TBufDataset is behaving in a very odd way from Release to Debug, and
going boom!
lazarus / 16-Databases

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Gustavo 'Gus' Carreno · 2023-09-26 23:00

TBufDataset is behaving in a very odd way from Release to debug, and
going boom!

Hey Y'all!!

I'm playing around with in memory tables.
Had a wee Google and found this: How to write in-memory database
applications in Lazarus/FPC.

So I went and started by playing with TMemDataset: Test Memory
Dataset.

So, with confidence from the above Lazarus Wiki entry, I proceeded to
do the exact same test app but using TBufDataset.

Immediately I found myself in trouble because:
Build Mode Default: After the first push of the Add Data button
inserts 3 rows, no data shows and on a subsequent push of the same
button we get an AV right on the first Post, as you can see on image
1.Build Mode Debug: The app does not give us an AV, but the data shown
in the DBGrid is rather suspicious, as you can see on image 2. And in
image 3 you see the very top of the humongous heaptrc log
produced.Build Mode Release: Behaves the same way as Build Mode
Default.
I'm completely baffled by this whole thing and I come here, very
humbled, to ask for your, very appreciated, help.

I'm attaching the code of the buggy TestBufferDataset attempt.

Many, oh so, many thanks in advance!!

EDIT: I forgot to mentions that I tested this on an Ubuntu 20.04 64b
with both Lazarus 2.2.6 and main(aka trunk)

Cheers,
Gus
--
Image 1:
(https://pasteboard.co/EzyWaNkWt11K.png)

Image 2:
(https://pasteboard.co/CpAFTaL63Dlc.png)

Image 3:
(https://pasteboard.co/etyXISEgRjVt.png)

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rvk · 2023-09-27 08:35

Creating the TBufDataset in code seems to work better.
I suspect that defining the fields in the Object Inspector is the
problem.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TfrmMain.FormCreate(Sender: TObject);//...  bdsAccounts :=
TBufDataset.Create(nil);  bdsAccounts.FieldDefs.Add('HASH', ftString,
50);  bdsAccounts.FieldDefs.Add('Alias', ftString, 50); 
bdsAccounts.FieldDefs.Add('Label', ftString, 50); 
bdsAccounts.FieldDefs.Add('Pending', ftCurrency, 0, 15, false, false,
4, 0);  bdsAccounts.FieldDefs.Add('Balance', ftCurrency, 0, 15, false,
false, 5, 0);  bdsAccounts.CreateDataset;  bdsAccounts.Open;  
dsAccounts.DataSet := bdsAccounts;  dsAccounts.Enabled := true;
(On Windows it also gives strange results when doing it design-time.)

----------------------------------------------------------------------
wp · 2023-09-27 08:41

Is there a reason why you did not set the BufDataset's Filename? I am
not sure if it is possible at all to use TBufdataset without a file,
buf even if it is you will lose all records when the application
terminates.

Second issue: persistent fields. Once you have persistent fields you
cannot access fields by FieldByName[fieldname], but only by their
variable name, e.g. bdsAccountsBalance rather than
bdsAccounts.FieldByName['Balance']. An annoyance which I already hated
in my Delphi times...

I deleted the persistent fields from the lfm file, added a Filename to
the bdsAccounts dataset and made sure that the dataset is created
properly - now the application does not crash any more:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TfrmMain.FormCreate(Sender: TObject);begin  Caption:= Format('%s v%s',
[ Application.Title, cVersion ]);  InitShortcuts; 
Application.OnHint:= @DisplayHint;  bdsAccounts.FileName :=
'test.db';  if not FileExists(bdsAccounts.FileName) then   
bdsAccounts.CreateDataset;  bdsAccounts.Open;end;
Still... Clear does not seam to work. It clears the dataset in the
current session, but when the app starts another time the data are
back again.

Filtering seems to crash the application still. Well - I would not
execute the filter in the OnChange event of the edit control, I would
add a button to toggle bdsAccounts.Filtered and use the edit filter
text once it is completed. This works, but I don't understand why your
code report "Index based on unknown field" while typing the
condition...

