Hi,

I create for temporary processes like printing etc. a local TEDBQuery. Run my command and free the local component at the end.
e.g.

var
 q : TEDBQuery;
begin
 q := TEDBQuery.Create(nil);

 q.SessionName      := MyDatabase.SessionName;
 q.DatabaseName    := MyDatabase.DatabaseName;
 q.RequestSensitive := True;
 try
   q.SQL.Text := 'SELECT * FROM ADDRESS';
   q.Open;
   .......  Do Printing here ....
 finally
   q.Free;
 end;
end;

When I call the open command there will be memory allocated by q. This memory will not be freed after I free q.
1. Why?
2. Can I force that behaviour?

Thanks for help, best regards
Michael

Volker


Why do you think memory isn't being freed?

Roy Lambert

Hello Roy,

I check the using of the memory with Process Explorer while I step trough my printing process. I see that memory using increase at the Open or ExecSQL line, but still hold the memory usage after the Free command. So I think,  memory isn´t beeing freed.

Do you not think so?

BTW I develop with BDS2006 Win32 app, Elevate DB 2.03.13

Thanks
Michael

Roy Lambert wrote:

Volker


Why do you think memory isn't being freed?

Roy Lambert

Volker


Its almost certainly down to timing. Windows doesn't free up memory as soon as an application releases it, and may often leave it sitting there. The best way to find out if memory is being leaked is to use the facilities in FastMM or some other memory checker.

Believe me if ElevateDB was leaking memory with every query created there would be a LOT of angry customers shouting at Tim.

Roy Lambert

Roy,

but if I create an TBitmap and load a picture to that and free this at the end of my operation, then I see immediately that the memory is freed. I think not that elevateDB has memory leaks, because the memory is freed when I close the application. I think elevateDB holds cache buffers or something else when I run a query. And this buffers will be freed on closing the connection.

BTW I will try the FastMM features to search for leaks.

Thanks for your help
Michael

Volker,

<< When I call the open command there will be memory allocated by q. This
memory will not be freed after I free q.
1. Why? >>

Do you have the ADDRESS table open elsewhere in your application ?  If so,
then ElevateDB will internally keep the physical table (and any cache
buffers loaded for it for rows, index pages, BLOB blocks, etc.) until all
references (TEDBTable, TEDBQuery, etc.) to the physical table are gone.

<< 2. Can I force that behaviour? >>

Yes, just close the TEDBDatabase component and that will force all internal
table structures to be discarded by ElevateDB.

Is there any particular reason that you're worried about (what should amount
to) several hundred KB of memory ?

--
Tim Young
Elevate Software
www.elevatesoft.com

Tim,

<<Do you have the ADDRESS table open elsewhere in your application ?  If so,
then ElevateDB will internally keep the physical table (and any cache
buffers loaded for it for rows, index pages, BLOB blocks, etc.) until all
references (TEDBTable, TEDBQuery, etc.) to the physical table are gone.>>

In that case when I do a query on a single table, yes! But most of my queries joins tables together, so there is no exact table matching.

<<Yes, just close the TEDBDatabase component and that will force all internal
table structures to be discarded by ElevateDB.>>

I read that in documentation, and so I create a second TEDBDatabase for that temporary queries. I connect this TEDBDatabase to the same Session Component as my MainDBDatabase. But when I close the Database after my printing process there is still no change in memory consuption.

<<Is there any particular reason that you're worried about (what should amount
to) several hundred KB of memory ?>>

When I start my application it uses 80.000kB of memory. A large part was the visual components (SkinLibrary of DevExpress). When I browse through application then uses each query additional memory, and I came never back to these 80.000kB. Especially printing, there was a lot of queries to find the needed informations. There are also pictures and large text blocks in blob and clob fields. When I start app I need 80.000kB of memory, go immediately to printing and print a large report the memory increases to 94.000kB while I´m in preview, and goes back to 93.000kB when I close preview. So if I browse through my app it´s no problem to bring memory to 170.000kB, but never back.
When I learned programming it was normal to give back what I had taken (<- bad english, sorry) as soon as possible. So I have a lot of try..finally blocks in my application to release the resources after use.

I use a function to create my temp used queries:

function CreateQuery(OnDatabase: TEDBDatabase): TEDBQuery;
begin
 Result := TEDBQuery.Create(nil);

 if OnDatabase = nil then
 begin
   FTempDB := FEDBSession.FindDatabase('TempDB');
   if FTempDB = nil then
   begin
     FTempDB                := TEDBDatabase.Create(Self);
     FTempDB.Temporary      := True;
     FTempDB.DatabaseName   := 'TempDB';
     FTempDB.Database       := FEDBDatabase.Database;
     FTempDB.KeepConnection := False;
     FTempDB.SessionName    := FEDBDatabase.SessionName;

     FEDBSession.OpenDatabase('TempDB');
   end;
   OnDatabase := FTempDB;
 end;

 Result.SessionName      := OnDatabase.SessionName;
 Result.DatabaseName     := OnDatabase.DatabaseName;
 Result.RequestSensitive := True;
end;

The first call creates the FTempDB, and any further call uses this FTempDB. At the end of my operation I free all my created queries and call then FTempDB.Close. But memory is not freed .

Hope you can help, best regards
Michael

Please don´t call me Volker, the elevate components was registered to Volker, but I work with them

Michael (sorry about Volker ,

<< I read that in documentation, and so I create a second TEDBDatabase for
that temporary queries. I connect this TEDBDatabase to the same Session
Component as my MainDBDatabase. But when I close the Database after my
printing process there is still no change in memory consuption. >>

TEDBDatabase components are just "shells" around the internal engine
objects, so using a temporary TEDBDatabase component won't really affect
anything in terms of the engine memory allocations if the database or any of
the tables are open elsewhere in your application.  Also, there is a good
chance that the memory manager may keep blocks of memory around because they
are sub-allocations from larger blocks of allocated memory.

<< When I start my application it uses 80.000kB of memory. A large part was
the visual components (SkinLibrary of DevExpress). When I browse through
application then uses each query additional memory, and I came never back to
these 80.000kB. Especially printing, there was a lot of queries to find the
needed informations. There are also pictures and large text blocks in blob
and clob fields. When I start app I need 80.000kB of memory, go immediately
to printing and print a large report the memory increases to 94.000kB while
I´m in preview, and goes back to 93.000kB when I close preview. So if I
browse through my app it´s no problem to bring memory to 170.000kB, but
never back.
When I learned programming it was normal to give back what I had taken (<-
bad english, sorry) as soon as possible. So I have a lot of try..finally
blocks in my application to release the resources after use. >>

Are you using the ElevateDB Server ?  If so, then you can see exactly what
tables are open, and how much memory is being used for buffering the table
contents, by quering this table:

http://www.elevatesoft.com/manual?action=viewtopic&id=edb2sql&topic=ServerSessionStatistics_Table

That may help shed some light on what is going on.  I can assure you that
ElevateDB is releasing memory as soon as it is no longer necessary, but it
may involve closing databases/tables/queries that you currently have open.

--
Tim Young
Elevate Software
www.elevatesoft.com