# OTL 4.0, Example 114 (OTL stream pooling, OTL/ODBC)

# Example 114 (OTL stream pooling, OTL/ODBC)

This example demonstrates the OTL stream pooling for OTL/ODBC. This example works with Oracle ODBC drivers for Oracle 8/8i. It also can work with MyODBC/MySQL.

It does NOT work with any of MS SQL Server ODBC drivers, because, simply put, they suck. They don't allow the program to keep more than one fetch sequence open (SELECT statements, prepared, and ready to be executed with new sets of input variables). Even the use of static cursors doesn't help in this case.

## Source Code

    #include <iostream>
    using namespace std;

    #include <stdio.h>

    #define OTL_ODBC // Compile OTL 4.0/ODBC
    #define OTL_STL // turn on OTL in the STL compliance mode
    #define OTL_STREAM_POOLING_ON
     // turn on OTL stream pooling.
     // #define OTL_STREAM_POOLING_ON line
     // can be commented out, the number of iterations in
     // the select() loop can be increased, and the difference
     // in performace with and without OTL_STREAM_POOLING_ON can
     // be benchmarked. The difference should grow with the overall
     // number of streams to be used in one program.

    #include <otlv4.h> // include the OTL 4.0 header file

    otl_connect db; // connect object

    void insert()
    // insert rows into table
    {
     otl_stream o(50, // buffer size
                  "insert into test_tab values(:f1<int>,:f2<char[31]>)",
                     // SQL statement
                  db // connect object
                 );
     char tmp[32];

     for(int i=1;i<=100;++i){
      sprintf(tmp,"Name%d",i);
      o<<i<<tmp;
     }
    #ifdef OTL_STREAM_POOLING_ON
     o.close(false); // do not save the stream in the stream pool.
                     // in other words, destroy it on the spot, since
                     // the stream is not going to be reused later.
    #else
     o.close();
    #endif
    }

    void select()
    { // when this function is called in a loop,
      // on the second iteration of the loop the streams i1, i2 will
      // will get the instances of the OTL stream from the stream
      // pool, "fast reopen", so to speak.

     otl_stream i1(50, // buffer size
                   "select * from test_tab where f1>=:f11<int> and f1<=:f12<int>*2",
                     // SELECT statement
                  db // connect object
                 );
       // create select stream

     otl_stream i2(33, // buffer size
                   "select f1,f2 from test_tab where f1>=:f11<int> and f1<=:f12<int>*2",
                     // SELECT statement
                  db // connect object
                 );
       // create select stream

    // i1 and i2 are NOT similar, because their buffer sizes as well
    // as SQL statements are not equal. It will generate two entry points in the
    // OTL stream pool.

     int f1;
     char f2[31];

     i1<<2<<2; // assigning :f11 = 2, :f12 = 2
       // SELECT automatically executes when all input variables are
       // assigned. First portion of output rows is fetched to the buffer

     while(!i1.eof()){ // while not end-of-data
      i1>>f1>>f2;
      cout<<"I1==> f1="<<f1<<", f2="<<f2<<endl;
     }

     i2<<3<<3; // assigning :f11 = 2, :f12 = 2
       // SELECT automatically executes when all input variables are
       // assigned. First portion of output rows is fetched to the buffer

     while(!i2.eof()){ // while not end-of-data
      i2>>f1>>f2;
      cout<<"I2==> f1="<<f1<<", f2="<<f2<<endl;
     }

    } // destructors of i1, i2 will call the close()
      // function for both of the streams and the OTL stream
      // instances will be placed in the stream pool.

