On Tue, 17 Jul 2012, Martin Schreiber wrote:
On Monday 16 July 2012 17:25:58 [email protected] wrote:
On Mon, 16 Jul 2012, Martin Schreiber wrote:
On Monday 16 July 2012 16:50:06 [email protected] wrote:
Well, from your code adding the following to the protected section:
Property ValueBuffer : Pointer Read FValueBuffer;
Property Validating : Boolean Read FValidating ;
Should be enough to remove the need for the TFieldCracker ?
Unfortunately no:
"
procedure tmsebufdataset.checkfreebuffer(const afield: tfield);
begin
{$ifdef FPC}{$warnings off}{$endif}
with tfieldcracker(afield) do begin
{$ifdef FPC}{$warnings on}{$endif}
if foffset and 2 <> 0 then begin
freemem(fvaluebuffer);
fvaluebuffer:= nil;
end;
end;
end;
"
If I understand correctly, you have in the record buffer just the pointer
of the (wide)string instead of the actual string data ?
Correct. The UnicodeString pointer. That has not directly to do with the
procedure above BTW. This one is to allow changing field values in OnValidate
IIRC.
If so, why then didn't you implement the string fields as blobs are
implemented in SQLDB (it is basically the same problem), in that case you
would not need the internal fields of TField at all ?
Maybe, but what about performance? Another complication is the "updatebuffer"
with the "oldvalues".
Thinking about it:
I would allocate the buffer as is, with for all string fields an
integer-sized slot in the buffer. The slot contains an index, pointing
to a separate array of strings containing N*M*2 strings. (N=number of
records, M= Number of string fields per record, factor 2 for old values)
Field value = Element [Index [+1 for old value]] in the array.
where the [Index] is stored in the buffer.
The speed performance penalty of this system should be negligable, since you
assume all records are in memory anyway.
And: everything can be done without meddling with the internals of TField.
Michael.
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