OTL 4.0, Example 346 (Insert/Update/Select with BYTEA in stream mode and otl_stream_read_iterator)

This example demonstrates INSERT, UPDATE, and SELECT statements with the TEXT datatype in the stream mode and otl_stream_read_iterator.

Source Code

#include <iostream>
using namespace std;

#include <stdio.h>
#define OTL_ODBC_ALTERNATE_RPC
#define OTL_ODBC_POSTGRESQL // Compile OTL 4.0/ODBC
#define OTL_MAP_SQL_VARBINARY_TO_RAW_LONG
#define OTL_STREAM_READ_ITERATOR_ON
#include <otlv4.h> // include the OTL 4.0 header file

otl_connect db; // connect object

void insert()
// insert rows into table
{otl_long_string f2(6000); // define long string variable
 otl_stream o; // defined an otl_stream variable
 o.set_lob_stream_mode(true); // set the "lob stream mode" flag
 o.open(1, // buffer size has to be set to 1 for operations with LOBs
        "insert into test_tab values(:f1<int>,:f2<varchar_long>, "
        ":f3<varchar_long>) ",
            // SQL statement
        db // connect object
       );
 o.set_commit(0); // setting stream "auto-commit" to "off". It is required
                  // when LOB stream mode is used.
 int i,j;
 otl_lob_stream lob; // LOB stream for reading/writing unlimited number
                     // of bytes regardless of the buffer size.
 otl_lob_stream lob2; // LOB stream for reading/writing unlimited number
                     // of bytes regardless of the buffer size.

 for(i=1;i<=20;++i){
  o<<i;
  o<<lob; // Initialize otl_lob_stream by writing it
          // into otl_stream.
  o<<lob2; // Initialize otl_lob_stream by writing it
          // into otl_stream.

  for(j=0;j<5000;++j)
   f2[j]='*';
  f2[5000]='?';
  f2.set_len(5001);

  lob.set_len(5001+2123); // setting the total  size of
                          // the TEXT to be written.
  
  lob<<f2; // writing first chunk of the TEXT into lob


  f2[2122]='?';
  f2.set_len(2123); // setting the size of the second chunk

  lob<<f2; // writing the second chunk of the TEXT into lob
  lob.close(); // closing the otl_lob_stream

  for(j=0;j<5000;++j)
   f2[j]='*';
  f2[5000]='?';
  f2.set_len(5001);
  lob2.set_len(5001+2123); // setting the total  size of
                          // the TEXT to be written.
  
  lob2<<f2; // writing first chunk of the TEXT into lob

  f2[2122]='?';
  f2.set_len(2123); // setting the size of the second chunk

  lob2<<f2; // writing the second chunk of the TEXT into lob
  lob2.close(); // closing the otl_lob_stream

 }

 db.commit(); // committing transaction.
}
void update()
// insert rows in table
{
 otl_long_string f2(6200); // define long string variable

 otl_stream o; // defined an otl_stream variable
 o.set_lob_stream_mode(true); // set the "lob stream mode" flag
 o.open(1, // buffer size has to be set to 1 for operations with LOBs
              "update test_tab "
              "   set f2=:f2<varchar_long> "
              "where f1=:f1<int> ",
                 // SQL statement
              db // connect object
             );

  otl_lob_stream lob;

  o.set_commit(0); // setting stream "auto-commit" to "off". 


 for(int j=0;j<6000;++j){
  f2[j]='#';
 }

 f2[6000]='?';
 f2.set_len(6001);

 o<<lob; // Initialize otl_lob_stream by writing it
         // into otl_stream.
 o<<5;

 lob.set_len(6001*4); // setting the total size of of the TEXT to be written
 for(int i=1;i<=4;++i)
  lob<<f2; // writing chunks of the TEXT into the otl_lob_stream

 lob.close(); // closing the otl_lob_stream

 db.commit(); // committing transaction

}

void select()

 otl_long_string f2(3000); // define long string variable

 otl_stream i;
i.set_lob_stream_mode(true); // set the "lob stream mode" flag
i.open(1, // buffer size. To read TEXT, it needs to be set to 1.
        "select * from test_tab where f1>=:f11<int> and f1<=:f12<int>*2",
           // SELECT statement
         db // connect object
        ); 
   // create select stream
 
