cube-js/cube

Native distinct counts in ClickHouse dialect

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#2,334 opened on Mar 11, 2021

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 (2 comments) (1 reaction) (0 assignees)Rust (1,965 forks)batch import
driver:clickhousegood first issuehelp wanted

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Description

Is your feature request related to a problem? Please describe. ClickHouse supports a number of functions to count distinct values: uniq, uniqExact, uniqHLL12. However, they are not used in ClickHouseQuery adapter to support countDistinctApprox and other types of aggregations.

Describe the solution you'd like With the guidance of the Cube.js team and taking other adapters as examples, these functions should be used in the adapter.

Describe alternatives you've considered —

Additional context Without this feature, countDistinctApprox is not supported at all, and — I think — countDistinct works slower than it could.

Contributor guide

Research direction
Examine the ClickHouseQuery adapter in cubejs schema compiler/src/adapter/ClickHouseQuery.js and add support for uniq, uniqExact, and uniqHLL12 functions for count distinct aggregations, following the pattern of other database adapters.
Tech stack
javascript
Domain
backenddatabase
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitJavaScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80