我有一個非常好的DirectMySQL單元,它已準備就緒,我希望它是一個TDataset後代,因此我可以將它與QuickReport一起使用,我只是希望與來自TDataset的後代的DirectMySQL進行MySQL查詢。TDataSet Descendant
一切都很好,直到我試圖訪問一個有10.000行和更多的大表。這是不穩定的,錯誤是不可預知的,並不總是顯示,但它可能發生在你與其他表玩。它發生在GetFieldData(Field:TField; Buffer:Pointer):boolean;用於從MySQL行獲取字段值。
下面的代碼,
function TMySQLQuery.GetFieldData(Field: TField; Buffer: Pointer): Boolean;
var
I, CT: Integer;
Row: TMySQL_Row;
TBuf: PChar;
FD: PMySQL_FieldDef;
begin
UpdateCursorPos; ------------> This code is after i got the error but no result
Resync([]); ------------> This code is after i got the error but no result
Result := false;
Row := oRecordset.CurrentRow;
I := Field.FieldNo-1;
FD := oRecordset.FieldDef(I);
if Not Assigned(FD) then
FD := oRecordset.FieldDef(I);
TBuf := PP(Row)[i];
Try
CT := MySQLWriteFieldData(fd.field_type, fd.length, fd.decimals, TBuf, PChar(Buffer));
Result := Buffer <> nil;
Finally
Row := nil; ------------> This code is after i got the error but no result
FD := nil; ------------> This code is after i got the error but no result
TBuf := nil; ------------> This code is after i got the error but no result
Buffer := nil; ------------> This code is after i got the error but no result
End;
end;
{
These codes below are to translate the data type
from MySQL Data type to a TDataset data type
and move mysql row (TBuf) to TDataset buffer to display.
And error always comes up from this function
when moving mysql row to buffer.
}
function TMySQLQuery.MySQLWriteFieldData(AType: byte;
ASize: Integer; ADec: cardinal; Source, Dest: PChar): Integer;
var
VI: Integer;
VF: Double;
VD: TDateTime;
begin
Result := MySQLDataSize(AType, ASize, ADec);
case AType of
FIELD_TYPE_TINY, FIELD_TYPE_SHORT, FIELD_TYPE_LONG, FIELD_TYPE_LONGLONG,
FIELD_TYPE_INT24:
begin
if Source <> '' then
VI := StrToInt(Source)
else
VI := 0;
Move(VI, Dest^, Result);
end;
FIELD_TYPE_DECIMAL, FIELD_TYPE_NEWDECIMAL:
begin
if source <> '' then
VF := internalStrToCurr(Source)
else
VF := 0;
Move(VF, Dest^, Result);
end;
FIELD_TYPE_FLOAT, FIELD_TYPE_DOUBLE:
begin
if Source <> '' then
VF := InternalStrToFloat(Source)
else
VF := 0;
Move(VF, Dest^, Result);
end;
FIELD_TYPE_TIMESTAMP:
begin
if Source <> '' then
VD := InternalStrToTimeStamp(Source)
else
VD := 0;
Move(VD, Dest^, Result);
end;
FIELD_TYPE_DATETIME:
begin
if Source <> '' then
VD := InternalStrToDateTime(Source)
else
VD := 0;
Move(VD, Dest^, Result);
end;
FIELD_TYPE_DATE:
begin
if Source <> '' then
VD := InternalStrToDate(Source)
else
VD := 0;
Move(VD, Dest^, Result);
end;
FIELD_TYPE_TIME:
begin
if Source <> '' then
VD := InternalStrToTime(Source)
else
VD := 0;
Move(VD, Dest^, Result);
end;
FIELD_TYPE_STRING, FIELD_TYPE_VAR_STRING,
FIELD_TYPE_ENUM, FIELD_TYPE_SET:
begin
if Source = nil then
Dest^ := #0
else
Move(Source^, Dest^, Result);
end;
Else
Result := 0;
Raise EMySQLError.Create('Write field data - Unknown type field');
end;
end;
我現在的猜測是它的內存相關的問題。
我堆放。任何人可以幫忙? 我還需要TDataset文檔列出可用後代函數以及如何使用它,或者如何從TDataset派生後代。任何人有他們?我缺乏這種心態。
methinks - TL; DR。 Delphi還提供TDataSet文檔和源代碼。無論如何,MySQL並不能真正處理大型行集。 – 2010-12-20 03:30:03