 int f1;
 otl_lob_stream* lob; // Pointer to Stream for reading TEXT
 otl_lob_stream* lob2; // Pointer to Stream for reading TEXT

 i<<4<<4; // assigning :f11 = 4, :f12 = 4
   // SELECT automatically executes when all input variables are
   // assigned. First portion of output rows is fetched to the buffer

otl_stream_read_iterator<otl_stream,otl_exception,otl_lob_stream> rs;
rs.attach(i); // attach the iterator "rs" to the stream "i".

 while(rs.next_row()){ // while not end-of-data
rs.get(1,f1);
  cout<<"f1="<<f1<<endl;
rs.get(2,lob); // get pointer to LOB stream
rs.get(3,lob2); // get pointer to LOB stream
  int n=0;
  while(!lob->eof()){ // read while not "end-of-file" -- end of TEXT
   ++n;
   (*lob)>>f2; // reading a chunk of TEXT
   cout<<"   chunk #"<<n;
   cout<<", f2="<<f2[0]<<f2[f2.len()-1]<<", len="<<f2.len()<<endl;
  }
  lob->close(); // closing the otl_lob_stream.
  n=0;
  while(!lob2->eof()){ // read while not "end-of-file" -- end of TEXT
   ++n;
   (*lob2)>>f2; // reading a chunk of TEXT
   cout<<"   chunk #"<<n;
   cout<<", f3="<<f2[0]<<f2[f2.len()-1]<<", len="<<f2.len()<<endl;
  }
  lob2->close(); // closing the otl_lob_stream. 
  
 }

}


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

  db.rlogon("scott/tiger@postgresql"); // connect to the database

  otl_cursor::direct_exec
   (
    db,
    "drop table test_tab",
    otl_exception::disabled // disable OTL exceptions
   ); // drop table
db.commit();
  otl_cursor::direct_exec
   (
    db,
    "create table test_tab(f1 int, f2 bytea, f3 bytea)"
    );  // create table
db.commit();
  insert(); // insert records into table
  update(); // update records in table
  select(); // select records from table

 }

 catch(otl_exception& p){ // intercept OTL exceptions
  cerr<<p.msg<<endl; // print out error message
  cerr<<p.sqlstate<<endl; // print out SQLSTATE 
  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

f1=4
chunk #1, f2=**, len=3000
chunk #2, f2=**, len=3000
chunk #3, f2=*?, len=1124
chunk #1, f3=**, len=3000
chunk #2, f3=**, len=3000
chunk #3, f3=*?, len=1124
f1=6
chunk #1, f2=**, len=3000
chunk #2, f2=**, len=3000
chunk #3, f2=*?, len=1124
chunk #1, f3=**, len=3000
chunk #2, f3=**, len=3000
chunk #3, f3=*?, len=1124
f1=7
chunk #1, f2=**, len=3000
chunk #2, f2=**, len=3000
chunk #3, f2=*?, len=1124
chunk #1, f3=**, len=3000
chunk #2, f3=**, len=3000
chunk #3, f3=*?, len=1124
f1=8
chunk #1, f2=**, len=3000
chunk #2, f2=**, len=3000
chunk #3, f2=*?, len=1124
chunk #1, f3=**, len=3000
chunk #2, f3=**, len=3000
chunk #3, f3=*?, len=1124
f1=5
chunk #1, f2=##, len=3000
chunk #2, f2=##, len=3000
chunk #3, f2=?#, len=3000
chunk #4, f2=##, len=3000
chunk #5, f2=##, len=3000
chunk #6, f2=##, len=3000
chunk #7, f2=##, len=3000
chunk #8, f2=##, len=3000
chunk #9, f2=#?, len=4
chunk #1, f3=**, len=3000
chunk #2, f3=**, len=3000
chunk #3, f3=*?, len=1124


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Copyright © 1996-2017, Sergei Kuchin, email: skuchin@gmail.com, skuchin@gmail.com .

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