Hello All:

   I need to automate the running of processes that restructure the data
within a DBISAM database - I have a concept and am seeking comments - I am
using version 1.21 which is file server only

   I have an awesome table restructuring tool which I use now - it compares
the client database structure (fields, indexes) to what the client has and
makes the appropriate changes.It works great.

   What I am talking about doing now - is adding a process that needs to be
run 1 time - that actually modifies the customers data - for instance - a
Tax parameter was Y,N for Yes/No - It is changed to Y,S,N  Y=Tax Products
together with other products S=Tax product seperately by itself N=NoTax

   So - each customer upgrading to build 455 or later of my app - needs to
run this tax conversion routine 1 time only

  I need to figure out a very reliable way for making thid happen

  I was thinking of doing the following
      1) Add a table to track restructure processes - call it the Restruct
Table
      2) When an update is run - the updater would check the restruct
Table - if "TaxUpdate1" is not listed then the "TaxUpdate1" process would be
run and then the "TaxUpdate1" would be added to the Restruct table
              A) What if this table is corrupted - should i run an indexx
repair before checking it ???
              B) Is it worth adding a version checking mechanism as a
double check .. ie "If Oldversion<455 and "TaxUpdate1" not found then run
"TaxUpdate1"
              C) before running the TaxUpdate1 the app will create a
subfolder TaxUpdate1 and copy all of the affected files (pre-update) into
it - is it worth checking for the existence of folder "TaxUpdate1" as a 3rd
check ???

   Obviously I am concerned about data integrity - during the update I have
exclusive access to the data

Thank you for your thoughts

PS - Once I run a few updates I will be switching to ElevateDB


Neil Huhta

Neil


I don't remember that far back. Does V1 have a table version that you could use to check? If so use that rather than an external table since it removes the need for 2 A & B

2C is an interesting point and my take would be yes from a view of if its done don't duplicate BUT someone can always come along in Windows and delete the directory so don't rely on it.

The other alternative which means more work on your side is to change the name of the field - easy to check then.

Can you change your name - I don't thing you are really news.elevatesoft.com

Roy Lambert [Team Elevate]

Roy:

   Version 1 has table versions - I could use that - but I am ver hesitant.
The reason I want to use a table is because in addition to restructuringthe
table, I need to modify data such as changing the primary key, or changing
the key that links a master/detail set of tables, etc.

   This table lets me know that 1) the re-organization of the data has run
2) I have 10-15 of these re-organizations to roll out - too complex to
manage by version number alone

    I just tried to change my name - thank you.

   My V1 app is awesome - but very fat client - I am looking forward to
playing with ElevateDB - it will be a significant re-write plus old code
cleanup.

Neil



"Roy Lambert" <roy@lybster.me.uk> wrote in message
news:3B399BB0-F44A-4444-9F79-14EC406FD78E@news.elevatesoft.com...
> Neil
>
>
> I don't remember that far back. Does V1 have a table version that you
> could use to check? If so use that rather than an external table since it
> removes the need for 2 A & B
>
> 2C is an interesting point and my take would be yes from a view of if its
> done don't duplicate BUT someone can always come along in Windows and
> delete the directory so don't rely on it.
>
> The other alternative which means more work on your side is to change the
> name of the field - easy to check then.
>
> Can you change your name - I don't thing you are really
> news.elevatesoft.com
>
> Roy Lambert [Team Elevate]
>

Huhtaman


>but very fat client

Show you be speaking of the people who pay you money in that manner?

Roy

That doesn't work with the typo - I'll try again

>but very fat client

Should you be speaking of the people who pay you money in that manner?

Roy

> The reason I want to use a table is because in addition to
> restructuringthe table, I need to modify data such as changing the
> primary key, or changing the key that links a master/detail set of
> tables, etc.

What I've always done is actually just check for the keys and fields that are
needed, and alter as appropriate. I'd never change the primary index on old tables -
a new index would be just fine so why bother. I've included the field check code
below.

Obviously any data conversion actually needs to be done too.

/Matthew Jones/

tableChecker := TDBISAMTable.Create(nil);
try
 tableChecker.SessionName := g_xThreadSession.SessionName;
 tableChecker.DatabaseName := szDatabaseLocation;


 CheckFieldPresent(tableChecker, 'MyTable.dat', 'apQuestionID', ftLargeint, 0);
...

procedure TMyObject.CheckFieldPresent(tableChecker: TDBISAMTable; szDbName: string;
szFieldName: string; ftType: TFieldType; nFieldLength: Integer);
var
   nLoop: Integer;
   nIndex: Integer;
begin
   tableChecker.Active := False;
   tableChecker.TableName := szDbName;
   tableChecker.IndexDefs.Update;

   tableChecker.FieldDefs.Updated := False;
   tableChecker.FieldDefs.Update;
   nIndex := -1;
   for nLoop := 0 to (tableChecker.FieldDefs.Count - 1) do
   begin
      // CodeSite.SendMsg('Field ' + IntToStr(nLoop) + ' = ' + TableLog.FieldDefs[nLoop]
..Name);
      if 0 = AnsiCompareText(tableChecker.FieldDefs[nLoop].Name, szFieldName) then
      begin
         nIndex := nLoop;
         break;
      end;
   end;

   if nIndex > 0 then
   begin
      if (tableChecker.FieldDefs[nLoop].DataType <> ftType) or
(tableChecker.FieldDefs[nLoop].Size <> nFieldLength) then
      begin
         tableChecker.FieldDefs[nLoop].DataType := ftType;
         tableChecker.FieldDefs[nLoop].Size := nFieldLength;
         Report('Database schema change: ' + szFieldName + '/' + IntToStr(nFieldLength));
         tableChecker.AlterTable(0, 0, 2, true, StringLength, 'DatabaseFile', 1024, 1024);
// ENCRYPTING
      end;
   end
   else
   begin
      tableChecker.FieldDefs.Add(szFieldName, ftType, nFieldLength, False, '', '', '',
'');
      Report('Database schema update: ' + szFieldName + '/' + IntToStr(nFieldLength));
      tableChecker.AlterTable(0, 0, 2, true, StringLength, 'DatabaseFile', 1024, 1024);
// ENCRYPTING
   end;
end;