Columnstore Dictionaries

Niko Neugebauer explains some interesting facts about columnstore index dictionaries:

From a recent experience at a customer, I had an opportunity to dive into the details of the Columnstore Indexes Dictionaries. I have to admit that my understanding of them was pretty low, from what I have learned in the recent days, and I would like to share what I have learned with everyone.

These are some of the key findings that I have discovered:
– The local dictionaries are not exclusively connected with just 1 Row Group, but with multiple ones;
– The dictionaries within Columnstore Indexes are compressed in a different way, depending on the type of the compression applied (Columnstore vs Columnstore Archival);

and let us dive into each one of them:

Read the whole thing.

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