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

      db.rlogon("scott/tiger@my_db"); // connect to the database
    #ifdef OTL_STREAM_POOLING_ON
      db.set_stream_pool_size(2);
       // set the maximum stream pool size and actually initializes
       // the stream pool.
       // if this function is not called, the stream pool
       // gets initialized anyway, with the default size of 32 entries.
    #endif

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

      otl_cursor::direct_exec
       (
        db,
        "create table test_tab(f1 int, f2 varchar(30))"
        );  // create table

      insert(); // insert records into table
      for(int i=1;i<=10; ++i){
        cout<<"===================> Iteration: "<<i<<endl;
        select(); // 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.var_info<<endl; // print out the variable that caused the error
     }

     db.logoff(); // disconnect from the database

     return 0;

    }

## Output

    ===================> Iteration: 1
    I1==> f1=2, f2=Name2
    I1==> f1=3, f2=Name3
    I1==> f1=4, f2=Name4
    I2==> f1=3, f2=Name3
    I2==> f1=4, f2=Name4
    I2==> f1=5, f2=Name5
    I2==> f1=6, f2=Name6
    ===================> Iteration: 2
    I1==> f1=2, f2=Name2
    I1==> f1=3, f2=Name3
    I1==> f1=4, f2=Name4
    I2==> f1=3, f2=Name3
    I2==> f1=4, f2=Name4
    I2==> f1=5, f2=Name5
    I2==> f1=6, f2=Name6
    ===================> Iteration: 3
    I1==> f1=2, f2=Name2
    I1==> f1=3, f2=Name3
    I1==> f1=4, f2=Name4
    I2==> f1=3, f2=Name3
    I2==> f1=4, f2=Name4
    I2==> f1=5, f2=Name5
    I2==> f1=6, f2=Name6
    ===================> Iteration: 4
    I1==> f1=2, f2=Name2
    I1==> f1=3, f2=Name3
    I1==> f1=4, f2=Name4
    I2==> f1=3, f2=Name3
    I2==> f1=4, f2=Name4
    I2==> f1=5, f2=Name5
    I2==> f1=6, f2=Name6
    ===================> Iteration: 5
    I1==> f1=2, f2=Name2
    I1==> f1=3, f2=Name3
    I1==> f1=4, f2=Name4
    I2==> f1=3, f2=Name3
    I2==> f1=4, f2=Name4
    I2==> f1=5, f2=Name5
    I2==> f1=6, f2=Name6
    ===================> Iteration: 6
    I1==> f1=2, f2=Name2
    I1==> f1=3, f2=Name3
    I1==> f1=4, f2=Name4
    I2==> f1=3, f2=Name3
    I2==> f1=4, f2=Name4
    I2==> f1=5, f2=Name5
    I2==> f1=6, f2=Name6
    ===================> Iteration: 7
    I1==> f1=2, f2=Name2
    I1==> f1=3, f2=Name3
    I1==> f1=4, f2=Name4
    I2==> f1=3, f2=Name3
    I2==> f1=4, f2=Name4
    I2==> f1=5, f2=Name5
    I2==> f1=6, f2=Name6
    ===================> Iteration: 8
    I1==> f1=2, f2=Name2
    I1==> f1=3, f2=Name3
    I1==> f1=4, f2=Name4
    I2==> f1=3, f2=Name3
    I2==> f1=4, f2=Name4
    I2==> f1=5, f2=Name5
    I2==> f1=6, f2=Name6
    ===================> Iteration: 9
    I1==> f1=2, f2=Name2
    I1==> f1=3, f2=Name3
    I1==> f1=4, f2=Name4
    I2==> f1=3, f2=Name3
    I2==> f1=4, f2=Name4
    I2==> f1=5, f2=Name5
    I2==> f1=6, f2=Name6
    ===================> Iteration: 10
    I1==> f1=2, f2=Name2
    I1==> f1=3, f2=Name3
    I1==> f1=4, f2=Name4
    I2==> f1=3, f2=Name3
    I2==> f1=4, f2=Name4
    I2==> f1=5, f2=Name5
    I2==> f1=6, f2=Name6

Examples Contents Go Home

Copyright © 1996, 2007, Sergei Kuchin, email: skuchin@ispwest.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.