Change “datadir” for MySQL Embedded Server

[Mephi]

Answer the question, please!

I use ZEOSDBO-6.6.0-beta and the library libmysqld41.dll.

Is it possible to change “datadir” for MySQL Embedded Server in my program?

I tried to pass the new value in ZConnection – it didn’t work.
I tried to destroy the TZConnection object and create it with new parameters – but with no results. Anyway “datadir” has the first (initial) value.

[mdaems]

Have a look at the embedded example directory provided with the package. Fduenas provided a readmefirst file and an example. Read it, PLEASE!!
(Next time I'll be a little more friendly )

Mark

[Mephi]

I read that example several times. As I have written everything goes well until I change the variable “datadir “.
I’m not a programmer, so correct me please.

There are two identical databases 'pr1' и 'pr2' in folders 'C:\Data' и 'C:\Temp\Data'.

This is my code:

private
FConnection: TZConnection;
public
property Connection: TZConnection read FConnection write FConnection;
......

procedure TForm1.CreateOurConnection(strDb,strDataDir:string);
var
tmpStringList: TStrings;
begin
Connection := TZConnection.Create(Self);
Connection.Protocol := 'mysqld-4.1';
Connection.HostName := '';
Connection.Database := strDb;
Connection.User := '';
Connection.Password := '';
Connection.Port:=0;
tmpStringList := TStringList.Create;
try
with tmpStringList do begin
Add('compress=yes');
Add('dbless=no');
Add('useresult=no');
Add('timeout=30');
Add('ServerArgument1=--basedir=./');
Add('ServerArgument2=--datadir='+strDataDir);
Add('ServerArgument3=--character-sets-dir=./share/charsets');
Add('ServerArgument4=--language=./share/english');
Add('ServerArgument5=--skip-innodb');
Add('ServerArgument6=--key_buffer_size=32M');
end;
Connection.Properties.Assign(tmpStringList);
finally
tmpStringList.free;
end;
end;

procedure TForm1.DestroyOurConnection;
begin
Connection.Connected := False;
Connection.Destroy;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
CreateOurConnection('pr1', 'C:/Data');
Connection.Connected := True;
DestroyOurConnection;
CreateOurConnection('pr2', 'C:/Temp/Data');
Connection.Connected := True;
end;

Appear the mistake “SQL Error: Unknown database ‘pr2’”.
If to change the variable of Database ‘pr2’ on ‘pr1’:

CreateOurConnection('pr1', 'C:/Temp/Data');

connection will be fixed without any mistake.

What is the mistake?

Thank you!

[mdaems]

I think the problem is that you are trying to use two embedded servers... Basicly it means you need 2 dll's being loaded as far as I know.

User tohenk has the same problem and provided a patch that can handle this.
I'll attach his SVN patch file to this reply. It can help you for now, I hope. This feature will probably not be implemented in 6.6 version. Remember, the only one who can help you with this patch is tohenk.

An other workaround : copy the embedded dll as libmysql41 and use 2 different protocols (mysql-4.1 and mysqld4.1). This is not a beautifull solution, but it should work unless you also need a regular server connection or more than 2 embedded servers.

Mark