OTL 4.0, Example 208 (otl_lob_stream and  SELECT INTO FOR UPDATE, Oracle)

Example 208 (otl_lob_stream and SELECT INTO FOR UPDATE, Oracle)

This example demonstrates INSERT, SELECT INTO FOR UPDATE, and SELECT statements with the Oracle 8,8i,9i CLOB datatype in the stream mode. The example is similar to example 56, and provided only as part of the package of examples to demonstrate the extended otl_lob_stream class.

Source Code

#include <iostream>
using namespace std;

#include <stdio.h>
//#define OTL_ORA8 // Compile OTL 4.0/OCI8
#define OTL_ORA8I // Compile OTL 4.0/OCI8i
//#define OTL_ORA9I // Compile OTL 4.0/OCI9i
#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(1, // buffer size has to be set to 1 for operations with LOBs
              "insert into test_tab values(:f1<int>,empty_clob(),empty_clob()) "
              "returning f2, f3 into :f2<clob>,:f3<clob> ",
                 // 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 CLOB to be written.
  
  lob<<f2; // writing first chunk of the CLOB into lob


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

  lob<<f2; // writing the second chunk of the CLOB 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 CLOB to be written.
  
  lob2<<f2; // writing first chunk of the CLOB into lob

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

  lob2<<f2; // writing the second chunk of the CLOB 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(1, // buffer size has to be set to 1 for operations with LOBs
              "begin "
              "  select f2 into :f2<clob,in> "
              "  from test_tab "
              "  where f1=:f1<int,in> "
              "  for update; "
              "end;",
                 // 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 CLOB to be written
 for(int i=1;i<=4;++i)
  lob<<f2; // writing chunks of the CLOB 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(10, // buffer size. To read CLOBs, it can be set to a size greater than 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; // Stream for reading CLOB
 otl_lob_stream lob2; // Stream for reading CLOB

 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

 while(!i.eof()){ // while not end-of-data
  i>>f1;
  cout<<"f1="<<f1<<endl;
  i>>lob; // initializing CLOB stream by reading the CLOB reference 
          // into the otl_lob_stream from the otl_stream.
  i>>lob2; // initializing CLOB stream by reading the CLOB reference 
          // into the otl_lob_stream from the otl_stream.
  int n=0;
  while(!lob.eof()){ // read while not "end-of-file" -- end of CLOB
   ++n;
   lob>>f2; // reading a chunk of CLOB
   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 CLOB
   ++n;
   lob2>>f2; // reading a chunk of CLOB
   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 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 clob, f3 clob)"
    );  // 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=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
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

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

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