DataGridView Optimization
本文关键字：Optimization DataGridView | 更新日期: 2023-09-27 18:03:26
我试图优化我的太慢的DataGridView，它使用SQLite数据库使用虚拟模式和缓存获取数据，我已经使用双缓冲的技巧，并删除自动大小的列和行。然而，尽管读了这些:http://msdn.microsoft.com/en-us/library/ha5xt0d9.aspx那就是:http://msdn.microsoft.com/en-us/library/ha5xt0d9.aspx
我的网格是超级慢，实际上查询数据库是相当快的，但似乎绘画的DataGridView是超级慢，即使数据已经通过缓存加载…
但也许我的缓存类不是好，所以我想知道如果我做错了什么。原理很简单，Cache分为3部分:Upper, Current(也可以称为"Middle"和Lower)，每个部分都由索引(start &end)，如果数据已经加载，缓存将根据这些非常简单的规则给出值:
- 如果值在当前部分没有问题，只需加载数据
- 如果需要的值是在上或下，没有问题，这部分成为当前的，只需要一个新的部分。
。
上半部分:0 - 100现行部分:101 - 201下部:202 - 302
需要的值在Lower Part内，没有问题，Current变为Lower, Upper变为Current，只有新的Lower Part需要重新加载。显然，如果所需值的行索引在缓存中不可用，则会重新加载这个值。
public class Cache
{
private Dictionary<PagePart, Page> _pages;
public Dictionary<PagePart, Page> Pages
{
get { return this._pages; }
set { this._pages = value; }
}
private String _tableName;
public String TableName
{
get { return this._tableName; }
set { this._tableName = value; }
}
private SQLiteConnection _connection;
public SQLiteConnection Connection
{
get { return this._connection; }
set { this._connection = value; }
}
public Cache(String tableName, SQLiteConnection connection)
{
this.Connection = connection;
this.TableName = tableName;
this.Pages = new Dictionary<PagePart, Page>(PageNumber);
IndexRange indexRangeUpper = new IndexRange(0, PageSize);
IndexRange indexRangeCurrent = new IndexRange(PageSize + 1, 2 * PageSize);
IndexRange indexRangeLower = new IndexRange(2 * PageSize + 1, 3 * PageSize);
DataTable dataTableUpper = this.GetDataTableFromTable(indexRangeUpper);
DataTable dataTableCurrent = this.GetDataTableFromTable(indexRangeCurrent);
DataTable dataTableLower = this.GetDataTableFromTable(indexRangeLower);
Page pageUpper = new Page(indexRangeUpper, dataTableUpper);
Page pageCurrent = new Page(indexRangeCurrent, dataTableCurrent);
Page pageLower = new Page(indexRangeLower, dataTableLower);
Pages.Add(PagePart.Upper, pageUpper);
Pages.Add(PagePart.Current, pageCurrent);
Pages.Add(PagePart.Lower, pageLower);
}
private IndexRange GetTableIndexRange()
{
String commandText = String.Format("SELECT MAX(RowId) FROM {0}", this.TableName);
SQLiteCommand command = new SQLiteCommand(commandText, this.Connection);
this.Connection.Open();
command.CommandText = commandText;
String maxRowIdString = command.ExecuteScalar().ToString();
this.Connection.Close();
Int32 maxRowId = Int32.Parse(maxRowIdString);
return new IndexRange(0, maxRowId);
}
public Object GetCellValue(Int32 rowIndex, Int32 columnIndex)
{
Int32 indexLowerStart = Pages[PagePart.Lower].Range.StartIndex;
Int32 indexLowerEnd = Pages[PagePart.Lower].Range.EndIndex;
Int32 indexCurrentStart = Pages[PagePart.Current].Range.StartIndex;
Int32 indexCurrentEnd = Pages[PagePart.Current].Range.EndIndex;
Int32 indexUpperStart = Pages[PagePart.Upper].Range.StartIndex;
Int32 indexUpperEnd = Pages[PagePart.Upper].Range.EndIndex;
IndexRange indexRangeTable = this.GetTableIndexRange();
Int32 indexTableStart = indexRangeTable.StartIndex;
Int32 indexTableEnd = indexRangeTable.EndIndex;
// Using the cache...
