Because the data is already sorted on the join key, the query optimizer can bypass the sort phase of the sort merge join. Redshift can skip reading entire blocks of data for that column because it keeps track of the minimum and maximum column values stored on each block and can skip blocks that dont apply to the predicate range. This comment is here just to keep track of what well set the sort and dist keys to in the CLI command below. If you frequently join a table, specify the join column as both the sort key and the distribution key.ĭoing this enables the query optimizer to choose a sort merge join instead of a slower hash join. If you do frequent range filtering or equality filtering on one column, specify that column as the sort key. It can do so because it tracks the minimum and maximum column values stored on each block and can skip blocks that don't apply to the predicate range. If you do frequent range filtering or equality filtering on one column, specify that column as the sort key.Īmazon Redshift can skip reading entire blocks of data for that column. Queries are more efficient because they can skip entire blocks that fall outside the time range. Amazon Redshift database administrators and SQL developers can check the existing sort key and distribution key of a database table by querying the. It also depends on how many new customers you get. If you have fact tables distributed by customer Id then make that the distribution key. The data should be distributed together with data that it will be joined to. a sales dashboard for the companys newest product line using data in Amazon Redshift. Customercategory would make a good secondary sort key. However I dont find anything on reverse compound sort key. Sort Key The ANALYZE Command Collects Statistics Redshift Automatically. If recent data is queried most frequently, specify the timestamp column as the leading column for the sort key. If you join often by customerid then make that the sort key. In this training class, students will learn Amazon Redshift Architecture. To have Amazon Redshift choose the appropriate sort order, specify AUTO for the sort key. Some suggestions for the best approach follow: For more information, see Working with automatic table optimization. When you use automatic table optimization, you don't need to choose the sort key of your table. The Amazon Redshift query optimizer uses sort order when it determines optimal query plans. Redshift is a fully managed service, meaning that you do not have to worry about provisioning or managing the underlying infrastructure. It is designed to handle large amounts of data and to make that data accessible to users for analysis and reporting. Amazon Redshift stores your data on disk in sorted order according to the sort key. What is AWS Redshift AWS Redshift is a cloud-based data warehousing service.
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