lance-format/lance

Don't materialize any data on `count_rows` if the filter can be satisfied by a scalar index

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#2,682 opened on Aug 2, 2024

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Description

If we can satisfy a filter with a scalar index then we should be able to implement a fast path for count_rows where we simply return the size of the allow_list or even possibly subtract the size of the block_list from the metadata-only count_rows (might be some tricky bits if there are deletion vectors) to quickly answer queries like count_rows("x != 'foo'").

Contributor guide

Research direction
Explore the existing count rows implementation and scalar index structures in Lance to identify where a fast path can be added.
Tech stack
rust
Domain
databasebackend
Issue type
Performance
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
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
RustDatabase concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30