[DUG] Searching ClientDataSet using locate

[Stephen Barker]

> I think you'll find the filtering is a "a brute force scan of all 
> records in code" :-)

Yeah but the performance depends on the database/tdataset design. I've never
used tclientdataset so can't comment, but for example with DBISAM running in
client-server mode, table filters are performed on the server the same as a
where clause in sql, whereas the onfilterrecord event is processing locally
as is a loop in code.

Steve



> 
> I'd like to know where the data is soming from because I 
> always think it 
> is better to
> to the selection in the database rather than loading lots of 
> records and 
> doing this kind of select locally
> 
> N
> > Hi John,
> >
> > Are you trying to locate the same string within multiple 
> fields? If so, I
> > don't think the locate will help you there.
> >
> > Try using the onfilterrecord event as Neven said, or a 
> filter expression
> > like this if your database allows it:
> >
> > .filter := 'name like ''%'+findstr+'%'' or address1 like 
> ''%'+findstr+'%''
> > or...
> >
> > or even do a brute force scan of all records in code.
> >
> >
> > hth
> > Steve 
> >
> >   
> >> -----Original Message-----
> >> From: John Bird [mailto:johnkbird at paradise.net.nz] 
> >> Sent: Thursday, 6 November 2008 6:13 p.m.
> >> To: NZ Borland Developers Group - Delphi List
> >> Subject: Re: [DUG] Searching ClientDataSet using locate
> >>
> >> Yes that would work for searching two fields, but do I do "n" 
> >> fields - ie
> >> what I am trying to do is generalise and build a list of 
> >> fields to search
> >> for at runtime where the number of fields to search changes
> >>
> >> (ie all where Datatype = ftString) - I can build a string 
> >> listing the wanted
> >> string fields, and this goes in the first parameter ok.
> >>
> >> What I have not figured yet is how to build the second 
> >> parameter when I am
> >> searching in an arbitrary number of fields  I am using the 
> same search
> >> string  on all the fields,  (it has to be passed as a variant 
> >> array with as
> >> many entries as the number of fields being searched if I understand
> >> correctly).
> >>
> >> I have tried something like
> >>
> >> Findstr:  String;                        //string to find in 
> >> the dataset
> >> AlphaFieldsList: String;           //fields list of all 
> >> string fields, eg
> >> 'Name;Address1;Address2;Description'
> >>                                              //this is built 
> >> at runtime by
> >> looking at the dataset
> >> vAlphaStringsList:variant;
> >> AlphaFieldsAmx: iinteger;        //This is set to the 
> number of string
> >> fields found in this dataset
> >>
> >>                 ...
> >>
> >>   if AlphaFieldsamx >=0 then
> >>  begin
> >>    vAlphaStringsList := VarArrayCreate([0, AlphaFieldsAmx],  
> >> varVariant);
> >>    for i := 0 to AlphaFieldsAmx do
> >>    begin
> >>        cAlphaStringsList[i] := Findstr;
> >>    end;
> >>
> >>
> >>   cdsFind.locate(AlphaFieldsList, vAlphaStringsList, [loPartialKey,
> >> loCaseInsensitive])
> >>
> >> I suspect I am doing something wrong building the variant 
> >> parameter and I am
> >> new to working with variants...
> >>
> >> But it don't seem to work.....any suggestions how to build 
> the second
> >> parameter?
> >>
> >> I have thought of doing the search by filtering, but some of 
> >> the datasets I
> >> want to search on are already filtered which makes it harder 
> >> to use filters
> >> for new functions..
> >>
> >> John
> >>     
> >>> .Locate('Field1;Field1', VarArrayOf([Variable1, Variable2])
> >>>
> >>> Works fine for me (all over the place but just with std TDataset)
> >>>       
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> >>
> >>
> >>     
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> >   
> 
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