Hi,
I have a simple thread that calls a function every second to check for new records in the database. I wrote a small application to demonstrate my problem which is included below.
When the thread (application) starts for the first time, it reads the data from the database correctly.
The problem is that even when I manually delete data from the database, the SQLQuery object continues to return the same data as read when the application started - it is almost as if the changes are not detected in the database, yet I can confirm there are no records in the database.
The interesting part is that when I compile this in the latests FPC (2.6.4) using the latest Lazarus IDE (1.4.0) available (SVN 48776), this error is simulated.
However, using an older version dated 2013-08-24, FPC 2.6.2 and Lazarus 1.0.12 (SVN 42479) I have no such problems and application and thread works just fine and detects changes in the database every time the query is executed.
It therefore appears that something has changed between the FPC releases which I am not taking into account, and I would appreciate it if someone can please tell me what I am doing wrong in the code?
Many thanks - the sample code is below:
unit conn_test_thread;
{$mode objfpc}{$H+}
interface
uses
Classes, SysUtils, mysql55conn, sqldb;
type
{ TMysqlConnTest }
TMysqlConnTest = class(TThread)
public
constructor Create();
protected
procedure Execute; override;
private
SQLConn : TMySQL55Connection;
SQLTrans : TSQLTransaction;
SQLQuery : TSQLQuery;
end;
implementation
{ TMysqlConnTest }
constructor TMysqlConnTest.Create;
begin
SQLConn := TMySQL55Connection.Create(nil);
SQLTrans := TSQLTransaction.Create(nil);
SQLQuery := TSQLQuery.Create(nil);
FreeOnTerminate := true;
inherited Create(false);
end;
procedure TMysqlConnTest.Execute;
var nCntr : integer;
begin
try
SQLConn.HostName := '127.0.0.1';
SQLConn.UserName := 'root';
SQLConn.Password := '';
SQLConn.Port := 3306;
SQLConn.DatabaseName := 'test_db';
SQLConn.Transaction := SQLTrans;
SQLQuery.DataBase := SQLConn;
SQLConn.Connected := true;
repeat
Writeln('Executing Query');
SQLQuery.SQL.Text := 'Select first_name, last_name from test_users';
SQLQuery.Open;
SQLQuery.Last;
SQLQuery.First;
Writeln('Found : ', SQLQuery.RecordCount, ' records');
for nCntr := 0 to SQLQuery.RecordCount -1 do
begin
Writeln('Firstname : ', SQLQuery.FieldByName('first_name').AsString + ' Lastname: ' + SQLQuery.FieldByName('last_name').AsString);
SQLQuery.Next;
end;
SQLQuery.Close;
Sleep(1000);
until false;
except
on e : Exception do
begin
Writeln('ERROR : ', e.Message);
end;
end;
end;
end.
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