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Get the guideSnowflake clustering is a technique that groups related rows in Snowflake tables into the same micro-partition to improve query performance. This organization of data allows Snowflake to avoid scanning unnecessary micro-partitions.
Snowflake clustering involves physically grouping similar values of one or more columns together. Users can manually define the clustering key to control how Snowflake creates micro-partitions. Snowflake automatically clusters data into micro-partitions to allow for faster retrieval of frequently requested data.
CREATE TABLE my_table (
id INT,
event_date DATE,
event_type STRING,
...
)
CLUSTER BY (event_date, event_type);
This code snippet shows how to create a table with clustering keys defined. By clustering on event_date and event_type, related rows are grouped into the same micro-partitions, improving query performance.
Snowflake clustering offers several benefits that enhance query performance and data management. These benefits include:
Clustering in Snowflake is typically worth it on tables greater than 1 TB. Query performance is the best indicator of how well-clustered a table is. If queries on a table are performing as needed or expected, the table is likely well-clustered. If query performance degrades over time, the table is likely no longer well-clustered and may benefit from clustering.
To create a table with Snowflake clustering enabled, define clustering keys during the table's creation or alteration using the CREATE TABLE or ALTER TABLE commands.
ALTER TABLE my_table
CLUSTER BY (event_date, event_type);
This command alters an existing table to include clustering keys.
After defining clustering keys, insert data into the table. Snowflake automatically reorganizes data into micro-partitions based on the clustering keys defined for the table.
INSERT INTO my_table (id, event_date, event_type, ...)
VALUES (1, '2023-01-01', 'click', ...);
Data insertion triggers the clustering process, grouping related rows into micro-partitions for optimized query performance.
Evaluate how your table is clustered by looking at certain columns that your users will interface with. Use the SYSTEM$CLUSTERING_INFORMATION function to return clustering information, including average clustering depth.
SELECT SYSTEM$CLUSTERING_INFORMATION('my_table');
This function helps monitor the clustering health of a large table and determine if it would benefit from explicitly defining a clustering key.
Snowflake clustering is best suited for tables that meet specific criteria. Use clustering when:
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