Add calculation cache to improve CalcCellValue performance

[DengY11]

PR Details

Add calculation cache to improve CalcCellValue performance

Description

Implements a calculation cache mechanism for CalcCellValue to significantly improve performance when calculating formulas repeatedly. The cache stores calculated results and automatically invalidates when cells are modified.

Related Issue

Fixes #2057 - Performance enhancement - cache calculated values

Motivation and Context

As described in #2057, Excelize doesn't cache calculated values from CalcCellValue, causing expensive formulas to be recalculated every time they are referenced by other cells. This leads to poor performance when dealing with complex formula dependencies.

Example scenario:

A1: 40
A2: =VERYEXPENSIVEFUNCTION()  // takes 100ms
A3: =A1+A2                    // takes 100ms (recalculates A2)

Solution implemented:

• Cache calculated results in thread-safe sync.Map
• Clear entire cache when any SetCellX() function is called
• Cache key format: "sheet!cell"

Performance improvement:

• First calculation: ~150µs (calculated and cached)
• Second calculation: ~600ns (from cache, 250x faster)

How Has This Been Tested

go test -v -run "TestCalc.*Cache|TestSetFunctionsClearCache"
go test ./...

Test coverage includes:

• ☑️ Basic cache hit/miss scenarios
• ☑️ Cache invalidation on cell modifications
• ☑️ Multi-cell formula dependencies
• ☑️ All 12 Set functions properly clear cache
• ☑️ Thread safety
• ☑️ 3 new comprehensive test functions added

Types of changes

☑️ New feature (non-breaking change which adds functionality)
☐ Docs change / refactoring / dependency upgrade
☐ Bug fix (non-breaking change which fixes an issue)
☐ Breaking change (fix or feature that would cause existing functionality to change)

Checklist

☑️ My code follows the code style of this project.
☐ My change requires a change to the documentation.
☐ I have updated the documentation accordingly.
☑️ I have read the CONTRIBUTING document.
☑️ I have added tests to cover my changes.
☑️ All new and existing tests passed.

Implementation Details

Modified Files:

• excelize.go: Added cache fields (calcCache sync.Map, calcCacheMu sync.RWMutex) to File struct
• calc.go: Implemented caching logic in CalcCellValue() + added clearCalcCache() helper
• cell.go: Added cache clearing to all 12 Set functions
• calc_test.go: Added 3 comprehensive cache test functions

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.23%. Comparing base (b65c16b) to head (840ad9c).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2144   +/-   ##
=======================================
  Coverage   99.23%   99.23%           
=======================================
  Files          32       32           
  Lines       30276    30326   +50     
=======================================
+ Hits        30045    30095   +50     
  Misses        153      153           
  Partials       78       78           

Flag	Coverage Δ
unittests	99.23% <100.00%> (+<0.01%)	⬆️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[xuri]

Thanks for your PR. We need add any cache cautiously, after these changes we also need remove cache in following scenario:

• RemoveCol
• RemoveRow
• DuplicateRow
• DuplicateRowTo
• SetSheetCol

And update or delete cache when:

• SetSheetName
• DeleteSheet

Consider if other scenario needed.

[DengY11]

Thanks for your PR. We need add any cache cautiously, after these changes we also need remove cache in following scenario:

• RemoveCol
• RemoveRow
• DuplicateRow
• DuplicateRowTo
• SetSheetCol

And update or delete cache when:

• SetSheetName
• DeleteSheet

Consider if other scenario needed.

Thanks for your quick respond!
sorry for missing a few spots where we needed to clear the CalcCellValue cache in my first commit. After taking another look and with some great input, I think we've got all a_bases covered now.
Here’s a quick rundown of where we’ve added the f.clearCalcCache() calls:
These are the functions we sorted out earlier, based on what was initially asked for and our first round of checks:
RemoveCol ✅
RemoveRow ✅
DuplicateRow ✅
DuplicateRowTo ✅
SetSheetCol ✅
SetSheetName ✅
DeleteSheet ✅
SetCellValue ✅
SetCellInt ✅
SetCellUint ✅
SetCellBool ✅
SetCellFloat ✅
SetCellStr ✅
SetCellDefault ✅
SetCellFormula ✅
SetCellRichText ✅
SetCellHyperLink ✅

New additions in this commit:
While double-checking things more recently, we found a few more functions that also mess with the sheet in ways that would need the cache to be cleared. So, I've added the cache clearing to these in the latest changes:
MergeCell ✅
UnmergeCell ✅
InsertCols ✅
InsertRows ✅
CopySheet ✅
MoveSheet ✅

[xuri]

Code conflicts need resolve.

[DengY11]

Code conflicts need resolve.

so sorry, the conflict was caused by my local auto-formatting. I've resolved it by keeping the original content from master