![]() ![]() Zone maps, that are stored in memory and generated automatically, are used to define the value extremes for each block of data. Table Columns used in WHERE clause predicates are a good choice for sort keys and date or time-related columns are used commonly. The physical order of data on a disk is defined by sort keys. Using the right distribution patterns can maximize the performance of JOIN, GROUP BY and INSERT INTO SELECT operations Refining Data Sorting In this style, a column value is hashed and the same hash value is placed on the same slice. KEY – Consists of frequently joined, fact tables or large dimension tables.EVEN – Consists of large, standalone fact tables that are not frequently joined or aggregated in a round-robin distribution across the slices.ALL – Consists of small, frequently joined and infrequently modified tables that are placed on the first slice of each compute node. ![]() AUTO – Starts with ALL and switches to EVEN as the table grows.The rows of a table are automatically distributed by Amazon Redshift across node slices, based on the following distribution styles: Keeping the number of resources in a queue to a minimum.Limiting maximum total concurrency for the main cluster to 15 or less, to maximize throughput. ![]()
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