if ((indexUpperStart <= rowIndex) && (rowIndex <= indexLowerEnd))
{
if ((indexLowerStart <= rowIndex) && (rowIndex <= indexLowerEnd))
{
if (indexTableEnd > indexLowerEnd)
{
this.Pages[PagePart.Upper] = this.Pages[PagePart.Current];
this.Pages[PagePart.Current] = this.Pages[PagePart.Lower];
IndexRange indexRangeLower = new IndexRange(this.Pages[PagePart.Current].Range.EndIndex + 1, this.Pages[PagePart.Current].Range.EndIndex + PageSize);
DataTable dataTableLower = this.GetDataTableFromTable(indexRangeLower);
Page pageLower = new Page(indexRangeLower, dataTableLower);
this.Pages[PagePart.Lower] = pageLower;
Int32 pageSize = this.Pages[PagePart.Current].Data.Rows.Count;
return this.Pages[PagePart.Current].Data.Rows[rowIndex % pageSize][columnIndex];
}
else
{
Int32 pageSize = this.Pages[PagePart.Lower].Data.Rows.Count;
return this.Pages[PagePart.Lower].Data.Rows[rowIndex % pageSize][columnIndex];
}
}
if ((indexCurrentStart <= rowIndex) && (rowIndex <= indexCurrentEnd))
{
Int32 pageSize = this.Pages[PagePart.Current].Data.Rows.Count;
return this.Pages[PagePart.Current].Data.Rows[rowIndex % pageSize][columnIndex];
}
if ((indexUpperStart <= rowIndex) && (rowIndex <= indexUpperEnd))
{
if (indexTableStart < indexUpperStart)
{
this.Pages[PagePart.Lower] = this.Pages[PagePart.Current];
this.Pages[PagePart.Current] = this.Pages[PagePart.Upper];
IndexRange indexRangeUpper = new IndexRange(this.Pages[PagePart.Current].Range.StartIndex - 1, this.Pages[PagePart.Current].Range.EndIndex - PageSize);
DataTable dataTableUpper = this.GetDataTableFromTable(indexRangeUpper);
Page pageUpper = new Page(indexRangeUpper, dataTableUpper);
this.Pages[PagePart.Upper] = pageUpper;
Int32 pageSize = this.Pages[PagePart.Current].Data.Rows.Count;
return this.Pages[PagePart.Current].Data.Rows[rowIndex % pageSize][columnIndex];
}
else
{
Int32 pageSize = this.Pages[PagePart.Upper].Data.Rows.Count;
return this.Pages[PagePart.Upper].Data.Rows[rowIndex % pageSize][columnIndex];
}
}
return null;
}
// Need to reload the cache...
else
{
IndexRange indexRangeCurrent = new IndexRange(rowIndex - (PageSize / 2), rowIndex + (PageSize / 2));
IndexRange indexRangeLower = new IndexRange(indexRangeCurrent.EndIndex + 1, indexRangeCurrent.EndIndex + PageSize);
IndexRange indexRangeUpper = new IndexRange(indexRangeCurrent.StartIndex - 1, indexRangeCurrent.StartIndex - PageSize );
DataTable dataTableUpper = this.GetDataTableFromTable(indexRangeUpper);
DataTable dataTableCurrent = this.GetDataTableFromTable(indexRangeCurrent);
DataTable dataTableLower = this.GetDataTableFromTable(indexRangeLower);
Page pageUpper = new Page(indexRangeUpper, dataTableUpper);
Page pageCurrent = new Page(indexRangeCurrent, dataTableCurrent);
Page pageLower = new Page(indexRangeLower, dataTableLower);
Pages[PagePart.Upper] = pageUpper;
Pages[PagePart.Current] = pageCurrent;
Pages[PagePart.Lower] = pageLower;
Int32 pageSize = this.Pages[PagePart.Current].Data.Rows.Count;
return this.Pages[PagePart.Current].Data.Rows[rowIndex % pageSize][columnIndex];
}
}
private DataTable GetDataTableFromTable(IndexRange indexRange)
{
if (this.Connection != null)
{
String commandText = String.Format("SELECT * FROM {0} WHERE RowId BETWEEN {1} AND {2}", this.TableName, indexRange.StartIndex, indexRange.EndIndex);
SQLiteCommand command = new SQLiteCommand(commandText, this.Connection);
SQLiteDataAdapter dataAdapter = new SQLiteDataAdapter(command);
DataTable dataTable = new DataTable(this.TableName, this.TableName);
dataAdapter.Fill(dataTable);
return dataTable;
}
else
{
return null;
}
}
private const Int32 PageNumber = 3;
private const Int32 PageSize = 128;
public class Page
{
public Page(IndexRange range, DataTable data)
{
this.Range = range;
this.Data = data;
}
private IndexRange _range;
public IndexRange Range
{
get { return this._range; }
set { this._range = value; }
}
private DataTable _data;
public DataTable Data
{
get { return this._data; }
set { this._data = value; }
}
}
public enum PagePart
{
Upper,
Current,
Lower,
}
public class IndexRange
{
private Int32 _startIndex;
public Int32 StartIndex
{
get { return this._startIndex; }
set { this._startIndex = value; }
}
private Int32 _endIndex;
public Int32 EndIndex
{
get { return this._endIndex; }
set { this._endIndex = value; }
}
public IndexRange(Int32 startIndex, Int32 stopIndex)
{
this.StartIndex = startIndex;
this.EndIndex = stopIndex;
}
}
}
但哇…画得太慢了……我该怎么办?
