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Merge pull request #292 from lynnlangit/patch-7

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added redshift distribution column type info
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Max Zanko 2016-11-11 05:34:57 -08:00 committed by GitHub
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@ -1403,7 +1403,7 @@ Redshift
- Redshift uses columnar storage, hence it does not have indexing capabilities. You can, however, use distribution key [distkey](http://docs.aws.amazon.com/redshift/latest/dg/c_best-practices-best-dist-key.html) and sort key [sortkey](docs.aws.amazon.com/redshift/latest/dg/c_best-practices-sort-key.html) to improve performance. Redshift has two type of sort keys: compounding sort key and interleaved sort key.
- A compound sort key is made up of all columns listed in the sort key definition. It is most useful when you have queries with operations using prefix of the sortkey.
- An interleaved sort key on the other hand gives equal weight to each column or a subset of columns in the sort key. So if you don't know ahead of time which column you want to choose for sorting and filtering, this is a much better choice than the compound key.[Here](https://aws.amazon.com/blogs/aws/quickly-filter-data-in-amazon-redshift-using-interleaved-sorting/) is an example using interleaved sort key.
- 🔸⏱ **Distribution strategies:** Since data in Redshift is physically distributed among nodes, choosing the right data **distribution key** and [distribution style](http://docs.aws.amazon.com/redshift/latest/dg/c_choosing_dist_sort.html) is crucial for adequate query performance. There are three possible distribution style settings settings — **EVEN** (the default), **KEY**, or **ALL**. Use KEY to collocate join key columns for tables which are joined in queries. Use ALL to place the data in small-sized tables on all cluster nodes.
### Redshift Gotchas and Limitations