OTL 4.0, Example 561 (set_transaction_isolation_level, ODBC, Sybase SQL)

This example demonstrates the use of otl_connect::set_transaction_isolation_level() for OTL/ODBC..

Source Code

#include <iostream>
using namespace std;

#include <stdio.h>
#define OTL_ODBC_UNIX // Compile OTL 4.0/ODBC
#include <otlv4.h> // include the OTL 4.0 header file

otl_connect db1, db2, db3; // connect objects

void insert()
// insert rows into table

 otl_stream o(50, // buffer size
              "insert into test_tab values(:f1<float>,:f2<char[31]>)", 
                 // SQL statement
              db1 // connect object
             );
 o.set_commit(0); // set stream's auto-commit to OFF

 char tmp[32];

 for(int i=1;i<=100;++i){
  sprintf(tmp,"Name%d",i);
  o<<(float)i<<tmp;
 }
 o.set_flush();
 // At this point, rows are posted but not yet committed to the database
}

void select(otl_connect& db)

 otl_stream i(50, // buffer size
              "select * from test_tab where f1>=:f<int> and f1<=:ff<int>*2",
                 // SELECT statement
              db // connect object
             ); 
   // create select stream
 
 float f1;
 char f2[31];

 i<<4<<4; // assigning :f = 4, :ff = 4
   // SELECT automatically executes when all input variables are
   // assigned. First portion of output rows is fetched to the buffer

 while(!i.eof()){ // while not end-of-data
  i>>f1>>f2;
  cout<<"f1="<<f1<<", f2="<<f2<<endl;
 }

}

int main()
{
 otl_connect::otl_initialize(); // initialize ODBC environment
 try{

  db1.rlogon("scott/tigger@freetds_sybsql"); // connect to ODBC
  db2.rlogon("scott/tigger@freetds_sybsql"); // connect to ODBC
  db3.rlogon("scott/tigger@freetds_sybsql"); // connect to ODBC

// It's recommended to use auto_commit_off() when OTL is used
// with FreeTDS/ODBC against Sybase in order to set the DB
// session's auto-commit to OFF. otl_connect::rlogon()'s auto-commit
// parameter has not effect. auto_commit_off() is a workaround, until
// a fix becomes available.

// FreeTDS 0.82RC3 and higher seems to have fixed the problem, therefore,
// the calls to auto_commit_off() are not required.

// db1.auto_commit_off();
// db2.auto_commit_off();
// db3.auto_commit_off();

// The feature is not really supported in FreeTDS/ODBC. It's recommended that
// "set isolation level 0" should be used
// instead, which is a server side setting. This example will be changed when the feature
// becomes available in FreeTDS/ODBC.
//  db2.set_transaction_isolation_level(otl_tran_read_uncommitted);
//  db3.set_transaction_isolation_level(otl_tran_read_committed);

db2<<"set transaction isolation level 0";

  otl_cursor::direct_exec
   (
    db1,
    "drop table test_tab",
    otl_exception::disabled // disable OTL exceptions
   ); // drop table

  otl_cursor::direct_exec
   (
    db1,
    "create table test_tab(f1 int not null, f2 varchar(30), primary key(f1))"
    );  // create table

  db1.commit(); // committing the DDLs to the database
  
  insert(); // insert records into table

  cout<<"=======> Reading uncommitted data..."<<endl; 
  select(db2); // select records from table

  db1.commit(); // committing the inserted rows to the database

  cout<<"=======> Reading committed data..."<<endl; 
  select(db3); // select records from table

 }

 catch(otl_exception& p){ // intercept OTL exceptions
  cerr<<p.msg<<endl; // print out error message
  cerr<<p.stm_text<<endl; // print out SQL that caused the error
  cerr<<p.sqlstate<<endl; // print out SQLSTATE message
  cerr<<p.var_info<<endl; // print out the variable that caused the error
 }

 db1.logoff(); // disconnect from ODBC
 db2.logoff(); // disconnect from ODBC
 db3.logoff(); // disconnect from ODBC


 return 0;

}

Output

=======> Reading uncommitted data...
f1=4, f2=Name4
f1=5, f2=Name5
f1=6, f2=Name6
f1=7, f2=Name7
f1=8, f2=Name8
=======> Reading committed data...
f1=4, f2=Name4
f1=5, f2=Name5
f1=6, f2=Name6
f1=7, f2=Name7
f1=8, f2=Name8

Examples ContentsGo Home

Copyright © 1996-2023, Sergei Kuchin, email: skuchin@gmail.com, skuchin@gmail.com .

Permission to use, copy, modify and redistribute this document for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.