Kia Orana All - particularly the ancient ones still running DBSIAM v3!

I'm getting an AV on closing a query.  Stepping through the code I get
to the marked line below and get the AV
------------------------------------
procedure TUnusedTenants.ActivateQuery;
begin
 if (pickBefore.Date <> dtLast)
   or (sPMLast <> cboPM.Text) then
 try
   dtLast := pickBefore.Date;
   sPMLast := cboPM.Text;
   Screen.Cursor := crSQLWait;
   StatusBar1.Panels[0].Text := 'Checking Tenants';
   Application.ProcessMessages;
   with qryTenants do
   begin
     Close;       // <<< AV here!!!! <<<<<<<<<<<<<<<<<<<<<<<<<<
     if cboPM.Text = 'ALL' then SQL[9] := ''
     else SQL[9] := 'AND UPPER(PM.Name) = ' +
QuotedStr(UpperCase(cboPM.Text));
     ParamByName('BeforeDate').AsDate := pickBefore.Date;
     Open;
     StatusBar1.Panels[0].Text := IntToStr(RecordCount) + ' Tenants
found';
   end;
 finally
   grdTenants.SetFocus;
   Screen.Cursor := crDefault;
 end;
end;
------------------------------------
I "OK" the AV message and end up in DBISAMEN.pas here:-

procedure TDataCursor.CheckForChangeDetection;
begin
>>>> here >>>>  if FDataDirectory.DataSession.StrictChangeDetection then
     ReadLockTable
  else
     CheckForCursorChanges;
end;
------------------------------------

Whatever is going on?  I'm in a bit of code that I haven't touched for
yonks and have no idea how to proceed.

Any suggestions welcome (yeah, yeah I know ... upgrade to v4 or EDB -
but that is a major mission!)

Kia Manuia

Jeff

-----------------
Here is some stuff from madExcept ...

exception class   : EAccessViolation
exception message : Access violation at address 005EDA66 in module
'apm.exe'. Read of address 00000004.

main thread ($e34):
005eda66 +00a apm.exe      dbisamen                 9967   +1
TDataCursor.CheckForChangeDetection
0060220f +01f apm.exe      dbisamen                21684   +3
TDataCursor.ResetFilter
005b8b46 +056 apm.exe      dbisamsq                 6305   +2
TDataQuery.BuildSubSelectFilter
0064158c +768 apm.exe      dbisamlb                11445 +226
EvaluateExpressionToken
00640f31 +10d apm.exe      dbisamlb                11241  +22
EvaluateExpressionToken
00604bd6 +036 apm.exe      dbisamen                23079   +3
TDataCursor.EvaluateFilterForRecord
00604aa2 +07e apm.exe      dbisamen                23033  +16
TDataCursor.NavigateNonIndexedRecords
005ea790 +058 apm.exe      dbisamen                 8595   +7
TFilter.BuildNonIndexedBitmap
005e917f +49f apm.exe      dbisamen                 7984 +136
TFilter.EvaluateFilter
005e8b95 +049 apm.exe      dbisamen                 7789   +7
TFilter.Update
00603fcf +1bf apm.exe      dbisamen                22626  +43
TDataCursor.UpdateAllFilters
005f8e3e +01e apm.exe      dbisamen                16023   +5
TDataCursor.RefreshRangeAndFilters
005eda41 +031 apm.exe      dbisamen                 9960   +6
TDataCursor.CheckForCursorChanges
005eda83 +027 apm.exe      dbisamen                 9970   +4
TDataCursor.CheckForChangeDetection
00601f63 +173 apm.exe      dbisamen                21595  +45
TDataCursor.DropFilter
005a858b +01f apm.exe      dbisamsq                 1290   +3
TJoin.FreeJoinFilterHandle
005a7f84 +014 apm.exe      dbisamsq                 1069   +1
TJoin.Destroy
00404178 +008 apm.exe      System
TObject.Free
005a8c43 +02f apm.exe      dbisamsq                 1488   +3
TSourceTable.FreeJoins
005abbb6 +036 apm.exe      dbisamsq                 3035   +3
TDataQuery.FreeSourceTables
005ab822 +022 apm.exe      dbisamsq                 2922   +2
TDataQuery.Destroy
00404178 +008 apm.exe      System
TObject.Free
005aad3d +029 apm.exe      dbisamsq                 2636   +3
TQueryStatement.FreeDataQueries
005a9cda +096 apm.exe      dbisamsq                 2020  +17



--
Jeff Cook
Aspect Systems Ltd
www.aspect.co.nz
+
Joan and Jeff Cook
The Cooks Oasis
www.cookislandsoasis.com

Jeff,

Assuming that qryTenants is not nil, is it possible that it was freed
somewhere else in code but the pointer was not set to nil? The access
violation on a nil or invalid object reference won't occur until a data
element of the instance is accessed, so it might take it until that
deeper method to run into a problem. From the point of the exception I'd
also be looking to make sure the session and database are valid.

