OTL 4.0, Example 386 (Insert/Update/Select with Oracle 8i/9i/10g BLOB in stream mode and otl_long_string::set_last_piece())

This example demonstrates INSERT, UPDATE, and SELECT statements with the Oracle 8 BLOB datatype in stream mode and otl_long_string::set_last_piece().

Source Code

#include <iostream>
using namespace std;

#include <stdio.h>

#define OTL_ORA8I // Compile OTL 4.0/OCI8i
//#define OTL_ORA9I // Compile OTL 4.0/OCI9i
//#define OTL_ORA10G // Compile OTL 4.0/OCI10g
//#define OTL_ORA10G_R2 // Compile OTL 4.0/OCI10gR2
#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(60000); // define long string variable
 otl_stream o(1, // buffer size has to be set to 1 for operations with LOBs
              "insert into test_tab values(:f1<int>,empty_blob()) "
              "returning f2 into :f2<blob> ",
                 // SQL statement
              db // connect object
             );
 o.set_commit(0); // setting stream "auto-commit" to "off". It is required
                  // when LOB stream mode is used.

 otl_lob_stream lob; // LOB stream for reading/writing unlimited number
                     // of bytes regardless of the buffer size.

 for(int i=1;i<=20;++i){
  for(int j=0;j<50000;++j)
   f2[j]='*';
  f2[50000]='?';
  f2.set_len(50001);

  o<<i;

  o<<lob; // Initialize otl_lob_stream by writing it
          // into otl_stream. Weird, isn't it?

// OTL 4.0.138 and higher does not require the LOB's total length to be 
// set beforehand. Instead, otl_long_string::last_piece can be used.
//  lob.set_len(50001+23123); // setting the total  size of
//                            // the BLOB to be written.
//   // It is required for compatibility
//   // with earlier releases of OCI8: OCI8.0.3, OCI8.0.4.
 
  f2.set_last_piece(false);
  lob<<f2; // writing first chunk of the BLOB into lob

  f2[23122]='?';
  f2.set_len(23123); // setting the size of the second chunk

  f2.set_last_piece(true);
  lob<<f2; // writing the second chunk of the BLOB into lob
  lob.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(1, // buffer size has to be set to 1 for operations with LOBs
              "update test_tab "
              "   set f2=empty_blob() "
              "where f1=:f1<int> "
              "returning f2 into :f2<blob> ",
                 // 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<<5;
 o<<lob; // Initialize otl_lob_stream by writing it
         // into otl_stream.

// OTL 4.0.138 and higher does not require the LOB's total length to be 
// set beforehand. Instead, otl_long_string::last_piece can be used.
// lob.set_len(6001*4); // setting the total size of of the BLOB to be written
 for(int i=1;i<=4;++i){
   f2.set_last_piece(i==4);
   lob<<f2; // writing chunks of the BLOB into the otl_lob_stream
 }
 lob.close(); // closing the otl_lob_stream

 db.commit(); // committing transaction

}

void select()
{ 
 otl_long_string f2(20000); // define long string variable

 otl_stream i(10, // buffer size. To read BLOBs, it can be set to a size greater than 1
              "select * from test_tab where f1>=:f<int> and f1<=:f*2",
                 // SELECT statement
              db // connect object
             ); 
   // create select stream
 
 float f1;
 otl_lob_stream lob; // Stream for reading BLOB

 i<<4; // assigning :f = 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;
  cout<<"f1="<<f1<<endl;
  i>>lob; // initializing BLOB stream by reading the BLOB reference 
          // into the otl_lob_stream from the otl_stream.
  int n=0;
  while(!lob.eof()){ // read while not "end-of-file" -- end of BLOB
   ++n;
   lob>>f2; // reading a chunk of BLOB
   cout<<"   chunk #"<<n;
   cout<<", f2="<<f2[0]<<f2[f2.len()-1]<<", len="<<f2.len()<<endl;
  }
  lob.close(); // closing the otl_lob_stream. This step may be skipped.
  
 }

}

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

  db.rlogon("scott/tiger"); // connect to Oracle

  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 number, f2 blob)"
    );  // create table

  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.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 Oracle

 return 0;

}

Output

f1=4
   chunk #1, f2=**, len=20000
   chunk #2, f2=**, len=20000
   chunk #3, f2=**, len=20000
   chunk #4, f2=*?, len=13124
f1=5
   chunk #1, f2=##, len=20000
   chunk #2, f2=#?, len=4004
f1=6
   chunk #1, f2=**, len=20000
   chunk #2, f2=**, len=20000
   chunk #3, f2=**, len=20000
   chunk #4, f2=*?, len=13124
f1=7
   chunk #1, f2=**, len=20000
   chunk #2, f2=**, len=20000
   chunk #3, f2=**, len=20000
   chunk #4, f2=*?, len=13124
f1=8
   chunk #1, f2=**, len=20000
   chunk #2, f2=**, len=20000
   chunk #3, f2=**, len=20000
   chunk #4, f2=*?, len=13124

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