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Findkey doesn't work with TClientDataSet - TDataSetProvider - TAdoTable

Posted on 2010-09-17
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Last Modified: 2012-05-10
Hi,

I have a access table with a filed primarykey (string file)
Last month i put a form in delphi to use this table with :
1°) Tadoconnection (i tried cursorlocation with clUseClient - and cluseserver aind i tried connectionstring based on Microsoft ole db provider for odbc driver and microsoft jet 4.0 old db provider)
2°) TAdotable (cursorlocation = clUserServer, Locktype = ltBatchOptimistic, Tabledirect = True) based on Tadoconnection
3°) TDataSetProvider based on TAdotable
4°) TClientDataSet (i tried with IndexFieldNames and without IndexFieldNames) based on TDataSetProvider
==> TClientDataSet.FindKey(['Value']) was OK

I re-do this form this week and TClientDataSet.FindKey(['Value']) not work (don't find the record).

The acces table has no change between this. I believe it's in the parameter of my components but i don't find where.
Other possibility : i d'ont remenber if last month i create the connection string in delphi conception or if i used a .udl filed : but normally there are no difference.

Thanks for your answer

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Question by:fprovin
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9 Comments
 
LVL 32

Expert Comment

by:Ephraim Wangoya
ID: 33704143
It works fine, you have to set the IndexFieldNames for the clientdataset eg

  Clientdataset1.IndexFieldNames := 'FIRSTNAME';
  Clientdataset1.FindKey([Edit1.Text]);
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LVL 32

Expert Comment

by:Ephraim Wangoya
ID: 33706064
Read this article about Locate and FindKey
http://edn.embarcadero.com/article/29176
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Author Comment

by:fprovin
ID: 33707057
Hi ewangoya,

Thanks but i tried this and it's not work too (return of findkey : False).
I agree that for this table i may use locate because it's a small table but i have the same problem with a big table (more than 100 000 records and it's going up) and i am afraid about locate performance when i will arrive at 500 000 records or more...

Best regards
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LVL 32

Expert Comment

by:Ephraim Wangoya
ID: 33709866
if the clientdataset is indexed, Locate will use the index. However if there are no appropriate indexes, then it resorts to scanning the dataset one record at a time, this is when you loose alot of performance
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Author Comment

by:fprovin
ID: 33710701
I 'am ok with you but if findkey does'nt work it's probably because it doesnt use the index ? and if yes locate will do the same thing ?

And i don't understand why findkey doesn't work.

Best regards
0
 

Author Comment

by:fprovin
ID: 33710827
Hi,

In the zip there are my delphi source and the access data base
Three comments :
1°) i add a ".txt" extension on many source file to have the possibilitie to send the zip here.
2°) When you open the sources you had to activate the TClientDataSet (unit and form 7).
3°) Depends on your path you will have to change the connection string on the tadoconnection (unit and form 8)

When you clic on the "button 2" you have first a try with findkey and second with locate.
If you look step by step the findkey doesn't work.

Best regards
TestFindkey.zip
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LVL 32

Expert Comment

by:Ephraim Wangoya
ID: 33713001
Here is your error, b is in lower case  
DataModule7.clientdataset1.IndexFieldNames := 'NomVariable';
  if (DataModule7.clientdataset1.FindKey(['bGestionFraisboursiers'])) then
  begin
    {coucou}
    stest := 'Ok' ;
  end ;

 bGestionFrais b oursiers   //b is in lowercase so the word is not found
check if your index is case sensitive
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LVL 32

Accepted Solution

by:
Ephraim Wangoya earned 2000 total points
ID: 33713073
Here is a solution
Create a case insensitive index on TClientDataset1 then change the IndexName before searching

procedure TForm4.Button2Click(Sender: TObject);
var
stest: String ;
begin
  //I created an Index called searchkey in DataModule7
  DataModule7.ClientDataSet1.IndexName := DataModule7.ClientDataSet1.IndexDefs.Items[0].Name;
  if (DataModule7.clientdataset1.FindKey(['bGestionFraisboursiers'])) then
  begin
    {coucou}
    stest := 'Ok' ;
  end ;

  {DataModule7.clientdataset1.IndexFieldNames := 'NomVariable';
  if (Datamodule7.ClientDataSet1.Locate('NomVariable','bGestionFraisBoursiers',[])) then
  begin
    {coucou}
    stest := 'Ok' ;
  end ;}
end;
Unit7.zip.zip
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Author Closing Comment

by:fprovin
ID: 33715796
Diagnostic OK
Solutions for the problem and more .
Very goog

Thanks
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