marked answer is wrong, or have a better explanation? Share it below — comments appear after review.
You must be logged in to post a comment.