Good hunting,

Sean

Jeff Cook wrote:
> Kia Orana All - particularly the ancient ones still running DBSIAM v3!
>
> I'm getting an AV on closing a query.  Stepping through the code I get
> to the marked line below and get the AV
> ------------------------------------
> procedure TUnusedTenants.ActivateQuery;
> begin
>   if (pickBefore.Date <> dtLast)
>     or (sPMLast <> cboPM.Text) then
>   try
>     dtLast := pickBefore.Date;
>     sPMLast := cboPM.Text;
>     Screen.Cursor := crSQLWait;
>     StatusBar1.Panels[0].Text := 'Checking Tenants';
>     Application.ProcessMessages;
>     with qryTenants do
>     begin
>       Close;       // <<< AV here!!!! <<<<<<<<<<<<<<<<<<<<<<<<<<
>       if cboPM.Text = 'ALL' then SQL[9] := ''
>       else SQL[9] := 'AND UPPER(PM.Name) = ' +
> QuotedStr(UpperCase(cboPM.Text));
>       ParamByName('BeforeDate').AsDate := pickBefore.Date;
>       Open;
>       StatusBar1.Panels[0].Text := IntToStr(RecordCount) + ' Tenants
> found';
>     end;
>   finally
>     grdTenants.SetFocus;
>     Screen.Cursor := crDefault;
>   end;
> end;
> ------------------------------------
> I "OK" the AV message and end up in DBISAMEN.pas here:-
>
> procedure TDataCursor.CheckForChangeDetection;
> begin
>>>>> here >>>>  if FDataDirectory.DataSession.StrictChangeDetection then
>       ReadLockTable
>    else
>       CheckForCursorChanges;
> end;
> ------------------------------------
>
> Whatever is going on?  I'm in a bit of code that I haven't touched for
> yonks and have no idea how to proceed.
>
> Any suggestions welcome (yeah, yeah I know ... upgrade to v4 or EDB -
> but that is a major mission!)
>
> Kia Manuia
>
> Jeff
>
> -----------------
> Here is some stuff from madExcept ...
>
> exception class   : EAccessViolation
> exception message : Access violation at address 005EDA66 in module
> 'apm.exe'. Read of address 00000004.
>
> main thread ($e34):
> 005eda66 +00a apm.exe      dbisamen                 9967   +1
> TDataCursor.CheckForChangeDetection
> 0060220f +01f apm.exe      dbisamen                21684   +3
> TDataCursor.ResetFilter
> 005b8b46 +056 apm.exe      dbisamsq                 6305   +2
> TDataQuery.BuildSubSelectFilter
> 0064158c +768 apm.exe      dbisamlb                11445 +226
> EvaluateExpressionToken
> 00640f31 +10d apm.exe      dbisamlb                11241  +22
> EvaluateExpressionToken
> 00604bd6 +036 apm.exe      dbisamen                23079   +3
> TDataCursor.EvaluateFilterForRecord
> 00604aa2 +07e apm.exe      dbisamen                23033  +16
> TDataCursor.NavigateNonIndexedRecords
> 005ea790 +058 apm.exe      dbisamen                 8595   +7
> TFilter.BuildNonIndexedBitmap
> 005e917f +49f apm.exe      dbisamen                 7984 +136
> TFilter.EvaluateFilter
> 005e8b95 +049 apm.exe      dbisamen                 7789   +7
> TFilter.Update
> 00603fcf +1bf apm.exe      dbisamen                22626  +43
> TDataCursor.UpdateAllFilters
> 005f8e3e +01e apm.exe      dbisamen                16023   +5
> TDataCursor.RefreshRangeAndFilters
> 005eda41 +031 apm.exe      dbisamen                 9960   +6
> TDataCursor.CheckForCursorChanges
> 005eda83 +027 apm.exe      dbisamen                 9970   +4
> TDataCursor.CheckForChangeDetection
> 00601f63 +173 apm.exe      dbisamen                21595  +45
> TDataCursor.DropFilter
> 005a858b +01f apm.exe      dbisamsq                 1290   +3
> TJoin.FreeJoinFilterHandle
> 005a7f84 +014 apm.exe      dbisamsq                 1069   +1
> TJoin.Destroy
> 00404178 +008 apm.exe      System
> TObject.Free
> 005a8c43 +02f apm.exe      dbisamsq                 1488   +3
> TSourceTable.FreeJoins
> 005abbb6 +036 apm.exe      dbisamsq                 3035   +3
> TDataQuery.FreeSourceTables
> 005ab822 +022 apm.exe      dbisamsq                 2922   +2
> TDataQuery.Destroy
> 00404178 +008 apm.exe      System
> TObject.Free
> 005aad3d +029 apm.exe      dbisamsq                 2636   +3
> TQueryStatement.FreeDataQueries
> 005a9cda +096 apm.exe      dbisamsq                 2020  +17
>
>
>

