Vector search lower recall when there is multiple ColumnFile in delta layer with vector index

[Lloyd-Pottiger]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. create a table with vector type column
2. insert more than 10K rows
3. vector search

2. What did you expect to see? (Required)

recall > 90%

3. What did you see instead (Required)

recall < 20%

4. What is your TiFlash version? (Required)

master

[Lloyd-Pottiger]

Introduce by https://github.com/pingcap/tiflash/pull/9547