----------------------------------------------------------------------
paweld · 2023-09-27 08:43

As @rvk wrote define dataset in code and:
1. for DBGrid, you don't need to call BeginUpdate and EndUpdate -
everything happens automatically when you change DataSet. when doing a
lot of data editing, it is recommended to use DisableControls and
EnableCotrols for DataSet  
2. using the Clear medtode for a DataSet will clear not only the data
but also the field definitions
3. currency has precision to 4 decimal places
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
Forms.Main; {$mode objfpc}{$H+} interface uses  Classes, SysUtils,
BufDataset, DB, Forms, Controls, Graphics, Dialogs, Menus, ActnList,
ComCtrls, StdActns, ExtCtrls, StdCtrls, DBGrids; type   { TfrmMain }  
TfrmMain = class(TForm)    actAccountsAddData: TAction;   
actAccountsClearData: TAction;    alMain: TActionList;    actFileExit:
TFileExit;    btnAccountsAddData: TButton;    btnAccountsClearData:
TButton;    bdsAccounts: TBufDataset;    dsAccounts: TDataSource;   
dgAccounts: TDBGrid;    edtAccountsFilterByAlias: TEdit;    gbFilter:
TGroupBox;    lblFilterByAlias: TLabel;    mnuFile: TMenuItem;   
mnuFileExit: TMenuItem;    mmMain: TMainMenu;    panButtons: TPanel; 
 sbMain: TStatusBar;    procedure FormCreate(Sender: TObject);   
procedure alMainUpdate(AAction: TBasicAction; var Handled: Boolean); 
 procedure actAccountsAddDataExecute(Sender: TObject);    procedure
actAccountsClearDataExecute(Sender: TObject);    procedure
edtAccountsFilterByAliasChange(Sender: TObject);    procedure
FormDestroy(Sender: TObject);  private    procedure InitShortcuts;   
procedure DisplayHint(Sender: TObject);    procedure CreateDBDef; 
public   end; var  frmMain: TfrmMain; implementation uses 
LCLType; const  cVersion = '0.1.0'; {$R *.lfm} { TfrmMain } procedure
TfrmMain.FormCreate(Sender: TObject);begin  Caption:= Format('%s v%s',
[ Application.Title, cVersion ]);  InitShortcuts; 
Application.OnHint:= @DisplayHint;  CreateDBDef; 
bdsAccounts.Open;end; procedure TfrmMain.InitShortcuts;begin{$IFDEF
UNIX}  actFileExit.ShortCut := KeyToShortCut(VK_Q,
[ssCtrl]);{$ENDIF}{$IFDEF WINDOWS}  actFileExit.ShortCut :=
KeyToShortCut(VK_X, [ssAlt]);{$ENDIF}end; procedure
TfrmMain.DisplayHint(Sender: TObject);begin  sbMain.SimpleText:=
GetShortHint(Application.Hint);end; procedure
TfrmMain.CreateDBDef;var  i: Integer;begin  bdsAccounts.Clear; 
bdsAccounts.FieldDefs.Add('HASH', ftString, 50); 
bdsAccounts.FieldDefs.Add('Alias', ftString, 50); 
bdsAccounts.FieldDefs.Add('Label', ftString, 50); 
bdsAccounts.FieldDefs.Add('Pending', ftCurrency); 
bdsAccounts.FieldDefs.Add('Balance', ftCurrency); 
bdsAccounts.IndexDefs.Add('idx_hash', 'HASH', [ixCaseInsensitive]); 
bdsAccounts.CreateDataset;  bdsAccounts.IndexFieldNames := 'HASH'; 
for i := 0 to bdsAccounts.Fields.Count - 1 do  begin    if
bdsAccounts.Fields[i].DataType = ftCurrency then     
TNumericField(bdsAccounts.Fields[i]).DisplayFormat:= '#,##0.0000 N'; 
end;end; procedure TfrmMain.alMainUpdate(AAction: TBasicAction; var
Handled: Boolean);begin  if AAction = actAccountsClearData then 
begin    actAccountsClearData.Enabled:= bdsAccounts.RecordCount > 0; 
 Handled:= True;  end;end; procedure
TfrmMain.actAccountsAddDataExecute(Sender: TObject);begin 
bdsAccounts.Insert;  bdsAccounts.FieldByName('HASH').AsString:=
'N2983096817236';  bdsAccounts.FieldByName('Alias').AsString:= 'Alias
1';  bdsAccounts.FieldByName('Label').AsString:= 'Label 1'; 
bdsAccounts.FieldByName('Pending').AsCurrency:= 0.0; 
bdsAccounts.FieldByName('Balance').AsCurrency:= 1000.0; 
bdsAccounts.Append;   bdsAccounts.Insert; 
bdsAccounts.FieldByName('HASH').AsString:= 'N2983096817696'; 
bdsAccounts.FieldByName('Alias').AsString:= 'Alias 2'; 
bdsAccounts.FieldByName('Label').AsString:= 'Label 2'; 
bdsAccounts.FieldByName('Pending').AsCurrency:= 0.0; 
bdsAccounts.FieldByName('Balance').AsCurrency:= 2000.0; 
bdsAccounts.Append;   bdsAccounts.Insert; 
bdsAccounts.FieldByName('HASH').AsString:= 'N2983696817236'; 
bdsAccounts.FieldByName('Alias').AsString:= 'Alias 3'; 
bdsAccounts.FieldByName('Label').AsString:= 'Label 3'; 
bdsAccounts.FieldByName('Pending').AsCurrency:= 0.0; 
bdsAccounts.FieldByName('Balance').AsCurrency:= 3000.0; 
bdsAccounts.Append;   bdsAccounts.Last;  
dgAccounts.AutoAdjustColumns;end; procedure
TfrmMain.actAccountsClearDataExecute(Sender: TObject);begin 
bdsAccounts.DisableControls;  bdsAccounts.First;  while not
bdsAccounts.EOF do    bdsAccounts.Delete; 
bdsAccounts.EnableControls;end; procedure
TfrmMain.edtAccountsFilterByAliasChange(Sender: TObject);begin  if
Trim(edtAccountsFilterByAlias.Text) = '' then    bdsAccounts.Filtered
:= False  else  begin    bdsAccounts.FilterOptions:=
[foCaseInsensitive];    bdsAccounts.Filter:= Format('Alias=''*%s*''',
[Trim(edtAccountsFilterByAlias.Text)]);    bdsAccounts.Filtered:=
True;  end;end; procedure TfrmMain.FormDestroy(Sender: TObject);begin 
bdsAccounts.Close;end; end.

