Tables with interleaved sort key can not be altered for both Alter distyle and Alter Sort key. Note: There are restrictions when altering distribution style and sort key. Example of alter statement :ĪLTER TABLE tablename ALTER DISTSTYLE ALL ĪLTER TABLE tablename ALTER SORTKEY (column_list) Multiple columns can be defined as interleaved sort key and it gives equal weight to each column, if the query has fixed columns in the filter clause, applying interleaved sort key is best suited to improve performance.ĭistribution style and sort key are defined at table creation, but they can be altered later after table creation. There are 2 types of sort keys :ĭata sorted based on order listed in table sort key definition. Choosing the right sort key can improve query performance because it allows the query planner to scan fewer data when doing a filter, join, group, and order operations. Sort key in Redshift determines how data to be sorted based on the key defined. In general : Small tables are distributed with ALL strategies, and large tables are distributed with EVEN strategy.
AUTO: Redshift automatically decides the best distribution key based on the usage pattern.ALL: Data is distributed in all nodes, and choose ALL for a smaller dataset that ranges between 1 to 10K.KEY: Data with the same value will be placed in the same slice.EVEN: Data distributed in round-robin across nodes.There is 4 distribution style in Redshift: The goal in selecting the distribution style is to have the rows distributed evenly throughout the node for parallel processes. Choosing the right distribution style and sort key can improve the query performance.Īmazon Redshift distributed rows to each node based on distribution style. Choose the Right distribution style and sort key:ĭistribution style and sort key are very important in Redshift. Use Spectrum for infrequently used data.Choose the right distribution style and sort key.Here are the summary of 10 performance tuning techniques : We have done optimisation at storage, compute and cluster level. This blog covers the optimisation techniques that have been followed at Halodoc to solve various problems. In the past few years we have faced various challenges while building and maintaining the data warehouse using Redshift.
At Halodoc, we use AWS Redshift as a data warehouse, it is the single source of truth for analytics and reporting.
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