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Carefully consider flows_raw sorting key #30

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leoluk opened this issue May 28, 2020 · 1 comment

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leoluk commented May 28, 2020

Optimize for main dasboard queries.
Low-cardinality values first for easy filtering (verify that this does what we think it does).
Sequence Num for sampling, but how? It's as high-cardinality as it gets.
Play with secondary idexes - are they more efficient than a carefully-considered sorting key?

leoluk added this to the v1.0.0 milestone

fionera added the clickhouse label

UnamedRus commented Dec 26, 2022 •

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Play with secondary idexes - are they more efficient than a carefully-considered sorting key?

No, they ~only make sense if you have some data locality for column used in skip index, (so there is some correlation between that column and table ORDER BY key) Some examples https://kb.altinity.com/altinity-kb-queries-and-syntax/skip-indexes/

Sequence Num for sampling, but how? It's as high-cardinality as it gets.

Sampling only make sense if you have good distribution of data across whole number range (min-max)

https://kb.altinity.com/altinity-kb-queries-and-syntax/altinity-kb-sample-by/

fionera removed this from the v1.0.0 milestone

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