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我正在尝试优化我的速度过慢的 DataGridView，它使用 SQLite 数据库来使用虚拟模式和缓存获取数据，我已经使用了双缓冲的技巧并删除了列和行的自动调整大小。然而，尽管阅读了这个：http: //msdn.microsoft.com/en-us/library/ha5xt0d9.aspx 和那个：http: //msdn.microsoft.com/en-us/library/ha5xt0d9.aspx

我的网格非常慢，实际上对数据库的查询非常快，但似乎 DataGridView 的绘制速度非常慢，即使数据已经通过缓存加载...

但也许我的 Cache 类不是那么好，所以我想知道我是否做错了什么。原理很简单，一个Cache分为3个部分：Upper、Current（也可以称为“Middle”和Lower），每个部分由索引（start & end）分隔，如果已经加载了数据，Cache会给出根据那些非常简单的规则的值：

  • 如果值在当前部分没问题，只需加载数据
  • 如果需要的值是在上还是下，没有问题，这部分成为当前部分，只需要一个新部分。

IE

上部分：0 - 100 当前部分：101 - 201 下部分：202 - 302

需要的值在 Lower Part 之内，没有问题，Current 变为 Lower，Upper 变为 Current，只需要重新加载新的 Lower Part。显然，如果需要的值具有缓存不可用的行索引，则重新加载该值。

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;
        }
    }
}

但是哎呀……画得太慢了……我该怎么办……？

4

1 回答 1

2

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对向上或向下滚动的偏移量产生任何混淆（是的，懒惰的方式，所以它不是那种......高效但仍然不仅仅是没有缓存非常容易使用[即不使用 3 个缓存，但最终它只提供了一个用于正确完成工作的缓存]）：

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，而且效果很好，不用大惊小怪，不用想那么多……

此代码段可用于使用 RowId 字段而不是主键（实际上不是真正的字段）创建 SQLite 数据库表查看器。

另一个更好的解决方案是通过... asc 或 desc 按顺序获取数据，然后使用模运算符查找此类数据，但我懒得执行该任务。我猜 SQLite dll 仍然比使用预先存在的 DataColumn 作为 PrimaryKey 更快地获取数据顺序......但正如我所说，我现在很懒惰......

于 2013-05-04T10:10:47.630 回答