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Restore sorted cell iteration order with lazy cache #1759

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Merged
tonyqus merged 1 commit into from
Mar 24, 2026
Merged

Restore sorted cell iteration order with lazy cache #1759

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17 changes: 14 additions & 3 deletions main/HSSF/UserModel/HSSFRow.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,7 @@ public class HSSFRow : IRow, IComparable<HSSFRow>

private int rowNum;
private Dictionary<int, ICell> cells = new Dictionary<int, ICell>();
private List<ICell> _sortedCellCache;

/**
* reference to low level representation
Expand Down Expand Up @@ -177,7 +178,7 @@ private void RemoveCell(ICell cell, bool alsoRemoveRecords)
((HSSFCell)cell).NotifyArrayFormulaChanging();
}
cells.Remove(column);

_sortedCellCache = null;

if (alsoRemoveRecords)
{
Expand Down Expand Up @@ -402,6 +403,7 @@ private void AddCell(ICell cell)
// Array.Copy(oldCells, 0, cells, 0, oldCells.Length);
//}
cells[column] = cell;
_sortedCellCache = null;

// fix up firstCol and lastCol indexes
if (row.IsEmpty|| column < row.FirstCol)
Expand Down Expand Up @@ -680,7 +682,7 @@ private short FindFirstCell(int firstcell)
public List<ICell> Cells
{
get {
return new List<ICell>(this.cells.Values);
return new List<ICell>(GetSortedCells());
}
}

Expand Down Expand Up @@ -720,7 +722,7 @@ public bool? Collapsed
/// </remarks>
public IEnumerator<ICell> GetEnumerator()
{
return this.cells.Values.GetEnumerator();
return GetSortedCells().GetEnumerator();
}

/// <summary>
Expand Down Expand Up @@ -789,5 +791,14 @@ public bool HasCustomHeight()
{
throw new NotImplementedException();
}

private List<ICell> GetSortedCells()
{
if (_sortedCellCache == null)
{
_sortedCellCache = cells.OrderBy(kv => kv.Key).Select(kv => kv.Value).ToList();
}
return _sortedCellCache;
}
}
}
16 changes: 14 additions & 2 deletions ooxml/XSSF/Streaming/SXSSFRow.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@ public class SXSSFRow : IRow, IComparable<SXSSFRow>
{
private readonly SXSSFSheet _sheet; // parent sheet
private readonly Dictionary<int, SXSSFCell> _cells = new Dictionary<int, SXSSFCell>();
private List<ICell> _sortedCellCache;
private short _style = -1; // index of cell style in style table
private bool _zHeight; // row zero-height (this is somehow different than being hidden)
private float _height = -1;
Expand All @@ -53,7 +54,7 @@ public virtual bool HasCustomHeight()

public List<ICell> Cells
{
get { return _cells.Values.Select(cell => (ICell) cell).ToList(); }
get { return new List<ICell>(GetSortedCells()); }
}

public short FirstCellNum
Expand Down Expand Up @@ -235,6 +236,7 @@ public ICell CreateCell(int column, CellType type)
CheckBounds(column);
SXSSFCell cell = new SXSSFCell(this, type);
_cells[column] = cell;
_sortedCellCache = null;
UpdateIndexWhenAdd(column);
return cell;
}
Expand Down Expand Up @@ -299,7 +301,7 @@ public ICell GetCell(int cellnum, MissingCellPolicy policy)
}
public IEnumerator<ICell> GetEnumerator()
{
return _cells.Values.GetEnumerator();
return GetSortedCells().GetEnumerator();
}

public void MoveCell(ICell cell, int newColumn)
Expand All @@ -311,6 +313,7 @@ public void RemoveCell(ICell cell)
{
int index = GetCellIndex((SXSSFCell)cell);
_cells.Remove(index);
_sortedCellCache = null;
if (index == _firstCellNum)
{
InvalidateFirstCellNum();
Expand Down Expand Up @@ -373,6 +376,15 @@ IEnumerator IEnumerable.GetEnumerator()
return this.GetEnumerator();
}

private List<ICell> GetSortedCells()
{
if (_sortedCellCache == null)
{
_sortedCellCache = _cells.OrderBy(kv => kv.Key).Select(kv => (ICell)kv.Value).ToList();
}
return _sortedCellCache;
}

