I’ve been looking at Redshift Zone Maps for some time, and so I was quite pleased with theRedshift session that Rahul Pathak delivered at re:Invent 2014.
Redshift is a columnar database, which means that each block holds data for only a single column. The zone map is held separately from the block, like an index. The zone map holds only two data points per block, the highest and lowest values in the block. Redshift consults the zone map when executing queries, and excludes the blocks that the zone map indicates won’t be returned by the WHERE clause filter.
There is a short description of Zone Maps at the 8:20 mark of the re:Invent session. I’ve written a more detailed example that I hope you will find easier to understand…
Read the rest on the Optimal BI blog.
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