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wp · 2023-09-27 09:14

Trying to keep the persistent fields... When they exist they must be
used in the following way:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TfrmMain.actAccountsAddDataExecute(Sender: TObject);begin 
actAccountsAddData.Enabled:= False;  Application.ProcessMessages;  
dgAccounts.BeginUpdate;   bdsAccounts.Append; 
bdsAccountsHASH.AsString:= 'N2983096817236';  // instead of
bdsAccounts.FieldByName('HASH').AsString := ... 
bdsAccountsAlias.AsString:= 'Alias 1';  bdsAccountsLabel.AsString:=
'Label 1';  bdsAccountsPending.AsCurrency:= 0.0; 
bdsAccountsBalance.AsCurrency:= 1000.0;  bdsAccounts.Post;  
bdsAccounts.Append;  bdsAccountsHASH.AsString:= 'N2983096817696'; 
bdsAccountsAlias.AsString:= 'Alias 2';  bdsAccountsLabel.AsString:=
'Label 2';  bdsAccountsPending.AsCurrency:= 0.0; 
bdsAccountsBalance.AsCurrency:= 2000.0;  bdsAccounts.Post;  
bdsAccounts.Append;  bdsAccountsHASH.AsString:= 'N2983696817236'; 
bdsAccountsAlias.AsString:= 'Alias 3';  bdsAccountsLabel.AsString:=
'Label 3';  bdsAccountsPending.AsCurrency:= 0.0; 
bdsAccountsBalance.AsCurrency:= 3000.0;  bdsAccounts.Post;  
dgAccounts.AutoAdjustColumns;  dgAccounts.EndUpdate(True);  
Application.ProcessMessages;  actAccountsAddData.Enabled:= True;end; 
After having added a filename to bdsAccounts and creating the dataset
at first run (like in my other reply), and pressing "Add data" I do
get the same empty rows and the crash at the end, as before.

For the next test, I ran the application and closed it immediately
afterwards (of course, after having deleted the created database file
for a new fresh start). This way an empty database file is created.
When I now run it again and click "Add data", the records are added
correctly, and the crash at the end does not occur either.

----------------------------------------------------------------------
wp · 2023-09-27 09:25

In order to clear the table replace the bdsAccounts.Clear by the
following lines:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  
bdsAccounts.First;  while not bdsAccounts.EoF do   
bdsAccounts.Delete;

----------------------------------------------------------------------
wp · 2023-09-27 10:10

Returning to the persistent fields... I add some DebugLn instructions
to the application after opening the dataset to print the FieldNo of
the fields:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TfrmMain.FormCreate(Sender: TObject);var  i: Integer;begin  ... 
bdsAccounts.Open;  for i := 0 to bdsAccounts.FieldCount-1 do   
DebugLn([bdsAccounts.Fields[i].FieldNo, ', ',
bdsAccounts.Fields[i].FieldName]);  end;When application starts for
the first time, i.e. without an existing database file, the output
always lists FieldNo = 0 - which looks very wrong because FieldNo is
an essential ingredient within the database management code. And in
fact, when the application is run for the second time (when the
database file already exists) the FieldNo values are as expected: 1,
2, 3, ...

