[fpc-pascal] How to save a huge XML?

[Michael Van Canneyt]

On Tue, 18 Jun 2013, Marcos Douglas wrote:

> On Tue, Jun 18, 2013 at 9:39 AM, Antonio Fortuny
> <a.fortuny at sitasoftware.lu> wrote:
>>
>>
>> Le 18/06/2013 14:35, Marcos Douglas a écrit :
>>
>> Hi,
>>
>> I need to save some huge XML files in HD.
>> Today I call WriteXMLFile(Doc, AFileName) but I have XML with 5G, 10G.. 30G...
>>
>> What the best way to save "line by line"?
>>
>> Append chuncks of lines to a TFileStream until source XML file is exhausted
>
> But I'm using TXMLDocument class to make the XML.
>
> For each line (log) I do this:
> (doesn't matter the information in Par variable)
>
> procedure TXMLLogger.Log;
> var
>  I: Integer;
>  No: TDOMElement;
>  Par: TParam;
> begin
>  No := FDoc.CreateElement('line');
>  for I := 0 to FParams.Count-1 do
>  begin
>    Par := FParams.Items[I];
>    TDOMElement(No).SetAttribute(Par.Name, Par.AsString);
>  end;
>  FRootNode.AppendChild(No);
>
>  FParams.Clear;
> end;
>
> At the end, I do some like:
> procedure TXMLLogger.Finish;
> var
>  No: TDOMElement;
> begin
>  No := FDoc.CreateElement('finish');
>  TDOMElement(No).SetAttribute('dh', FmtDateTime(Now));
>  FRootNode.AppendChild(No);
> end;
>
> And the application call:
> procedure TXMLLogger.SaveToFile(const AFileName: string);
> begin
>  WriteXMLFile(FDoc, AFileName);
> end;
>
> So, there is a way to use TXMLDocument but save line by line more faster?
>

No. 
The writer already uses a fixed buffer. Your problem is the use of TXMLDocument.

Simply put: logging to XML (worse: using DOM) is a VERY bad idea.

Michael.