test: Querying files from a large number of files takes time

[simlecode]

关联的Issues (Related Issues)

改动 (Proposed Changes)

测试 piecestorage 存在大量文件时查找文件的耗时。

file name tmp_0_1103 took 1.660636479s
file name 3_555 took 112.515107ms
file name tmp_6_2760 took 1.614398641s
file name 9_369 took 256.373337ms
file name tmp_12_1706 took 1.624127085s
file name 15_369 took 46.811549ms

附注 (Additional Info)

自查清单 (Checklist)

在你认为本 PR 满足被审阅的标准之前，需要确保 / Before you mark the PR ready for review, please make sure that:

• 符合Venus项目管理规范中关于PR的相关标准 / The PR follows the PR standards set out in the Venus project management guidelines
• 具有清晰明确的commit message / All commits have a clear commit message.
• 包含相关的的测试用例或者不需要新增测试用例 / This PR has tests for new functionality or change in behaviour or not need to add new tests.
• 包含相关的的指南以及文档或者不需要新增文档 / This PR has updated usage guidelines and documentation or not need
• 通过必要的检查项 / All checks are green

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c06a473) 25.48% compared to head (f404211) 25.49%.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #507   +/-   ##
=======================================
  Coverage   25.48%   25.49%           
=======================================
  Files         178      178           
  Lines       21068    21068           
=======================================
+ Hits         5370     5371    +1     
+ Misses      14788    14787    -1     
  Partials      910      910           

Flag	Coverage Δ
unittests	25.49% <ø> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

see 1 file with indirect coverage changes

[LinZexiao]

LGTM