I copied the bufdsdataset unit from the FPC installation over to my
test project (in order to be able to edit it) and added
"BindFields(true)" to "TCustomBufDataset.InternalOpen" (before
searching for the AutoInc field) - now the issue is gone, and the
application works now even without a filename and without
CreateDataset.

I am not sure whether the position where I added BindFields is the
correct one. But I think it is a good hint for a bug report which I
will prepare next.

[EDIT] Bug report:
https://gitlab.com/freepascal.org/fpc/source/-/issues/40450

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Gustavo 'Gus' Carreno · 2023-09-27 10:34

Hey WP,

First and foremost, thank you so very much for taking the time to suss
things out!!
Really appreciate it.

As a preamble: I was just playing around with things under the
impression that TBufDataset was gonna be the same beast as
TMemDataset, but with internal changes only, not the polar opposite of
it.

In this context, I tried to transfer what I learned with TMemDataset,
which was easy, simple and worked right out of the box, to TBufDataset
and the thing was like nitroglycerine without the stabilising compound
that turns it into dynamite. It went boom at the slightest touch.

Quote from: wp on September 27, 2023, 10:41:54 amIs there a reason why
you did not set the BufDataset's Filename?

More than one:
The wiki article for TMemDataset did not mention the need for it, but
I do realise that the section dedicated to TBufDataset was just
focusing on sorting, and nothing more.Again, TMemDataset worked ok
without it.My main purpose for this whole endeavour of testing
TMemDataset, TBufDataset, TRxMemoryData and ZMSQL is to not rely on,
what I'm assuming should only be memory only and volatile by nature, a
file or database engine, but to have the Dataset holding the data, a
visual component that has way better features than a TStringGrid and
some small piece of code to make filter and sorting happen.
I want the persistence of the data to be some custom, black box, thing
that I can create, re-create and have my mind changed on how to
read/write it every time I need to display the data.
So, in this context, having a file on the TBufDataset, made no sense
and because TMemDataset did not have an issue with it's absence, I
guess I made a bad assumption.

Quote from: wp on September 27, 2023, 10:41:54 amI am not sure if it
is possible at all to use TBufdataset without a file, buf even if it
is you will lose all records when the application terminates.

That does not have any impact, the data will come and be persisted by
other means.

Quote from: wp on September 27, 2023, 10:41:54 amSecond issue:
persistent fields. Once you have persistent fields you cannot access
fields by FieldByName[fieldname], but only by their variable name,
e.g. bdsAccountsBalance rather than
bdsAccounts.FieldByName['Balance']. An annoyance which I already hated
in my Delphi times...

Okies, that's going on the notepad for future reference, many, many
thanks!!

Quote from: wp on September 27, 2023, 10:41:54 amI deleted the
persistent fields from the lfm file, added a Filename to the
bdsAccounts dataset and made sure that the dataset is created properly
- now the application does not crash any more:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TfrmMain.FormCreate(Sender: TObject);begin  Caption:= Format('%s v%s',
[ Application.Title, cVersion ]);  InitShortcuts; 
Application.OnHint:= @DisplayHint;  bdsAccounts.FileName :=
'test.db';  if not FileExists(bdsAccounts.FileName) then   
bdsAccounts.CreateDataset;  bdsAccounts.Open;end;
These things should either be better documented, or raise an exception
if it impacts the more simplistic operation I'm aiming, wouldn't you
agree?

Quote from: wp on September 27, 2023, 10:41:54 amStill... Clear does
not seam to work. It clears the dataset in the current session, but
when the app starts another time the data are back again.

This Clear was a naive attempt to mimic TMemDataset.
Even the Lazarus wiki mentions that a clear is too slow and it
provides a quicker solution, a bit hefty on the code, hence me being a
bit lazy and tried it the easy and less optimal way.
And the loss of data between sessions is of no consequence.

Quote from: wp on September 27, 2023, 10:41:54 amFiltering seems to
crash the application still. Well - I would not execute the filter in
the OnChange event of the edit control, I would add a button to toggle
bdsAccounts.Filtered and use the edit filter text once it is
completed. This works, but I don't understand why your code report
"Index based on unknown field" while typing the condition...