"Jeff Cook" <jeffc@aspect.co.nz> wrote in message
news:3D0D7D2C-A379-4484-9952-6E3888E54D99@news.elevatesoft.com...
> Whatever is going on?  I'm in a bit of code that I haven't touched for
> yonks and have no idea how to proceed.
>
> Any suggestions welcome (yeah, yeah I know ... upgrade to v4 or EDB -
> but that is a major mission!)
>

There is an obscure bug in Delphi that can cause some or all of the
databases sessions etc in a datamodule to become disconnected from each
other. I think (long time ago, vague recollection) it had something to do
with opening the same project with two copies of Delphi running on the same
computer. Regardless, I would check the query to make sure it points to the
right places.

Another option, to delete que tQuery and re-add it to the datamodule.

Don't you love this stuff?

Robert

Robert wrote:
>
> There is an obscure bug in Delphi that can cause some or all of the
> databases sessions etc in a datamodule to become disconnected from
> each other. I think (long time ago, vague recollection) it had
> something to do with opening the same project with two copies of
> Delphi running on the same computer. Regardless, I would check the
> query to make sure it points to the right places.
>

Hi Robert

Thanks for the suggestions.  

As far as I can see everything is hooked up properly and I tried
deleting the query and creating it again and (once I had got my
datasources hooked up againeverything works the same - including
the AV

Cheers

Jeff

--
Jeff Cook
Aspect Systems Ltd
www.aspect.co.nz
+
Joan and Jeff Cook
The Cooks Oasis
www.cookislandsoasis.com

Sean wrote:
>
> Assuming that qryTenants is not nil, is it possible that it was freed
> somewhere else in code but the pointer was not set to nil? The access
> violation on a nil or invalid object reference won't occur until a
> data element of the instance is accessed, so it might take it until
> that deeper method to run into a problem. From the point of the
> exception I'd also be looking to make sure the session and database
> are valid.
>
Proved that qryTenants is not nil and there is no "Free", "Release" or
"nil" in the module - and the module isn't "used" anywhere apart from
the main screen call - and the query isn't passed as a parameter to any
other module.  I've removed all manual "prepares" on all queries for
good measure.

Might leave this til tomorrow as it is doing my head in trying to think
of other things to look at and try!

Thanks for your ideas.

Cheers

Jeff

--
Jeff Cook
Aspect Systems Ltd
www.aspect.co.nz
+
Joan and Jeff Cook
The Cooks Oasis
www.cookislandsoasis.com

Bummer. Have you tried creating the query completely in code and then
destroying it when you are finished? Slower, but you get a clean
starting point every time - maybe there is a subtle bug in your version
of DBISAM from reusing the query object in the manner that it is being used.

Good luck,

Sean

Jeff Cook wrote:
> Sean wrote:
>> Assuming that qryTenants is not nil, is it possible that it was freed
>> somewhere else in code but the pointer was not set to nil? The access
>> violation on a nil or invalid object reference won't occur until a
>> data element of the instance is accessed, so it might take it until
>> that deeper method to run into a problem. From the point of the
>> exception I'd also be looking to make sure the session and database
>> are valid.
>>
> Proved that qryTenants is not nil and there is no "Free", "Release" or
> "nil" in the module - and the module isn't "used" anywhere apart from
> the main screen call - and the query isn't passed as a parameter to any
> other module.  I've removed all manual "prepares" on all queries for
> good measure.
>
> Might leave this til tomorrow as it is doing my head in trying to think
> of other things to look at and try!
>
> Thanks for your ideas.
>
> Cheers
>
> Jeff
>

Jeff Cook wrote:

>
> Might leave this til tomorrow as it is doing my head in trying to
> think of other things to look at and try!
>

Tomorrow came and it isn't looking better (though Cyclone Ken has just
passed by without hitting us except for almighty precipitation!).

Decided not to reactivate my query at the end of the processing and
simple exit the module - but now I get exactly the same error on
closing the module - as I should have expected as freeing the form will
close the query.

So I'm back to where I started - why does closing the query cause an
AV????

Cheers

Jeff

--
Jeff Cook
Aspect Systems Ltd
www.aspect.co.nz
+
Joan and Jeff Cook
The Cooks Oasis
www.cookislandsoasis.com

Sean wrote:

> Bummer. Have you tried creating the query completely in code and then
> destroying it when you are finished? Slower, but you get a clean
> starting point every time - maybe there is a subtle bug in your
> version of DBISAM from reusing the query object in the manner that it
> is being used.
>

OK, now I have tried that and get exactly the same problem.

