pingcap / pingcap/tiflash

Support late materialization

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#5,829 1 comment 0 reactions 1 assignee View on GitHub

@Lloyd-Pottiger is already working on this.

Since Oct 14, 2022.

component/storage type/feature-request type/performance
Dominant language
C++
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Description

Feature Request

Is your feature request related to a problem? Please describe:

For some query like select * from t where a + b <> 0;, we now scan all columns and then do filter, which is heavy and we can do better.

Describe the feature you'd like:

Support late materialization. We can scan column(s) at first to filter out unnecessary data segment, and then just scan the rest columns.

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

Subtask:

  • support late materialization in Selection
  • support late materialization in fast scan
  • support late materialization in disaggregated TiFlash
  • better scan context after some filter conditions pushed down
  • (optional) support push down TopN
  • (optional) support late materialization in Join

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