The filtering has a blatant error due to my ignorance of the syntax
needed.
After I posted this, I progressed in doing my tests with
TRxMemoryData, and after some head butting with the wall I realized
that I need:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
DataSet.Filter:= 'Alias="*<value or partial>*"';And with this, it now
works.
I've always struggled with the many syntaxes(SQL with the Like and the
% and never knowing if I should quote the value or not) for this
filtering since there is not a place where this is discussed in any
docs or examples that I've stumbled upon!
There is a blatant lack of documentation on the correct syntax parsed
in this Filter property, that's for sure!!

Ok, summarising your findings:
Have a filename on the respective propertyDo not use the FieldByName
wayMaybe not use the Fields, just the FieldDefs. (Is this what you
mean by persistent fields?)
Am I missing something?

Nonetheless, oh so many thanks for the time you've spent on this !!!

Cheers,
Gus

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rvk · 2023-09-27 10:38

I don't think TBufDataset.Filename is (or should be) mandatory.

I used it for in-mem database where there is no need to save to a
file.
(But I created everything in code.)

The problems of using FieldByName when also having persistent fields
is new to me.
(But I never use persistent fields anyway)

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Gustavo 'Gus' Carreno · 2023-09-27 10:49

Hey Pawel,

First of all, many many thanks for the time you spent on this !!!
It is really appreciated !!

Quote from: paweld on September 27, 2023, 10:43:07 amAs @rvk wrote
define dataset in code and:

This for me is a bit hard to swallow. Mainly due to the fact that the
component has the functionality to be manipulated via the Designer.
If that makes it go boom by design, then probably not allow the
manipulation via the IDE?
Makes no sense to have it RAD just to explode in your face when used,
amirite?!

Quote from: paweld on September 27, 2023, 10:43:07 am1. for DBGrid,
you don't need to call BeginUpdate and EndUpdate - everything happens
automatically when you change DataSet. when doing a lot of data
editing, it is recommended to use DisableControls and EnableCotrols
for DataSet  

That makes quite a lot of sense, thanks very much for the necessary
schooling

Quote from: paweld on September 27, 2023, 10:43:07 am2. using the
Clear medtode for a DataSet will clear not only the data but also the
field definitions

Yeah, that was a lame ass and lazy attempt on my part 

Quote from: paweld on September 27, 2023, 10:43:07 am3. currency has
precision to 4 decimal places

The default from the Designer is actually 15, witch is even a bit much
for what I need: 8.
Actually, those fields should be uInt64 and then manipulated to have
decimal place between the 9th and 8th from the right.
It's a whole thing in crypto not to use Floating point arithmetic due
to the loss of data, which in any currency context is not acceptable.

And I think that even negative values are not, kinda, used.
A transaction is always abs and you can prepend a negative character
when displaying on the Sender's side and a plus sign on the Receiver's
side.
Using uInt64 makes sense, since it's the max a current register is
capable of manipulating in one go.
And, like previously stated, never use Floating Point arithmetic !!

Again, many thanks for adding code to better explain your meaning!!

Cheers,
Gus

----------------------------------------------------------------------
Gustavo 'Gus' Carreno · 2023-09-27 10:55

Hey WP,

Quote from: wp on September 27, 2023, 11:14:30 amTrying to keep the
persistent fields... When they exist they must be used in the
following way:

Okies, also jotted down on the notepad

Quote from: wp on September 27, 2023, 11:14:30 amAfter having added a
filename to bdsAccounts and creating the dataset at first run (like in
my other reply), and pressing "Add data" I do get the same empty rows
and the crash at the end, as before.

For the next test, I ran the application and closed it immediately
afterwards (of course, after having deleted the created database file
for a new fresh start). This way an empty database file is created.
When I now run it again and click "Add data", the records are added
correctly, and the crash at the end does not occur either.

Ok, looks like the key is actually having a file.

I think my main problem stems from the fact that:
I was completely ignorant of what the CreateDataset did in reality,
even if it is one of the option when you Right-Click on it in the
DesignerThe whole thing worked fine in TMemDataset
Ok, I can amend my previous list to be just:
Have a filename on the respective propertyDo not use the FieldByName
way
Thanks my good friend, this helps a lot!!!

Cheers,
Gus

----------------------------------------------------------------------
Gustavo 'Gus' Carreno · 2023-09-27 11:01

Hey WP,

Quote from: wp on September 27, 2023, 12:10:56 pmI am not sure whether
the position where I added BindFields is the correct one. But I think
it is a good hint for a bug report which I will prepare next.