However I now know what causes the problem - but not how to fix it!

The SQL is used to select Tenants for deletion.  The SQL can be opened
and closed multiple times with no problem (e.g. changing the selection
criteria and thus the WHERE).

BUT if I use the query result in a "while not EOF do .. Next" loop to
actually delete the tenants - using the tenantcode from the query, then
I get an AV as I close the query.  Same happens if I use SQL to delete
the tenant or .Delete.   Comment out the delete and it all works OK -
except the purpose is defeated

The query is below

Cheers

Jeff
============================================================
SELECT T.TenantCode, T.SortKey, T.StartDate, T.VacateDate,
             P.StreetNumber, P.StreetName, P.Suburb,
             IF(P.Managed THEN "Yes" ELSE "No") AS Managed,
             True AS Selected, PM.Name
FROM Tenants T
JOIN Properties P ON P.PropertyCode = T.PropertyCode
JOIN Portfolios Pf ON Pf.PortfolioCode = P.PortfolioCode
JOIN PropertyManagers PM on PM.PMCode = Pf.PMCode
WHERE VacateDate < :BeforeDate
/*  9  */
AND TenantCode NOT IN
(
SELECT DISTINCT TT.TenantCode
FROM TenantTrans TT
WHERE (( TT.TransType <> "B/Fwd")
         OR (TT.Balance <> 0)
         OR (TT.RentDue <> 0)
         OR (TT.Rent <> 0)
         OR (TT.Debt <> 0)
         OR (TT.LettingFee <> 0)
         OR (TT.Bond <> 0))
)
AND TenantCode NOT IN
(
SELECT DISTINCT AT.TenantCode
FROM AdminTrans AT
WHERE (AT.BondDisbursed = 'Y' )
)
ORDER BY T.SortKey
--
Jeff Cook
Aspect Systems Ltd
www.aspect.co.nz
+
Joan and Jeff Cook
The Cooks Oasis
www.cookislandsoasis.com

Jeff,

How about fill a temp table or list with the primary keys of the records
you want to delete during the loop, close the query, and then perform
the delete from the list. Shouldn't have to do it, but it may get you
around the bug.

Sean

Jeff Cook wrote:
> Sean wrote:
>
>> Bummer. Have you tried creating the query completely in code and then
>> destroying it when you are finished? Slower, but you get a clean
>> starting point every time - maybe there is a subtle bug in your
>> version of DBISAM from reusing the query object in the manner that it
>> is being used.
>>
>
> OK, now I have tried that and get exactly the same problem.
>
> However I now know what causes the problem - but not how to fix it!
>
> The SQL is used to select Tenants for deletion.  The SQL can be opened
> and closed multiple times with no problem (e.g. changing the selection
> criteria and thus the WHERE).
>
> BUT if I use the query result in a "while not EOF do .. Next" loop to
> actually delete the tenants - using the tenantcode from the query, then
> I get an AV as I close the query.  Same happens if I use SQL to delete
> the tenant or .Delete.   Comment out the delete and it all works OK -
> except the purpose is defeated
>
> The query is below
>
> Cheers
>
> Jeff
> ============================================================
> SELECT T.TenantCode, T.SortKey, T.StartDate, T.VacateDate,
>               P.StreetNumber, P.StreetName, P.Suburb,
>               IF(P.Managed THEN "Yes" ELSE "No") AS Managed,
>               True AS Selected, PM.Name
> FROM Tenants T
> JOIN Properties P ON P.PropertyCode = T.PropertyCode
> JOIN Portfolios Pf ON Pf.PortfolioCode = P.PortfolioCode
> JOIN PropertyManagers PM on PM.PMCode = Pf.PMCode
> WHERE VacateDate < :BeforeDate
> /*  9  */
> AND TenantCode NOT IN
> (
> SELECT DISTINCT TT.TenantCode
> FROM TenantTrans TT
> WHERE (( TT.TransType <> "B/Fwd")
>           OR (TT.Balance <> 0)
>           OR (TT.RentDue <> 0)
>           OR (TT.Rent <> 0)
>           OR (TT.Debt <> 0)
>           OR (TT.LettingFee <> 0)
>           OR (TT.Bond <> 0))
> )
> AND TenantCode NOT IN
> (
> SELECT DISTINCT AT.TenantCode
> FROM AdminTrans AT
> WHERE (AT.BondDisbursed = 'Y' )
> )
> ORDER BY T.SortKey

Jeff,

<< I'm getting an AV on closing a query.  Stepping through the code I get to
the marked line below and get the AV >>

If you can send me a project that reproduces this, I'll have a look and see
if I can get you a source code fix.

--
Tim Young
Elevate Software
www.elevatesoft.com