amazon-redshiftHow can I optimize my Amazon Redshift queries?
Use appropriate data types: Redshift is optimized for columnar data storage, so it is important to use the right data types for the columns. For example, use
INTfor values that are always less than 32767.
Analyze query plan: Redshift provides an explain plan feature which can be used to analyze the query execution plan and identify areas for improvement. For example, the following query plan shows that the
joinoperation is taking up the majority of the query time:
Explain select * from table1 t1 join table2 t2 on t1.id = t2.id; QUERY PLAN ----------------------------------------- Gather Motion 2:1 (slice1; segments: 2) (cost=0.00..18.75 rows=1 width=0) -> Hash Join (cost=0.00..18.75 rows=1 width=0) Hash Cond: (t1.id = t2.id) -> Seq Scan on table1 t1 (cost=0.00..9.00 rows=100 width=4) -> Hash (cost=9.00..9.00 rows=100 width=4) -> Seq Scan on table2 t2 (cost=0.00..9.00 rows=100 width=4)
Sort data: Redshift distributes data across nodes based on the sort key. If the data is already sorted, the query optimizer can take advantage of this and reduce the cost of the query.
Distribute data evenly: Redshift distributes data across nodes based on the distribution key. If the data is not evenly distributed across the nodes, queries can be slow.
Use compression: Redshift supports several types of compression which can significantly reduce the size of the data and improve query performance.
Use Vacuum: Redshift uses a columnar storage format which can become fragmented over time. Vacuuming the table can help improve query performance.
Use Materialized Views: Redshift supports materialized views which can be used to store pre-computed results of a query. This can significantly improve query performance if the underlying data is not changing frequently.
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