This was my hope, that one of you more versed in the guts of these
components had the opportunity to chase that eluding bug.

Like I said previously to Pawel, it made no sense that the component
had all the bells and whistles to work in RAD, to just explode in your
face in such a strange way between Default/Release and Debug when you
use it.

Much, MUCH appreciation for your time, and patience, to get into a bug
report !!

Cheers,
Gus

----------------------------------------------------------------------
Gustavo 'Gus' Carreno · 2023-09-27 11:20

Hey rvk,

Quote from: rvk on September 27, 2023, 12:38:31 pmI don't think
TBufDataset.Filename is (or should be) mandatory.

I could not agree more with this. After all, the "product" IS
advertised as an in memory thingamaboob, so why the mandatory need of
a file, right?

Quote from: rvk on September 27, 2023, 12:38:31 pmI used it for in-mem
database where there is no need to save to a file.
(But I created everything in code.)

Yeah, I kinda was lazy and used the RAD option that is clearly
something that should be supported since it allows us to use it.

Quote from: rvk on September 27, 2023, 12:38:31 pmThe problems of
using FieldByName when also having persistent fields is new to me.
(But I never use persistent fields anyway)

Yeah, that also tickles me a bit. But looks like WP has been annoyed
by that lill detail ever since his Delphi time, so chalk it to
"seniority", I guess?

As a disclaimer, my main aim for all this testing was to evaluate a
visual thing that I could use instead of the very work intense
TStringGrid to achieve data auto refresh, filtering and sorting.
Hence me doing the whole thing via the RAD path.
I was quite happy with TMemDataset, but a bit sad for the lack of
sorting. So after evaluating it, I went on to TBufDatset under the
little information provided by the mentioned Wiki entry.
Looks like it was a good path, since from the looks of it, there were
bugs hiding in the shadows

Can not thank you enough for the time and patience you devoted to
chasing this alongside me!!

Cheers,
Gus

----------------------------------------------------------------------
wp · 2023-09-27 11:32

Now that the bugreport has been sent
(https://gitlab.com/freepascal.org/fpc/source/-/issues/40450) let me
correct my wrong statements made during this thread:
TBufDataset does NOT need a filenamePersistent fields DO work (the
reason why I don't like them is that it is a pain to rename fields
once persistent fields are created).Is is NOT necessary to call
CreateDataset for a bufdataset with persistent fields.Gus, do I
understand correctly that the Filter works for you. So, I do not need
to look into this issue?

----------------------------------------------------------------------
Gustavo 'Gus' Carreno · 2023-09-27 11:35

Hey WP,

Quote from: wp on September 27, 2023, 11:25:12 amIn order to clear the
table replace the bdsAccounts.Clear by the following lines:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  
bdsAccounts.First;  while not bdsAccounts.EoF do   
bdsAccounts.Delete;
From the wiki article, this is not the best way to do it, while it is
a possibility.

They have a 20+ LoC of an example on how to just create a new dataset,
fill in the fields and just return it after freeing the old one.
Makes sense, and I'll look into it. But to be honest, the need of a
clear is just for the that test context.
In my particular need, the clear will not be needed... I think

Cheers,
Gus

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Gustavo 'Gus' Carreno · 2023-09-27 11:43

Hey WP,

Quote from: wp on September 27, 2023, 01:32:05 pmNow that the
bugreport has been sent
(https://gitlab.com/freepascal.org/fpc/source/-/issues/40450) let me
correct my wrong statements made during this thread:
TBufDataset does NOT need a filenamePersistent fields DO work (the
reason why I don't like them is that it is a pain to rename fields
once persistent fields are created).Is is NOT necessary to call
CreateDataset for a bufdataset with persistent fields.
This is quite awesome to read!!
I cannot thank you enough for your time on this!!

Quote from: wp on September 27, 2023, 01:32:05 pmGus, do I understand
correctly that the Filter works for you. So, I do not need to look
into this issue?

Yes, that is correct, I made it work in the end.

Once I realised that it needed quotations and it was using the star
"*" instead of any other symbol for globbing, it works:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
Dataset.Filter:= 'Alias="*<full value or partial value>*"';// Then
Filter On and a refresh
So, yeah, that's sorted and was only an issue due to my ignorance of
the particular syntax of the VCL/LCL Dataset's filtering.
No need to pursue that further, I guess!!

Cheers,
Gus