![]() ![]() VACUUM FULL because a VACUUM REINDEX operation requires an extra analysis of the distribution of the values in interleaved columns before performing a VACUUM FULL operation. The total time of VACUUM REINDEX will be longer than that of To keep fully benefit of Interleaved sorting, you need to periodically execute VACUUM REINDEX to the tables. Especially, when filtering with the WHERE clause, or when the sort key column has a long (more than 8 bytes) common prefix, interleaved sorting will give better performance than compound sorting. That is using only the secondary column can still work. On the other hand, Interleaved sort key is also made up of one or more of its columns, but each sort key column has equal importance. Both join columns are the distribution key and include the primary of Compound sort key.Īlso, Compound sort keys help improve compression of the column. ![]() Used for INNER JOIN and OUTER JOIN, not for FULL JOIN.If the criteria are not met, Redshift chooses Hash Join or Nested Loop for the join operator instead. ![]() However, the more complex tables or data are, the harder achieving Merge Join is, because the criteria are very strict. Merge Join is the fastest way to join in Redshift and that advantage can be seen in my examination, too. One of the major advantages of Compound sort key is that it enables Merge Join when the following criteria are met. For example, when you want to query the following table which has Compound sort key, the primary dateid can be used only in ORDER BY operations, but the secondary eventid is definitely used with the primary dateid otherwise the sorting performance will be degraded. Querying only by the primary column has a good effect on the speed, while the secondary column and following columns can't be powerful without simultaneously using the primary. When using Compound sorting, you need to consider the order of columns in Compound sort key, the first one is called primary and the second one is called secondary. Basically, Compound sorting is effective with these SQL operations ORDER BY, GROUP BY and PARTITION BY used in window functions. ![]()
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