这是回答我自己的问题的一种方法，我只是使用主键来避免任何关于偏移量的混淆，无论我是向上还是向下滚动(是的，懒惰的方式，所以它不是…效率很高，但仍然比完全没有缓存更容易使用[即不使用3个缓存，但最终只有一个缓存可以正确完成工作]):
public class Cache
{
protected SQLiteConnection Connection { get; set; }
protected String TableName { get; set; }
protected const Int32 PageSize = 512;
protected CachePage PageCurrent { get; set; }
protected IndexRange IndexRangeTable { get; set; }
public Cache(SQLiteConnection connection, String tableName)
{
SQLiteConnection.ClearAllPools();
this.Connection = connection;
this.TableName = tableName;
IndexRange indexRangeCurrent = new IndexRange(0, PageSize - 1);
DataTable dataTableCurrent = this.GetDataTableFromTable(indexRangeCurrent);
this.PageCurrent = new CachePage(indexRangeCurrent, dataTableCurrent);
}
public Object GetCellValue(Int32 rowIndex, Int32 columnIndex)
{
DataRow dataRowFound = this.PageCurrent.Data.Rows.Find(rowIndex);
if (dataRowFound != null)
{
return dataRowFound[columnIndex];
}
else
{
this.ShiftPageToIndex(rowIndex);
return GetCellValue(rowIndex, columnIndex);
}
}
private void ShiftPageToIndex(Int32 index)
{
this.PageCurrent.Range.Start = index;
this.PageCurrent.Range.Stop = index + PageSize;
this.PageCurrent.Data = this.GetDataTableFromTable(this.PageCurrent.Range);
this.PageCurrent.Range.Start = index;
this.PageCurrent.Range.Stop = index + this.PageCurrent.Data.Rows.Count;
}
private IndexRange GetTableIndexRange()
{
String commandText = String.Format("SELECT MAX(RowId) FROM {0}", this.TableName);
SQLiteCommand command = new SQLiteCommand(commandText, this.Connection);
this.Connection.Open();
command.CommandText = commandText;
String maxRowIdString = command.ExecuteScalar().ToString();
this.Connection.Close();
Int32 maxRowId = Int32.Parse(maxRowIdString);
return new IndexRange(0, maxRowId);
}
private DataTable GetDataTableFromTable(IndexRange indexRange)
{
if (this.Connection != null)
{
String commandText = String.Format("SELECT * FROM {0} WHERE RowId BETWEEN {1} AND {2}", this.TableName, indexRange.Start, indexRange.Stop);
SQLiteCommand command = new SQLiteCommand(commandText, this.Connection);
SQLiteDataAdapter dataAdapter = new SQLiteDataAdapter(command);
DataTable dataTable = new DataTable(this.TableName, this.TableName);
dataAdapter.Fill(dataTable);
dataTable.Columns.Add("RowId", typeof(Int64));
for (Int32 i = 0; i < dataTable.Rows.Count; i++)
{
dataTable.Rows[i]["RowId"] = i + indexRange.Start;
}
dataTable.PrimaryKey = new DataColumn[] { dataTable.Columns["Rowid"] };
return dataTable;
}
else
{
return null;
}
}
}
public class CachePage
{
public CachePage(IndexRange range, DataTable data)
{
this.Range = range;
this.Data = data;
}
public IndexRange Range {get; set;}
public DataTable Data {get; set;}
}
public class IndexRange
{
public Int32 Start {get; set;}
public Int32 Stop { get; set; }
public IndexRange(Int32 start, Int32 stop)
{
this.Start = start;
this.Stop = stop;
}
}
//如何从虚拟DataGridView调用它?
private void dataGridViewMain_CellValueNeeded(Object sender, DataGridViewCellValueEventArgs e)
{
if (this.Cache != null)
{
e.Value = this.Cache.GetCellValue(e.RowIndex, e.ColumnIndex);
}
}
所以它很酷，不用大惊小怪，不用想那么多就能很好地工作…
这个代码片段可以用来创建一个SQLite数据库表查看器，使用RowId字段而不是Primary Key(它实际上不是一个字段)。
另一个更好的解决方案是按…asc或desc，然后使用模运算符寻找这样的数据，但我太懒了，无法完成这项任务。我猜SQLite dll仍然比使用预先存在的datacolum列作为PrimaryKey更快地获得数据顺序…但正如我所说，我现在很懒…