Загрузить сразу все записи в TStringList

Delphi , Компоненты и Классы , Списки

Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

{ Loading millions of records into a stringlist can be very slow }

 procedure TForm1.SlowLoadingIntoStringList(StringList: TStringList);
 begin
   StringList.Clear;
   with SourceTable do
   begin
     Open;
     DisableControls;
     try
       while not EOF do
       begin
         StringList.Add(FieldByName('OriginalData').AsString);
         Next;
       end;
     finally
       EnableControls;
       Close;
     end;
   end;
 end;

 { This is much, much faster }
 procedure TForm1.QuickLoadingIntoStringList(StringList: TStringList);
 begin
   with CacheTable do
   begin
     Open;
     try
       StringList.Text := FieldByName('Data').AsString;
     finally
       Close;
     end;
   end;
 end;

 { How can this be done? 

  In Microsoft SQL Server 7, you can write a stored procedure that updates every night 
  a cache table that holds all the data you want in a single column and row. 
  In this example, you get the data from a SourceTable and put it all in a Cachetable. 
  The CacheTable has one blob column and must have only one row. 
  Here it is the SQL code: }


 Create Table CacheTable
 (Data Text NULL)
 GO

 Create

  procedure PopulateCacheTable as
   begin
   set NOCOUNT on
   DECLARE @ptrval binary(16), @Value varchar(600) -
   - a good Value for the expected maximum Length
   - - You must set 'select into/bulkcopy' option to True in order to run this sp
   DECLARE @dbname nvarchar(128)
   set @dbname = db_name()
 EXEC sp_dboption @dbname, 'select into/bulkcopy', 'true'
 - - Declare a cursor
 DECLARE scr CURSOR for
 SELECT  OriginalData + char(13) + char(10) - - each line in a TStringList is
 separated by a #13#10
FROM   SourceTable
 - - The CacheTable Table must have only one record
 if EXISTS (SELECT * FROM CacheTable)
 Update CacheTable set Data = ''
 else
 Insert CacheTable VALUES('')
 - - Get a Pointer to the field we want to Update
 SELECT @ptrval = TEXTPTR(Data) FROM CacheTable

 Open scr
 FETCH Next FROM scr INTO @Value
 while @ @FETCH_STATUS = 0
 begin - - This UPDATETEXT appends each Value to the
  end
  of the blob field
 UPDATETEXT CacheTable.Data @ptrval NULL 0 @Value
 FETCH Next FROM scr INTO @Value
 end
 Close scr
 DEALLOCATE scr
 - - Reset this option to False
 EXEC sp_dboption @dbname, 'select into/bulkcopy', 'false'
 end
 GO

 { You may need to increase the BLOB SIZE parameter if you use BDE }

Статья Загрузить сразу все записи в TStringList раздела Компоненты и Классы Списки может быть полезна для разработчиков на Delphi и FreePascal.

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