/**
* Create an iterator over the cells from [0, getLastCellNum()).
* Includes blank cells, excludes empty cells
Expand Down
52 changes: 34 additions & 18 deletions ooxml/XSSF/UserModel/XSSFRow.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,12 @@ public class XSSFRow : IRow, IComparable<XSSFRow>
/// Avoids O(n) LINQ Max() scan on every LastCellNum access.
/// </summary>
private int _cachedLastCellNum = -1;

/// <summary>
/// Lazily-built list of cells sorted by column index.
/// Null when invalidated; rebuilt on first read access.
/// </summary>
private List<ICell> _sortedCellCache;
#endregion

#region Public properties
Expand Down Expand Up @@ -561,8 +567,8 @@ public CT_Row GetCTRow()
/// </summary>
internal void OnDocumentWrite()
{
var orderedCells = _cells.OrderBy(kv => kv.Key).Select(kv => (XSSFCell)kv.Value).ToList();
var sortedCells = GetSortedCells();

bool isOrdered = true;
if (_row.SizeOfCArray() != _cells.Count)
{
Expand All @@ -571,9 +577,9 @@ internal void OnDocumentWrite()
else
{
int i = 0;
foreach (XSSFCell cell in orderedCells)
foreach (ICell cell in sortedCells)
{
CT_Cell c1 = cell.GetCTCell();
CT_Cell c1 = ((XSSFCell)cell).GetCTCell();
CT_Cell c2 = _row.GetCArray(i++);

string r1 = c1.r;
Expand All @@ -590,7 +596,7 @@ internal void OnDocumentWrite()
{
CT_Cell[] cArray = new CT_Cell[_cells.Count];
int i = 0;
foreach (XSSFCell c in orderedCells)
foreach (XSSFCell c in sortedCells.Cast<XSSFCell>())
{
cArray[i++] = c.GetCTCell();
}
Expand Down Expand Up @@ -653,28 +659,29 @@ internal void RebuildCells()
_row.c.Sort((col1, col2) => col1.r.CompareTo(col2.r));

// Cache is invalid after rebuild — keys may have changed
_sortedCellCache = null;
_cachedFirstCellNum = -1;
_cachedLastCellNum = -1;
}
#endregion

#region IEnumerable and IComparable members
/// <summary>
/// Cell iterator over the physically defined cell
/// Cell iterator over the physically defined cells, sorted by column index.
/// </summary>
/// <returns>an iterator over cells in this row.</returns>
public Dictionary<int, ICell>.ValueCollection.Enumerator CellIterator()
/// <returns>an iterator over cells in this row in ascending column order.</returns>
public IEnumerator<ICell> CellIterator()
{
return _cells.Values.GetEnumerator();
return GetSortedCells().GetEnumerator();
}

/// <summary>
/// Alias for <see cref="CellIterator"/> to allow foreach loops
/// </summary>
/// <returns>an iterator over cells in this row.</returns>
/// <returns>an iterator over cells in this row in ascending column order.</returns>
public IEnumerator<ICell> GetEnumerator()
{
return _cells.Values.GetEnumerator();
return GetSortedCells().GetEnumerator();
}

/// <summary>
Expand Down Expand Up @@ -723,13 +730,7 @@ public List<ICell> Cells
{
get
{
List<ICell> cells = new List<ICell>();
foreach (ICell cell in _cells.Values)
{
cells.Add(cell);
}

return cells;
return new List<ICell>(GetSortedCells());
}
}

Expand Down Expand Up @@ -836,11 +837,25 @@ private int GetLastKey()
return _cells.Keys.Max();
}

/// <summary>
/// Returns cells sorted by column index, using a lazily-built cache.
/// The cache is invalidated on any cell mutation (add/remove/rebuild).
/// </summary>
private List<ICell> GetSortedCells()
{
if (_sortedCellCache == null)
{
_sortedCellCache = _cells.OrderBy(kv => kv.Key).Select(kv => kv.Value).ToList();
}
return _sortedCellCache;
}

/// <summary>
/// Update cached min/max on cell addition. O(1) — just compare with current bounds.
/// </summary>
private void UpdateCacheOnAdd(int columnIndex)
{
_sortedCellCache = null;
if (_cachedFirstCellNum < 0 || columnIndex < _cachedFirstCellNum)
{
_cachedFirstCellNum = columnIndex;
Expand All @@ -857,6 +872,7 @@ private void UpdateCacheOnAdd(int columnIndex)
/// </summary>
private void InvalidateCacheOnRemove(int removedIndex)
{
_sortedCellCache = null;
if (_cells.Count == 0)
{
_cachedFirstCellNum = -1;
Expand Down
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