Alternatives in ClickHouse to types Maps for mixed/variable schema [Newbie]

[ste...@activitystream.com]

Hi,

I'm reading up on ClickHouse while looking for an alternative columnar storage/analytics engine for us at Activity Stream and I see a lot to like, thank you.

We have been using Parquet+Drill/Presto for a while and if fits perfectly for some of our use-cases but not as well for others.

Looking at the data types in ClickHouse I see a range of types and the support for complex structures but we need to implement support for "unknown" dimensions (pairs of String,String values) and "unknown" metrics (Pairs of String,Double values) for our tenants as we do not control this part of the schema (or it varies greatly).

Parquet offers a simple way to deal with this using typed Maps and I'm wondering what would be the best way to deal with this scenario in ClickHouse.

Hope someone can shed a light on this or point me to material that may be covering this topic already.

Best regards,

 -Stefán Baxter

[Yegor Andreenko]

You could look at https://clickhouse.yandex/reference_en.html#Nested data structures

We use it to store query parameters

In your case it's

props Nested(String, String) 

or 

props Nested(String, Double)

[ste...@activitystream.com]

Hi Yegor,

This approach seems to have considerable performance implications, is that incorrect?

Regards,

 -Stefán